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1 | \versionid $Id: faq.but,v 1.25 2002/05/11 16:45:29 simon Exp $ |
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2 | |
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3 | \A{faq} PuTTY FAQ |
4 | |
5 | This FAQ is published on the PuTTY web site, and also provided as an |
6 | appendix in the manual. |
7 | |
8 | \H{faq-support} Features supported in PuTTY |
9 | |
10 | In general, if you want to know if PuTTY supports a particular |
11 | feature, you should look for it on the |
12 | \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/}{PuTTY web site}. |
13 | In particular: |
14 | |
15 | \b try the |
16 | \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/changes.html}{changes |
17 | page}, and see if you can find the feature on there. If a feature is |
18 | listed there, it's been implemented. If it's listed as a change made |
19 | \e{since} the latest version, it should be available in the |
20 | development snapshots, in which case testing will be very welcome. |
21 | |
22 | \b try the |
23 | \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/wishlist.html}{Wishlist |
24 | page}, and see if you can find the feature there. If it's on there, |
25 | it probably \e{hasn't} been implemented. |
26 | |
a1d2976b |
27 | \S{faq-ssh2}{Question} Does PuTTY support SSH v2? |
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28 | |
29 | Yes. SSH v2 support has been available in PuTTY since version 0.50. |
30 | However, currently the \e{default} SSH protocol is v1; to select SSH |
31 | v2 if your server supports both, go to the SSH panel and change the |
32 | \e{Preferred SSH protocol version} option. |
33 | |
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34 | Public key authentication (both RSA and DSA) in SSH v2 is new in |
35 | version 0.52. |
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36 | |
a1d2976b |
37 | \S{faq-ssh2-keyfmt}{Question} Does PuTTY support reading OpenSSH or |
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38 | \cw{ssh.com} SSHv2 private key files? |
39 | |
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40 | Version 0.52 doesn't, but in the latest development snapshots |
41 | PuTTYgen can load OpenSSH private keys. We plan to add an export |
42 | feature so that it can save them as well, and we also plan to |
43 | support the \cw{ssh.com} key format. |
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44 | |
a1d2976b |
45 | \S{faq-ssh1}{Question} Does PuTTY support SSH v1? |
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46 | |
47 | Yes. SSH 1 support has always been available in PuTTY. |
48 | |
a1d2976b |
49 | \S{faq-localecho}{Question} Does PuTTY support local echo? |
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50 | |
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51 | Yes. Version 0.52 has proper support for local echo. |
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52 | |
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53 | In version 0.51 and before, local echo could not be separated from |
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54 | local line editing (where you type a line of text locally, and it is |
55 | not sent to the server until you press Return, so you have the |
56 | chance to edit it and correct mistakes \e{before} the server sees |
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57 | it). New in version 0.52, local echo and local line editing are |
58 | separate options, and by default PuTTY will try to determine |
59 | automatically whether to enable them or not, based on which protocol |
60 | you have selected and also based on hints from the server. If you |
61 | have a problem with PuTTY's default choice, you can force each |
62 | option to be enabled or disabled as you choose. The controls are in |
63 | the Terminal panel, in the section marked \q{Line discipline |
64 | options}. |
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65 | |
a1d2976b |
66 | \S{faq-disksettings}{Question} Does PuTTY support storing its |
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67 | settings in a disk file? |
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68 | |
69 | Not at present, although \k{config-file} in the documentation gives |
70 | a method of achieving the same effect. |
71 | |
a1d2976b |
72 | \S{faq-fullscreen}{Question} Does PuTTY support full-screen mode, |
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73 | like a DOS box? |
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74 | |
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75 | Yes; this is a new feature in version 0.52. |
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76 | |
babac7bd |
77 | \S{faq-password-remember}{Question} Does PuTTY have the ability to |
78 | remember my password so I don't have to type it every time? |
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79 | |
80 | No, it doesn't. |
81 | |
82 | Remembering your password is a bad plan for obvious security |
83 | reasons: anyone who gains access to your machine while you're away |
84 | from your desk can find out the remembered password, and use it, |
85 | abuse it or change it. |
86 | |
87 | In addition, it's not even \e{possible} for PuTTY to automatically |
88 | send your password in a Telnet session, because Telnet doesn't give |
89 | the client software any indication of which part of the login |
90 | process is the password prompt. PuTTY would have to guess, by |
91 | looking for words like \q{password} in the session data; and if your |
92 | login program is written in something other than English, this won't |
93 | work. |
94 | |
95 | In SSH, remembering your password would be possible in theory, but |
96 | there doesn't seem to be much point since SSH supports public key |
97 | authentication, which is more flexible and more secure. See |
98 | \k{pubkey} in the documentation for a full discussion of public key |
99 | authentication. |
100 | |
a1d2976b |
101 | \S{faq-hostkeys}{Question} Is there an option to turn off the |
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102 | annoying host key prompts? |
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103 | |
104 | No, there isn't. And there won't be. Even if you write it yourself |
105 | and send us the patch, we won't accept it. |
106 | |
