\define{versionidfaq} \versionid $Id$
-\A{faq} PuTTY FAQ
+\A{faq} PuTTY \i{FAQ}
This FAQ is published on the PuTTY web site, and also provided as an
appendix in the manual.
\H{faq-support} Features supported in PuTTY
-In general, if you want to know if PuTTY supports a particular
-feature, you should look for it on the
+\I{supported features}In general, if you want to know if PuTTY supports
+a particular feature, you should look for it on the
\W{http://www.chiark.greenend.org.uk/~sgtatham/putty/}{PuTTY web site}.
In particular:
and not in the \q{Recently fixed} section, it probably \e{hasn't} been
implemented.
-\S{faq-ssh2}{Question} Does PuTTY support SSH v2?
+\S{faq-ssh2}{Question} Does PuTTY support SSH-2?
-Yes. SSH v2 support has been available in PuTTY since version 0.50.
+Yes. SSH-2 support has been available in PuTTY since version 0.50.
-Public key authentication (both RSA and DSA) in SSH v2 is new in
+Public key authentication (both RSA and DSA) in SSH-2 is new in
version 0.52.
\S{faq-ssh2-keyfmt}{Question} Does PuTTY support reading OpenSSH or
-\cw{ssh.com} SSHv2 private key files?
+\cw{ssh.com} SSH-2 private key files?
PuTTY doesn't support this natively, but as of 0.53
PuTTYgen can convert both OpenSSH and \cw{ssh.com} private key
files into PuTTY's format.
-\S{faq-ssh1}{Question} Does PuTTY support SSH v1?
+\S{faq-ssh1}{Question} Does PuTTY support SSH-1?
-Yes. SSH 1 support has always been available in PuTTY.
+Yes. SSH-1 support has always been available in PuTTY.
-\S{faq-localecho}{Question} Does PuTTY support local echo?
+\S{faq-localecho}{Question} Does PuTTY support \i{local echo}?
Yes. Version 0.52 has proper support for local echo.
so I don't have to change them every time?
Yes, all of PuTTY's settings can be saved in named session profiles.
+You can also change the default settings that are used for new sessions.
See \k{config-saving} in the documentation for how to do this.
\S{faq-disksettings}{Question} Does PuTTY support storing its
Yes; this is a new feature in version 0.52.
\S{faq-password-remember}{Question} Does PuTTY have the ability to
-remember my password so I don't have to type it every time?
+\i{remember my password} so I don't have to type it every time?
No, it doesn't.
authentication.
\S{faq-hostkeys}{Question} Is there an option to turn off the
-annoying host key prompts?
+\I{verifying the host key}annoying host key prompts?
No, there isn't. And there won't be. Even if you write it yourself
and send us the patch, we won't accept it.
ones will not. Adding an option to turn host key checking off
completely is the wrong solution and we will not do it.
-If you have host keys available in the common \c{known_hosts} format,
+If you have host keys available in the common \i\c{known_hosts} format,
we have a script called
\W{http://www.tartarus.org/~simon-anonsvn/viewcvs.cgi/putty/contrib/kh2reg.py?view=markup}\c{kh2reg.py}
to convert them to a Windows .REG file, which can be installed ahead of
anyone else wants to try it.
\S{faq-pscp-ascii}{Question} Can PSCP or PSFTP transfer files in
-ASCII mode?
+\i{ASCII} mode?
Unfortunately not.
There are some third-party ports to various platforms, mentioned
on the Links page of our website.
-\S{faq-unix}{Question} Is there a port to Unix?
+\S{faq-unix}{Question} \I{Unix version}Is there a port to Unix?
As of 0.54, there are Unix ports of most of the traditional PuTTY
tools, and also one entirely new application.
If you look at the source release, you should find a \c{unix}
subdirectory containing \c{Makefile.gtk}, which should build you Unix
ports of Plink, PuTTY itself, PuTTYgen, PSCP, PSFTP, and also
-\c{pterm} - an \cw{xterm}-type program which supports the same
+\i\c{pterm} - an \cw{xterm}-type program which supports the same
terminal emulation as PuTTY. We do not yet have a Unix port of
Pageant.
-If you don't have Gtk, you should still be able to build the
+If you don't have \i{Gtk}, you should still be able to build the
command-line tools.
