PuTTY User Manual ================= PuTTY is a free (MIT-licensed) Win32 Telnet and SSH client. This manual documents PuTTY, and its companion utilities PSCP, Plink, Pageant and PuTTYgen. This manual is copyright 2001 Simon Tatham. All rights reserved. You may distribute this documentation under the MIT licence. See appendix C for the licence text in full. Chapter 1: Introduction to PuTTY -------------------------------- PuTTY is a free SSH, Telnet and Rlogin client for 32-bit Windows systems. 1.1 What are SSH, Telnet and Rlogin? If you already know what SSH, Telnet and Rlogin are, you can safely skip on to the next section. SSH, Telnet and Rlogin are three ways of doing the same thing: logging in to a multi-user computer from another computer, over a network. Multi-user operating systems, such as Unix and VMS, usually present a command-line interface to the user, much like the `Command Prompt' or `MS-DOS Prompt' in Windows. The system prints a prompt, and you type commands which the system will obey. Using this type of interface, there is no need for you to be sitting at the same machine you are typing commands to. The commands, and responses, can be sent over a network, so you can sit at one computer and give commands to another one, or even to more than one. SSH, Telnet and Rlogin are _network protocols_ that allow you to do this. On the computer you sit at, you run a _client_, which makes a network connection to the other computer (the _server_). The network connection carries your keystrokes and commands from the client to the server, and carries the server's responses back to you. These protocols can also be used for other types of keyboard-based interactive session. In particular, there are a lot of bulletin boards, talker systems and MUDs (Multi-User Dungeons) which support access using Telnet. There are even a few that support SSH. You might want to use SSH, Telnet or Rlogin if: - you have an account on a Unix or VMS system which you want to be able to access from somewhere else - your Internet Service Provider provides you with a login account on a web server. (This might also be known as a _shell account_. A _shell_ is the program that runs on the server and interprets your commands for you.) - you want to use a bulletin board system, talker or MUD which can be accessed using Telnet. You probably do _not_ want to use SSH, Telnet or Rlogin if: - you only use Windows. Windows computers have their own ways of networking between themselves, and unless you are doing something fairly unusual, you will not need to use any of these remote login protocols. 1.2 How do SSH, Telnet and Rlogin differ? This list summarises some of the differences between SSH, Telnet and Rlogin. - SSH is a recently designed, high-security protocol. It uses strong cryptography to protect your connection against eavesdropping, hijacking and other attacks. Telnet and Rlogin are both older protocols offering minimal security. - Telnet allows you to pass some settings on to the server, such as environment variables. (These control various aspects of the server's behaviour. You can usually set them by entering commands into the server once you're connected, but it's easier to have Telnet do it automatically.) SSH and Rlogin do not support this. However, most modern Telnet servers don't allow it either, because it has been a constant source of security problems. - SSH and Rlogin both allow you to log in to the server without having to type a password. (Rlogin's method of doing this is insecure, and can allow an attacker to access your account on the server. SSH's method is much more secure, and typically breaking the security requires the attacker to have gained access to your actual client machine.) - SSH allows you to connect to the server and automatically send a command, so that the server will run that command and then disconnect. So you can use it in automated processing. The Internet is a hostile environment and security is everybody's responsibility. If you are connecting across the open Internet, then we recommend you use SSH. If the server you want to connect to doesn't support SSH, it might be worth trying to persuade the administrator to install it. If you are behind a good firewall, it is more likely to be safe to use Telnet or Rlogin, but we still recommend you use SSH. Chapter 2: Getting started with PuTTY ------------------------------------- This chapter gives a quick guide to the simplest types of interactive login session using PuTTY. 2.1 Starting a session When you start PuTTY, you will see a dialog box. This dialog box allows you to control everything PuTTY can do. See chapter 4 for details of all the things you can control. You don't usually need to change most of the configuration options. To start the simplest kind of session, all you need to do is to enter a few basic parameters. In the `Host Name' box, enter the Internet host name of the server you want to connect to. You should have been told this by the provider of your login account. Now select a login protocol to use, from the `Protocol' buttons. For a login session, you should select Telnet, Rlogin or SSH. See section 1.2 for a description of the differences between the three protocols, and advice on which one to use. The fourth protocol, _Raw_, is not used for interactive login sessions; you would usually use this for debugging other Internet services. When you change the selected protocol, the number in the `Port' box will change. This is normal: it happens because the various login services are usually provided on different network ports by the server machine. Most servers will use the standard port numbers, so you will not need to change the port setting. If your server provides login services on a non-standard port, your system administrator should have told you which one. (For example, many MUDs run Telnet service on a port other than 23.) Once you have filled in the `Host Name', `Protocol', and possibly `Port' settings, you are ready to connect. Press the `Open' button at the bottom of the dialog box, and PuTTY will begin trying to connect you to the server. 2.2 Verifying the Host Key (SSH only) If you are not using the SSH protocol, you can skip this section. If you are using SSH to connect to a server for the first time, you will probably see a message looking something like this: The server's host key is not cached in the registry. You have no guarantee that the server is the computer you think it is. The server's key fingerprint is: ssh-rsa 1024 7b:e5:6f:a7:f4:f9:81:62:5c:e3:1f:bf:8b:57:6c:5a If you trust this host, hit Yes to add the key to PuTTY's cache and carry on connecting. If you want to carry on connecting just once, without adding the key to the cache, hit No. If you do not trust this host, hit Cancel to abandon the connection. This is a feature of the SSH protocol. It is designed to protect you against a network attack known as _spoofing_: secretly redirecting your connection to a different computer, so that you send your password to the wrong machine. Using this technique, an attacker would be able to learn the password that guards your login account, and could then log in as if they were you and use the account for their own purposes. To prevent this attack, each server has a unique identifying code, called a _host key_. These keys are created in a way that prevents one server from forging another server's key. So if you connect to a server and it sends you a different host key from the one you were expecting, PuTTY can warn you that the server may have been switched and that a spoofing attack might be in progress. PuTTY records the host key for each server you connect to, in the Windows Registry. Every time you connect to a server, it checks that the host key presented by the server is the same host key as it was the last time you connected. If it is not, you will see a warning, and you will have the chance to abandon your connection before you type any private information (such as a password) into it. However, when you connect to a server you have not connected to before, PuTTY has no way of telling whether the host key is the right one or not. So it gives the warning shown above, and asks you whether you want to trust this host key or not. Whether or not to trust the host key is your choice. If you are connecting within a company network, you might feel that all the network users are on the same side and spoofing attacks are unlikely, so you might choose to trust the key without checking it. If you are connecting across a hostile network (such as the Internet), you should check with your system administrator, perhaps by telephone or in person. (Some modern servers have more than one host key. If the system administrator sends you more than one fingerprint, you should make sure the one PuTTY shows you is on the list, but it doesn't matter which one it is.) 2.3 Logging In After you have connected, and perhaps verified the server's host key, you will be asked to log in, probably using a username and a password. Your system administrator should have provided you with these. Enter the username and the password, and the server should grant you access and begin your session. If you have mistyped your password, most servers will give you several chances to get it right. If you are using SSH, be careful not to type your username wrongly, because you will not have a chance to correct it after you press Return. This is an unfortunate feature of the SSH protocol: it does not allow you to make two login attempts using different usernames. If you type your username wrongly, you must close PuTTY and start again. If your password is refused but you are sure you have typed it correctly, check that Caps Lock is not enabled. Many login servers, particularly Unix computers, treat upper case and lower case as different when checking your password; so if Caps Lock is on, your password will probably be refused. 2.4 After Logging In After you log in to the server, what happens next is up to the server! Most servers will print some sort of login message and then present a prompt, at which you can type commands which the server will carry out. Some servers will offer you on-line help; others might not. If you are in doubt about what to do next, consult your system administrator. 2.5 Logging Out When you have finished your session, you should log out by typing the server's own logout command. This might vary between servers; if in doubt, try `logout' or `exit', or consult a manual or your system administrator. When the server processes your logout command, the PuTTY window should close itself automatically. You _can_ close a PuTTY session using the Close button in the window border, but this might confuse the server - a bit like hanging up a telephone unexpectedly in the middle of a conversation. We recommend you do not do this unless the server has stopped responding to you and you cannot close the window any other way. Chapter 3: Using PuTTY ---------------------- This chapter provides a general introduction to some more advanced features of PuTTY. For extreme detail and reference purposes, chapter 4 is likely to contain more information. 3.1 During your session A lot of PuTTY's complexity and features are in the configuration panel. Once you have worked your way through that and started a session, things should be reasonably simple after that. Nevertheless, there are a few more useful features available. 3.1.1 Copying and pasting text Often in a PuTTY session you will find text on your terminal screen which you want to type in again. Like most other terminal emulators, PuTTY allows you to copy and paste the text rather than having to type it again. Also, copy and paste uses the Windows clipboard, so that you can paste (for example) URLs into a web browser, or paste from a word processor or spreadsheet into your terminal session. PuTTY's copy and paste works entirely with the mouse. In order to copy text to the clipboard, you just click the left mouse button in the terminal window, and drag to select text. When you let go of the button, the text is _automatically_ copied to the clipboard. You do not need to press Ctrl-C or Ctrl-Ins; in fact, if you do press Ctrl-C, PuTTY will send a Ctrl-C character down your session to the server where it will probably cause a process to be interrupted. Pasting is done using the right button (or the middle mouse button, if you have a three-button mouse and have set it up; see section 4.10.3). When you click the right mouse button, PuTTY will read whatever is in the Windows Clipboard and paste it into your session, _exactly_ as if it had been typed at the keyboard. (Therefore, be careful of pasting formatted text into an editor that does automatic indenting; you may find that the spaces pasted from the clipboard plus the spaces added by the editor add up to too many spaces and ruin the formatting. There is nothing PuTTY can do about this.) If you double-click the left mouse button, PuTTY will select a whole word. If you double-click, hold down the second click, and drag the mouse, PuTTY will select a sequence of whole words. (You can adjust precisely what PuTTY considers to be part of a word; see section 4.10.6.) If you _triple_-click, or triple-click and drag, then PuTTY will select a whole line or sequence of lines. If you want to select a rectangular region instead of selecting to the end of each line, you can do this by holding down Alt when you make your selection. (You can also configure rectangular selection to be the default, and then holding down Alt gives the normal behaviour instead. See section 4.10.5 for details.) If you have a middle mouse button, then you can use it to adjust an existing selection if you selected something slightly wrong. (If you have configured the middle mouse button to paste, then the right mouse button does this instead.) Click the button on the screen, and you can pick up the nearest end of the selection and drag it to somewhere else. 3.1.2 Scrolling the screen back PuTTY keeps track of text that has scrolled up off the top of the terminal. So if something appears on the screen that you want to read, but it scrolls too fast and it's gone by the time you try to look for it, you can use the scrollbar on the right side of the window to look back up the session history and find it again. As well as using the scrollbar, you can also page the scrollback up and down by pressing Shift-PgUp and Shift-PgDn. These are still available if you configure the scrollbar to be invisible. By default the last 200 lines scrolled off the top are preserved for you to look at. You can increase (or decrease) this value using the configuration box; see section 4.6.3. 