1 \versionid $Id: using.but,v 1.21 2004/03/25 11:33:17 jacob Exp $
5 This chapter provides a general introduction to some more advanced
6 features of PuTTY. For extreme detail and reference purposes,
7 \k{config} is likely to contain more information.
9 \H{using-session} During your session
11 A lot of PuTTY's complexity and features are in the configuration
12 panel. Once you have worked your way through that and started
13 a session, things should be reasonably simple after that.
14 Nevertheless, there are a few more useful features available.
16 \S{using-selection} Copying and pasting text
18 Often in a PuTTY session you will find text on your terminal screen
19 which you want to type in again. Like most other terminal emulators,
20 PuTTY allows you to copy and paste the text rather than having to
21 type it again. Also, copy and paste uses the Windows clipboard, so
22 that you can paste (for example) URLs into a web browser, or paste
23 from a word processor or spreadsheet into your terminal session.
25 PuTTY's copy and paste works entirely with the mouse. In order to
26 copy text to the clipboard, you just click the left mouse button in
27 the terminal window, and drag to select text. When you let go of the
28 button, the text is \e{automatically} copied to the clipboard. You
29 do not need to press Ctrl-C or Ctrl-Ins; in fact, if you do press
30 Ctrl-C, PuTTY will send a Ctrl-C character down your session to the
31 server where it will probably cause a process to be interrupted.
33 Pasting is done using the right button (or the middle mouse button,
34 if you have a three-button mouse and have set it up; see
35 \k{config-mouse}). (Pressing Shift-Ins, or selecting \q{Paste} from
36 the Ctrl+right-click context menu, have the same effect.)
37 When you click the right mouse button, PuTTY will
38 read whatever is in the Windows Clipboard and paste it into your
39 session, \e{exactly} as if it had been typed at the keyboard.
40 (Therefore, be careful of pasting formatted text into an editor that
41 does automatic indenting; you may find that the spaces pasted from
42 the clipboard plus the spaces added by the editor add up to too many
43 spaces and ruin the formatting. There is nothing PuTTY can do about
46 If you double-click the left mouse button, PuTTY will select a whole
47 word. If you double-click, hold down the second click, and drag the
48 mouse, PuTTY will select a sequence of whole words. (You can adjust
49 precisely what PuTTY considers to be part of a word; see
50 \k{config-charclasses}.) If you \e{triple}-click, or triple-click
51 and drag, then PuTTY will select a whole line or sequence of lines.
53 If you want to select a rectangular region instead of selecting to
54 the end of each line, you can do this by holding down Alt when you
55 make your selection. (You can also configure rectangular selection
56 to be the default, and then holding down Alt gives the normal
57 behaviour instead. See \k{config-rectselect} for details.)
59 If you have a middle mouse button, then you can use it to adjust an
60 existing selection if you selected something slightly wrong. (If you
61 have configured the middle mouse button to paste, then the right
62 mouse button does this instead.) Click the button on the screen, and
63 you can pick up the nearest end of the selection and drag it to
66 It's possible for the server to ask to handle mouse clicks in the
67 PuTTY window itself. If this happens, the mouse cursor will turn
68 into an arrow, and using the mouse to copy and paste will only work if
69 you hold down Shift. See \k{config-features-mouse} and
70 \k{config-mouseshift} for details of this feature and how to configure
73 \S{using-scrollback} Scrolling the screen back
75 PuTTY keeps track of text that has scrolled up off the top of the
76 terminal. So if something appears on the screen that you want to
77 read, but it scrolls too fast and it's gone by the time you try to
78 look for it, you can use the scrollbar on the right side of the
79 window to look back up the session history and find it again.
81 As well as using the scrollbar, you can also page the scrollback up
82 and down by pressing Shift-PgUp and Shift-PgDn. You can scroll a
83 line at a time using Ctrl-PgUp and Ctrl-PgDn. These are still
84 available if you configure the scrollbar to be invisible.
86 By default the last 200 lines scrolled off the top are
87 preserved for you to look at. You can increase (or decrease) this
88 value using the configuration box; see \k{config-scrollback}.
90 \S{using-sysmenu} The System menu
92 If you click the left mouse button on the icon in the top left
93 corner of PuTTY's window, or click the right mouse button on the
94 title bar, you will see the standard Windows system menu containing
95 items like Minimise, Move, Size and Close.