Note that Unix PuTTY has mostly only been tested on Linux so far;
There's also a third-party port at
\W{http://pocketputty.duxy.net/}\c{http://pocketputty.duxy.net/}.
-\S{faq-win31}{Question} Is there a port to Windows 3.1?
+\S{faq-win31}{Question} Is there a port to \i{Windows 3.1}?
PuTTY is a 32-bit application from the ground up, so it won't run on
Windows 3.1 as a native 16-bit program; and it would be \e{very}
allocation mechanisms.
However, it is possible in theory to compile the existing PuTTY
-source in such a way that it will run under Win32s (an extension to
+source in such a way that it will run under \i{Win32s} (an extension to
Windows 3.1 to let you run 32-bit programs). In order to do this
you'll need the right kind of C compiler - modern versions of Visual
C at least have stopped being backwards compatible to Win32s. Also,
If you're interested in running PuTTY under Windows 3.1, help and
testing in this area would be very welcome!
-\S{faq-mac-port}{Question} Will there be a port to the Mac?
+\S{faq-mac-port}{Question} Will there be a port to the \I{Mac OS}Mac?
-There is a port to the Mac OS in progress. It's just about usable, but
-has an awful lot of gaps and rough edges that will need cleaning up
-before release (such as useful random numbers).
+There are several answers to this question:
-A separate port to Mac OS X is also underway.
+\b The Unix/Gtk port is already fully working under Mac OS X as an X11
+application.
+
+\b A native (Cocoa) Mac OS X port is in progress. It's just about
+usable, but is of nowhere near release quality yet, and is likely to
+behave in unexpected ways.
+
+\b A separate port to the classic Mac OS (pre-OSX) is also in
+progress; it too is not ready yet.
\S{faq-epoc}{Question} Will there be a port to EPOC?
\H{faq-details} Details of PuTTY's operation
-\S{faq-term}{Question} What terminal type does PuTTY use?
+\S{faq-term}{Question} What \i{terminal type} does PuTTY use?
For most purposes, PuTTY can be considered to be an \cw{xterm}
terminal.
-PuTTY also supports some terminal control sequences not supported by
+PuTTY also supports some terminal \i{control sequences} not supported by
the real \cw{xterm}: notably the Linux console sequences that
reconfigure the colour palette, and the title bar control sequences
-used by \cw{DECterm} (which are different from the \cw{xterm} ones;
+used by \i\cw{DECterm} (which are different from the \cw{xterm} ones;
PuTTY supports both).
By default, PuTTY announces its terminal type to the server as
\S{faq-settings}{Question} Where does PuTTY store its data?
On Windows, PuTTY stores most of its data (saved sessions, SSH host
-keys) in the Registry. The precise location is
+keys) in the \i{Registry}. The precise location is
\c HKEY_CURRENT_USER\Software\SimonTatham\PuTTY
PuTTY also requires a random number seed file, to improve the
unpredictability of randomly chosen data needed as part of the SSH
-cryptography. This is stored by default in your Windows home
-directory (\c{%HOMEDRIVE%\\%HOMEPATH%}), or in the actual Windows
-directory (such as \c{C:\\WINDOWS}) if the home directory doesn't
-exist, for example if you're using Win95. If you want to change the
-location of the random number seed file, you can put your chosen
-pathname in the Registry, at
+cryptography. This is stored by default in a file called \i\c{PUTTY.RND}
+in your Windows home directory (\c{%HOMEDRIVE%\\%HOMEPATH%}), or in
+the actual Windows directory (such as \c{C:\\WINDOWS}) if the home
+directory doesn't exist, for example if you're using Win95. If you
+want to change the location of the random number seed file, you can
+put your chosen pathname in the Registry, at
\c HKEY_CURRENT_USER\Software\SimonTatham\PuTTY\RandSeedFile
\H{faq-howto} HOWTO questions
-\S{faq-startmax}{Question} How can I make PuTTY start up maximised?
+\S{faq-commands}{Question} \I{commands on the server}What commands
+can I type into my PuTTY terminal window?
+
+This is not a question you should be asking \e{us}. You need to read
+the manuals, or ask the administrator, of \e{the computer you have
+connected to}.
