Hi all,

I am examining the workings of a terminal server and have come up to a dead end.

The setup is a central PC with XDMCP getting connections from two peripheral PCs. All PCs have normal Slackware installations (12.0 the central one, 13.1 the others). XDMCP works fine and the users login to KDE. The users have a common directory with appropriate permissions for group work.

The problem is file locking. More than one users can open and work on the same file in the common directory, eg. foto editing the same jpg with GIMP.

Googling around I found that file locking is advisory in Linux, meaning its up to the applications to honour it. Also that there is a mand (mandatory locking) mount option which seems like the solution, but there are warnings [1], [2]. Other finds point to the use of versioning systems (svn, git) to take care of file locking, or network file systems (cifs, nfs): I'd prefer not to burden casual users with having to come to terms with a versioning system, and the network file systems seem wrong since the users work locally.

Considering Linux is a multiuser OS I am taken aback from this apparent lack of file locking support and tend to think I'm missing something obvious.

Has anyone experienced/solved a similar setup? Any words of advice? Many thanks in advance.

A couple of last points. The common directory is on a normal mount (ext3, RAID1), fstab entry:
And I'm aware of options like TSLP, but I'd rather resolve the issue generically.



[1] man fcntl(2) says "The Linux implementation of mandatory locking is unreliable."
[2] http://www.mjmwired.net/kernel/Docum...ry-locking.txt

No, you aren't. Linux's behavior is consistent with its Unix roots.

You can perhaps use standard file permissions to "lock out" other users from accessing/modifying it once someone has acquired the lock. That would probably require a special script/executable.

So Richard, if I understand you right, I'd have to devise a script which will do the file locking? Recursively for all files in a given dir, intervening in the file open of all applications? Is it really that complex?

Well, you aren't going to be able to get a script to intervene in the file open of all applications.

You can have a script that your users can invoke to give themselves exclusive rights to a given set of files. Or run your stuff under windows, where NTFS provides the file system semantics that appear to match what you expect. (I don't know if the linux implementation of NTFS does the same.)

Thank you for your input. I'd rather stay away from windows and am still rather bemused by all this. I guess I'm in for a long set of trials and errors.