-\versionid $Id: faq.but,v 1.79 2004/09/09 10:37:17 jacob Exp $
+\define{versionidfaq} \versionid $Id$
\A{faq} PuTTY FAQ
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?
If you have host keys available in the common \c{known_hosts} format,
we have a script called
-\W{http://cvs.tartarus.org/putty/contrib/kh2reg.py}\c{kh2reg.py}
+\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
time by double-clicking or using \c{REGEDIT}.
\S{faq-mac-port}{Question} Will there be a port to the 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-howto} HOWTO questions
+\S{faq-commands}{Question} 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 maximised?
Create a Windows shortcut to start PuTTY from, and set it as \q{Run
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 SSH-2 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.
\c http://www.microsoft.com/windows95/downloads/contents/
\c wuadmintools/s_wunetworkingtools/w95sockets2/
-\S{faq-outofmem}{Question} After trying to establish an SSH 2
+\S{faq-outofmem}{Question} After trying to establish an SSH-2
connection, PuTTY says \q{Out of memory} and dies.
If this happens just while the connection is starting up, this often
is a much simpler protocol.)
\S{faq-bce}{Question} When I run full-colour applications, I see
-areas of black space where colour ought to be.
+areas of black space where colour ought to be, or vice versa.
+
+You almost certainly need to change the \q{Use 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}.)
-You almost certainly need to enable the \q{Use background colour to
-erase screen} setting in the Terminal panel. Note that if you do
-this in mid-session, in versions before 0.54, it may not take effect
-until you reset the terminal (see \k{faq-resetterm}).
+In old versions of PuTTY, this was disabled by default, and would not
+take effect until you reset the terminal (see \k{faq-resetterm}).
+Since 0.54, it is enabled by default, and changes take effect
+immediately.
\S{faq-resetterm}{Question} When I change some terminal settings,
nothing happens.
try harder to keep connections alive instead of abandoning them.
\S{faq-puttyputty}{Question} When I \cw{cat} a binary file, I get
-`PuTTYPuTTYPuTTY' on my command line.
+\q{PuTTYPuTTYPuTTY} on my command line.
Don't do that, then.
\e{OpenSSH 3.1p1:} configurations known to be broken (and symptoms):
-\b SSH 2 with AES cipher (PuTTY says "Assertion failed! Expression:
+\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 3DES (PuTTY says "Incorrect MAC received on packet")
+\b SSH-2 with 3DES (PuTTY says "Incorrect MAC received on packet")
-\b SSH 1 with Blowfish (PuTTY says "Incorrect CRC received on
+\b SSH-1 with Blowfish (PuTTY says "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.
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
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
This is apparently an issue with SP2 that is acknowledged by Microsoft
in MS Knowledge Base article
\W{http://support.microsoft.com/default.aspx?scid=kb;en-us;884020}{884020}.
-
-For a fix, you'll need to contact Microsoft support, as mentioned in
-the KB article. We've been told that the process is reasonably easy,
-and is free of charge; and that the fix will be included in the next
-Windows XP Service Pack (but probably not before).
+The article links to a fix you can download.
(\e{However}, we've been told that SP2 \e{also} fixes the bug that
means you need to use non-\cw{127.0.0.1} addresses to forward
Terminal Services in the first place.)
+\S{faq-missing-slash}{Question} PSFTP commands seem to be missing a
+directory separator (slash).
+
+Some people have reported the following incorrect behaviour with
+PSFTP:
+
+\c psftp> pwd
+\e iii
+\c Remote directory is /dir1/dir2
+\c psftp> get filename.ext
+\e iiiiiiiiiiiiiiii
+\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
+(\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
+reported to us).
+
+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.
+
\H{faq-secure} Security questions
\S{faq-publicpc}{Question} Is it safe for me to download PuTTY and
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}. Uninstallation does not currently
+remove the above-mentioned registry entries and file.
\S{faq-dsa}{Question} How come PuTTY now supports DSA, when the
website used to say how insecure it was?
Also, security reasons. PuTTY is a security product, and as such it
is particularly important to guard the code and the web site against
unauthorised modifications which might introduce subtle security
-flaws. Therefore, we prefer that the CVS repository, web site and
+flaws. Therefore, we prefer that the Subversion repository, web site and
FTP site remain where they are, under the direct control of system
administrators we know and trust personally, rather than being run
by a large organisation full of people we've never met and which is
If someone else wants to set up a mailing list or other forum for
PuTTY users to help each other with common problems, that would be
fine with us, though the PuTTY team would almost certainly not have the
-time to read it. It's probably better to use the established
-newsgroup \cw{comp.security.ssh} for this purpose.
+time to read it. It's probably better to use one of the established
+newsgroups for this purpose (see \k{feedback-other-fora}).
\S{faq-donations}{Question} How can I donate to PuTTY development?
Yes. You need not bother asking us explicitly for permission. You
already have permission. Redistribution of the unmodified PuTTY
-binary in this way is entirely permitted by our licence, and you are
-welcome to do it as much as you like.
+binary in this way is entirely permitted by our licence (see
+\k{licence}), and you are welcome to do it as much as you like.
If you are distributing PuTTY within your own organisation, or for
use with your own product, then we recommend (but do not insist)
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?
projects / u / mdw / putty / blobdiff