-\versionid $Id: faq.but,v 1.55 2004/02/10 18:22:00 simon Exp $
+\versionid $Id$
\A{faq} PuTTY FAQ
\H{faq-intro} Introduction
-\S{faq-what} What is PuTTY?
+\S{faq-what}{Question} What is PuTTY?
PuTTY is a client program for the SSH, Telnet and Rlogin network
protocols.
the Terminal panel, in the section marked \q{Line discipline
options}.
+\S{faq-savedsettings}{Question} Does PuTTY support storing settings,
+so I don't have to change them every time?
+
+Yes, all of PuTTY's settings can be saved in named session profiles.
+See \k{config-saving} in the documentation for how to do this.
+
\S{faq-disksettings}{Question} Does PuTTY support storing its
settings in a disk file?
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}.
present time. If anyone told you we had an EPOC port, or an iPaq port,
or any other port of PuTTY, they were mistaken. We don't.
+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?
As of 0.54, there are Unix ports of most of the traditional PuTTY
portability problems such as BSD-style ptys or different header file
requirements are expected.
+\S{faq-unix-why}{Question} What's the point of the Unix port? Unix
+has OpenSSH.
+
+All sorts of little things. \c{pterm} is directly useful to anyone
+who prefers PuTTY's terminal emulation to \c{xterm}'s, which at
+least some people do. Unix Plink has apparently found a niche among
+people who find the complexity of OpenSSL makes OpenSSH hard to
+install (and who don't mind Plink not having as many features). Some
+users want to generate a large number of SSH keys on Unix and then
+copy them all into PuTTY, and the Unix PuTTYgen should allow them to
+automate that conversion process.
+
+There were development advantages as well; porting PuTTY to Unix was
+a valuable path-finding effort for other future ports, and also
+allowed us to use the excellent Linux tool
+\W{http://valgrind.kde.org/}{Valgrind} to help with debugging, which
+has already improved PuTTY's stability on \e{all} platforms.
+
+However, if you're a Unix user and you can see no reason to switch
+from OpenSSH to PuTTY/Plink, then you're probably right. We don't
+expect our Unix port to be the right thing for everybody.
+
\S{faq-wince}{Question} Will there be a port to Windows CE or PocketPC?
It's currently being worked on, but it's only in its early stages yet,
clearly be a useful thing, so in the long term I hope it can be
brought up to release quality.
+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?
PuTTY is a 32-bit application from the ground up, so it won't run on
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.
+before release (such as useful random numbers).
+
+A separate port to Mac OS X is also underway.
\S{faq-epoc}{Question} Will there be a port to EPOC?
However, some of the work has been done by other people, and a beta
port of PuTTY for the Nokia 9200 Communicator series is available
-from \W{http://www.s2.org/putty/}\cw{http://www.s2.org/putty/}
+from \W{http://s2putty.sourceforge.net/}\cw{http://s2putty.sourceforge.net/}
\H{faq-embedding} Embedding PuTTY in other programs
\S{faq-settings}{Question} Where does PuTTY store its data?
-PuTTY stores most of its data (saved sessions, SSH host keys) in the
-Registry. The precise location is
+On Windows, PuTTY stores most of its data (saved sessions, SSH host
+keys) in the Registry. The precise location is
\c HKEY_CURRENT_USER\Software\SimonTatham\PuTTY
\c HKEY_CURRENT_USER\Software\SimonTatham\PuTTY\RandSeedFile
+On Unix, PuTTY stores all of this data in a directory \cw{~/.putty}.
+
\H{faq-howto} HOWTO questions
\S{faq-startmax}{Question} How can I make PuTTY start up maximised?
You can also paste by pressing Shift-Ins.
-\S{faq-tunnels}{Question} How do I use X forwarding and port
-forwarding? I can't find the Tunnels panel.
-
-This is a new feature in version 0.52. You should upgrade.
-
\S{faq-options}{Question} How do I use all PuTTY's features (public
keys, proxying, cipher selection, etc.) in PSCP, PSFTP and Plink?
the
\W{http://www.microsoft.com/windows95/downloads/contents/wuadmintools/s_wunetworkingtools/w95sockets2/}{WinSock 2 upgrade}:
-\c http://www.microsoft.com/windows95/downloads/contents/wuadmintools/
-\c s_wunetworkingtools/w95sockets2/
-
-\S{faq-rekey}{Question} My PuTTY sessions close after an hour and
-tell me \q{Server failed host key check}.
-
-This is a bug in all versions of PuTTY up to and including 0.51. SSH
-v2 servers from \cw{ssh.com} will require the key exchange to be
-repeated one hour after the start of the connection, and PuTTY will
-get this wrong.
-
-Upgrade to version 0.52 or better and the problem should go away.
+\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-psftp-slow}{Question} PSFTP transfers files much slower than PSCP.
-We believe this is because the SFTP and SSH2 protocols are less
-efficient at bulk data transfer than SCP and SSH1, because every
-block of data transferred requires an acknowledgment from the far
-end. It would in theory be possible to queue several blocks of data
-to get round this speed problem, but as yet we haven't done the
-coding. If you really want this fixed, feel free to offer to help.
+The throughput of PSFTP 0.54 should be much better than 0.53b and
+prior; we've added code to the SFTP backend to queue several blocks
+of data rather than waiting for an acknowledgement for each. (The
+SCP backend did not suffer from this performance issue because SCP
+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.
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, it may not take effect until you reset the
-terminal (see \k{faq-resetterm}).