107 | Those annoying host key prompts are the \e{whole point} of SSH. |
108 | Without them, all the cryptographic technology SSH uses to secure |
109 | your session is doing nothing more than making an attacker's job |
110 | slightly harder; instead of sitting between you and the server with |
111 | a packet sniffer, the attacker must actually subvert a router and |
112 | start modifying the packets going back and forth. But that's not all |
113 | that much harder than just sniffing; and without host key checking, |
114 | it will go completely undetected by client or server. |
115 | |
116 | Host key checking is your guarantee that the encryption you put on |
117 | your data at the client end is the \e{same} encryption taken off the |
118 | data at the server end; it's your guarantee that it hasn't been |
119 | removed and replaced somewhere on the way. Host key checking makes |
120 | the attacker's job \e{astronomically} hard, compared to packet |
121 | sniffing, and even compared to subverting a router. Instead of |
122 | applying a little intelligence and keeping an eye on Bugtraq, the |
123 | attacker must now perform a brute-force attack against at least one |
124 | military-strength cipher. That insignificant host key prompt really |
125 | does make \e{that} much difference. |
126 | |
127 | If you're having a specific problem with host key checking - perhaps |
128 | you want an automated batch job to make use of PSCP or Plink, and |
129 | the interactive host key prompt is hanging the batch process - then |
130 | the right way to fix it is to add the correct host key to the |
131 | Registry in advance. That way, you retain the \e{important} feature |
132 | of host key checking: the right key will be accepted and the wrong |
133 | ones will not. Adding an option to turn host key checking off |
134 | completely is the wrong solution and we will not do it. |
135 | |
a1d2976b |
136 | \S{faq-server}{Question} Will you write an SSH server for the PuTTY |
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137 | suite, to go with the client? |
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138 | |
139 | No. The only reason we might want to would be if we could easily |
140 | re-use existing code and significantly cut down the effort. We don't |
141 | believe this is the case; there just isn't enough common ground |
142 | between an SSH client and server to make it worthwhile. |
143 | |
144 | If someone else wants to use bits of PuTTY in the process of writing |
145 | a Windows SSH server, they'd be perfectly welcome to of course, but |
146 | I really can't see it being a lot less effort for us to do that than |
147 | it would be for us to write a server from the ground up. We don't |
148 | have time, and we don't have motivation. The code is available if |
149 | anyone else wants to try it. |
150 | |
67325335 |
151 | \S{faq-pscp-ascii}{Question} Can PSCP or PSFTP transfer files in |
152 | ASCII mode? |
153 | |
154 | Unfortunately not. This is a limitation of the file transfer |
155 | protocols: the SCP and SFTP protocols have no notion of transferring |
156 | a file in anything other than binary mode. |
157 | |
158 | SFTP is designed to be extensible, so it's possible that an |
159 | extension might be proposed at some later date that implements ASCII |
160 | transfer. But the PuTTY team can't do anything about it until that |
161 | happens. |
162 | |
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163 | \H{faq-ports} Ports to other operating systems |
164 | |
165 | The eventual goal is for PuTTY to be a multi-platform program, able |
166 | to run on at least Windows, MacOS and Unix. Whether this will |
167 | actually ever happen I have no idea, but it is the plan. A Mac port |
168 | has been started, but is only half-finished and currently not moving |
169 | very fast. |
170 | |
171 | Porting will become easier once PuTTY has a generalised porting |
172 | layer, drawing a clear line between platform-dependent and |
173 | platform-independent code. The general intention is for this porting |
174 | layer to evolve naturally as part of the process of doing the first |
175 | port. One particularly nasty part of this will be separating the |
176 | many configuration options into platform-dependent and |
177 | platform-independent ones; for example, the options controlling when |
178 | the Windows System menu appears will be pretty much meaningless |
179 | under X11 or perhaps other windowing systems, whereas Telnet Passive |
180 | Mode is universal and shouldn't need to be specified once for each |
181 | platform. |
182 | |
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183 | \S{faq-ports-general}{Question} What ports of PuTTY exist? |
184 | |
185 | Currently, PuTTY only runs on full Win32 systems. This includes |
186 | Windows 95, 98, and ME, and it includes Windows NT, Windows 2000 and |
187 | Windows XP. |
188 | |
189 | It does \e{not} include Windows CE (see \k{faq-wince}), and it does |
190 | not quite include the Win32s environment under Windows 3.1 (see |
191 | \k{faq-win31}). |
192 | |
193 | We do not have ports for any other systems at the present time. If |
194 | anyone told you we had a Unix port, or an iPaq port, or any other |
195 | port of PuTTY, they were mistaken. We don't. |
196 | |
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197 | \S{faq-wince}{Question} Will there be a port to Windows CE? |
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198 | |
199 | Probably not in the particularly near future. Despite sharing large |
200 | parts of the Windows API, in practice WinCE doesn't appear to be |
201 | significantly easier to port to than a totally different operating |
202 | system. |
203 | |
204 | However, PuTTY on portable devices would clearly be a useful thing, |
205 | so in the long term I hope there will be a WinCE port. |
206 | |
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207 | \S{faq-win31}{Question} Is there a port to Windows 3.1? |
208 | |
209 | PuTTY is a 32-bit application from the ground up, so it won't run on |
210 | Windows 3.1 as a native 16-bit program; and it would be \e{very} |
211 | hard to port it to do so, because of Windows 3.1's vile memory |
212 | allocation mechanisms. |
213 | |
214 | However, it is possible in theory to compile the existing PuTTY |
215 | source in such a way that it will run under Win32s (an extension to |
