Re: nfs unmount: can it be done from (to) a croaked system?

["Jonathan A. Kollasch" <jakllsch%kollasch.net@localhost>]

On Tue, May 23, 2017 at 11:15:55AM +0000, Christos Zoulas wrote:
> In article <201705221949.56425.mlr%rse.com@localhost>,
> Mike Riechers  <mlr%rse.com@localhost> wrote:
> >Hello, all.
> >
> >A few weeks ago one of our computers bit the big one: the root disc
> >drive croaked (bad).  One of these days I'll get to replacing the
> >drive, but I'm not shedding too many tears, for 1)it's a little used
> >system, and 2) the important data was on other drives.
> >
> >What is annoying is, however, the fact that we had files nfs mounted
> >on our network that were serviced from this computer.  Now any time we
> >do a "df", an unmount, or any operation that references the nfs from
> >that computer, the program "locks up," and ps shows:
> >
> >             D       Marks a process in device or other short term,
> >                     uninterruptible wait.
> >
> >I did a "df" on one of our computers a couple of weeks ago, and ps
> >still shows the process in device or other short term, uninterruptible
> >wait.  So much for short term.
> >
> >I believe that the df inquiry is going to wait forever, demanding to
> >palaver with the nfs that isn't there anymore.  (It's inconvenient to
> >try to remember to do a "df -l," and of course, there goes info
> >concerning my other nfs mounts.)
> >
> >I tried a "umount -fh mydeadcomputer.com" on the nfs mount, but all
> >that got me was a locked-up "umount."
> >
> >I've rebooted one computer, and of course that worked, but I'd rather
> >not do the same thing to all the rest.  Is there a more elegant
> >solution I'm missing?
> >
> >I've tried starting up another computer to imitate the failed one as
> >to IP and interface name, but that didn't work.  It looks like the
> >only thing that will satisfy my live computers is an actual commune
> >with the dead nfs system (or a reboot).
> >
> >Any help?  Thanks in advance,
> 
> Umount -f is supposed to work, but it never has. Please file a PR.
> 

It sometimes does, but you pretty much always have to use -R with dead NFS.

	Jonathan Kollasch