3.1.3 The System menu If you click the left mouse button on the icon in the top left corner of PuTTY's window, or click the right mouse button on the title bar, you will see the standard Windows system menu containing items like Minimise, Move, Size and Close. PuTTY's system menu contains extra program features in addition to the Windows standard options. These extra menu commands are described below. 3.1.3.1 The PuTTY Event Log If you choose `Event Log' from the system menu, a small window will pop up in which PuTTY logs significant events during the connection. Most of the events in the log will probably take place during session startup, but a few can occur at any point in the session, and one or two occur right at the end. You can use the mouse to select one or more lines of the Event Log, and hit the Copy button to copy them to the clipboard. If you are reporting a bug, it's often useful to paste the contents of the Event Log into your bug report. 3.1.3.2 Starting new sessions PuTTY's system menu provides some shortcut ways to start new sessions: - Selecting `New Session' will start a completely new instance of PuTTY, and bring up the configuration box as normal. - Selecting `Duplicate Session' will start a session with precisely the same options as your current one - connecting to the same host using the same protocol, with all the same terminal settings and everything. - The `Saved Sessions' submenu gives you quick access to any sets of stored session details you have previously saved. See section 4.1.2 for details of how to create saved sessions. 3.1.3.3 Changing your session settings If you select `Change Settings' from the system menu, PuTTY will display a cut-down version of its initial configuration box. This allows you to adjust most properties of your current session. You can change the terminal size, the font, the actions of various keypresses, the colours, and so on. Some of the options that are available in the main configuration box are not shown in the cut-down Change Settings box. These are usually options which don't make sense to change in the middle of a session (for example, you can't switch from SSH to Telnet in mid-session). 3.1.3.4 Copy All to Clipboard This system menu option provides a convenient way to copy the whole contents of the terminal screen and scrollback to the clipboard in one go. 3.1.3.5 Clearing and resetting the terminal The `Clear Scrollback' option on the system menu tells PuTTY to discard all the lines of text that have been kept after they scrolled off the top of the screen. This might be useful, for example, if you displayed sensitive information and wanted to make sure nobody could look over your shoulder and see it. (Note that this only prevents a casual user from using the scrollbar to view the information; the text is not guaranteed not to still be in PuTTY's memory.) The `Reset Terminal' option causes a full reset of the terminal emulation. A VT-series terminal is a complex piece of software and can easily get into a state where all the text printed becomes unreadable. (This can happen, for example, if you accidentally output a binary file to your terminal.) If this happens, selecting Reset Terminal should sort it out. 3.1.3.6 Full screen mode If you find the title bar on a maximised window to be ugly or distracting, you can select Full Screen mode to maximise PuTTY `even more'. When you select this, PuTTY will expand to fill the whole screen and its borders, title bar and scrollbar will disappear. (You can configure the scrollbar not to disappear in full-screen mode if you want to keep it; see section 4.6.3.) When you are in full-screen mode, you can still access the system menu if you click the left mouse button in the _extreme_ top left corner of the screen. 3.2 Creating a log file of your session For some purposes you may find you want to log everything that appears on your screen. You can do this using the `Logging' panel in the configuration box. To begin a session log, select `Change Settings' from the system menu and go to the Logging panel. Enter a log file name, and select a logging mode. (You can log all session output including the terminal control sequences, or you can just log the printable text. It depends what you want the log for.) Click `Apply' and your log will be started. Later on, you can go back to the Logging panel and select `Logging turned off completely' to stop logging; then PuTTY will close the log file and you can safely read it. See section 4.2 for more details and options. 3.3 Altering your character set configuration If you find that special characters (accented characters, for example) are not being displayed correctly in your PuTTY session, it may be that PuTTY is interpreting the characters sent by the server according to the wrong _character set_. There are a lot of different character sets available, so it's entirely possible for this to happen. If you click `Change Settings' and look at the `Translation' panel, you should see a large number of character sets which you can select. Now all you need is to find out which of them you want! 3.4 Using X11 forwarding in SSH The SSH protocol has the ability to securely forward X Window System applications over your encrypted SSH connection, so that you can run an application on the SSH server machine and have it put its windows up on your local machine without sending any X network traffic in the clear. In order to use this feature, you will need an X display server for your Windows machine, such as X-Win32 or Exceed. This will probably install itself as display number 0 on your local machine; if it doesn't, the manual for the X server should tell you what it does do. You should then tick the `Enable X11 forwarding' box in the Tunnels panel (see section 4.17.1) before starting your SSH session. The `X display location' box reads `localhost:0' by default, which is the usual display location where your X server will be installed. If that needs changing, then change it. Now you should be able to log in to the SSH server as normal. To check that X forwarding has been successfully negotiated during connection startup, you can check the PuTTY Event Log (see section 3.1.3.1). It should say something like this: 2001-12-05 17:22:01 Requesting X11 forwarding 2001-12-05 17:22:02 X11 forwarding enabled If the remote system is Unix or Unix-like, you should also be able to see that the `DISPLAY' environment variable has been set to point at display 10 or above on the SSH server machine itself: fred@unixbox:~$ echo $DISPLAY unixbox:10.0 If this works, you should then be able to run X applications in the remote session and have them display their windows on your PC. Note that if your PC X server requires authentication to connect, then PuTTY cannot currently support it. If this is a problem for you, you should mail the authors and give details. 3.5 Using port forwarding in SSH The SSH protocol has the ability to forward arbitrary network connections over your encrypted SSH connection, to avoid the network traffic being sent in clear. For example, you could use this to connect from your home computer to a POP-3 server on a remote machine without your POP-3 password being visible to network sniffers. In order to use port forwarding to connect from your local machine to a port on a remote server, you need to: - Choose a port number on your local machine where PuTTY should listen for incoming connections. There are likely to be plenty of unused port numbers above 3000. - Now, before you start your SSH connection, go to the Tunnels panel (see section 4.17.2). Make sure the `Local' radio button is set. Enter the local port number into the `Source port' box. Enter the destination host name and port number into the `Destination' box, separated by a colon (for example, `popserver.example.com:110' to connect to a POP-3 server). - Now click the `Add' button. The details of your port forwarding should appear in the list box. Now start your session and log in. (Port forwarding will not be enabled until after you have logged in; otherwise it would be easy to perform completely anonymous network attacks, and gain access to anyone's virtual private network). To check that PuTTY has set up the port forwarding correctly, you can look at the PuTTY Event Log (see section 3.1.3.1). It should say something like this: 2001-12-05 17:22:10 Local port 3110 forwarding to popserver.example.com:110 Now if you connect to the source port number on your local PC, you should find that it answers you exactly as if it were the service running on the destination machine. So in this example, you could then configure an e-mail client to use `localhost:3110' as a POP- 3 server instead of `popserver.example.com:110'. (Of course, the forwarding will stop happening when your PuTTY session closes down.) You can also forward ports in the other direction: arrange for a particular port number on the _server_ machine to be forwarded back to your PC as a connection to a service on your PC or near it. To do this, just select the `Remote' radio button instead of the `Local' one. The `Source port' box will now specify a port number on the _server_ (note that most servers will not allow you to use port numbers under 1024 for this purpose). The source port for a forwarded connection usually does not accept connections from any machine except the SSH client or server machine itself (for local and remote forwardings respectively). There are controls in the Tunnels panel to change this: - The `Local ports accept connections from other hosts' option allows you to set up local-to-remote port forwardings in such a way that machines other than your client PC can connect to the forwarded port. - The `Remote ports do the same' option does the same thing for remote-to-local port forwardings (so that machines other than the SSH server machine can connect to the forwarded port.) Note that this feature is only available in the SSH 2 protocol, and not all SSH 2 servers support it (OpenSSH 3.0 does not, for example). 3.6 Making raw TCP connections A lot of Internet protocols are composed of commands and responses in plain text. For example, SMTP (the protocol used to transfer e- mail), NNTP (the protocol used to transfer Usenet news), and HTTP (the protocol used to serve Web pages) all consist of commands in readable plain text. Sometimes it can be useful to connect directly to one of these services and speak the protocol `by hand', by typing protocol commands and watching the responses. On Unix machines, you can do this using the system's `telnet' command to connect to the right port number. For example, `telnet mailserver.example.com 25' might enable you to talk directly to the SMTP service running on a mail server. Although the Unix `telnet' program provides this functionality, the protocol being used is not really Telnet. Really there is no actual protocol at all; the bytes sent down the connection are exactly the ones you type, and the bytes shown on the screen are exactly the ones sent by the server. Unix `telnet' will attempt to detect or guess whether the service it is talking to is a real Telnet service or not; PuTTY prefers to be told for certain. In order to make a debugging connection to a service of this type, you simply select the fourth protocol name, `Raw', from the `Protocol' buttons in the `Session' configuration panel. (See section 4.1.1.) You can then enter a host name and a port number, and make the connection. Chapter 4: Configuring PuTTY ---------------------------- This chapter describes all the configuration options in PuTTY. PuTTY is configured using the control panel that comes up before you start a session. Some options can also be changed in the middle of a session, by selecting `Change Settings' from the window menu. 4.1 The Session panel The Session configuration panel contains the basic options you need to specify in order to open a session at all, and also allows you to save your settings to be reloaded later. 4.1.1 The host name section The top box on the Session panel, labelled `Specify your connection by host name', contains the details that need to be filled in before PuTTY can open a session at all. - The `Host Name' box is where you type the name, or the IP address, of the server you want to connect to. - The `Protocol' radio buttons let you choose what type of connection you want to make: a raw connection, a Telnet connection, an rlogin connection or an SSH connection. (See section 1.2 for a summary of the differences between SSH, Telnet and rlogin.) - The `Port' box lets you specify which port number on the server to connect to. If you select Telnet, Rlogin, or SSH, this box will be filled in automatically to the usual value, and you will only need to change it if you have an unusual server. If you select Raw mode (see section 3.6), you will almost certainly need to fill in the `Port' box. 4.1.2 Loading and storing saved sessions The next part of the Session configuration panel allows you to save your preferred PuTTY options so they will appear automatically the next time you start PuTTY. It also allows you to create _saved sessions_, which contain a full set of configuration options plus a host name and protocol. A saved session contains all the information PuTTY needs to start exactly the session you want. - To save your default settings: first set up the settings the way you want them saved. Then come back to the Session panel. Select the `Default Settings' entry in the saved sessions list, with a single click. Then press the `Save' button. Note that PuTTY does not allow you to save a host name into the Default Settings entry. This ensures that when PuTTY is started up, the host name box is always empty, so a user can always just type in a host name and connect. If there is a specific host you want to store the details of how to connect to, you should create a saved session, which will be separate from the Default Settings. - To save a session: first go through the rest of the configuration box setting up all the options you want. Then come back to the Session panel. Enter a name for the saved session in the `Saved Sessions' input box. (The server name is often a good choice for a saved session name.) Then press the `Save' button. Your saved session name should now appear in the list box. - To reload a saved session: single-click to select the session name in the list box, and then press the `Load' button. Your saved settings should all appear in the configuration panel. - To modify a saved session: first load it as described above. Then make the changes you want. Come back to the Session panel, single- click to select the session name in the list box, and press the `Save' button. The new settings will be saved over the top of the old ones. - To start a saved session immediately: double-click on the session name in the list box. - To delete a saved session: single-click to select the session name in the list box, and then press the `Delete' button. Each saved session is independent of the Default Settings configuration. If you change your preferences and update Default Settings, you must also update every saved session separately. 