216 | Windows 3.1 to let you run 32-bit programs). In order to do this |
217 | you'll need the right kind of C compiler - modern versions of Visual |
218 | C at least have stopped being backwards compatible to Win32s. Also, |
219 | the last time we tried this it didn't work very well. |
220 | |
221 | If you're interested in running PuTTY under Windows 3.1, help and |
222 | testing in this area would be very welcome! |
223 | |
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224 | \S{faq-mac-port}{Question} Will there be a port to the Mac? |
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225 | |
226 | A Mac port was started once and is half-finished, but development |
227 | has been static for some time and the main PuTTY code has moved on, |
228 | so it's not clear how quickly development would resume even if |
229 | developer effort were available. |
230 | |
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231 | \S{faq-unix}{Question} Will there be a port to Unix? |
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232 | |
233 | I hope so, if only so that I can have an \cw{xterm}-like program |
234 | that supports exactly the same terminal emulation as PuTTY. If and |
235 | when we do do a Unix port, it will have a local-terminal back end so |
236 | it can be used like an \cw{xterm}, rather than only being usable as |
237 | a network utility. |
238 | |
a1d2976b |
239 | \S{faq-epoc}{Question} Will there be a port to EPOC? |
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240 | |
241 | I hope so, but given that ports aren't really progressing very fast |
242 | even on systems the developers \e{do} already know how to program |
243 | for, it might be a long time before any of us get round to learning |
244 | a new system and doing the port for that. |
245 | |
246 | \H{faq-embedding} Embedding PuTTY in other programs |
247 | |
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248 | \S{faq-dll}{Question} Is the SSH or Telnet code available as a DLL? |
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249 | |
250 | No, it isn't. It would take a reasonable amount of rewriting for |
251 | this to be possible, and since the PuTTY project itself doesn't |
252 | believe in DLLs (they make installation more error-prone) none of us |
253 | has taken the time to do it. |
254 | |
255 | Most of the code cleanup work would be a good thing to happen in |
256 | general, so if anyone feels like helping, we wouldn't say no. |
257 | |
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258 | \S{faq-vb}{Question} Is the SSH or Telnet code available as a Visual |
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259 | Basic component? |
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260 | |
261 | No, it isn't. None of the PuTTY team uses Visual Basic, and none of |
262 | us has any particular need to make SSH connections from a Visual |
263 | Basic application. In addition, all the preliminary work to turn it |
264 | into a DLL would be necessary first; and furthermore, we don't even |
265 | know how to write VB components. |
266 | |
267 | If someone offers to do some of this work for us, we might consider |
268 | it, but unless that happens I can't see VB integration being |
269 | anywhere other than the very bottom of our priority list. |
270 | |
a1d2976b |
271 | \S{faq-ipc}{Question} How can I use PuTTY to make an SSH connection |
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272 | from within another program? |
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273 | |
274 | Probably your best bet is to use Plink, the command-line connection |
275 | tool. If you can start Plink as a second Windows process, and |
276 | arrange for your primary process to be able to send data to the |
277 | Plink process, and receive data from it, through pipes, then you |
278 | should be able to make SSH connections from your program. |
279 | |
280 | This is what CVS for Windows does, for example. |
281 | |
282 | \H{faq-details} Details of PuTTY's operation |
283 | |
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284 | \S{faq-term}{Question} What terminal type does PuTTY use? |
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285 | |
286 | For most purposes, PuTTY can be considered to be an \cw{xterm} |
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287 | terminal. |
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288 | |
289 | PuTTY also supports some terminal control sequences not supported by |
290 | the real \cw{xterm}: notably the Linux console sequences that |
291 | reconfigure the colour palette, and the title bar control sequences |
292 | used by \cw{DECterm} (which are different from the \cw{xterm} ones; |
293 | PuTTY supports both). |
294 | |
295 | By default, PuTTY announces its terminal type to the server as |
296 | \c{xterm}. If you have a problem with this, you can reconfigure it |
297 | to say something else; \c{vt220} might help if you have trouble. |
298 | |
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299 | \S{faq-settings}{Question} Where does PuTTY store its data? |
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300 | |
301 | PuTTY stores most of its data (saved sessions, SSH host keys) in the |
302 | Registry. The precise location is |
303 | |
304 | \c HKEY_CURRENT_USER\Software\SimonTatham\PuTTY |
305 | |
306 | and within that area, saved sessions are stored under \c{Sessions} |
307 | while host keys are stored under \c{SshHostKeys}. |
308 | |
309 | PuTTY also requires a random number seed file, to improve the |
310 | unpredictability of randomly chosen data needed as part of the SSH |
311 | cryptography. This is stored by default in your Windows home |
312 | directory (\c{%HOMEDRIVE%\\%HOMEPATH%}), or in the actual Windows |
313 | directory (such as \c{C:\\WINDOWS}) if the home directory doesn't |
314 | exist, for example if you're using Win95. If you want to change the |
315 | location of the random number seed file, you can put your chosen |
316 | pathname in the Registry, at |
317 | |
318 | \c HKEY_CURRENT_USER\Software\SimonTatham\PuTTY\RandSeedFile |
319 | |
320 | \H{faq-howto} HOWTO questions |
321 | |
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322 | \S{faq-startmax}{Question} How can I make PuTTY start up maximised? |
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323 | |
324 | Create a Windows shortcut to start PuTTY from, and set it as \q{Run |
