I've got a weird NFS server problem that I can't figure out.

I've had a long-time running NFS server on a Debian Stable 3.1 system. Within the last few weeks, I noticed that clients were hanging when trying to access the NFS shared files on my file server. Also, the startup of NFS is suddenly very slow, and I frequently get RPC Timed Out error messages when mounting clients.

Here are the symptoms:

1. "Mount server:/exportedfile /localfile" usually works, but takes 15+ secs to connect, and often (20% of the time) fails with an "RPC Timeout" failure. Previously, they connected almost immediately. The problem is worse if I use a script to mount several shares in quick succession.
2. Clients frequently hang trying to access previously-mounted NFS shares.
3. Start up of NFS-Kernel server hangs for 60+ secs during the "exporting files" step.


Here is data I know:

1. The system is a stable Debian and has not been messed with (other than Debian apt-get upgrades). It has been running for almost a year without any trouble.
2. rpc.mounted and portmap are running and don't put any errors in the logs.
3. The problems appears on multiple clients. I'm pretty sure it's a server issue.
4. rpcinfo reports the server is running fine
5. All the directories listed in "exports" seem OK. I can access those files locally on the server without any trouble.
6. /etc/hosts.allow has an entry of "ALL: 192.168.1.0/24(rw,async,no_root_squash)", so I don't think that's the problem
7. All other programs running on this server (music, ntp, etc) seem fine.
8. The kernel is a stock Debian 2.6.8.2-386
9. Network traffic is low. Nothing "weird" is showing up in ethereal scans.
10. I have plenty of disk space and plenty of free memory.


Here is a clue I think might be significant:

1. running "exportfs -r -v" lists the files in the "/etc/exports" file quickly, then pauses for a very long time before it loads the previously mounted exports into the kernel. This step is very quick, however, if I remove all the entries from /var/lib/nfs/rmtab.


This problem has me totally confused. I don't know where else to look for troubleshooting clues. Anybody have any suggestions?

Thanks!

Casey Bralla
http://www.NerdWorld.org

I had the "RPC Timeout..." errors when I wasnt running the portmap service properly. I just did a reinstall (only portmap) and everything worked well. You could try that out.

Good suggestion, since the symptoms are just like not having portmap running. Unfortunately, it didn't do any good.

I'll probably try reinstalling NFS too.

It turns out that my problem was with my DNS server, which was not serving reverse name lookups.

I presume that the NFS server was updated as part of a Debian security enhancement. (I load these ugrades automatically every night.)

Putting name and IP values into my /etc/hosts file fixed the problem. I've also now added reverse domain lookups to my DNS server and every thing is fine.


So.... NFS acted flaky because portmap didn't work because DNS did not serve reverse names. Fixed!