4.1.3 `Close Window on Exit' Finally in the Session panel, there is an option labelled `Close Window on Exit'. This controls whether the PuTTY session window disappears as soon as the session inside it terminates. If you are likely to want to copy and paste text out of the session after it has terminated, you should arrange this option to be off. `Close Window On Exit' has three settings. `Always' means always close the window on exit; `Never' means never close on exit (always leave the window open). The third setting, and the default one, is `Only on clean exit'. In this mode, a session which terminates normally will cause its window to close, but one which is aborted unexpectedly by network trouble or a confusing message from the server will leave the window up. 4.2 The Logging panel The Logging configuration panel allows you to save log files of your PuTTY sessions, for debugging, analysis or future reference. The main option is a radio-button set that specifies whether PuTTY will log anything at all. The options are - `Logging turned off completely'. This is the default option; in this mode PuTTY will not create a log file at all. - `Log printable output only'. In this mode, a log file will be created and written to, but only printable text will be saved into it. The various terminal control codes that are typically sent down an interactive session alongside the printable text will be omitted. This might be a useful mode if you want to read a log file in a text editor and hope to be able to make sense of it. - `Log all session output'. In this mode, _everything_ sent by the server into your terminal session is logged. If you view the log file in a text editor, therefore, you may well find it full of strange control characters. This is a particularly useful mode if you are experiencing problems with PuTTY's terminal handling: you can record everything that went to the terminal, so that someone else can replay the session later in slow motion and watch to see what went wrong. - `Log SSH packet data'. In this mode (which is only used by SSH connections), the SSH message packets sent over the encrypted connection are written to the log file. You might need this to debug a network-level problem, or more likely to send to the PuTTY authors as part of a bug report. _BE WARNED_ that if you log in using a password, the password will appear in the log file, so be sure to edit it out before sending the log file to anyone else! 4.2.1 `Log file name' In this edit box you enter the name of the file you want to log the session to. The `Browse' button will let you look around your file system to find the right place to put the file; or if you already know exactly where you want it to go, you can just type a pathname into the edit box. There are a few special features in this box. If you use the `&' character in the file name box, PuTTY will insert details of the current session in the name of the file it actually opens. The precise replacements it will do are: - `&Y' will be replaced by the current year, as four digits. - `&M' will be replaced by the current month, as two digits. - `&D' will be replaced by the current day of the month, as two digits. - `&T' will be replaced by the current time, as six digits (HHMMSS) with no punctuation. - `&H' will be replaced by the host name you are connecting to. For example, if you enter the host name `c:\puttylogs\log-&h-&y&m&d- &t.dat', you will end up with files looking like log-server1.example.com-20010528-110859.dat log-unixbox.somewhere.org-20010611-221001.dat 4.2.2 `What to do if the log file already exists' This control allows you to specify what PuTTY should do if it tries to start writing to a log file and it finds the file already exists. You might want to automatically destroy the existing log file and start a new one with the same name. Alternatively, you might want to open the existing log file and add data to the _end_ of it. Finally (the default option), you might not want to have any automatic behaviour, but to ask the user every time the problem comes up. 4.3 The Terminal panel The Terminal configuration panel allows you to control the behaviour of PuTTY's terminal emulation. 4.3.1 `Auto wrap mode initially on' Auto wrap mode controls what happens when text printed in a PuTTY window reaches the right-hand edge of the window. With auto wrap mode on, if a long line of text reaches the right- hand edge, it will wrap over on to the next line so you can still see all the text. With auto wrap mode off, the cursor will stay at the right-hand edge of the screen, and all the characters in the line will be printed on top of each other. If you are running a full-screen application and you occasionally find the screen scrolling up when it looks as if it shouldn't, you could try turning this option off. Auto wrap mode can be turned on and off by control sequences sent by the server. This configuration option only controls the _default_ state. If you modify this option in mid-session using `Change Settings', you will need to reset the terminal (see section 3.1.3.5) before the change takes effect. 4.3.2 `DEC Origin Mode initially on' DEC Origin Mode is a minor option which controls how PuTTY interprets cursor-position control sequences sent by the server. The server can send a control sequence that restricts the scrolling region of the display. For example, in an editor, the server might reserve a line at the top of the screen and a line at the bottom, and might send a control sequence that causes scrolling operations to affect only the remaining lines. With DEC Origin Mode on, cursor coordinates are counted from the top of the scrolling region. With it turned off, cursor coordinates are counted from the top of the whole screen regardless of the scrolling region. It is unlikely you would need to change this option, but if you find a full-screen application is displaying pieces of text in what looks like the wrong part of the screen, you could try turning DEC Origin Mode on to see whether that helps. DEC Origin Mode can be turned on and off by control sequences sent by the server. This configuration option only controls the _default_ state. If you modify this option in mid-session using `Change Settings', you will need to reset the terminal (see section 3.1.3.5) before the change takes effect. 4.3.3 `Implicit CR in every LF' Most servers send two control characters, CR and LF, to start a new line of the screen. The CR character makes the cursor return to the left-hand side of the screen. The LF character makes the cursor move one line down (and might make the screen scroll). Some servers only send LF, and expect the terminal to move the cursor over to the left automatically. If you come across a server that does this, you will see a stepped effect on the screen, like this: First line of text Second line Third line If this happens to you, try enabling the `Implicit CR in every LF' option, and things might go back to normal: First line of text Second line Third line 4.3.4 `Use background colour to erase screen' Not all terminals agree on what colour to turn the screen when the server sends a `clear screen' sequence. Some terminals believe the screen should always be cleared to the _default_ background colour. Others believe the screen should be cleared to whatever the server has selected as a background colour. There exist applications that expect both kinds of behaviour. Therefore, PuTTY can be configured to do either. With this option disabled, screen clearing is always done in the default background colour. With this option enabled, it is done in the _current_ background colour. Background-colour erase can be turned on and off by control sequences sent by the server. This configuration option only controls the _default_ state. If you modify this option in mid- session using `Change Settings', you will need to reset the terminal (see section 3.1.3.5) before the change takes effect. 4.3.5 `Enable blinking text' The server can ask PuTTY to display text that blinks on and off. This is very distracting, so PuTTY allows you to turn blinking text off completely. When blinking text is disabled and the server attempts to make some text blink, PuTTY will instead display the text with a bolded background colour. Blinking text can be turned on and off by control sequences sent by the server. This configuration option only controls the _default_ state. If you modify this option in mid-session using `Change Settings', you will need to reset the terminal (see section 3.1.3.5) before the change takes effect. 4.3.6 `Answerback to ^E' This option controls what PuTTY will send back to the server if the server sends it the ^E enquiry character. Normally it just sends the string `PuTTY'. If you accidentally write the contents of a binary file to your terminal, you will probably find that it contains more than one ^E character, and as a result your next command line will probably read `PuTTYPuTTYPuTTY...' as if you had typed the answerback string multiple times at the keyboard. If you set the answerback string to be empty, this problem should go away, but doing so might cause other problems. 4.3.7 `Local echo' With local echo disabled, characters you type into the PuTTY window are not echoed in the window _by PuTTY_. They are simply sent to the server. (The _server_ might choose to echo them back to you; this can't be controlled from the PuTTY control panel.) Some types of session need local echo, and many do not. In its default mode, PuTTY will automatically attempt to deduce whether or not local echo is appropriate for the session you are working in. If you find it has made the wrong decision, you can use this configuration option to override its choice: you can force local echo to be turned on, or force it to be turned off, instead of relying on the automatic detection. 4.3.8 `Local line editing' Normally, every character you type into the PuTTY window is sent immediately to the server the moment you type it. If you enable local line editing, this changes. PuTTY will let you edit a whole line at a time locally, and the line will only be sent to the server when you press Return. If you make a mistake, you can use the Backspace key to correct it before you press Return, and the server will never see the mistake. Since it is hard to edit a line locally without being able to see it, local line editing is mostly used in conjunction with local echo (section 4.3.7). This makes it ideal for use in raw mode or when connecting to MUDs or talkers. (Although some more advanced MUDs do occasionally turn local line editing on and turn local echo off, in order to accept a password from the user.) Some types of session need local line editing, and many do not. In its default mode, PuTTY will automatically attempt to deduce whether or not local line editing is appropriate for the session you are working in. If you find it has made the wrong decision, you can use this configuration option to override its choice: you can force local line editing to be turned on, or force it to be turned off, instead of relying on the automatic detection. 4.4 The Keyboard panel The Keyboard configuration panel allows you to control the behaviour of the keyboard in PuTTY. 4.4.1 Changing the action of the Backspace key Some terminals believe that the Backspace key should send the same thing to the server as Control-H (ASCII code 8). Other terminals believe that the Backspace key should send ASCII code 127 (usually known as Control-?) so that it can be distinguished from Control-H. This option allows you to choose which code PuTTY generates when you press Backspace. If you are connecting to a Unix system, you will probably find that the Unix `stty' command lets you configure which the server expects to see, so you might not need to change which one PuTTY generates. On other systems, the server's expectation might be fixed and you might have no choice but to configure PuTTY. If you do have the choice, we recommend configuring PuTTY to generate Control-? and configuring the server to expect it, because that allows applications such as `emacs' to use Control-H for help. 4.4.2 Changing the action of the Home and End keys The Unix terminal emulator `rxvt' disagrees with the rest of the world about what character sequences should be sent to the server by the Home and End keys. `xterm', and other terminals, send `ESC [1~' for the Home key, and `ESC [4~' for the End key. `rxvt' sends `ESC [H' for the Home key and `ESC [Ow' for the End key. If you find an application on which the Home and End keys aren't working, you could try switching this option to see if it helps. 