325 | Maximized}. |
326 | |
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327 | \S{faq-startsess}{Question} How can I create a Windows shortcut to |
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328 | start a particular saved session directly? |
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329 | |
330 | To run a PuTTY session saved under the name \q{\cw{mysession}}, |
331 | create a Windows shortcut that invokes PuTTY with a command line |
332 | like |
333 | |
334 | \c \path\name\to\putty.exe @mysession |
335 | |
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336 | \S{faq-startssh}{Question} How can I start an SSH session straight |
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337 | from the command line? |
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338 | |
339 | Use the command line \c{putty -ssh host.name}. Alternatively, create |
340 | a saved session that specifies the SSH protocol, and start the saved |
341 | session as shown in \k{faq-startsess}. |
342 | |
a1d2976b |
343 | \S{faq-cutpaste}{Question} How do I copy and paste between PuTTY and |
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344 | other Windows applications? |
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345 | |
346 | Copy and paste works similarly to the X Window System. You use the |
347 | left mouse button to select text in the PuTTY window. The act of |
348 | selection \e{automatically} copies the text to the clipboard: there |
349 | is no need to press Ctrl-Ins or Ctrl-C or anything else. In fact, |
350 | pressing Ctrl-C will send a Ctrl-C character to the other end of |
351 | your connection (just like it does the rest of the time), which may |
352 | have unpleasant effects. The \e{only} thing you need to do, to copy |
353 | text to the clipboard, is to select it. |
354 | |
355 | To paste the clipboard contents into a PuTTY window, by default you |
356 | click the right mouse button. If you have a three-button mouse and |
357 | are used to X applications, you can configure pasting to be done by |
358 | the middle button instead, but this is not the default because most |
359 | Windows users don't have a middle button at all. |
360 | |
361 | You can also paste by pressing Shift-Ins. |
362 | |
a1d2976b |
363 | \S{faq-tunnels}{Question} How do I use X forwarding and port |
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364 | forwarding? I can't find the Tunnels panel. |
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365 | |
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366 | This is a new feature in version 0.52. You should upgrade. |
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367 | |
a1d2976b |
368 | \S{faq-options}{Question} How do I use all PuTTY's features (public |
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369 | keys, port forwarding, SSH v2, etc.) in PSCP, PSFTP and Plink? |
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370 | |
371 | The command-line tools are currently rather short of command line |
372 | options to enable this sort of thing. However, you can use most of |
373 | PuTTY's features if you create a PuTTY saved session, and then use |
374 | the name of the saved session on the command line in place of a |
375 | hostname. This works for PSCP, PSFTP and Plink (but don't expect |
376 | port forwarding in the file transfer applications!). |
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377 | |
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378 | \S{faq-pscp}{Question} How do I use PSCP.EXE? When I double-click it |
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379 | gives me a command prompt window which then closes instantly. |
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380 | |
381 | PSCP is a command-line application, not a GUI application. If you |
382 | run it without arguments, it will simply print a help message and |
383 | terminate. |
384 | |
385 | To use PSCP properly, run it from a Command Prompt window. See |
386 | \k{pscp} in the documentation for more details. |
387 | |
a1d2976b |
388 | \S{faq-pscp-spaces}{Question} How do I use PSCP to copy a file whose |
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389 | name has spaces in? |
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390 | |
391 | If PSCP is using the traditional SCP protocol, this is confusing. If |
392 | you're specifying a file at the local end, you just use one set of |
393 | quotes as you would normally do: |
394 | |
395 | \c pscp "local filename with spaces" user@host: |
396 | \c pscp user@host:myfile "local filename with spaces" |
397 | |
398 | But if the filename you're specifying is on the \e{remote} side, you |
399 | have to use backslashes and two sets of quotes: |
400 | |
401 | \c pscp user@host:"\"remote filename with spaces\"" local_filename |
402 | \c pscp local_filename user@host:"\"remote filename with spaces\"" |
403 | |
404 | Worse still, in a remote-to-local copy you have to specify the local |
405 | file name explicitly, otherwise PSCP will complain that they don't |
406 | match (unless you specified the \c{-unsafe} option). The following |
407 | command will give an error message: |
408 | |
409 | \c c:\>pscp user@host:"\"oo er\"" . |
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410 | \c warning: remote host tried to write to a file called 'oo er' |
411 | \c when we requested a file called '"oo er"'. |
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412 | |
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413 | Instead, you need to specify the local file name in full: |
414 | |
415 | \c c:\>pscp user@host:"\"oo er\"" "oo er" |
416 | |
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417 | If PSCP is using the newer SFTP protocol, none of this is a problem, |
418 | and all filenames with spaces in are specified using a single pair |
419 | of quotes in the obvious way: |
420 | |
421 | \c pscp "local file" user@host: |
422 | \c pscp user@host:"remote file" . |
423 | |
424 | \H{faq-trouble} Troubleshooting |
425 | |
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426 | \S{faq-incorrect-mac}{Question} Why do I see \q{Incorrect MAC |
427 | received on packet}? |
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428 | |
429 | This is due to a bug in old SSH 2 servers distributed by |
430 | \cw{ssh.com}. Version 2.3.0 and below of their SSH 2 server |