97 PuTTY's system menu contains extra program features in addition to
98 the Windows standard options. These extra menu commands are
101 (These options are also available in a context menu brought up
102 by holding Ctrl and clicking with the right mouse button anywhere
103 in the PuTTY window.)
105 \S2{using-eventlog} The PuTTY Event Log
107 If you choose \q{Event Log} from the system menu, a small window
108 will pop up in which PuTTY logs significant events during the
109 connection. Most of the events in the log will probably take place
110 during session startup, but a few can occur at any point in the
111 session, and one or two occur right at the end.
113 You can use the mouse to select one or more lines of the Event Log,
114 and hit the Copy button to copy them to the clipboard. If you are
115 reporting a bug, it's often useful to paste the contents of the
116 Event Log into your bug report.
118 \S2{using-specials} Special commands
120 Depending on the protocol used for the current session, there may be a
121 submenu of \q{special commands}. These are protocol-specific tokens,
122 such as a \q{break} signal, that can be sent down a connection in
123 addition to normal data. Currently only Telnet and SSH have special
126 \S2{using-newsession} Starting new sessions
128 PuTTY's system menu provides some shortcut ways to start new
131 \b Selecting \q{New Session} will start a completely new instance of
132 PuTTY, and bring up the configuration box as normal.
134 \b Selecting \q{Duplicate Session} will start a session with
135 precisely the same options as your current one - connecting to the
136 same host using the same protocol, with all the same terminal
137 settings and everything.
139 \b The \q{Saved Sessions} submenu gives you quick access to any
140 sets of stored session details you have previously saved. See
141 \k{config-saving} for details of how to create saved sessions.
143 \S2{using-changesettings} Changing your session settings
145 If you select \q{Change Settings} from the system menu, PuTTY will
146 display a cut-down version of its initial configuration box. This
147 allows you to adjust most properties of your current session. You
148 can change the terminal size, the font, the actions of various
149 keypresses, the colours, and so on.
151 Some of the options that are available in the main configuration box
152 are not shown in the cut-down Change Settings box. These are usually
153 options which don't make sense to change in the middle of a session
154 (for example, you can't switch from SSH to Telnet in mid-session).
156 \S2{using-copyall} Copy All to Clipboard
158 This system menu option provides a convenient way to copy the whole
159 contents of the terminal screen (up to the last nonempty line) and
160 scrollback to the clipboard in one go.
162 \S2{reset-terminal} Clearing and resetting the terminal
164 The \q{Clear Scrollback} option on the system menu tells PuTTY to
165 discard all the lines of text that have been kept after they
166 scrolled off the top of the screen. This might be useful, for
167 example, if you displayed sensitive information and wanted to make
168 sure nobody could look over your shoulder and see it. (Note that
169 this only prevents a casual user from using the scrollbar to view
170 the information; the text is not guaranteed not to still be in
173 The \q{Reset Terminal} option causes a full reset of the terminal
174 emulation. A VT-series terminal is a complex piece of software and
175 can easily get into a state where all the text printed becomes
176 unreadable. (This can happen, for example, if you accidentally
177 output a binary file to your terminal.) If this happens, selecting
178 Reset Terminal should sort it out.
180 \S2{using-fullscreen} Full screen mode
182 If you find the title bar on a maximised window to be ugly or
183 distracting, you can select Full Screen mode to maximise PuTTY
184 \q{even more}. When you select this, PuTTY will expand to fill the
185 whole screen and its borders, title bar and scrollbar will
186 disappear. (You can configure the scrollbar not to disappear in
187 full-screen mode if you want to keep it; see \k{config-scrollback}.)
189 When you are in full-screen mode, you can still access the system
190 menu if you click the left mouse button in the \e{extreme} top left
191 corner of the screen.
193 \H{using-logging} Creating a log file of your session
195 For some purposes you may find you want to log everything that
196 appears on your screen. You can do this using the \q{Logging} panel
197 in the configuration box.
199 To begin a session log, select \q{Change Settings} from the system
200 menu and go to the Logging panel. Enter a log file name, and select
201 a logging mode. (You can log all session output including the
202 terminal control sequences, or you can just log the printable text.
203 It depends what you want the log for.) Click \q{Apply} and your log
204 will be started. Later on, you can go back to the Logging panel and
205 select \q{Logging turned off completely} to stop logging; then PuTTY
206 will close the log file and you can safely read it.