4.4.3 Changing the action of the function keys and keypad This option affects the function keys (F1 to F12) and the top row of the numeric keypad. - In the default mode, labelled `ESC [n~', the function keys generate sequences like `ESC [11~', `ESC [12~' and so on. This matches the general behaviour of Digital's terminals. - In Linux mode, F6 to F12 behave just like the default mode, but F1 to F5 generate `ESC [[A' through to `ESC [[E'. This mimics the Linux virtual console. - In Xterm R6 mode, F5 to F12 behave like the default mode, but F1 to F4 generate `ESC OP' through to `ESC OS', which are the sequences produced by the top row of the _keypad_ on Digital's terminals. - In VT400 mode, all the function keys behave like the default mode, but the actual top row of the numeric keypad generates `ESC OP' through to `ESC OS'. - In VT100+ mode, the function keys generate `ESC OP' through to `ESC O[' - In SCO mode, the function keys F1 to F12 generate `ESC [M' through to `ESC [X'. Together with shift, they generate `ESC [Y' through to `ESC [j'. With control they generate `ESC [k' through to `ESC [v', and with shift and control together they generate `ESC [w' through to `ESC [{'. If you don't know what any of this means, you probably don't need to fiddle with it. 4.4.4 Controlling Application Cursor Keys mode Application Cursor Keys mode is a way for the server to change the control sequences sent by the arrow keys. In normal mode, the arrow keys send `ESC [A' through to `ESC [D'. In application mode, they send `ESC OA' through to `ESC OD'. Application Cursor Keys mode can be turned on and off by the server, depending on the application. PuTTY allows you to configure the initial state, and also allows you to disable application mode completely. 4.4.5 Controlling Application Keypad mode Application Keypad mode is a way for the server to change the behaviour of the numeric keypad. In normal mode, the keypad behaves like a normal Windows keypad: with NumLock on, the number keys generate numbers, and with NumLock off they act like the arrow keys and Home, End etc. In application mode, all the keypad keys send special control sequences, _including_ Num Lock. Num Lock stops behaving like Num Lock and becomes another function key. Depending on which version of Windows you run, you may find the Num Lock light still flashes on and off every time you press Num Lock, even when application mode is active and Num Lock is acting like a function key. This is unavoidable. Application keypad mode can be turned on and off by the server, depending on the application. PuTTY allows you to configure the initial state, and also allows you to disable application mode completely. 4.4.6 Using NetHack keypad mode PuTTY has a special mode for playing NetHack. You can enable it by selecting `NetHack' in the `Initial state of numeric keypad' control. In this mode, the numeric keypad keys 1-9 generate the NetHack movement commands (hjklyubn). The 5 key generates the `.' command (do nothing). Better still, pressing Shift with the keypad keys generates the capital forms of the commands (HJKLYUBN), which tells NetHack to keep moving you in the same direction until you encounter something interesting. For some reason, this feature only works properly when Num Lock is on. We don't know why. 4.4.7 Enabling a DEC-like Compose key DEC terminals have a Compose key, which provides an easy-to-remember way of typing accented characters. You press Compose and then type two more characters. The two characters are `combined' to produce an accented character. The choices of character are designed to be easy to remember; for example, composing `e' and ``' produces the `è' character. If you enable the `Application and AltGr act as Compose key' option, the Windows Application key and the AltGr key will both have this behaviour. 4.4.8 `Control-Alt is different from AltGr' Some old keyboards do not have an AltGr key, which can make it difficult to type some characters. PuTTY can be configured to treat the key combination Ctrl + Left Alt the same way as the AltGr key. By default, this checkbox is checked, and the key combination Ctrl + Left Alt does something completely different. PuTTY's usual handling of the left Alt key is to prefix the Escape (Control-[) character to whatever character sequence the rest of the keypress would generate. For example, Alt-A generates Escape followed by `a'. So Alt-Ctrl-A would generate Escape, followed by Control-A. If you uncheck this box, Ctrl-Alt will become a synonym for AltGr, so you can use it to type extra graphic characters if your keyboard has any. 4.5 The Bell panel The Bell panel controls the terminal bell feature: the server's ability to cause PuTTY to beep at you. In the default configuration, when the server sends the character with ASCII code 7 (Control-G), PuTTY will play the Windows Default Beep sound. This is not always what you want the terminal bell feature to do; the Bell panel allows you to configure alternative actions. 4.5.1 `Set the style of bell' This control allows you to select various different actions to occur on a terminal bell: - Selecting `None' disables the bell completely. In this mode, the server can send as many Control-G characters as it likes and nothing at all will happen. - `Play Windows Default Sound' is the default setting. It causes the Windows `Default Beep' sound to be played. To change what this sound is, or to test it if nothing seems to be happening, use the Sound configurer in the Windows Control Panel. - `Play a custom sound file' allows you to specify a particular sound file to be used by PuTTY alone, or even by a particular individual PuTTY session. This allows you to distinguish your PuTTY beeps from any other beeps on the system. If you select this option, you will also need to enter the name of your sound file in the edit control `Custom sound file to play as a bell'. - `Visual bell' is a silent alternative to a beeping computer. In this mode, when the server sends a Control-G, the whole PuTTY window will flash white for a fraction of a second. 4.5.2 `Taskbar/caption indication on bell' This feature controls what happens to the PuTTY window's entry in the Windows Taskbar if a bell occurs while the window does not have the input focus. In the default state (`Disabled') nothing unusual happens. If you select `Steady', then when a bell occurs and the window is not in focus, the window's Taskbar entry and its title bar will change colour to let you know that PuTTY session is asking for your attention. The change of colour will persist until you select the window, so you can leave several PuTTY windows minimised in your terminal, go away from your keyboard, and be sure not to have missed any important beeps when you get back. `Flashing' is even more eye-catching: the Taskbar entry will continuously flash on and off until you select the window. 4.5.3 `Control the bell overload behaviour' A common user error in a terminal session is to accidentally run the Unix command `cat' (or equivalent) on an inappropriate file type, such as an executable, image file, or ZIP file. This produces a huge stream of non-text characters sent to the terminal, which typically includes a lot of bell characters. As a result of this the terminal often doesn't stop beeping for ten minutes, and everybody else in the office gets annoyed. To try to avoid this behaviour, or any other cause of excessive beeping, PuTTY includes a bell overload management feature. In the default configuration, receiving more than five bell characters in a two-second period will cause the overload feature to activate. Once the overload feature is active, further bells will have no effect at all, so the rest of your binary file will be sent to the screen in silence. After a period of five seconds during which no further bells are received, the overload feature will turn itself off again and bells will be re-enabled. If you want this feature completely disabled, you can turn it off using the checkbox `Bell is temporarily disabled when over-used'. Alternatively, if you like the bell overload feature but don't agree with the settings, you can configure the details: how many bells constitute an overload, how short a time period they have to arrive in to do so, and how much silent time is required before the overload feature will deactivate itself. 4.6 The Window panel The Window configuration panel allows you to control aspects of the PuTTY window. 4.6.1 Setting the size of the PuTTY window The `Rows' and `Columns' boxes let you set the PuTTY window to a precise size. Of course you can also drag the window to a new size while a session is running. 4.6.2 What to do when the window is resized These options allow you to control what happens when the user tries to resize the PuTTY window. When you resize the PuTTY window, one of four things can happen: - Nothing (if you have completely disabled resizes). - The font size can stay the same and the number of rows and columns in the terminal can change. - The number of rows and columns in the terminal can stay the same, and the font size can change. - You can allow PuTTY to change _either_ the terminal size or the font size. In this mode it will change the terminal size most of the time, but enlarge the font when you maximise the window. You can control which of these happens using the `Lock terminal size against resizing' and `Lock font size against resizing' options. If you lock both, the window will refuse to be resized at all. If you lock just the terminal size, the font size will change when you resize the window. If you lock just the font size, the terminal size will change when you resize the window. 4.6.3 Controlling scrollback These options let you configure the way PuTTY keeps text after it scrolls off the top of the screen (see section 3.1.2). The `Lines of scrollback' box lets you configure how many lines of text PuTTY keeps. The `Display scrollbar' options allow you to hide the scrollbar (although you can still view the scrollback using Shift-PgUp and Shift-PgDn). You can separately configure whether the scrollbar is shown in full-screen mode and in normal modes. If you are viewing part of the scrollback when the server sends more text to PuTTY, the screen will revert to showing the current terminal contents. You can disable this behaviour by turning off `Reset scrollback on display activity'. You can also make the screen revert when you press a key, by turning on `Reset scrollback on keypress'. 4.7 The Appearance panel The Appearance configuration panel allows you to control aspects of the appearance of PuTTY's window. 4.7.1 Controlling the appearance of the cursor The `Cursor appearance' option lets you configure the cursor to be a block, an underline, or a vertical line. A block cursor becomes an empty box when the window loses focus; an underline or a vertical line becomes dotted. The `Cursor blinks' option makes the cursor blink on and off. This works in any of the cursor modes. 4.7.2 Controlling the font used in the terminal window This option allows you to choose what font, in what size, the PuTTY terminal window uses to display the text in the session. You will be offered a choice from all the fixed-width fonts installed on the system. (VT100-style terminal handling can only deal with fixed- width fonts.) 4.7.3 Controlling the window title The `Window title' edit box allows you to set the title of the PuTTY window. By default the window title will contain the host name followed by `PuTTY', for example `server1.example.com - PuTTY'. If you want a different window title, this is where to set it. PuTTY allows the server to send `xterm' control sequences which modify the title of the window in mid-session. There is also an `xterm' sequence to modify the title of the window's _icon_. This makes sense in a windowing system where the window becomes an icon when minimised, such as Windows 3.1 or most X Window System setups; but in the Windows 95-like user interface it isn't as applicable. By default PuTTY's window title and Taskbar caption will change into the server-supplied icon title if you minimise the PuTTY window, and change back to the server-supplied window title if you restore it. (If the server has not bothered to supply a window or icon title, none of this will happen.) By checking the box marked `Avoid ever using icon title', you can arrange that PuTTY will always display the window title, and completely ignore any icon titles the server sends it. 4.7.4 `Hide mouse pointer when typing in window' If you enable this option, the mouse pointer will disappear if the PuTTY window is selected and you press a key. This way, it will not obscure any of the text in the window while you work in your session. As soon as you move the mouse, the pointer will reappear. This option is disabled by default, so the mouse pointer remains visible at all times. 4.7.5 Controlling the window border PuTTY allows you to configure the appearance of the window border to some extent. The checkbox marked `Sunken-edge border' changes the appearance of the window border to something more like a DOS box: the inside edge of the border is highlighted as if it sank down to meet the surface inside the window. This makes the border a little bit thicker as well. It's hard to describe well. Try it and see if you like it. You can also configure a completely blank gap between the text in the window and the border, using the `Gap between text and window edge' control. By default this is set at one pixel. You can reduce it to zero, or increase it further. 4.8 The Behaviour panel The Behaviour configuration panel allows you to control aspects of the behaviour of PuTTY's window. 4.8.1 `Warn before closing window' If you press the Close button in a PuTTY window that contains a running session, PuTTY will put up a warning window asking if you really meant to close the window. A window whose session has already terminated can always be closed without a warning. If you want to be able to close a window quickly, you can disable the `Warn before closing window' option. 4.8.2 `Window closes on ALT-F4' By default, pressing ALT-F4 causes the window to close (or a warning box to appear; see section 4.8.1). If you disable the `Window closes on ALT-F4' option, then pressing ALT-F4 will simply send a key sequence to the server. 4.8.3 `System menu appears on ALT-Space' If this option is enabled, then pressing ALT-Space will bring up the PuTTY window's menu, like clicking on the top left corner. If it is disabled, then pressing ALT-Space will just send `ESC SPACE' to the server. Some accessibility programs for Windows may need this option enabling to be able to control PuTTY's window successfully. For instance, Dragon NaturallySpeaking requires it both to open the system menu via voice, and to close, minimise, maximise and restore the window. 