On Mon, 23 May 2005 [EMAIL PROTECTED] wrote: > I've been investigating a bug report about bind mounting an autofs > controlled mount point. It is indeed disastrous for autofs. It would be > simple enough it to check and fail silently but that won't give sensible > behavior. > > What should the semantics be for these type of mount requests against > autofs?
So in the reported bug, the person did a bind mount on the toplevel autofs mount point. I was expecting to see a particular server, or more likely a particular NFS-mounted dir from that server, as the subject of the mount. It's not too unreasonable to expect any of these to work transparently, since autofs does its magic when the user looks up a name in the autofs directory, and it shouldn't matter whether he got there from the original mount point or the bind target. The kernel module would send the name to the userspace daemon, which would spawn a submount daemon or mount something in the original location, and the subdir and whatever is mounted on it ought to be visible even from the bind target. But evidently that's not true. As you say, if it can't be made to work transparently, the next best is to make the bind mount fail. A distant third choice is to say "don't do that" in the documnetation. Sorry, no insights in the code; I'm just acting as a sounding board. I wonder what the person is trying to do. Maybe a chroot jail, but it's unlikely that the client would be allowed to use the whole automount mechanism. How about this concept (not what's described in the bug report): the client's homedir server is autofs mounted (i.e. a submount process is spawned) and the server dir is bind-mounted into the jail. Then a shell is jailed. He can use anything on his server, using the out-of-jail autofs daemon to mount the filesystems, but no other host will be accessible. Certainly a "move" mount should be illegal: how would the userspace daemon know where the main mount point had gone? Am I correct that if a filesystem is unmounted by force majeure, e.g. manually by the sysadmin or any other reason, the userspace daemon that mounted it may be a little unhappy but it will not suffer any permanent damage? I've always assumed that to be true, in case of stubborn messed-up mounts. James F. Carter Voice 310 825 2897 FAX 310 206 6673 UCLA-Mathnet; 6115 MSA; 405 Hilgard Ave.; Los Angeles, CA, USA 90095-1555 Email: [EMAIL PROTECTED] http://www.math.ucla.edu/~jimc (q.v. for PGP key) _______________________________________________ autofs mailing list [email protected] http://linux.kernel.org/mailman/listinfo/autofs