208 See \k{config-logging} for more details and options.
210 \H{using-translation} Altering your character set configuration
212 If you find that special characters (accented characters, for
213 example) are not being displayed correctly in your PuTTY session, it
214 may be that PuTTY is interpreting the characters sent by the server
215 according to the wrong \e{character set}. There are a lot of
216 different character sets available, so it's entirely possible for
219 If you click \q{Change Settings} and look at the \q{Translation}
220 panel, you should see a large number of character sets which you can
221 select. Now all you need is to find out which of them you want!
223 \H{using-x-forwarding} Using X11 forwarding in SSH
225 The SSH protocol has the ability to securely forward X Window System
226 applications over your encrypted SSH connection, so that you can run
227 an application on the SSH server machine and have it put its windows
228 up on your local machine without sending any X network traffic in
231 In order to use this feature, you will need an X display server for
232 your Windows machine, such as X-Win32 or Exceed. This will probably
233 install itself as display number 0 on your local machine; if it
234 doesn't, the manual for the X server should tell you what it does
237 You should then tick the \q{Enable X11 forwarding} box in the
238 Tunnels panel (see \k{config-ssh-x11}) before starting your SSH
239 session. The \q{X display location} box reads \c{localhost:0} by
240 default, which is the usual display location where your X server
241 will be installed. If that needs changing, then change it.
243 Now you should be able to log in to the SSH server as normal. To
244 check that X forwarding has been successfully negotiated during
245 connection startup, you can check the PuTTY Event Log (see
246 \k{using-eventlog}). It should say something like this:
248 \c 2001-12-05 17:22:01 Requesting X11 forwarding
249 \c 2001-12-05 17:22:02 X11 forwarding enabled
251 If the remote system is Unix or Unix-like, you should also be able
252 to see that the \c{DISPLAY} environment variable has been set to
253 point at display 10 or above on the SSH server machine itself:
255 \c fred@unixbox:~$ echo $DISPLAY
258 If this works, you should then be able to run X applications in the
259 remote session and have them display their windows on your PC.
261 Note that if your PC X server requires authentication to connect,
262 then PuTTY cannot currently support it. If this is a problem for
263 you, you should mail the PuTTY authors \#{FIXME} and give details
266 \H{using-port-forwarding} Using port forwarding in SSH
268 The SSH protocol has the ability to forward arbitrary network
269 connections over your encrypted SSH connection, to avoid the network
270 traffic being sent in clear. For example, you could use this to
271 connect from your home computer to a POP-3 server on a remote
272 machine without your POP-3 password being visible to network
275 In order to use port forwarding to connect from your local machine
276 to a port on a remote server, you need to:
278 \b Choose a port number on your local machine where PuTTY should
279 listen for incoming connections. There are likely to be plenty of
280 unused port numbers above 3000. (You can also use a local loopback
281 address here; see below for more details.)
283 \b Now, before you start your SSH connection, go to the Tunnels
284 panel (see \k{config-ssh-portfwd}). Make sure the \q{Local} radio
285 button is set. Enter the local port number into the \q{Source port}
286 box. Enter the destination host name and port number into the
287 \q{Destination} box, separated by a colon (for example,
288 \c{popserver.example.com:110} to connect to a POP-3 server).
290 \b Now click the \q{Add} button. The details of your port forwarding
291 should appear in the list box.
293 Now start your session and log in. (Port forwarding will not be
294 enabled until after you have logged in; otherwise it would be easy
295 to perform completely anonymous network attacks, and gain access to
296 anyone's virtual private network). To check that PuTTY has set up
297 the port forwarding correctly, you can look at the PuTTY Event Log
298 (see \k{using-eventlog}). It should say something like this:
300 \c 2001-12-05 17:22:10 Local port 3110 forwarding to
301 \c popserver.example.com:110
303 Now if you connect to the source port number on your local PC, you
304 should find that it answers you exactly as if it were the service
305 running on the destination machine. So in this example, you could
306 then configure an e-mail client to use \c{localhost:3110} as a POP-3
307 server instead of \c{popserver.example.com:110}. (Of course, the
308 forwarding will stop happening when your PuTTY session closes down.)
310 You can also forward ports in the other direction: arrange for a
311 particular port number on the \e{server} machine to be forwarded
312 back to your PC as a connection to a service on your PC or near it.