431 | constructs Message Authentication Codes in the wrong way, and |
432 | expects the client to construct them in the same wrong way. PuTTY |
433 | constructs the MACs correctly by default, and hence these old |
434 | servers will fail to work with it. |
435 | |
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436 | If you are using PuTTY version 0.52 or better, this should work |
437 | automatically: PuTTY should detect the buggy servers from their |
438 | version number announcement, and automatically start to construct |
439 | its MACs in the same incorrect manner as they do, so it will be able |
440 | to work with them. |
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441 | |
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442 | If you are using PuTTY version 0.51 or below, you can enable the |
443 | workaround by going to the SSH panel and ticking the box labelled |
444 | \q{Imitate SSH 2 MAC bug}. It's possible that you might have to do |
445 | this with 0.52 as well, if a buggy server exists that PuTTY doesn't |
446 | know about. |
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447 | |
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448 | In this context MAC stands for Message Authentication Code. It's a |
449 | cryptographic term, and it has nothing at all to do with Ethernet |
450 | MAC (Media Access Control) addresses. |
451 | |
67325335 |
452 | \S{faq-pscp-protocol}{Question} Why do I see \q{Fatal: Protocol |
453 | error: Expected control record} in PSCP? |
454 | |
455 | This happens because PSCP was expecting to see data from the server |
456 | that was part of the PSCP protocol exchange, and instead it saw data |
457 | that it couldn't make any sense of at all. |
458 | |
459 | This almost always happens because the startup scripts in your |
460 | account on the server machine are generating output. This is |
461 | impossible for PSCP, or any other SCP client, to work around. You |
462 | should never use startup files (\c{.bashrc}, \c{.cshrc} and so on) |
463 | which generate output in non-interactive sessions. |
464 | |
465 | This is not actually a PuTTY problem. If PSCP fails in this way, |
466 | then all other SCP clients are likely to fail in exactly the same |
467 | way. The problem is at the server end. |
468 | |
a1d2976b |
469 | \S{faq-colours}{Question} I clicked on a colour in the Colours |
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470 | panel, and the colour didn't change in my terminal. |
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471 | |
472 | That isn't how you're supposed to use the Colours panel. |
473 | |
474 | During the course of a session, PuTTY potentially uses \e{all} the |
475 | colours listed in the Colours panel. It's not a question of using |
476 | only one of them and you choosing which one; PuTTY will use them |
477 | \e{all}. The purpose of the Colours panel is to let you adjust the |
478 | appearance of all the colours. So to change the colour of the |
479 | cursor, for example, you would select \q{Cursor Colour}, press the |
480 | \q{Modify} button, and select a new colour from the dialog box that |
481 | appeared. Similarly, if you want your session to appear in green, |
482 | you should select \q{Default Foreground} and press \q{Modify}. |
483 | Clicking on \q{ANSI Green} won't turn your session green; it will |
484 | only allow you to adjust the \e{shade} of green used when PuTTY is |
485 | instructed by the server to display green text. |
486 | |
a1d2976b |
487 | \S{faq-winsock2}{Question} Plink on Windows 95 says it can't find |
70706890 |
488 | \cw{WS2_32.DLL}. |
ee46ef84 |
489 | |
490 | Plink requires the extended Windows network library, WinSock version |
491 | 2. This is installed as standard on Windows 98 and above, and on |
492 | Windows NT, and even on later versions of Windows 95; but early |
493 | Win95 installations don't have it. |
494 | |
495 | In order to use Plink on these systems, you will need to download |
496 | the |
497 | \W{http://www.microsoft.com/windows95/downloads/contents/wuadmintools/s_wunetworkingtools/w95sockets2/}{WinSock 2 upgrade}: |
498 | |
499 | \c http://www.microsoft.com/windows95/downloads/contents/wuadmintools/ |
500 | \c s_wunetworkingtools/w95sockets2/ |
501 | |
a1d2976b |
502 | \S{faq-rekey}{Question} My PuTTY sessions close after an hour and |
70706890 |
503 | tell me \q{Server failed host key check}. |
ee46ef84 |
504 | |
505 | This is a bug in all versions of PuTTY up to and including 0.51. SSH |
506 | v2 servers from \cw{ssh.com} will require the key exchange to be |
507 | repeated one hour after the start of the connection, and PuTTY will |
508 | get this wrong. |
509 | |
32c37ecd |
510 | Upgrade to version 0.52 and the problem should go away. |
ee46ef84 |
511 | |
a1d2976b |
512 | \S{faq-outofmem}{Question} After trying to establish an SSH 2 |
70706890 |
513 | connection, PuTTY says \q{Out of memory} and dies. |
ee46ef84 |
514 | |
515 | If this happens just while the connection is starting up, this often |
516 | indicates that for some reason the client and server have failed to |
517 | establish a session encryption key. Somehow, they have performed |
518 | calculations that should have given each of them the same key, but |
519 | have ended up with different keys; so data encrypted by one and |
520 | decrypted by the other looks like random garbage. |
521 | |
522 | This causes an \q{out of memory} error because the first encrypted |
523 | data PuTTY expects to see is the length of an SSH message. Normally |
524 | this will be something well under 100 bytes. If the decryption has |
525 | failed, PuTTY will see a completely random length in the region of |
526 | two \e{gigabytes}, and will try to allocate enough memory to store |
527 | this non-existent message. This will immediately lead to it thinking |
528 | it doesn't have enough memory, and panicking. |
529 | |
530 | If this happens to you, it is quite likely to still be a PuTTY bug |
531 | and you should report it (although it might be a bug in your SSH |
532 | server instead); but it doesn't necessarily mean you've actually run |
533 | out of memory. |
534 | |
9accb45d |
535 | \S{faq-outofmem2}{Question} When attempting a file transfer, either |
536 | PSCP or PSFTP says \q{Out of memory} and dies. |
537 | |
538 | This is almost always caused by your login scripts on the server |