+
+PuTTY does not process the commands you type into it. It's only a
+communications tool. It makes a connection to another computer; it
+passes the commands you type to that other computer; and it passes
+the other computer's responses back to you. Therefore, the precise
+range of commands you can use will not depend on PuTTY, but on what
+kind of computer you have connected to and what software is running
+on it. The PuTTY team cannot help you with that.
+
+(Think of PuTTY as being a bit like a telephone. If you phone
+somebody up and you don't know what language to speak to make them
+understand you, it isn't \e{the telephone company}'s job to find
+that out for you. We just provide the means for you to get in touch;
+making yourself understood is somebody else's problem.)
+
+If you are unsure of where to start looking for the administrator of
+your server, a good place to start might be to remember how you
+found out the host name in the PuTTY configuration. If you were
+given that host name by e-mail, for example, you could try asking
+the person who sent you that e-mail. If your company's IT department
+provided you with ready-made PuTTY saved sessions, then that IT
+department can probably also tell you something about what commands
+you can type during those sessions. But the PuTTY maintainer team
+does not administer any server you are likely to be connecting to,
+and cannot help you with questions of this type.
+
+\S{faq-startmax}{Question} How can I make PuTTY start up \i{maximise}d?
Create a Windows shortcut to start PuTTY from, and set it as \q{Run
Maximized}.
-\S{faq-startsess}{Question} How can I create a Windows shortcut to
+\S{faq-startsess}{Question} How can I create a \i{Windows shortcut} to
start a particular saved session directly?
To run a PuTTY session saved under the name \q{\cw{mysession}},
a saved session that specifies the SSH protocol, and start the saved
session as shown in \k{faq-startsess}.
-\S{faq-cutpaste}{Question} How do I copy and paste between PuTTY and
+\S{faq-cutpaste}{Question} How do I \i{copy and paste} between PuTTY and
other Windows applications?
Copy and paste works similarly to the X Window System. You use the
To use PSCP properly, run it from a Command Prompt window. See
\k{pscp} in the documentation for more details.
-\S{faq-pscp-spaces}{Question} How do I use PSCP to copy a file whose
-name has spaces in?
+\S{faq-pscp-spaces}{Question} \I{spaces in filenames}How do I use
+PSCP to copy a file whose name has spaces in?
If PSCP is using the traditional SCP protocol, this is confusing. If
you're specifying a file at the local end, you just use one set of
received on packet}?
One possible cause of this that used to be common is a bug in old
-SSH 2 servers distributed by \cw{ssh.com}. (This is not the only
+SSH-2 servers distributed by \cw{ssh.com}. (This is not the only
possible cause; see \k{errors-crc} in the documentation.)
-Version 2.3.0 and below of their SSH 2 server
+Version 2.3.0 and below of their SSH-2 server
constructs Message Authentication Codes in the wrong way, and
expects the client to construct them in the same wrong way. PuTTY
constructs the MACs correctly by default, and hence these old
If you are using PuTTY version 0.51 or below, you can enable the
workaround by going to the SSH panel and ticking the box labelled
-\q{Imitate SSH 2 MAC bug}. It's possible that you might have to do
+\q{Imitate SSH2 MAC bug}. It's possible that you might have to do
this with 0.52 as well, if a buggy server exists that PuTTY doesn't
know about.
-In this context MAC stands for Message Authentication Code. It's a
+In this context MAC stands for \ii{Message Authentication Code}. It's a
cryptographic term, and it has nothing at all to do with Ethernet
MAC (Media Access Control) addresses.
that was part of the PSCP protocol exchange, and instead it saw data
that it couldn't make any sense of at all.
-This almost always happens because the startup scripts in your
+This almost always happens because the \i{startup scripts} in your
account on the server machine are generating output. This is
impossible for PSCP, or any other SCP client, to work around. You
should never use startup files (\c{.bashrc}, \c{.cshrc} and so on)
then all other SCP clients are likely to fail in exactly the same
way. The problem is at the server end.
-\S{faq-colours}{Question} I clicked on a colour in the Colours
+\S{faq-colours}{Question} I clicked on a colour in the \ii{Colours}
panel, and the colour didn't change in my terminal.