313 To do this, just select the \q{Remote} radio button instead of the
314 \q{Local} one. The \q{Source port} box will now specify a port
315 number on the \e{server} (note that most servers will not allow you
316 to use port numbers under 1024 for this purpose).
318 An alternative way to forward local connections to remote hosts is
319 to use dynamic SOCKS proxying. For this, you will need to select the
320 \q{Dynamic} radio button instead of \q{Local}, and then you should
321 not enter anything into the \q{Destination} box (it will be
322 ignored). This will cause PuTTY to listen on the port you have
323 specified, and provide a SOCKS proxy service to any programs which
324 connect to that port. So, in particular, you can forward other PuTTY
325 connections through it by setting up the Proxy control panel (see
326 \k{config-proxy} for details).
328 The source port for a forwarded connection usually does not accept
329 connections from any machine except the SSH client or server machine
330 itself (for local and remote forwardings respectively). There are
331 controls in the Tunnels panel to change this:
333 \b The \q{Local ports accept connections from other hosts} option
334 allows you to set up local-to-remote port forwardings (including
335 dynamic port forwardings) in such a way that machines other than
336 your client PC can connect to the forwarded port.
338 \b The \q{Remote ports do the same} option does the same thing for
339 remote-to-local port forwardings (so that machines other than the
340 SSH server machine can connect to the forwarded port.) Note that
341 this feature is only available in the SSH 2 protocol, and not all
342 SSH 2 servers support it (OpenSSH 3.0 does not, for example).
344 You can also specify an IP address to listen on. Typically a
345 Windows machine can be asked to listen on any single IP address in
346 the \cw{127.*.*.*} range, and all of these are loopback addresses
347 available only to the local machine. So if you forward (for
348 example) \c{127.0.0.5:79} to a remote machine's \cw{finger} port,
349 then you should be able to run commands such as \c{finger
350 fred@127.0.0.5}. This can be useful if the program connecting to
351 the forwarded port doesn't allow you to change the port number it
352 uses. This feature is available for local-to-remote forwarded
353 ports; SSH1 is unable to support it for remote-to-local ports,
354 while SSH2 can support it in theory but servers will not
355 necessarily cooperate.
357 \H{using-rawprot} Making raw TCP connections
359 A lot of Internet protocols are composed of commands and responses
360 in plain text. For example, SMTP (the protocol used to transfer
361 e-mail), NNTP (the protocol used to transfer Usenet news), and HTTP
362 (the protocol used to serve Web pages) all consist of commands in
365 Sometimes it can be useful to connect directly to one of these
366 services and speak the protocol \q{by hand}, by typing protocol
367 commands and watching the responses. On Unix machines, you can do
368 this using the system's \c{telnet} command to connect to the right
369 port number. For example, \c{telnet mailserver.example.com 25} might
370 enable you to talk directly to the SMTP service running on a mail
373 Although the Unix \c{telnet} program provides this functionality,
374 the protocol being used is not really Telnet. Really there is no
375 actual protocol at all; the bytes sent down the connection are
376 exactly the ones you type, and the bytes shown on the screen are
377 exactly the ones sent by the server. Unix \c{telnet} will attempt to
378 detect or guess whether the service it is talking to is a real
379 Telnet service or not; PuTTY prefers to be told for certain.
381 In order to make a debugging connection to a service of this type,
382 you simply select the fourth protocol name, \q{Raw}, from the
383 \q{Protocol} buttons in the \q{Session} configuration panel. (See
384 \k{config-hostname}.) You can then enter a host name and a port
385 number, and make the connection.
387 \H{using-cmdline} The PuTTY command line
389 PuTTY can be made to do various things without user intervention by
390 supplying command-line arguments (e.g., from a command prompt window,
391 or a Windows shortcut).
393 \S{using-cmdline-session} Starting a session from the command line
395 These options allow you to bypass the configuration window and launch
396 straight into a session.
398 To start a connection to a server called \c{host}:
400 \c putty.exe [-ssh | -telnet | -rlogin | -raw] [user@]host
402 If this syntax is used, settings are taken from the Default Settings
403 (see \k{config-saving}); \c{user} overrides these settings if
404 supplied. Also, you can specify a protocol, which will override the
405 default protocol (see \k{using-cmdline-protocol}).