+this in mid-session, in versions before 0.54, it may not take effect
+until you reset the terminal (see \k{faq-resetterm}).
\S{faq-resetterm}{Question} When I change some terminal settings,
nothing happens.
In version 0.54, the behaviour has changed - changes to these
settings take effect immediately.
-\S{faq-altgr}{Question} I can't type characters that require the
-AltGr key.
-
-In PuTTY version 0.51, the AltGr key was broken. Upgrade to version
-0.52 or better.
-
\S{faq-idleout}{Question} My PuTTY sessions unexpectedly close after
they are idle for a while.
can't be set on per application or per session basis. To increase
the TCP timeout globally, you need to tinker with the Registry.
-On Windows 95, 98 or ME, the registry key you need to change is
+On Windows 95, 98 or ME, the registry key you need to create or
+change is
\c HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\
\c MSTCP\MaxDataRetries
(it must be of type DWORD in Win95, or String in Win98/ME).
+(See MS Knowledge Base article
+\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
\c Parameters\TcpMaxDataRetransmissions
and it must be of type DWORD.
+(See MS Knowledge Base article
+\W{http://support.microsoft.com/default.aspx?scid=kb;en-us;120642}{120642}
+for more information.)
Set the key's value to something like 10. This will cause Windows to
try harder to keep connections alive instead of abandoning them.
right place is \c{/etc/sysconfig/i18n}, but this shouldn't be
necessary.
+\S{faq-screen}{Question} Since I upgraded to PuTTY 0.54, the
+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.
+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
+scrollback with a large amount of unhelpfully disordered text, and
+(b) they contain their \e{own} method for the user to scroll back to
+the bit they were interested in. We have generally found this policy
+to do the Right Thing in almost all situations.
+
+Unfortunately, \c{screen} is one exception: it uses the alternate
+screen, but it's still usually helpful to have PuTTY's scrollback
+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.)
+
+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
+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
+they upgraded to WinXP SP2.
+
+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}.
+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).
+
\H{faq-secure} Security questions
\S{faq-publicpc}{Question} Is it safe for me to download PuTTY and
We already have some, thanks.
+\S{faq-link}{Question} Would you link to my web site from the PuTTY
+web site?
+
+Only if the content of your web page is of definite direct interest
+to PuTTY users. If your content is unrelated, or only tangentially
+related, to PuTTY, then the link would simply be advertising for
+you.
+
+One very nice effect of the Google ranking mechanism is that by and
+large, the most popular web sites get the highest rankings. This
+means that when an ordinary person does a search, the top item in
+the search is very likely to be a high-quality site or the site they
+actually wanted, rather than the site which paid the most money for
+its ranking.
+
+The PuTTY web site is held in high esteem by Google, for precisely
+this reason: lots of people have linked to it simply because they
+like PuTTY, without us ever having to ask anyone to link to us. We
+feel that it would be an abuse of this esteem to use it to boost the
+ranking of random advertisers' web sites. If you want your web site
+to have a high Google ranking, we'd prefer that you achieve this the
+way we did - by being good enough at what you do that people will
+link to you simply because they like you.
+
+In particular, we aren't interested in trading links for money (see
+above), and we \e{certainly} aren't interested in trading links for
+other links (since we have no advertising on our web site, our
+Google ranking is not even directly worth anything to us). If we
+don't want to link to you for free, then we probably won't want to
+link to you at all.
+
+If you have software based on PuTTY, or specifically designed to
+interoperate with PuTTY, or in some other way of genuine interest to
+PuTTY users, then we will probably be happy to add a link to you on
+our Links page. And if you're running a mirror of the PuTTY web
+site, we're \e{definitely} interested.
+
\S{faq-sourceforge}{Question} Why don't you move PuTTY to
SourceForge?
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?
Having said all that, if you still really \e{want} to give us money,
we won't argue :-) The easiest way for us to accept donations is if
-you go to \W{http://www.e-gold.com}\cw{www.e-gold.com}, and deposit
-your donation in account number 174769. Then send us e-mail to let
-us know you've done so (otherwise we might not notice for months!).
-Alternatively, if e-gold isn't convenient for you, you can donate to
-\cw{<anakin@pobox.com>} using PayPal
-(\W{http://www.paypal.com/}\cw{www.paypal.com}).
+you send money to \cw{<anakin@pobox.com>} using PayPal
+(\W{http://www.paypal.com/}\cw{www.paypal.com}). Alternatively, if
+you don't trust PayPal, you could donate through e-gold
+(\W{http://www.e-gold.com}\cw{www.e-gold.com}): deposit your
+donation in account number 174769, then send us e-mail to let us
+know you've done so (otherwise we might not notice for months!).
Small donations (tens of dollars or tens of euros) will probably be
spent on beer or curry, which helps motivate our volunteer team to
something worthwhile, ask us first. If you don't like these terms,
feel perfectly free not to donate. We don't mind.
+\S{faq-permission}{Question} Can I have permission to put PuTTY on a
+cover disk / distribute it with other software / etc?
+
+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 (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)
+that you offer your own first-line technical support, to answer
+questions directly relating to the interaction of PuTTY with your
+particular environment. If your users mail us directly, we won't be
+able to give them very much help about things specific to your own
+setup.
+
\H{faq-misc} Miscellaneous questions
\S{faq-openssh}{Question} Is PuTTY a port of OpenSSH, or based on
projects / u / mdw / putty / blobdiff