That isn't how you're supposed to use the Colours panel.
only allow you to adjust the \e{shade} of green used when PuTTY is
instructed by the server to display green text.
-\S{faq-winsock2}{Question} Plink on Windows 95 says it can't find
-\cw{WS2_32.DLL}.
+\S{faq-winsock2}{Question} Plink on \i{Windows 95} says it can't find
+\i\cw{WS2_32.DLL}.
Plink requires the extended Windows network library, WinSock version
2. This is installed as standard on Windows 98 and above, and on
\c http://www.microsoft.com/windows95/downloads/contents/
\c wuadmintools/s_wunetworkingtools/w95sockets2/
-\S{faq-outofmem}{Question} After trying to establish an SSH 2
-connection, PuTTY says \q{Out of memory} and dies.
+\S{faq-outofmem}{Question} After trying to establish an SSH-2
+connection, PuTTY says \q{\ii{Out of memory}} and dies.
If this happens just while the connection is starting up, this often
indicates that for some reason the client and server have failed to
out of memory.
\S{faq-outofmem2}{Question} When attempting a file transfer, either
-PSCP or PSFTP says \q{Out of memory} and dies.
+PSCP or PSFTP says \q{\ii{Out of memory}} and dies.
-This is almost always caused by your login scripts on the server
+This is almost always caused by your \i{login scripts} on the server
generating output. PSCP or PSFTP will receive that output when they
were expecting to see the start of a file transfer protocol, and
they will attempt to interpret the output as file-transfer protocol.
\S{faq-bce}{Question} When I run full-colour applications, I see
areas of black space where colour ought to be, or vice versa.
-You almost certainly need to change the \q{Use background colour to
+You almost certainly need to change the \q{Use \i{background colour} to
erase screen} setting in the Terminal panel. If there is too much
black space (the commoner situation), you should enable it, while if
there is too much colour, you should disable it. (See \k{config-erase}.)
\S{faq-resetterm}{Question} When I change some terminal settings,
nothing happens.
-Some of the terminal options (notably Auto Wrap and
+Some of the terminal options (notably \ii{Auto Wrap} and
background-colour screen erase) actually represent the \e{default}
setting, rather than the currently active setting. The server can
send sequences that modify these options in mid-session, but when
settings take effect immediately.
\S{faq-idleout}{Question} My PuTTY sessions unexpectedly close after
-they are idle for a while.
+they are \I{idle connections}idle for a while.
-Some types of firewall, and almost any router doing Network Address
-Translation (NAT, also known as IP masquerading), will forget about
+Some types of \i{firewall}, and almost any router doing Network Address
+Translation (\i{NAT}, also known as IP masquerading), will forget about
a connection through them if the connection does nothing for too
long. This will cause the connection to be rudely cut off when
contact is resumed.
this.
\S{faq-timeout}{Question} PuTTY's network connections time out too
-quickly when network connectivity is temporarily lost.
+quickly when \I{breaks in connectivity}network connectivity is
+temporarily lost.
This is a Windows problem, not a PuTTY problem. The timeout value
can't be set on per application or per session basis. To increase
\W{http://support.microsoft.com/default.aspx?scid=kb;en-us;158474}{158474}
for more information.)
-On Windows NT or 2000, the registry key is
+On Windows NT, 2000, or XP, the registry key to create or change is
\c HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\
\c Parameters\TcpMaxDataRetransmissions
and it must be of type DWORD.
-(See MS Knowledge Base article
+(See MS Knowledge Base articles
\W{http://support.microsoft.com/default.aspx?scid=kb;en-us;120642}{120642}
+and
+\W{http://support.microsoft.com/default.aspx?scid=kb;en-us;314053}{314053}
for more information.)
Set the key's value to something like 10. This will cause Windows to
your terminal is likely to cause various other unpleasant behaviour,
so this is only a small remedy.
-\S{faq-wintitle}{Question} When I \cw{cat} a binary file, my window
-title changes to a nonsense string.
+\S{faq-wintitle}{Question} When I \cw{cat} a binary file, my \i{window
+title} changes to a nonsense string.
Don't do that, then.
manual), and follow the guidelines contained in that.
\S{faq-openssh-bad-openssl}{Question} Since my SSH server was upgraded
-to OpenSSH 3.1p1/3.4p1, I can no longer connect with PuTTY.