539 | generating output. PSCP or PSFTP will receive that output when they |
540 | were expecting to see the start of a file transfer protocol, and |
541 | they will attempt to interpret the output as file-transfer protocol. |
542 | This will usually lead to an \q{out of memory} error for much the |
543 | same reasons as given in \k{faq-outofmem}. |
544 | |
545 | This is a setup problem in your account on your server, \e{not} a |
546 | PSCP/PSFTP bug. Your login scripts should \e{never} generate output |
547 | during non-interactive sessions; secure file transfer is not the |
548 | only form of remote access that will break if they do. |
549 | |
550 | On Unix, a simple fix is to ensure that all the parts of your login |
551 | script that might generate output are in \c{.profile} (if you use a |
552 | Bourne shell derivative) or \c{.login} (if you use a C shell). |
553 | Putting them in more general files such as \c{.bashrc} or \c{.cshrc} |
554 | is liable to lead to problems. |
555 | |
556 | \S{faq-psftp-slow} PSFTP transfers files much slower than PSCP. |
557 | |
558 | We believe this is because the SFTP and SSH2 protocols are less |
559 | efficient at bulk data transfer than SCP and SSH1, because every |
560 | block of data transferred requires an acknowledgment from the far |
561 | end. It would in theory be possible to queue several blocks of data |
562 | to get round this speed problem, but as yet we haven't done the |
563 | coding. If you really want this fixed, feel free to offer to help. |
564 | |
a1d2976b |
565 | \S{faq-bce}{Question} When I run full-colour applications, I see |
70706890 |
566 | areas of black space where colour ought to be. |
f1453e5c |
567 | |
568 | You almost certainly need to enable the \q{Use background colour to |
569 | erase screen} setting in the Terminal panel. Note that if you do |
570 | this in mid-session, it won't take effect until you reset the |
571 | terminal (see \k{faq-resetterm}). |
572 | |
a1d2976b |
573 | \S{faq-resetterm}{Question} When I change some terminal settings, |
70706890 |
574 | nothing happens. |
f1453e5c |
575 | |
576 | Some of the terminal options (notably Auto Wrap and |
577 | background-colour screen erase) actually represent the \e{default} |
578 | setting, rather than the currently active setting. The server can |
579 | send sequences that modify these options in mid-session, but when |
580 | the terminal is reset (by server action, or by you choosing \q{Reset |
581 | Terminal} from the System menu) the defaults are restored. |
582 | |
583 | If you want to change one of these options in the middle of a |
584 | session, you will find that the change does not immediately take |
585 | effect. It will only take effect once you reset the terminal. |
586 | |
a1d2976b |
587 | \S{faq-altgr}{Question} I can't type characters that require the |
70706890 |
588 | AltGr key. |
ee46ef84 |
589 | |
32c37ecd |
590 | In PuTTY version 0.51, the AltGr key was broken. Upgrade to version |
591 | 0.52. |
ee46ef84 |
592 | |
a1d2976b |
593 | \S{faq-idleout}{Question} My PuTTY sessions unexpectedly close after |
70706890 |
594 | they are idle for a while. |
ee46ef84 |
595 | |
596 | Some types of firewall, and almost any router doing Network Address |
597 | Translation (NAT, also known as IP masquerading), will forget about |
598 | a connection through them if the connection does nothing for too |
599 | long. This will cause the connection to be rudely cut off when |
600 | contact is resumed. |
601 | |
602 | You can try to combat this by telling PuTTY to send \e{keepalives}: |
603 | packets of data which have no effect on the actual session, but |
604 | which reassure the router or firewall that the network connection is |
605 | still active and worth remembering about. |
606 | |
607 | Keepalives don't solve everything, unfortunately; although they |
608 | cause greater robustness against this sort of router, they can also |
609 | cause a \e{loss} of robustness against network dropouts. See |
610 | \k{config-keepalive} in the documentation for more discussion of |
611 | this. |
612 | |
a1d2976b |
613 | \S{faq-timeout}{Question} PuTTY's network connections time out too |
70706890 |
614 | quickly when network connectivity is temporarily lost. |
ee46ef84 |
615 | |
616 | This is a Windows problem, not a PuTTY problem. The timeout value |
617 | can't be set on per application or per session basis. To increase |
618 | the TCP timeout globally, you need to tinker with the Registry. |
619 | |
620 | On Windows 95, 98 or ME, the registry key you need to change is |
621 | |
622 | \c HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\ |
623 | \c MSTCP\MaxDataRetries |
624 | |
625 | (it must be of type DWORD in Win95, or String in Win98/ME). |
626 | |
627 | On Windows NT or 2000, the registry key is |
628 | |
629 | \c HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\ |
630 | \c Parameters\TcpMaxDataRetransmissions |
631 | |
632 | and it must be of type DWORD. |
633 | |
634 | Set the key's value to something like 10. This will cause Windows to |
635 | try harder to keep connections alive instead of abandoning them. |
636 | |
a1d2976b |
637 | \S{faq-puttyputty}{Question} When I \cw{cat} a binary file, I get |
ee46ef84 |
638 | `PuTTYPuTTYPuTTY' on my command line. |
639 | |
a5a6cb30 |
640 | Don't do that, then. |
ee46ef84 |
641 | |
642 | This is designed behaviour; when PuTTY receives the character |
643 | Control-E from the remote server, it interprets it as a request to |
644 | identify itself, and so it sends back the string \q{\cw{PuTTY}} as |
645 | if that string had been entered at the keyboard. Control-E should |
646 | only be sent by programs that are prepared to deal with the |
647 | response. Writing a binary file to your terminal is likely to output |
648 | many Control-E characters, and cause this behaviour. Don't do it. |
649 | It's a bad plan. |
650 | |
a5a6cb30 |
651 | To mitigate the effects, you could configure the answerback string |
652 | to be empty (see \k{config-answerback}); but writing binary files to |
653 | your terminal is likely to cause various other unpleasant behaviour, |
654 | so this is only a small remedy. |
655 | |
babac7bd |
656 | \S{faq-wintitle}{Question} When I \cw{cat} a binary file, my window |
657 | title changes to a nonsense string. |
ee46ef84 |
658 | |
a5a6cb30 |
659 | Don't do that, then. |
ee46ef84 |
660 | |