407 For telnet sessions, the following alternative syntax is supported
408 (this makes PuTTY suitable for use as a URL handler for telnet URLs in
411 \c putty.exe telnet://host[:port]/
413 In order to start an existing saved session called \c{sessionname},
414 use the \c{-load} option (described in \k{using-cmdline-load}).
416 \c putty.exe -load "session name"
418 \S{using-cleanup} \c{-cleanup}
420 If invoked with the \c{-cleanup} option, rather than running as
421 normal, PuTTY will remove its registry entries and random seed file
422 from the local machine (after confirming with the user).
424 \S{using-general-opts} Standard command-line options
426 PuTTY and its associated tools support a range of command-line
427 options, most of which are consistent across all the tools. This
428 section lists the available options in all tools. Options which are
429 specific to a particular tool are covered in the chapter about that
432 \S2{using-cmdline-load} \c{-load}: load a saved session
434 The \c{-load} option causes PuTTY to load configuration details out
435 of a saved session. If these details include a host name, then this
436 option is all you need to make PuTTY start a session (although Plink
437 still requires an explicitly specified host name).
439 You need double quotes around the session name if it contains spaces.
441 If you want to create a Windows shortcut to start a PuTTY saved
442 session, this is the option you should use: your shortcut should
445 \c d:\path\to\putty.exe -load "my session"
447 (Note that PuTTY itself supports an alternative form of this option,
448 for backwards compatibility. If you execute \c{putty @sessionname}
449 it will have the same effect as \c{putty -load "sessionname"}. With
450 the \c{@} form, no double quotes are required, and the \c{@} sign
451 must be the very first thing on the command line. This form of the
452 option is deprecated.)
454 \S2{using-cmdline-protocol} Selecting a protocol: \c{-ssh},
455 \c{-telnet}, \c{-rlogin}, \c{-raw}
457 To choose which protocol you want to connect with, you can use one
460 \b \c{-ssh} selects the SSH protocol.
462 \b \c{-telnet} selects the Telnet protocol.
464 \b \c{-rlogin} selects the Rlogin protocol.
466 \b \c{-raw} selects the raw protocol.
468 These options are not available in the file transfer tools PSCP and
469 PSFTP (which only work with the SSH protocol).
471 These options are equivalent to the protocol selection buttons in
472 the Session panel of the PuTTY configuration box (see
473 \k{config-hostname}).
475 \S2{using-cmdline-v} \c{-v}: increase verbosity
477 Most of the PuTTY tools can be made to tell you more about what they
478 are doing by supplying the \c{-v} option. If you are having trouble
479 when making a connection, or you're simply curious, you can turn
480 this switch on and hope to find out more about what is happening.
482 \S2{using-cmdline-l} \c{-l}: specify a login name
484 You can specify the user name to log in as on the remote server
485 using the \c{-l} option. For example, \c{plink login.example.com -l
488 These options are equivalent to the username selection box in the
489 Connection panel of the PuTTY configuration box (see
490 \k{config-username}).
492 \S2{using-cmdline-portfwd} \c{-L}, \c{-R} and \c{-D}: set up port forwardings
494 As well as setting up port forwardings in the PuTTY configuration
495 (see \k{config-ssh-portfwd}), you can also set up forwardings on the
496 command line. The command-line options work just like the ones in
497 Unix \c{ssh} programs.
499 To forward a local port (say 5110) to a remote destination (say
500 \cw{popserver.example.com} port 110), you can write something like
503 \c putty -L 5110:popserver.example.com:110 -load mysession
504 \c plink mysession -L 5110:popserver.example.com:110
506 To forward a remote port to a local destination, just use the \c{-R}
507 option instead of \c{-L}:
509 \c putty -R 5023:mytelnetserver.myhouse.org:23 -load mysession
510 \c plink mysession -R 5023:mytelnetserver.myhouse.org:23
512 To specify an IP address for the listening end of the tunnel,
513 prepend it to the argument:
515 \c plink -L 127.0.0.5:23:localhost:23 myhost
517 To set up SOCKS-based dynamic port forwarding on a local port, use
518 the \c{-D} option. For this one you only have to pass the port
521 \c putty -D 4096 -load mysession
523 For general information on port forwarding, see
524 \k{using-port-forwarding}.