4.8.4 `System menu appears on Alt alone' If this option is enabled, then pressing and releasing ALT will bring up the PuTTY window's menu, like clicking on the top left corner. If it is disabled, then pressing and releasing ALT will have no effect. 4.8.5 `Ensure window is always on top' If this option is enabled, the PuTTY window will stay on top of all other windows. 4.8.6 `Full screen on Alt-Enter' If this option is enabled, then pressing Alt-Enter will cause the PuTTY window to become full-screen. Pressing Alt-Enter again will restore the previous window size. The full-screen feature is also available from the System menu, even when it is configured not to be available on the Alt-Enter key. See section 3.1.3.6. 4.9 The Translation panel The Translation configuration panel allows you to control the translation between the character set understood by the server and the character set understood by PuTTY. 4.9.1 Controlling character set translation During an interactive session, PuTTY receives a stream of 8-bit bytes from the server, and in order to display them on the screen it needs to know what character set to interpret them in. There are a lot of character sets to choose from. The `Received data assumed to be in which character set' option lets you select one. By default PuTTY will attempt to choose a character set that is right for your locale as reported by Windows; if it gets it wrong, you can select a different one using this control. A few notable character sets are: - The ISO-8859 series are all standard character sets that include various accented characters appropriate for different sets of languages. - The Win125x series are defined by Microsoft, for similar purposes. In particular Win1252 is almost equivalent to ISO-8859-1, but contains a few extra characters such as matched quotes and the Euro symbol. - If you want the old IBM PC character set with block graphics and line-drawing characters, you can select `CP437'. - PuTTY also supports Unicode mode, in which the data coming from the server is interpreted as being in the UTF-8 encoding of Unicode. If you select `UTF-8' as a character set you can use this mode. Not all server-side applications will support it. 4.9.2 `Caps Lock acts as Cyrillic switch' This feature allows you to switch between a US/UK keyboard layout and a Cyrillic keyboard layout by using the Caps Lock key, if you need to type (for example) Russian and English side by side in the same document. Currently this feature is not expected to work properly if your native keyboard layout is not US or UK. 4.9.3 Controlling display of line drawing characters VT100-series terminals allow the server to send control sequences that shift temporarily into a separate character set for drawing lines and boxes. PuTTY has a variety of ways to support this capability. In general you should probably try lots of options until you find one that your particular font supports. - `Font has XWindows encoding' is for use with fonts that have a special encoding, where the lowest 32 character positions (below the ASCII printable range) contain the line-drawing characters. This is unlikely to be the case with any standard Windows font; it will probably only apply to custom-built fonts or fonts that have been automatically converted from the X Window System. - `Use font in both ANSI and OEM modes' tries to use the same font in two different character sets, to obtain a wider range of characters. This doesn't always work; some fonts claim to be a different size depending on which character set you try to use. - `Use font in OEM mode only' is more reliable than that, but can miss out other characters from the main character set. - `Poor man's line drawing' assumes that the font _cannot_ generate the line and box characters at all, so it will use the `+', `-' and `|' characters to draw approximations to boxes. You should use this option if none of the other options works. - `Unicode mode' tries to use the box characters that are present in Unicode. For good Unicode-supporting fonts this is probably the most reliable and functional option. 4.10 The Selection panel The Selection panel allows you to control the way copy and paste work in the PuTTY window. 4.10.1 Controlling the pasting of line drawing characters By default, when you copy and paste a piece of the PuTTY screen that contains VT100 line and box drawing characters, PuTTY will translate them into the `poor man's' line-drawing characters `+', `-' and `|'. The checkbox `Don't translate line drawing chars' disables this feature, so line-drawing characters will be pasted as if they were in the normal character set. This will typically mean they come out mostly as `q' and `x', with a scattering of `jklmntuvw' at the corners. This might be useful if you were trying to recreate the same box layout in another program, for example. 4.10.2 Pasting in Rich Text Format If you enable `Paste to clipboard in RTF as well as plain text', PuTTY will write formatting information to the clipboard as well as the actual text you copy. Currently the only effect of this will be that if you paste into (say) a word processor, the text will appear in the word processor in the same font PuTTY was using to display it. In future it is likely that other formatting information (bold, underline, colours) will be copied as well. This option can easily be inconvenient, so by default it is disabled. 4.10.3 Changing the actions of the mouse buttons PuTTY's copy and paste mechanism is modelled on the Unix `xterm' application. The X Window System uses a three-button mouse, and the convention is that the left button selects, the right button extends an existing selection, and the middle button pastes. Windows typically only has two mouse buttons, so in PuTTY's default configuration, the _right_ button pastes, and the _middle_ button (if you have one) extends a selection. If you have a three-button mouse and you are already used to the `xterm' arrangement, you can select it using the `Action of mouse buttons' control. 4.10.4 `Shift overrides application's use of mouse' PuTTY allows the server to send control codes that let it take over the mouse and use it for purposes other than copy and paste. Applications which use this feature include the text-mode web browser `links', the Usenet newsreader `trn' version 4, and the file manager `mc' (Midnight Commander). When running one of these applications, pressing the mouse buttons no longer performs copy and paste. If you do need to copy and paste, you can still do so if you hold down Shift while you do your mouse clicks. However, it is possible in theory for applications to even detect and make use of Shift + mouse clicks. We don't know of any applications that do this, but in case someone ever writes one, unchecking the `Shift overrides application's use of mouse' checkbox will cause Shift + mouse clicks to go to the server as well (so that mouse-driven copy and paste will be completely disabled). 4.10.5 Default selection mode As described in section 3.1.1, PuTTY has two modes of selecting text to be copied to the clipboard. In the default mode (`Normal'), dragging the mouse from point A to point B selects to the end of the line containing A, all the lines in between, and from the very beginning of the line containing B. In the other mode (`Rectangular block'), dragging the mouse between two points defines a rectangle, and everything within that rectangle is copied. Normally, you have to hold down Alt while dragging the mouse to select a rectangular block. Using the `Default selection mode' control, you can set rectangular selection as the default, and then you have to hold down Alt to get the _normal_ behaviour. 4.10.6 Configuring word-by-word selection PuTTY will select a word at a time in the terminal window if you double-click to begin the drag. This panel allows you to control precisely what is considered to be a word. Each character is given a _class_, which is a small number (typically 0, 1 or 2). PuTTY considers a single word to be any number of adjacent characters in the same class. So by modifying the assignment of characters to classes, you can modify the word-by-word selection behaviour. In the default configuration, the character classes are: - Class 0 contains white space and control characters. - Class 1 contains most punctuation. - Class 2 contains letters, numbers and a few pieces of punctuation (the double quote, minus sign, period, forward slash and underscore). So, for example, if you assign the `@' symbol into character class 2, you will be able to select an e-mail address with just a double click. In order to adjust these assignments, you start by selecting a group of characters in the list box. Then enter a class number in the edit box below, and press the `Set' button. This mechanism currently only covers ASCII characters, because it isn't feasible to expand the list to cover the whole of Unicode. 4.11 The Colours panel The Colours panel allows you to control PuTTY's use of colour. 4.11.1 `Bolded text is a different colour' When the server sends a control sequence indicating that some text should be displayed in bold, PuTTY can handle this two ways. It can either change the font for a bold version, or use the same font in a brighter colour. This control lets you choose which. By default the box is checked, so non-bold text is displayed in light grey and bold text is displayed in bright white (and similarly in other colours). If you uncheck the box, bold and non-bold text will be displayed in the same colour, and instead the font will change to indicate the difference. 4.11.2 `Attempt to use logical palettes' Logical palettes are a mechanism by which a Windows application running on an 8-bit colour display can select precisely the colours it wants instead of going with the Windows standard defaults. If you are not getting the colours you ask for on an 8-bit display, you can try enabling this option. However, be warned that it's never worked very well. 4.11.3 Adjusting the colours in the terminal window The main colour control allows you to specify exactly what colours things should be displayed in. To modify one of the PuTTY colours, use the list box to select which colour you want to modify. The RGB values for that colour will appear on the right-hand side of the list box. Now, if you press the `Modify' button, you will be presented with a colour selector, in which you can choose a new colour to go in place of the old one. PuTTY allows you to set the cursor colour, the default foreground and background, and the precise shades of all the ANSI configurable colours (black, red, green, yellow, blue, magenta, cyan, and white). In addition, if you have selected `Bolded text is a different colour', you can also modify the precise shades used for the bold versions of these colours. 4.12 The Connection panel The Connection panel allows you to configure options that apply to more than one type of connection. 4.12.1 `Terminal-type string' Most servers you might connect to with PuTTY are designed to be connected to from lots of different types of terminal. In order to send the right control sequences to each one, the server will need to know what type of terminal it is dealing with. Therefore, each of the SSH, Telnet and Rlogin protocols allow a text string to be sent down the connection describing the terminal. PuTTY attempts to emulate the Unix `xterm' program, and by default it reflects this by sending `xterm' as a terminal-type string. If you find this is not doing what you want - perhaps the remote terminal reports `Unknown terminal type' - you could try setting this to something different, such as `vt220'. If you're not sure whether a problem is due to the terminal type setting or not, you probably need to consult the manual for your application or your server. 4.12.2 `Auto-login username' All three of the SSH, Telnet and Rlogin protocols allow you to specify what user name you want to log in as, without having to type it explicitly every time. (Some Telnet servers don't support this.) In this box you can type that user name. 4.12.3 Using keepalives to prevent disconnection If you find your sessions are closing unexpectedly (`Connection reset by peer') after they have been idle for a while, you might want to try using this option. Some network routers and firewalls need to keep track of all connections through them. Usually, these firewalls will assume a connection is dead if no data is transferred in either direction after a certain time interval. This can cause PuTTY sessions to be unexpectedly closed by the firewall if no traffic is seen in the session for some time. The keepalive option (`Seconds between keepalives') allows you to configure PuTTY to send data through the session at regular intervals, in a way that does not disrupt the actual terminal session. If you find your firewall is cutting idle connections off, you can try entering a non-zero value in this field. The value is measured in seconds; so, for example, if your firewall cuts connections off after ten minutes then you might want to enter 300 seconds (5 minutes) in the box. Note that keepalives are not always helpful. They help if you have a firewall which drops your connection after an idle period; but if the network between you and the server suffers from breaks in connectivity then keepalives can actually make things worse. If a session is idle, and connectivity is temporarily lost between the endpoints, but the connectivity is restored before either side tries to send anything, then there will be no problem - neither endpoint will notice that anything was wrong. However, if one side does send something during the break, it will repeatedly try to re-send, and eventually give up and abandon the connection. Then when connectivity is restored, the other side will find that the first side doesn't believe there is an open connection any more. Keepalives can make this sort of problem worse, because they increase the probability that PuTTY will attempt to send data during a break in connectivity. Therefore, you might find they help connection loss, or you might find they make it worse, depending on what _kind_ of network problems you have between you and the server. Keepalives are only supported in Telnet and SSH; the Rlogin and Raw protocols offer no way of implementing them. 4.12.4 `Disable Nagle's algorithm' Nagle's algorithm is a detail of TCP/IP implementations that tries to minimise the number of small data packets sent down a network connection. With Nagle's algorithm enabled, PuTTY's bandwidth usage will be slightly more efficient; with it disabled, you may find you get a faster response to your keystrokes when connecting to some types of server. The Nagle algorithm is disabled by default. 