661 | It is designed behaviour that PuTTY should have the ability to |
662 | adjust the window title on instructions from the server. Normally |
663 | the control sequence that does this should only be sent |
664 | deliberately, by programs that know what they are doing and intend |
665 | to put meaningful text in the window title. Writing a binary file to |
666 | your terminal runs the risk of sending the same control sequence by |
667 | accident, and cause unexpected changes in the window title. Don't do |
668 | it. |
669 | |
babac7bd |
670 | \S{faq-password-fails}{Question} My keyboard stops working once |
671 | PuTTY displays the password prompt. |
59c1f1f6 |
672 | |
673 | No, it doesn't. PuTTY just doesn't display the password you type, so |
674 | that someone looking at your screen can't see what it is. |
675 | |
676 | Unlike the Windows login prompts, PuTTY doesn't display the password |
677 | as a row of asterisks either. This is so that someone looking at |
678 | your screen can't even tell how \e{long} your password is, which |
679 | might be valuable information. |
680 | |
b5bee048 |
681 | \S{faq-keyboard}{Question} One or more function keys don't do what I |
682 | expected in a server-side application. |
683 | |
684 | If you've already tried all the relevant options in the PuTTY |
685 | Keyboard panel, you may need to mail the PuTTY maintainers and ask. |
686 | |
687 | It is \e{not} usually helpful just to tell us which application, |
688 | which server operating system, and which key isn't working; in order |
689 | to replicate the problem we would need to have a copy of every |
690 | operating system, and every application, that anyone has ever |
691 | complained about. |
692 | |
693 | PuTTY responds to function key presses by sending a sequence of |
694 | control characters to the server. If a function key isn't doing what |
695 | you expect, it's likely that the character sequence your application |
696 | is expecting to receive is not the same as the one PuTTY is sending. |
697 | Therefore what we really need to know is \e{what} sequence the |
698 | application is expecting. |
699 | |
700 | The simplest way to investigate this is to find some other terminal |
701 | environment, in which that function key \e{does} work; and then |
702 | investigate what sequence the function key is sending in that |
703 | situation. One reasonably easy way to do this on a Unix system is to |
704 | type the command \c{cat}, and then press the function key. This is |
705 | likely to produce output of the form \c{^[[11~}. You can also do |
706 | this in PuTTY, to find out what sequence the function key is |
707 | producing in that. Then you can mail the PuTTY maintainers and tell |
708 | us \q{I wanted the F1 key to send \c{^[[11~}, but instead it's |
709 | sending \c{^[OP}, can this be done?}, or something similar. |
710 | |
711 | You should still read the |
712 | \W{http://www.chiark.greenend.org.uk/~sgtatham/putty/feedback.html}{Feedback |
713 | page} on the PuTTY website (also provided as \k{feedback} in the |
714 | manual), and follow the guidelines contained in that. |
715 | |
1d2a9c9c |
716 | \S{faq-broken-openssh31}{Question} Since my SSH server was upgraded to |
717 | OpenSSH 3.1p1, I can no longer connect with PuTTY. |
718 | |
719 | There is a known problem when OpenSSH has been built against an |
720 | incorrect version of OpenSSL; the quick workaround is to configure |
721 | PuTTY to use SSH protocol 2 and the Blowfish cipher. |
722 | |
723 | This is not a PuTTY-specific problem; if you try to connect with |
724 | another client you'll likely have similar problems. |
725 | |
9712b085 |
726 | Configurations known to be broken (and symptoms): |
1d2a9c9c |
727 | |
728 | \b SSH 2 with AES cipher (PuTTY says "Assertion failed! Expression: |
729 | (len & 15) == 0" in sshaes.c, or "Out of memory", or crashes) |
730 | |
9712b085 |
731 | \b SSH 2 with 3DES (PuTTY says "Incorrect MAC received on packet") |
732 | |
1d2a9c9c |
733 | \b SSH 1 with Blowfish (PuTTY says "Incorrect CRC received on |
734 | packet") |
735 | |
736 | \b SSH 1 with 3DES |
737 | |
738 | For more details and OpenSSH patches, see |
739 | \W{http://bugzilla.mindrot.org/show_bug.cgi?id=138}{bug 138} in the |
740 | OpenSSH BTS. |
741 | |
ee46ef84 |
742 | \H{faq-secure} Security questions |
743 | |
a1d2976b |
744 | \S{faq-publicpc}{Question} Is it safe for me to download PuTTY and |
70706890 |
745 | use it on a public PC? |
ee46ef84 |
746 | |
747 | It depends on whether you trust that PC. If you don't trust the |
748 | public PC, don't use PuTTY on it, and don't use any other software |
749 | you plan to type passwords into either. It might be watching your |
750 | keystrokes, or it might tamper with the PuTTY binary you download. |
751 | There is \e{no} program safe enough that you can run it on an |
752 | actively malicious PC and get away with typing passwords into it. |
753 | |
754 | If you do trust the PC, then it's probably OK to use PuTTY on it |
755 | (but if you don't trust the network, then the PuTTY download might |
756 | be tampered with, so it would be better to carry PuTTY with you on a |
757 | floppy). |
758 | |
a1d2976b |
759 | \S{faq-cleanup}{Question} What does PuTTY leave on a system? How can |
70706890 |
760 | I clean up after it? |
ee46ef84 |
761 | |
762 | PuTTY will leave some Registry entries, and a random seed file, on |
763 | the PC (see \k{faq-settings}). If you are using PuTTY on a public |
764 | PC, or somebody else's PC, you might want to clean these up when you |
765 | leave. You can do that automatically, by running the command |
766 | \c{putty -cleanup}. |
767 | |
a1d2976b |
768 | \S{faq-dsa}{Question} How come PuTTY now supports DSA, when the |
70706890 |
769 | website used to say how insecure it was? |
ee46ef84 |
770 | |
771 | DSA has a major weakness \e{if badly implemented}: it relies on a |
772 | random number generator to far too great an extent. If the random |
773 | number generator produces a number an attacker can predict, the DSA |
774 | private key is exposed - meaning that the attacker can log in as you |
775 | on all systems that accept that key. |
776 | |
777 | The PuTTY policy changed because the developers were informed of |
778 | ways to implement DSA which do not suffer nearly as badly from this |
779 | weakness, and indeed which don't need to rely on random numbers at |