+to \i{OpenSSH} 3.1p1/3.4p1, I can no longer connect with PuTTY.
There is a known problem when OpenSSH has been built against an
incorrect version of OpenSSL; the quick workaround is to configure
\e{OpenSSH 3.1p1:} configurations known to be broken (and symptoms):
-\b SSH 2 with AES cipher (PuTTY says "Assertion failed! Expression:
-(len & 15) == 0" in sshaes.c, or "Out of memory", or crashes)
+\b SSH-2 with AES cipher (PuTTY says \q{Assertion failed! Expression:
+(len & 15) == 0} in \cw{sshaes.c}, or \q{Out of memory}, or crashes)
-\b SSH 2 with 3DES (PuTTY says "Incorrect MAC received on packet")
+\b SSH-2 with 3DES (PuTTY says \q{Incorrect MAC received on packet})
-\b SSH 1 with Blowfish (PuTTY says "Incorrect CRC received on
-packet")
+\b SSH-1 with Blowfish (PuTTY says \q{Incorrect CRC received on
+packet})
-\b SSH 1 with 3DES
+\b SSH-1 with 3DES
-\e{OpenSSH 3.4p1:} as of 3.4p1, only the problem with SSH 1 and
+\e{OpenSSH 3.4p1:} as of 3.4p1, only the problem with SSH-1 and
Blowfish remains. Rebuild your server, apply the patch linked to from
bug 138 above, or use another cipher (e.g., 3DES) instead.
and workarounds with older versions of OpenSSH, although it's not
clear the underlying cause is the same.
-\S{faq-ssh2key-ssh1conn}{Question} Why do I see "Couldn't load private
-key from ..."? Why can PuTTYgen load my key but not PuTTY?
+\S{faq-ssh2key-ssh1conn}{Question} Why do I see \q{Couldn't load
+private key from ...}? Why can PuTTYgen load my key but not PuTTY?
It's likely that you've generated an SSH protocol 2 key with PuTTYgen,
-but you're trying to use it in an SSH 1 connection. SSH1 and SSH2 keys
+but you're trying to use it in an SSH-1 connection. SSH-1 and SSH-2 keys
have different formats, and (at least in 0.52) PuTTY's reporting of a
key in the wrong format isn't optimal.
-To connect using SSH 2 to a server that supports both versions, you
+To connect using SSH-2 to a server that supports both versions, you
need to change the configuration from the default (see \k{faq-ssh2}).
-\S{faq-rh8-utf8}{Question} When I'm connected to a Red Hat Linux 8.0
+\S{faq-rh8-utf8}{Question} When I'm connected to a \i{Red Hat Linux} 8.0
system, some characters don't display properly.
A common complaint is that hyphens in man pages show up as a-acute.
-With release 8.0, Red Hat appear to have made UTF-8 the default
+With release 8.0, Red Hat appear to have made \i{UTF-8} the default
character set. There appears to be no way for terminal emulators such
as PuTTY to know this (as far as we know, the appropriate escape
sequence to switch into UTF-8 mode isn't sent).
scrollback has stopped working when I run \c{screen}.
PuTTY's terminal emulator has always had the policy that when the
-\q{alternate screen} is in use, nothing is added to the scrollback.
+\q{\i{alternate screen}} is in use, nothing is added to the scrollback.
This is because the usual sorts of programs which use the alternate
screen are things like text editors, which tend to scroll back and
forth in the same document a lot; so (a) they would fill up the
continue working. The simplest solution is to go to the Features
control panel and tick \q{Disable switching to alternate terminal
screen}. (See \k{config-features-altscreen} for more details.)
+Alternatively, you can tell \c{screen} itself not to use the
+alternate screen: the
+\W{http://www4.informatik.uni-erlangen.de/~jnweiger/screen-faq.html}{\c{screen}
+FAQ} suggests adding the line \cq{termcapinfo xterm ti@:te@} to your
+\cw{.screenrc} file.
The reason why this only started to be a problem in 0.54 is because
\c{screen} typically uses an unusual control sequence to switch to
the alternate screen, and previous versions of PuTTY did not support
this sequence.