4.13 The Telnet panel The Telnet panel allows you to configure options that only apply to Telnet sessions. 4.13.1 `Terminal-speed string' Telnet allows the client to send a text string that describes the terminal speed. PuTTY lets you configure this, in case you find the server is reacting badly to the default value. (I'm not aware of any servers that do have a problem with it.) 4.13.2 Setting environment variables on the server The Telnet protocol also provides a means for the client to pass environment variables to the server. Many Telnet servers have stopped supporting this feature due to security flaws, but PuTTY still supports it for the benefit of any servers which have found other ways around the security problems than just disabling the whole mechanism. To add an environment variable to the list transmitted down the connection, you enter the variable name in the `Variable' box, enter its value in the `Value' box, and press the `Add' button. To remove one from the list, select it in the list box and press `Remove'. 4.13.3 `Handling of OLD_ENVIRON ambiguity' The original Telnet mechanism for passing environment variables was badly specified. At the time the standard (RFC 1408) was written, BSD telnet implementations were already supporting the feature, and the intention of the standard was to describe the behaviour the BSD implementations were already using. Sadly there was a typing error in the standard when it was issued, and two vital function codes were specified the wrong way round. BSD implementations did not change, and the standard was not corrected. Therefore, it's possible you might find either BSD or RFC-compliant implementations out there. This switch allows you to choose which one PuTTY claims to be. The problem was solved by issuing a second standard, defining a new Telnet mechanism called NEW_ENVIRON, which behaved exactly like the original OLD_ENVIRON but was not encumbered by existing implementations. Most Telnet servers now support this, and it's unambiguous. This feature should only be needed if you have trouble passing environment variables to quite an old server. 4.13.4 Passive and active Telnet negotiation modes In a Telnet connection, there are two types of data passed between the client and the server: actual text, and _negotiations_ about which Telnet extra features to use. PuTTY can use two different strategies for negotiation: - In _active_ mode, PuTTY starts to send negotiations as soon as the connection is opened. - In _passive_ mode, PuTTY will wait to negotiate until it sees a negotiation from the server. The obvious disadvantage of passive mode is that if the server is also operating in a passive mode, then negotiation will never begin at all. For this reason PuTTY defaults to active mode. However, sometimes passive mode is required in order to successfully get through certain types of firewall and Telnet proxy server. If you have confusing trouble with a firewall, you could try enabling passive mode to see if it helps. 4.13.5 `Keyboard sends telnet Backspace and Interrupt' If this box is checked, the Backspace key on the keyboard will send the Telnet special backspace code, and Control-C will send the Telnet special interrupt code. You probably shouldn't enable this unless you know what you're doing. 4.13.6 `Return key sends telnet New Line instead of ^M' Unlike most other remote login protocols, the Telnet protocol has a special `new line' code that is not the same as the usual line endings of Control-M or Control-J. By default, PuTTY sends the Telnet New Line code when you press Return, instead of sending Control-M as it does in most other protocols. Most Unix-style Telnet servers don't mind whether they receive Telnet New Line or Control-M; some servers do expect New Line, and some servers prefer to see ^M. If you are seeing surprising behaviour when you press Return in a Telnet session, you might try turning this option off to see if it helps. 4.14 The Rlogin panel The Rlogin panel allows you to configure options that only apply to Rlogin sessions. 4.14.1 `Terminal-speed string' Like Telnet, Rlogin allows the client to send a text string that describes the terminal speed. PuTTY lets you configure this, in case you find the server is reacting badly to the default value. (I'm not aware of any servers that do have a problem with it.) 4.14.2 `Local username' Rlogin allows an automated (password-free) form of login by means of a file called `.rhosts' on the server. You put a line in your `.rhosts' file saying something like `jbloggs@pc1.example.com', and then when you make an Rlogin connection the client transmits the username of the user running the Rlogin client. The server checks the username and hostname against `.rhosts', and if they match it does not ask for a password. This only works because Unix systems contain a safeguard to stop a user from pretending to be another user in an Rlogin connection. Rlogin connections have to come from port numbers below 1024, and Unix systems prohibit this to unprivileged processes; so when the server sees a connection from a low-numbered port, it assumes the client end of the connection is held by a privileged (and therefore trusted) process, so it believes the claim of who the user is. Windows does not have this restriction: _any_ user can initiate an outgoing connection from a low-numbered port. Hence, the Rlogin `.rhosts' mechanism is completely useless for securely distinguishing several different users on a Windows machine. If you have a `.rhosts' entry pointing at a Windows PC, you should assume that _anyone_ using that PC can spoof your username in an Rlogin connection and access your account on the server. The `Local username' control allows you to specify what user name PuTTY should claim you have, in case it doesn't match your Windows user name (or in case you didn't bother to set up a Windows user name). 4.15 The SSH panel The SSH panel allows you to configure options that only apply to SSH sessions. 4.15.1 Executing a specific command on the server In SSH, you don't have to run a general shell session on the server. Instead, you can choose to run a single specific command (such as a mail user agent, for example). If you want to do this, enter the command in the `Remote command' box. 4.15.2 `Don't allocate a pseudo-terminal' When connecting to a Unix system, most interactive shell sessions are run in a _pseudo-terminal_, which allows the Unix system to pretend it's talking to a real physical terminal device but allows the SSH server to catch all the data coming from that fake device and send it back to the client. Occasionally you might find you have a need to run a session _not_ in a pseudo-terminal. In PuTTY, this is generally only useful for very specialist purposes; although in Plink (see chapter 7) it is the usual way of working. 4.15.3 `Enable compression' This enables data compression in the SSH connection: data sent by the server is compressed before sending, and decompressed at the client end. Likewise, data sent by PuTTY to the server is compressed first and the server decompresses it at the other end. This can help make the most of a low-bandwidth connection. 4.15.4 `Preferred SSH protocol version' This allows you to select whether you would like to use SSH protocol version 1 or version 2. PuTTY will attempt to use protocol 1 if the server you connect to does not offer protocol 2, and vice versa. 4.15.5 `Imitate SSH 2 MAC bug' This option _should_ now be unnecessary. It existed in order to work around a bug in early versions (2.3.0 and below) of the SSH server software from ssh.com. The symptom of this problem would be that PuTTY would die unexpectedly at the beginning of the session, saying `Incorrect MAC received on packet'. Current versions of PuTTY attempt to detect these faulty servers and enable the bug compatibility automatically, so you should never need to use this option any more. 4.15.6 Encryption algorithm selection PuTTY supports a variety of different encryption algorithms, and allows you to choose which one you prefer to use. You can do this by dragging the algorithms up and down in the list box (or moving them using the Up and Down buttons) to specify a preference order. When you make an SSH connection, PuTTY will search down the list from the top until it finds an algorithm supported by the server, and then use that. If the algorithm PuTTY finds is below the `warn below here' line, you will see a warning box when you make the connection: The first cipher supported by the server is single-DES, which is below the configured warning threshold. Do you want to continue with this connection? This warns you that the first available encryption is not a very secure one. Typically you would put the `warn below here' line between the encryptions you consider secure and the ones you consider substandard. By default, PuTTY supplies a preference order intended to reflect a reasonable preference in terms of security and speed. Single-DES is not supported natively in the SSH 2 draft protocol standards. One or two server implementations do support it, by a non-standard name. PuTTY can use single-DES to interoperate with these servers if you enable the `Enable non-standard single-DES in SSH 2' option; by default this is disabled and PuTTY will stick to the standard. 4.16 The Auth panel The Auth panel allows you to configure authentication options for SSH sessions. 4.16.1 `Attempt TIS or CryptoCard authentication' TIS and CryptoCard authentication are simple challenge/response forms of authentication available in SSH protocol version 1 only. You might use them if you were using S/Key one-time passwords, for example, or if you had a physical security token that generated responses to authentication challenges. With this switch enabled, PuTTY will attempt these forms of authentication if the server is willing to try them. You will be presented with a challenge string (which will be different every time) and must supply the correct response in order to log in. If your server supports this, you should talk to your system administrator about precisely what form these challenges and responses take. 4.16.2 `Attempt keyboard-interactive authentication' The SSH 2 equivalent of TIS authentication is called `keyboard- interactive'. It is a flexible authentication method using an arbitrary sequence of requests and responses; so it is not only useful for challenge/response mechanisms such as S/Key, but it can also be used for (for example) asking the user for a new password when the old one has expired. PuTTY leaves this option enabled by default, but supplies a switch to turn it off in case you should have trouble with it. 4.16.3 `Allow agent forwarding' This option allows the SSH server to open forwarded connections back to your local copy of Pageant. If you are not running Pageant, this option will do nothing. See chapter 9 for general information on Pageant, and section 9.4 for information on agent forwarding. Note that there is a security risk involved with enabling this option; see section 9.5 for details. 4.16.4 `Allow attempted changes of username in SSH2' In the SSH 1 protocol, it is impossible to change username after failing to authenticate. So if you mis-type your username at the PuTTY `login as:' prompt, you will not be able to change it except by restarting PuTTY. The SSH 2 protocol _does_ allow changes of username, in principle, but does not make it mandatory for SSH 2 servers to accept them. In particular, OpenSSH does not accept a change of username; once you have sent one username, it will reject attempts to try to authenticate as another user. (Depending on the version of OpenSSH, it may quietly return failure for all login attempts, or it may send an error message.) For this reason, PuTTY will by default not prompt you for your username more than once, in case the server complains. If you know your server can cope with it, you can enable the `Allow attempted changes of username' option to modify PuTTY's behaviour. 4.16.5 `Private key file for authentication' This box is where you enter the name of your private key file if you are using public key authentication. See chapter 8 for information about public key authentication in SSH. 4.17 The Tunnels panel The Tunnels panel allows you to configure tunnelling of other connection types through an SSH connection. 4.17.1 X11 forwarding If your server lets you run X Window System applications, X11 forwarding allows you to securely give those applications access to a local X display on your PC. To enable X11 forwarding, check the `Enable X11 forwarding' box. If your X display is not the primary display on your local machine (which it almost certainly will be unless you have deliberately arranged otherwise), you need to enter its location in the `X display location' box. See section 3.4 for more information about X11 forwarding. 4.17.2 Port forwarding Port forwarding allows you to tunnel other types of network connection down an SSH session. See section 3.5 for a general discussion of port forwarding and how it works. The port forwarding section in the Tunnels panel shows a list of all the port forwardings that PuTTY will try to set up when it connects to the server. By default no port forwardings are set up, so this list is empty. To add a port forwarding: - Set one of the `Local' or `Remote' radio buttons, depending on whether you want to forward a local port to a remote destination (`Local') or forward a remote port to a local destination (`Remote'). - Enter a source port number into the `Source port' box. For local forwardings, PuTTY will listen on this port of your PC. For remote forwardings, your SSH server will listen on this port of the remote machine. Note that most servers will not allow you to listen on port numbers less than 1024. - Enter a hostname and port number separated by a colon, in the `Destination' box. Connections received on the source port will be directed to this destination. For example, to connect to a POP-3 server, you might enter `popserver.example.com:110'. - Click the `Add' button. Your forwarding details should appear in the list box. To remove a port forwarding, simply select its details in the list box, and click the `Remove' button. 