780 | all. For this reason we now believe PuTTY's DSA implementation is |
781 | probably OK. However, if you have the choice, we still recommend you |
782 | use RSA instead. |
783 | |
784 | \H{faq-admin} Administrative questions |
785 | |
a1d2976b |
786 | \S{faq-domain}{Question} Would you like me to register you a nicer |
70706890 |
787 | domain name? |
ee46ef84 |
788 | |
789 | No, thank you. Even if you can find one (most of them seem to have |
790 | been registered already, by people who didn't ask whether we |
791 | actually wanted it before they applied), we're happy with the PuTTY |
792 | web site being exactly where it is. It's not hard to find (just type |
793 | \q{putty} into \W{http://www.google.com/}{google.com} and we're the |
794 | first link returned), and we don't believe the administrative hassle |
795 | of moving the site would be worth the benefit. |
796 | |
797 | In addition, if we \e{did} want a custom domain name, we would want |
798 | to run it ourselves, so we knew for certain that it would continue |
799 | to point where we wanted it, and wouldn't suddenly change or do |
800 | strange things. Having it registered for us by a third party who we |
801 | don't even know is not the best way to achieve this. |
802 | |
a1d2976b |
803 | \S{faq-webhosting}{Question} Would you like free web hosting for the |
70706890 |
804 | PuTTY web site? |
ee46ef84 |
805 | |
806 | We already have some, thanks. |
807 | |
a1d2976b |
808 | \S{faq-sourceforge}{Question} Why don't you move PuTTY to |
70706890 |
809 | SourceForge? |
ee46ef84 |
810 | |
811 | Partly, because we don't want to move the web site location (see |
812 | \k{faq-domain}). |
813 | |
814 | Also, security reasons. PuTTY is a security product, and as such it |
815 | is particularly important to guard the code and the web site against |
816 | unauthorised modifications which might introduce subtle security |
817 | flaws. Therefore, we prefer that the CVS repository, web site and |
818 | FTP site remain where they are, under the direct control of system |
819 | administrators we know and trust personally, rather than being run |
820 | by a large organisation full of people we've never met and which is |
821 | known to have had breakins in the past. |
822 | |
823 | No offence to SourceForge; I think they do a wonderful job. But |
824 | they're not ideal for everyone, and in particular they're not ideal |
825 | for us. |
826 | |
a1d2976b |
827 | \S{faq-mailinglist1}{Question} Why can't I subscribe to the |
70706890 |
828 | putty-bugs mailing list? |
ee46ef84 |
829 | |
830 | Because you're not a member of the PuTTY core development team. The |
831 | putty-bugs mailing list is not a general newsgroup-like discussion |
832 | forum; it's a contact address for the core developers, and an |
833 | \e{internal} mailing list for us to discuss things among ourselves. |
834 | If we opened it up for everybody to subscribe to, it would turn into |
835 | something more like a newsgroup and we would be completely |
836 | overwhelmed by the volume of traffic. It's hard enough to keep up |
837 | with the list as it is. |
838 | |
a1d2976b |
839 | \S{faq-mailinglist2}{Question} If putty-bugs isn't a |
70706890 |
840 | general-subscription mailing list, what is? |
ee46ef84 |
841 | |
842 | There isn't one, that we know of. |
843 | |
844 | If someone else wants to set up a mailing list for PuTTY users to |
845 | help each other with common problems, that would be fine with us; |
846 | but the PuTTY team would almost certainly not have the time to read |
847 | it, so any questions the list couldn't answer would have to be |
848 | forwarded on to us by the questioner. In any case, it's probably |
849 | better to use the established newsgroup \cw{comp.security.ssh} for |
850 | this purpose. |
851 | |
a1d2976b |
852 | \S{faq-donations}{Question} How can I donate to PuTTY development? |
ee46ef84 |
853 | |
854 | Please, \e{please} don't feel you have to. PuTTY is completely free |
855 | software, and not shareware. We think it's very important that |
856 | \e{everybody} who wants to use PuTTY should be able to, whether they |
857 | have any money or not; so the last thing we would want is for a |
858 | PuTTY user to feel guilty because they haven't paid us any money. If |
859 | you want to keep your money, please do keep it. We wouldn't dream of |
860 | asking for any. |
861 | |
862 | Having said all that, if you still really \e{want} to give us money, |
863 | we won't argue :-) The easiest way for us to accept donations is if |
864 | you go to \W{http://www.e-gold.com}\cw{www.e-gold.com}, and deposit |
865 | your donation in account number 174769. Then send us e-mail to let |
866 | us know you've done so (otherwise we might not notice for months!). |
9cd3f7b0 |
867 | Alternatively, if e-gold isn't convenient for you, you can donate to |
868 | \cw{<anakin@pobox.com>} using PayPal |
869 | (\W{http://www.paypal.com/}\cw{www.paypal.com}). |
ee46ef84 |
870 | |
871 | Small donations (tens of dollars or tens of euros) will probably be |
872 | spent on beer or curry, which helps motivate our volunteer team to |
873 | continue doing this for the world. Larger donations will be spent on |
874 | something that actually helps development, if we can find anything |
9cd3f7b0 |
875 | (perhaps new hardware, or a copy of Windows XP), but if we can't |
ee46ef84 |
876 | find anything then we'll just distribute the money among the |
877 | developers. If you want to be sure your donation is going towards |
878 | something worthwhile, ask us first. If you don't like these terms, |
879 | feel perfectly free not to donate. We don't mind. |
880 | |
606398fb |
881 | \S{faq-sillyputty}{Question} Where can I buy silly putty? |
882 | |
883 | You're looking at the wrong web site; the only PuTTY we know about |
884 | here is the name of a computer program. |
885 | |
886 | If you want the kind of putty you can buy as an executive toy, the |
887 | PuTTY team can personally recommend Thinking Putty, which you can |
888 | buy from Crazy Aaron's Putty World, at |
889 | \W{http://www.puttyworld.com}\cw{www.puttyworld.com}. |
890 | |
a1d2976b |
891 | \S{faq-pronounce}{Question} How do I pronounce PuTTY? |
ee46ef84 |
892 | |
893 | Exactly like the normal word \q{putty}. Just like the stuff you put |
894 | on window frames. (One of the reasons it's called PuTTY is because |
895 | it makes Windows usable. :-) |