526 These options are not available in the file transfer tools PSCP and
529 \S2{using-cmdline-m} \c{-m}: read a remote command or script from a
532 The \c{-m} option performs a similar function to the \q{Remote
533 command} box in the SSH panel of the PuTTY configuration box (see
534 \k{config-command}). However, the \c{-m} option expects to be given
535 a local file name, and it will read a command from that file. On most Unix
536 systems, you can even put multiple lines in this file and execute
537 more than one command in sequence, or a whole shell script.
539 This option is not available in the file transfer tools PSCP and
542 \S2{using-cmdline-p} \c{-P}: specify a port number
544 The \c{-P} option is used to specify the port number to connect to. If
545 you have a Telnet server running on port 9696 of a machine instead of
546 port 23, for example:
548 \c putty -telnet -P 9696 host.name
549 \c plink -telnet -P 9696 host.name
551 (Note that this option is more useful in Plink than in PuTTY,
552 because in PuTTY you can write \c{putty -telnet host.name 9696} in
555 These options are equivalent to the protocol selection buttons in
556 the Session panel of the PuTTY configuration box (see
557 \k{config-hostname}).
559 \S2{using-cmdline-pw} \c{-pw}: specify a password
561 A simple way to automate a remote login is to supply your password
562 on the command line. This is \e{not recommended} for reasons of
563 security. If you possibly can, we recommend you set up public-key
564 authentication instead. See \k{pubkey} for details.
566 Note that the \c{-pw} option only works when you are using the SSH
567 protocol. Due to fundamental limitations of Telnet and Rlogin, these
568 protocols do not support automated password authentication.
570 \S2{using-cmdline-agent} \c{-A} and \c{-a}: control agent forwarding
572 The \c{-A} option turns on SSH agent forwarding, and \c{-a} turns it
573 off. These options are only meaningful if you are using SSH.
575 See \k{pageant} for general information on Pageant, and
576 \k{pageant-forward} for information on agent forwarding. Note that
577 there is a security risk involved with enabling this option; see
578 \k{pageant-security} for details.
580 These options are equivalent to the agent forwarding checkbox in the
581 Auth panel of the PuTTY configuration box (see \k{config-ssh-agentfwd}).
583 These options are not available in the file transfer tools PSCP and
586 \S2{using-cmdline-x11} \c{-X} and \c{-x}: control X11 forwarding
588 The \c{-X} option turns on X11 forwarding in SSH, and \c{-x} turns
589 it off. These options are only meaningful if you are using SSH.
591 For information on X11 forwarding, see \k{using-x-forwarding}.
593 These options are equivalent to the X11 forwarding checkbox in the
594 Tunnels panel of the PuTTY configuration box (see
597 These options are not available in the file transfer tools PSCP and
600 \S2{using-cmdline-pty} \c{-t} and \c{-T}: control pseudo-terminal
603 The \c{-t} option ensures PuTTY attempts to allocate a
604 pseudo-terminal at the server, and \c{-T} stops it from allocating
605 one. These options are only meaningful if you are using SSH.
607 These options are equivalent to the \q{Don't allocate a
608 pseudo-terminal} checkbox in the SSH panel of the PuTTY
609 configuration box (see \k{config-ssh-pty}).
611 These options are not available in the file transfer tools PSCP and
614 \S2{using-cmdline-compress} \c{-C}: enable compression
616 The \c{-C} option enables compression of the data sent across the
617 network. This option is only meaningful if you are using SSH.
619 This option is equivalent to the \q{Enable compression} checkbox in
620 the SSH panel of the PuTTY configuration box (see
621 \k{config-ssh-comp}).
623 \S2{using-cmdline-sshprot} \c{-1} and \c{-2}: specify an SSH protocol
626 The \c{-1} and \c{-2} options force PuTTY to use version 1 or
627 version 2 of the SSH protocol. These options are only meaningful if
630 These options are equivalent to selecting your preferred SSH
631 protocol version as \q{1 only} or \q{2 only} in the SSH panel of the
632 PuTTY configuration box (see \k{config-ssh-prot}).
634 \S2{using-cmdline-identity} \c{-i}: specify an SSH private key
636 The \c{-i} option allows you to specify the name of a private key
637 file in \c{*.PPK} format which PuTTY will use to authenticate with the
638 server. This option is only meaningful if you are using SSH.
640 For general information on public-key authentication, see \k{pubkey}.
642 This option is equivalent to the \q{Private key file for
643 authentication} box in the Auth panel of the PuTTY configuration box
644 (see \k{config-ssh-privkey}).