4.17.3 Controlling the visibility of forwarded ports The source port for a forwarded connection usually does not accept connections from any machine except the SSH client or server machine itself (for local and remote forwardings respectively). There are controls in the Tunnels panel to change this: - The `Local ports accept connections from other hosts' option allows you to set up local-to-remote port forwardings in such a way that machines other than your client PC can connect to the forwarded port. - The `Remote ports do the same' option does the same thing for remote-to-local port forwardings (so that machines other than the SSH server machine can connect to the forwarded port.) Note that this feature is only available in the SSH 2 protocol, and not all SSH 2 servers support it (OpenSSH 3.0 does not, for example). 4.18 Storing configuration in a file PuTTY does not currently support storing its configuration in a file instead of the Registry. However, you can work around this with a couple of batch files. You will need a file called (say) `PUTTY.BAT' which imports the contents of a file into the Registry, then runs PuTTY, exports the contents of the Registry back into the file, and deletes the Registry entries. This can all be done using the Regedit command line options, so it's all automatic. Here is what you need in `PUTTY.BAT': @ECHO OFF regedit /s putty.reg regedit /s puttyrnd.reg start /w putty.exe regedit /e puttynew.reg HKEY_CURRENT_USER\Software\SimonTatham\PuTTY copy puttynew.reg putty.reg del puttynew.reg regedit /s puttydel.reg This batch file needs two auxiliary files: `PUTTYRND.REG' which sets up an initial safe location for the `PUTTY.RND' random seed file, and `PUTTYDEL.REG' which destroys everything in the Registry once it's been successfully saved back to the file. Here is `PUTTYDEL.REG': REGEDIT4 [-HKEY_CURRENT_USER\Software\SimonTatham\PuTTY] Here is an example `PUTTYRND.REG' file: REGEDIT4 [HKEY_CURRENT_USER\Software\SimonTatham\PuTTY] "RandSeedFile"="a:\putty.rnd" You should replace `a:\putty.rnd' with the location where you want to store your random number data. If the aim is to carry around PuTTY and its settings on one floppy, you probably want to store it on the floppy. Chapter 5: Using PSCP to transfer files securely ------------------------------------------------ PSCP, the PuTTY Secure Copy client, is a tool for transferring files securely between computers using an SSH connection. If you have an SSH 2 server, you might prefer PSFTP (see chapter 6) for interactive use. PSFTP does not in general work with SSH 1 servers, however. 5.1 Starting PSCP PSCP is a command line application. This means that you cannot just double-click on its icon to run it and instead you have to bring up a console window. With Windows 95, 98, and ME, this is called an `MS-DOS Prompt' and with Windows NT and 2000 it is called a `Command Prompt'. It should be available from the Programs section of your Start Menu. To start PSCP it will need either to be on your `PATH' or in your current directory. To add the directory containing PSCP to your `PATH' environment variable, type into the console window: set PATH=C:\path\to\putty\directory;%PATH% This will only work for the lifetime of that particular console window. To set your `PATH' more permanently on Windows NT, use the Environment tab of the System Control Panel. On Windows 95, 98, and ME, you will need to edit your `AUTOEXEC.BAT' to include a `set' command like the one above. 5.2 PSCP Usage Once you've got a console window to type into, you can just type `pscp' on its own to bring up a usage message. This tells you the version of PSCP you're using, and gives you a brief summary of how to use PSCP: Z:\owendadmin>pscp PuTTY Secure Copy client Release 0.50 Usage: pscp [options] [user@]host:source target pscp [options] source [source...] [user@]host:target pscp [options] -ls user@host:filespec Options: -p preserve file attributes -q quiet, don't show statistics -r copy directories recursively -v show verbose messages -P port connect to specified port -pw passw login with specified password (PSCP's interface is much like the Unix `scp' command, if you're familiar with that.) 5.2.1 The basics To receive (a) file(s) from a remote server: pscp [options] [user@]host:source target So to copy the file `/etc/hosts' from the server `example.com' as user `fred' to the file `c:\temp\example-hosts.txt', you would type: pscp fred@example.com:/etc/hosts c:\temp\example-hosts.txt To send (a) file(s) to a remote server: pscp [options] source [source...] [user@]host:target So to copy the local file `c:\documents\csh-whynot.txt' to the server `example.com' as user `fred' to the file `/tmp/csh-whynot' you would type: pscp c:\documents\csh-whynot.txt fred@example.com:/tmp/csh-whynot You can use wildcards to transfer multiple files in either direction, like this: pscp c:\documents\*.doc fred@example.com:docfiles pscp fred@example.com:source/*.c c:\source However, in the second case (using a wildcard for multiple remote files) you may see a warning like this: warning: remote host tried to write to a file called 'terminal.c' when we requested a file called '*.c'. If this is a wildcard, consider upgrading to SSH 2 or using the '-unsafe' option. Renaming of this file has been disallowed. This is due to a fundamental insecurity in the old-style SCP protocol: the client sends the wildcard string (`*.c') to the server, and the server sends back a sequence of file names that match the wildcard pattern. However, there is nothing to stop the server sending back a _different_ pattern and writing over one of your other files: if you request `*.c', the server might send back the file name `AUTOEXEC.BAT' and install a virus for you. Since the wildcard matching rules are decided by the server, the client cannot reliably verify that the filenames sent back match the pattern. PSCP will attempt to use the newer SFTP protocol (part of SSH 2) where possible, which does not suffer from this security flaw. If you are talking to an SSH 2 server which supports SFTP, you will never see this warning. If you really need to use a server-side wildcard with an SSH 1 server, you can use the `-unsafe' command line option with PSCP: pscp -unsafe fred@example.com:source/*.c c:\source This will suppress the warning message and the file transfer will happen. However, you should be aware that by using this option you are giving the server the ability to write to _any_ file in the target directory, so you should only use this option if you trust the server administrator not to be malicious (and not to let the server machine be cracked by malicious people). 5.2.1.1 `user' The login name on the remote server. If this is omitted, and `host' is a PuTTY saved session, PSCP will use any username specified by that saved session. Otherwise, PSCP will attempt to use the local Windows username. 5.2.1.2 `host' The name of the remote server, or the name of an existing PuTTY saved session. In the latter case, the session's settings for hostname, port number, cipher type and username will be used. 5.2.1.3 `source' One or more source files. Wildcards are allowed. The syntax of wildcards depends on the system to which they apply, so if you are copying _from_ a Windows system _to_ a UNIX system, you should use Windows wildcard syntax (e.g. `*.*'), but if you are copying _from_ a UNIX system _to_ a Windows system, you would use the wildcard syntax allowed by your UNIX shell (e.g. `*'). If the source is a remote server and you do not specify a full pathname (in UNIX, a pathname beginning with a `/' (slash) character), what you specify as a source will be interpreted relative to your home directory on the remote server. 5.2.1.4 `target' The filename or directory to put the file(s). When copying from a remote server to a local host, you may wish simply to place the file(s) in the current directory. To do this, you should specify a target of `.'. For example: pscp fred@example.com:/home/tom/.emacs . ...would copy `/home/tom/.emacs' on the remote server to the current directory. As with the `source' parameter, if the target is on a remote server and is not a full path name, it is interpreted relative to your home directory on the remote server. 5.2.2 Options These are the command line options that PSCP accepts. 5.2.2.1 `-p' preserve file attributes By default, files copied with PSCP are timestamped with the date and time they were copied. The `-p' option preserves the original timestamp on copied files. 5.2.2.2 `-q' quiet, don't show statistics By default, PSCP displays a meter displaying the progress of the current transfer: mibs.tar | 168 kB | 84.0 kB/s | ETA: 00:00:13 | 13% The fields in this display are (from left to right), filename, size (in kilobytes) of file transferred so far, estimate of how fast the file is being transferred (in kilobytes per second), estimated time that the transfer will be complete, and percentage of the file so far transferred. The `-q' option to PSCP suppresses the printing of these statistics. 5.2.2.3 `-r' copies directories recursively By default, PSCP will only copy files. Any directories you specify to copy will be skipped, as will their contents. The `-r' option tells PSCP to descend into any directories you specify, and to copy them and their contents. This allows you to use PSCP to transfer whole directory structures between machines. 5.2.2.4 `-v' show verbose messages The `-v' option to PSCP makes it print extra information about the file transfer. For example: Logging in as "fred". fred@example.com's password: Sending command: scp -v -f mibs.tar Connected to example.com Sending file modes: C0644 1320960 mibs.tar mibs.tar | 1290 kB | 67.9 kB/s | ETA: 00:00:00 | 100% Remote exit status 0 Closing connection This information may be useful for debugging problems with PSCP. 5.2.2.5 `-P port' connect to specified port If the `host' you specify is a saved session, PSCP uses any port number specified in that saved session. If not, PSCP uses the default SSH port, 22. The `-P' option allows you specify the port number to connect to for PSCP's SSH connection. 5.2.2.6 `-pw passw' login with specified password If a password is required to connect to the `host', PSCP will interactively prompt you for it. However, this may not always be appropriate. If you are running PSCP as part of some automated job, it will not be possible to enter a password by hand. The `-pw' option to PSCP lets you specify the password to use on the command line. Since specifying passwords in scripts is a bad idea for security reasons, you might want instead to consider using public-key authentication; see section 5.2.4. 5.2.2.7 `-batch' avoid interactive prompts If you use the `-batch' option, PSCP will never give an interactive prompt while establishing the connection. If the server's host key is invalid, for example (see section 2.2), then the connection will simply be abandoned instead of asking you what to do next. This may help PSCP's behaviour when it is used in automated scripts: using `-batch', if something goes wrong at connection time, the batch job will fail rather than hang. 5.2.3 Return value PSCP returns an ERRORLEVEL of zero (success) only if the files were correctly transferred. You can test for this in a batch file, using code such as this: pscp file*.* user@hostname: if errorlevel 1 echo There was an error 5.2.4 Using public key authentication with PSCP Like PuTTY, PSCP can authenticate using a public key instead of a password. There are two ways you can do this. Firstly, PSCP can use PuTTY saved sessions in place of hostnames (see section 5.2.1.2). So you would do this: - Run PuTTY, and create a PuTTY saved session (see section 4.1.2) which specifies your private key file (see section 4.16.5). You will probably also want to specify a username to log in as (see section 4.12.2). - In PSCP, you can now use the name of the session instead of a hostname: type `pscp sessionname:file localfile', where `sessionname' is replaced by the name of your saved session. Secondly, PSCP will attempt to authenticate using Pageant if Pageant is running (see chapter 9). So you would do this: - Ensure Pageant is running, and has your private key stored in it. - Specify a user and host name to PSCP as normal. PSCP will automatically detect Pageant and try to use the keys within it. For more general information on public-key authentication, see chapter 8. 5.3 Secure iXplorer Lars Gunnarson has written a graphical interface for PSCP. You can get it from his web site, at www.i-tree.org. Chapter 6: Using PSFTP to transfer files securely ------------------------------------------------- PSFTP, the PuTTY SFTP client, is a tool for transferring files securely between computers using an SSH connection. PSFTP differs from PSCP in the following ways: - PSCP should work on virtually every SSH server. PSFTP uses the new SFTP protocol, which is a feature of SSH 2 only. (PSCP will also use this protocol if it can, but there is an SSH 1 equivalent it can fall back to if it cannot.) - PSFTP allows you to run an interactive file transfer session, much like the Windows `ftp' program. You can list the contents of directories, browse around the file system, issue multiple `get' and `put' commands, and eventually log out. By contrast, PSCP is designed to do a single file transfer operation and immediately terminate. 