[DRBD-user] symlink /var/lib/nfs

Dave Dykstra dwdha at drdykstra.us
Thu Jun 8 04:29:48 CEST 2006

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

On Tue, Jun 06, 2006 at 08:37:07PM -0700, mike wrote:
> On 6/6/06, Montse Seisdedos <mseisdedos at mediafusion.es> wrote:
> >
> >Hello everybody:
> >
> >I'm trying to built a HA nfs server  in a FC4.
> >
> >I've been reading about link or not to link /var/lib/nfs to the share fs.
> >I did it, but when i try to start nfs i get the following errors
> >
> >Jun  6 11:01:17 mfs-01 exportfs[5969]: can't open /var/lib/nfs/rmtab for
> >reading
> >Jun  6 11:01:17 mfs-01 exportfs[5969]: could not open /var/lib/nfs/xtab for
> >locking
> >Jun  6 11:01:17 mfs-01 exportfs[5969]: could not open /var/lib/nfs/etab for
> >locking
> >Jun  6 11:01:17 mfs-01 exportfs[5969]: can't lock /var/lib/nfs/etab for
> >writing
> >Jun  6 11:01:17 mfs-01 exportfs[5969]: could not open /var/lib/nfs/xtab for
> >locking
> >Jun  6 11:01:17 mfs-01 exportfs[5969]: can't lock /var/lib/nfs/xtab for
> >writing
> >
> ># ls -l /var/lib/nfs
> >lrwxrwxrwx  1 root root 12 jun  6 10:02 /var/lib/nfs -> /u/varlibnfs
> ># ls -la /var/lib/nfs/
> >total 120
> >drwxr-xr-x   4 root    root     4096 jun  6 10:08 .
> >drwxr-xr-x  17 root    root    77824 jun  6 10:07 ..
> >-rw-r--r--   1 root    root        0 sep 27  2005 etab
> >-rw-r--r--   1 root    root        0 sep 27  2005 rmtab
> >drwxr-xr-x   2 root    root     4096 sep 27  2005 rpc_pipefs
> >drwx------   2 rpcuser rpcuser  4096 sep 27  2005 statd:
> >-rw-------   1 root    root        0 s:ep 27  2005 state
> >-rw-r--r--   1 root    root        0 sep 27  2005 xtab

I think those errors show that you must not be properly stopping and
starting all the nfs services.  I'm not very familiar with what the
packages are called in FC4, but please post your haresources file and
hopefully someone can point out what's wrong with it.  You should only
be attempting to access the shared /var/lib/nfs files on the machine
that's the active server and so that directory should be available.

> >somebody can help me, is really necesary to mv /var/lib/nfs to the share 
> >fs?
> I was getting weird errors too trying to symlink the shared NFS dir
> (I'm using NFS v4 on CentOS 4.3) so DRBD could propogate it.
> What I realized (and I could be wrong, but it appears to work) is that
> it doesn't *need* to be shared, as long as on failover you restart the
> NFS services (portmapper, nfsd, all the RPC crap) - it seems to pick
> up where it left off.
> The only thing I can think is possibly if it was in the middle of some
> process/transaction like writing a large file when it crashed, it
> might have been able to persist that, but for my setup, those were
> odds I could live with.

As far as I have been able to figure out, /var/lib/nfs contains the state
of exported filesystems and of locks.  If you're re-exporting everything
when you start up the HA service, re-using the exported state from the
previous active server doesn't really help much.  In theory you should be
able to keep locks across fail-overs, but in practice I've not been able
to get that to work.  I was experimenting with that in order to figure out
what exactly should be on the http://linux-ha.org/HaNFS web page but I got
stuck on that problem so I asked for help on the linux-ha mailing list and
stopped working on the web page.  I never did figure out an answer and
then I got too busy with other things and never got back to it.  So in
practice I don't think it's really necessary to have the /var/lib/nfs
symlinks even though that's been the advice for the linux-ha+drbd+NFS
configuration for a long time.  I really should clean up that page.

- Dave Dykstra

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