Re: CygwinX at MS Terminalserver?

[Steffen Sledz <sledz@zone42.org>]

Am 12.08.2010 18:04, schrieb Jon TURNEY:
> On 12/08/2010 08:31, Steffen Sledz wrote:
>> Does anyone has experiences running CygwinX at an MS
>> Terminalserver? We like to use it at one based on Windows
>> Server 2003 with NTFS.
>>
>> Is it possible to run multiple XWin instances for multiple
>> user sessions in parallel?
>>
>> Any suggestions how to setup the rights in /tmp, /var/log,
>> /var/run, etc.?
> 
> You shouldn't change the rights on any of these, as this could
> affect the security or functioning of other cygwin apps.
> 
> Fortunately, you shouldn't need to, as, provided each X server
> instance has a unique display number, everything should work :-)

This seems not to be right. :(

Here are the results of my tests:

testuser0001 starts an X server using the item "XWin Server" from the start menu. This results in the creation of some files/dirs with these rights.

------------>snip<----------------
$ ls -la /tmp /var/log
/tmp:
total 1
drwxrwxrwt+ 1 Administrator Administrators  0 Aug 13 08:55 .
drwxr-xr-x+ 1 Administrator Administrators  0 May 17 15:51 ..
-r--r--r--  1 testuser0001  Domain Users   11 Aug 13 08:54 .X0-lock
drwxrwxrwt+ 1 testuser0001  Domain Users    0 Aug 13 08:54 .X11-unix

/var/log:
total 2316
drwxrwxrwt+ 1 Administrator Administrators       0 Aug 13 08:54 .
drwxr-xr-x+ 1 Administrator Administrators       0 May 17 16:21 ..
-rw-r--r--  1 Administrator Administrators  139786 Aug 13 08:48 setup.log
-rw-r--r--  1 Administrator Administrators 2219958 Aug 13 08:48 setup.log.full
-rw-r--r--  1 testuser0001  Domain Users      4447 Aug 13 08:54 XWin.0.log
------------>snap<----------------

Now testuser0002 tries to start another server in parallel. This gives this error:

/usr/bin/startxwin:  Resource temporarily unavailable (errno 11):  Another X server instance is running on DISPLAY :0

Now testuser0001 stops his server by using the "Exit" item from the server menu. After this the files/dirs look like this.

------------>snip<----------------
$ ls -la /tmp /var/log
/tmp:
total 0
drwxrwxrwt+ 1 Administrator Administrators 0 Aug 13 08:58 .
drwxr-xr-x+ 1 Administrator Administrators 0 May 17 15:51 ..
drwxrwxrwt+ 1 testuser0001  Domain Users   0 Aug 13 08:58 .X11-unix

/var/log:
total 2316
drwxrwxrwt+ 1 Administrator Administrators       0 Aug 13 08:54 .
drwxr-xr-x+ 1 Administrator Administrators       0 May 17 16:21 ..
-rw-r--r--  1 Administrator Administrators  139786 Aug 13 08:48 setup.log
-rw-r--r--  1 Administrator Administrators 2219958 Aug 13 08:48 setup.log.full
-rw-r--r--  1 testuser0001  Domain Users      4871 Aug 13 08:58 XWin.0.log
------------>snap<----------------

Now testuser0002 tries to start a server. This results in an error popup:

------------>snip<----------------
A fatal error has occured and Cygwin/X will now exit.

Cannot open log file "/var/log/XWin.0.log"

Please open /var/log/XWin.%s.log for more information.

Vendor: The Cygwin/X Project
Release: 1.8.2.0 (10802000)
Contact: cygwin-xfree@cygwin.com
Build Date: 2010-08-06

XWin was started with the following command-line:

X :0 -multiwindow
------------>snap<----------------

> Where you may experience problems is if the X server crashes
> whilst being run by an Administrator, and then a non-Adminstrator
> user tries to run X server using the same display number, which
> will fail due being unable to remove the stale lock file and unix
> socket.  Unfortunately, there is no obvious way to fix that
> without introducing a security hole (not that it is known to be
> secure anyhow)

I think that's not the problem in this case.

Steffen


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