6.1 Starting PSFTP The usual way to start PSFTP is from a command prompt, much like PSCP. To do this, it will need either to be on your `PATH' or in your current directory. To add the directory containing PSFTP to your `PATH' environment variable, type into the console window: set PATH=C:\path\to\putty\directory;%PATH% Unlike PSCP, however, PSFTP has no complex command-line syntax; you just specify a host name and perhaps a user name: psftp server.example.com or perhaps psftp fred@server.example.com Alternatively, if you just type `psftp' on its own (or double-click the PSFTP icon in the Windows GUI), you will see the PSFTP prompt, and a message telling you PSFTP has not connected to any server: C:\>psftp psftp: no hostname specified; use "open host.name" to connect psftp> At this point you can type `open server.example.com' or `open fred@server.example.com' to start a session. The following sections describe PSFTP's command-line options. 6.1.1 `-l': specify a user name The `-l' option is an alternative way to specify the user name to log in as, on the command line. Instead of typing `psftp user@host', you can also type `psftp host -l user'. This option does not work in the `open' command once PSFTP has started. 6.1.2 `-P': specify a port number If the `host' you specify is a saved session, PSFTP uses any port number specified in that saved session. If not, PSFTP uses the default SSH port, 22. The `-P' option allows you specify the port number to connect to for PSFTP's SSH connection. 6.1.3 `-v': show verbose messages The `-v' option to PSFTP makes it print verbose information about the establishing of the SSH connection. The information displayed is equivalent to what is shown in the PuTTY Event Log (section 3.1.3.1). This information may be useful for debugging problems with PSFTP. 6.1.4 `-pw': specify a password If a password is required to connect to the `host', PSFTP will interactively prompt you for it. However, this may not always be appropriate. If you are running PSFTP as part of some automated job, it will not be possible to enter a password by hand. The `-pw' option to PSFTP lets you specify the password to use on the command line. Since specifying passwords in scripts is a bad idea for security reasons, you might want instead to consider using public-key authentication; see section 6.3. 6.1.5 `-b': specify a file containing batch commands In normal operation, PSFTP is an interactive program which displays a command line and accepts commands from the keyboard. If you need to do automated tasks with PSFTP, you would probably prefer to specify a set of commands in advance and have them executed automatically. The `-b' option allows you to do this. You use it with a file name containing batch commands. For example, you might create a file called `myscript.scr' containing lines like this: cd /home/ftp/users/jeff del jam-old.tar.gz ren jam.tar.gz jam-old.tar.gz put jam.tar.gz chmod a+r jam.tar.gz quit and then you could run the script by typing psftp user@hostname -b myscript.scr When you run a batch script in this way, PSFTP will abort the script if any command fails to complete successfully. To change this behaviour, you can use the `-be' option (section 6.1.7). 6.1.6 `-bc': display batch commands as they are run The `-bc' option alters what PSFTP displays while processing a batch script. With the `-bc' option, PSFTP will display prompts and commands just as if the commands had been typed at the keyboard. So instead of seeing this: Sent username "fred" Remote working directory is /home/fred Listing directory /home/fred/lib drwxrwsr-x 4 fred fred 1024 Sep 6 10:42 . drwxr-sr-x 25 fred fred 2048 Dec 14 09:36 .. drwxrwsr-x 3 fred fred 1024 Apr 17 2000 jed lrwxrwxrwx 1 fred fred 24 Apr 17 2000 timber drwxrwsr-x 2 fred fred 1024 Mar 13 2000 trn you might see this: Sent username "fred" Remote working directory is /home/fred psftp> dir lib Listing directory /home/fred/lib drwxrwsr-x 4 fred fred 1024 Sep 6 10:42 . drwxr-sr-x 25 fred fred 2048 Dec 14 09:36 .. drwxrwsr-x 3 fred fred 1024 Apr 17 2000 jed lrwxrwxrwx 1 fred fred 24 Apr 17 2000 timber drwxrwsr-x 2 fred fred 1024 Mar 13 2000 trn psftp> quit 6.1.7 `-be': continue batch processing on errors When running a batch file, this option causes PSFTP to continue processing even if a command fails to complete successfully. You might want this to happen if you wanted to delete a file and didn't care if it was already not present, for example. 6.1.8 `-batch': avoid interactive prompts If you use the `-batch' option, PSFTP will never give an interactive prompt while establishing the connection. If the server's host key is invalid, for example (see section 2.2), then the connection will simply be abandoned instead of asking you what to do next. This may help PSFTP's behaviour when it is used in automated scripts: using `-batch', if something goes wrong at connection time, the batch job will fail rather than hang. 6.2 Running PSFTP Once you have started your PSFTP session, you will see a `psftp>' prompt. You can now type commands to perform file-transfer functions. This section lists all the available commands. 6.2.1 General quoting rules for PSFTP commands Most PSFTP commands are considered by the PSFTP command interpreter as a sequence of words, separated by spaces. For example, the command `ren oldfilename newfilename' splits up into three words: `ren' (the command name), `oldfilename' (the name of the file to be renamed), and `newfilename' (the new name to give the file). Sometimes you will need to specify file names that _contain_ spaces. In order to do this, you can surround the file name with double quotes. This works equally well for local file names and remote file names: psftp> get "spacey file name.txt" "save it under this name.txt" The double quotes themselves will not appear as part of the file names; they are removed by PSFTP and their only effect is to stop the spaces inside them from acting as word separators. If you need to _use_ a double quote (on some types of remote system, such as Unix, you are allowed to use double quotes in file names), you can do this by doubling it. This works both inside and outside double quotes. For example, this command psftp> ren ""this"" "a file with ""quotes"" in it" will take a file whose current name is `"this"' (with a double quote character at the beginning and the end) and rename it to a file whose name is `a file with "quotes" in it'. (The one exception to the PSFTP quoting rules is the `!' command, which passes its command line straight to Windows without splitting it up into words at all. See section 6.2.16.) 6.2.2 The `open' command: start a session If you started PSFTP by double-clicking in the GUI, or just by typing `psftp' at the command line, you will need to open a connection to an SFTP server before you can issue any other commands (except `help' and `quit'). To create a connection, type `open host.name', or if you need to specify a user name as well you can type `open user@host.name'. Once you have issued this command, you will not be able to issue it again, _even_ if the command fails (for example, if you mistype the host name or the connection times out). So if the connection is not opened successfully, PSFTP will terminate immediately. 6.2.3 The `quit' command: end your session When you have finished your session, type the command `quit' to terminate PSFTP and return to the command line (or just close the PSFTP console window if you started it from the GUI). You can also use the `bye' and `exit' commands, which have exactly the same effect. 6.2.4 The `help' command: get quick online help If you type `help', PSFTP will give a short list of the available commands. If you type `help' with a command name - for example, `help get' - then PSFTP will give a short piece of help on that particular command. 6.2.5 The `cd' and `pwd' commands: changing the remote working directory PSFTP maintains a notion of your `working directory' on the server. This is the default directory that other commands will operate on. For example, if you type `get filename.dat' then PSFTP will look for `filename.dat' in your remote working directory on the server. To change your remote working directory, use the `cd' command. To display your current remote working directory, type `pwd'. 6.2.6 The `lcd' and `lpwd' commands: changing the local working directory As well as having a working directory on the remote server, PSFTP also has a working directory on your local machine (just like any other Windows process). This is the default local directory that other commands will operate on. For example, if you type `get filename.dat' then PSFTP will save the resulting file as `filename.dat' in your local working directory. To change your local working directory, use the `lcd' command. To display your current local working directory, type `lpwd'. 6.2.7 The `get' command: fetch a file from the server To download a file from the server and store it on your local PC, you use the `get' command. In its simplest form, you just use this with a file name: get myfile.dat If you want to store the file locally under a different name, specify the local file name after the remote one: get myfile.dat newname.dat This will fetch the file on the server called `myfile.dat', but will save it to your local machine under the name `newname.dat'. 6.2.8 The `put' command: send a file to the server To upload a file to the server from your local PC, you use the `put' command. In its simplest form, you just use this with a file name: put myfile.dat If you want to store the file remotely under a different name, specify the remote file name after the local one: put myfile.dat newname.dat This will send the local file called `myfile.dat', but will store it on the server under the name `newname.dat'. 6.2.9 The `reget' and `reput' commands: resuming file transfers If a file transfer fails half way through, and you end up with half the file stored on your disk, you can resume the file transfer using the `reget' and `reput' commands. These work exactly like the `get' and `put' commands, but they check for the presence of the half- written destination file and start transferring from where the last attempt left off. The syntax of `reget' and `reput' is exactly the same as the syntax of `get' and `put': reget myfile.dat reget myfile.dat newname.dat 6.2.10 The `dir' command: list remote files To list the files in your remote working directory, just type `dir'. You can also list the contents of a different directory by typing `dir' followed by the directory name: dir /home/fred dir sources The `ls' command works exactly the same way as `dir'. 6.2.11 The `chmod' command: change permissions on remote files PSFTP allows you to modify the file permissions on files on the server. You do this using the `chmod' command, which works very much like the Unix `chmod' command. The basic syntax is `chmod modes file', where `modes' represents a modification to the file permissions, and `file' is the filename to modify. For example: chmod go-rwx,u+w privatefile chmod a+r publicfile chmod 640 groupfile The `modes' parameter can be a set of octal digits in the Unix style. (If you don't know what this means, you probably don't want to be using it!) Alternatively, it can be a list of permission modifications, separated by commas. Each modification consists of: - The people affected by the modification. This can be `u' (the owning user), `g' (members of the owning group), or `o' (everybody else - `others'), or some combination of those. It can also be `a' (`all') to affect everybody at once. - A `+' or `-' sign, indicating whether permissions are to be added or removed. - The actual permissions being added or removed. These can be `r' (permission to read the file), `w' (permission to write to the file), and `x' (permission to execute the file, or in the case of a directory, permission to access files within the directory). So the above examples would do: - The first example: `go-rwx' removes read, write and execute permissions for members of the owning group and everybody else (so the only permissions left are the ones for the file owner). `u+w' adds write permission for the file owner. - The second example: `a+r' adds read permission for everybody. In addition to all this, there are a few extra special cases for Unix systems. On non-Unix systems these are unlikely to be useful: - You can specify `u+s' and `u-s' to add or remove the Unix set-user- ID bit. This is typically only useful for special purposes; refer to your Unix documentation if you're not sure about it. - You can specify `g+s' and `g-s' to add or remove the Unix set-group- ID bit. On a file, this works similarly to the set-user-ID bit (see your Unix documentation again); on a directory it ensures that files created in the directory are accessible by members of the group that owns the directory. - You can specify `+t' and `-t' to add or remove the Unix `sticky bit'. When applied to a directory, this means that the owner of a file in that directory can delete the file (whereas normally only the owner of the _directory_ would be allowed to). 6.2.12 The `del' command: delete remote files To delete a file on the server, type `del' and then the filename: del oldfile.dat The `rm' command works exactly the same way as `del'. 6.2.13 The `mkdir' command: create remote directories To create a directory on the server, type `mkdir' and then the directory name: mkdir newstuff 6.2.14 The `rmdir' command: remove remote directories To remove a directory on the server, type `rmdir' and then the directory name: rmdir oldstuff Most SFTP servers will probably refuse to remove a directory if the directory has anything in it, so you will need to delete the contents first. 6.2.15 The `ren' command: rename remote files To rename a file on the server, type `ren', then the current file name, and then the new file name: ren oldfile newname The `rename' and `mv' commands work exactly the same way as `ren'. 6.2.16 The `!' command: run a local Windows command You can run local Windows commands using the `!' command. This is the only PSFTP command that is not subject to the command quoting rules given in section 6.2.1. If any command line begins with the `!' character, then the rest of the line will be passed straight to Windows without further translation. For example, if you want to move an existing copy of a file out of the way before downloading an updated version, you might type: psftp> !ren myfile.dat myfile.bak psftp> get myfile.dat using the Windows `ren' command to rename files on your local PC. 6.3 Using public key authentication with PSFTP Like PuTTY, PSFTP can authenticate using a public key instead of a password. The