Re: Switch-off problem

[Bob McGowan]

Jan Willem Stumpel wrote:

Ron Johnson wrote:

On 07/19/08 04:46, Jan Willem Stumpel wrote:[..]

Now my theory is that the switch-off problem occurs after the
 following events:

1 - I mount the remote usb drive.
2 - my wife switches off her computer.
3 - I try to umount the remote usb drive -- this cannot be
    done.

I suppose the shutdown program also tries to umount nfs mounts, but fails, and then instead of skipping this step, just hangs. Does this make sense? If so, is there a way to solve this problem?

Manually "umount -l" the remote drive before you shutdown?

This does not work. Manually umounting the nfs drive (after the
computer which hosts the nfs drive is switched off) just leads to
a hang, whether the "lazy" switch is applied or not. In fact I
cannot even type the umount command entirely: the system hangs
immediately after typing the first 3 characters (including the
leading /) of the mount point.

   strace -o nfs_hang.trace -f bash -c 'umount /...' &

This hanging at "cannot even type the umount command entirely: the system hangs immediately after typing the first 3 characters" sounds very strange. The NFS subsystem can't know that a umount has been entered until the shell takes the full command line, forks a copy of itself and then execs the new command. At least, that's how I understand things. ;) I'd suggest focusing on this, though I have no good suggestions for debugging it. The only thing I can think of is to run a subshell under strace, to a file, and try the umount in the subshell. Perhaps there'll be something there to indicate what's going on. I've never worked with strace and an interactive program like a shell, so you may not get much from the above. You could force non-interactive operation by using the shell '-c' argument: By backgrounding the program, you should get a prompt from which you can issue a 'kill' to the 'bash' process. If you can kill it, then strace should print to and close the trace file "normally".

<<deleted NFS comments>>

Regards, Jan

--
Bob McGowan

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