-\S{faq-alternate-localhost}{Question} Since I upgraded Windows XP
+\S{faq-alternate-localhost}{Question} Since I upgraded \i{Windows XP}
to Service Pack 2, I can't use addresses like \cw{127.0.0.2}.
-Some people who ask PuTTY to listen on localhost addresses other
-than \cw{127.0.0.1} to forward services such as SMB and Windows
-Terminal Services have found that doing so no longer works since
+Some people who ask PuTTY to listen on \i{localhost} addresses other
+than \cw{127.0.0.1} to forward services such as \i{SMB} and \i{Windows
+Terminal Services} have found that doing so no longer works since
they upgraded to WinXP SP2.
This is apparently an issue with SP2 that is acknowledged by Microsoft
\c /dir1/dir2filename.ext: no such file or directory
This is not a bug in PSFTP. There is a known bug in some versions of
-portable OpenSSH
+portable \i{OpenSSH}
(\W{http://bugzilla.mindrot.org/show_bug.cgi?id=697}{bug 697}) that
causes these symptoms; it appears to have been introduced around
3.7.x. It manifests only on certain platforms (AIX is what has been
There is a patch for OpenSSH attached to that bug; it's also fixed in
recent versions of portable OpenSSH (from around 3.8).
+\S{faq-connaborted}{Question} Do you want to hear about \q{Software
+caused connection abort}?
+
+In the documentation for PuTTY 0.53 and 0.53b, we mentioned that we'd
+like to hear about any occurrences of this error. Since the release
+of PuTTY 0.54, however, we've been convinced that this error doesn't
+indicate that PuTTY's doing anything wrong, and we don't need to hear
+about further occurrences. See \k{errors-connaborted} for our current
+documentation of this error.
+
+\S{faq-rekey}{Question} My SSH-2 session \I{locking up, SSH-2
+sessions}locks up for a few seconds every so often.
+
+Recent versions of PuTTY automatically initiate \i{repeat key
+exchange} once per hour, to improve session security. If your client
+or server machine is slow, you may experience this as a delay of
+anything up to thirty seconds or so.
+
+These \I{delays, in SSH-2 sessions}delays are inconvenient, but they
+are there for your protection. If they really cause you a problem,
+you can choose to turn off periodic rekeying using the \q{Kex}
+configuration panel (see \k{config-ssh-kex}), but be aware that you
+will be sacrificing security for this. (Falling back to SSH-1 would
+also remove the delays, but would lose a \e{lot} more security
+still. We do not recommend it.)
+
\H{faq-secure} Security questions
\S{faq-publicpc}{Question} Is it safe for me to download PuTTY and
floppy).
\S{faq-cleanup}{Question} What does PuTTY leave on a system? How can
-I clean up after it?
+I \i{clean up} after it?
PuTTY will leave some Registry entries, and a random seed file, on
the PC (see \k{faq-settings}). If you are using PuTTY on a public
PC, or somebody else's PC, you might want to clean these up when you
leave. You can do that automatically, by running the command
-\c{putty -cleanup}.
+\c{putty -cleanup}. (Note that this only removes settings for
+the currently logged-in user on \i{multi-user systems}.)
+
+If PuTTY was installed from the installer package, it will also
+appear in \q{Add/Remove Programs}. Older versions of the uninstaller
+do not remove the above-mentioned registry entries and file.
-\S{faq-dsa}{Question} How come PuTTY now supports DSA, when the
+\S{faq-dsa}{Question} How come PuTTY now supports \i{DSA}, when the
website used to say how insecure it was?
DSA has a major weakness \e{if badly implemented}: it relies on a
\H{faq-misc} Miscellaneous questions
-\S{faq-openssh}{Question} Is PuTTY a port of OpenSSH, or based on
+\S{faq-openssh}{Question} Is PuTTY a port of \i{OpenSSH}, or based on
OpenSSH?
No, it isn't. PuTTY is almost completely composed of code written
from scratch for PuTTY. The only code we share with OpenSSH is the
-detector for SSH1 CRC compensation attacks, written by CORE SDI S.A.
+detector for SSH-1 CRC compensation attacks, written by CORE SDI S.A.
\S{faq-sillyputty}{Question} Where can I buy silly putty?
~mdw / sgt / putty / blobdiff