The missing link

[David Cureton <davidc@catapult.com>]

Hi,
    I am using a SuSE 9.2 system as an NFS server and are seeing some 
strange results. The server holds our home directories and exports a 
number of disks to all the other workstations in the group.  The setup 
is somewhat strange in that the first NFS mount, a directory called 
"server", containing all the mountpoint for the subsequent mounting of 
the other exported partitions


eg.  /server exported from the fileserver contains

drwxr-xr-x   4 root root 288 2005-04-01 15:32 .
lrwxrwxrwx   1 root root  27 2005-03-24 16:25 ./Shared -> 
/server/volumes/vol0/Shared
lrwxrwxrwx   1 root root  26 2005-03-24 10:55 ./Staff -> 
/server/volumes/vol0/Staff
lrwxrwxrwx   1 root root  27 2005-03-24 10:52 ./users -> 
/server/volumes/vol0/users/
lrwxrwxrwx   1 root root  26 2005-03-24 10:51 ./usr1 -> 
/server/volumes/vol0/usr1/
lrwxrwxrwx   1 root root  26 2005-03-24 10:51 ./usr2 -> 
/server/volumes/vol0/usr2/
lrwxrwxrwx   1 root root  25 2005-03-24 10:53 ./usr3 -> 
/server/volumes/vol0/usr3
lrwxrwxrwx   1 root root  25 2005-03-24 10:54 ./usr4 -> 
/server/volumes/vol0/usr4
lrwxrwxrwx   1 root root  25 2005-03-24 10:54 ./usr5 -> 
/server/volumes/vol0/usr5
drwxr-xr-x   5 root root 120 2005-03-29 13:52 ./volumes
drwxr-xr-x  12 root root 272 2005-04-01 16:00 ./volumes/vol0
drwxr-xr-x   4 root root  80 2005-03-23 17:53 ./volumes/vol1
drwxr-xr-x   2 root root  48 2005-03-29 13:52 ./volumes/vol2


The fstab of a client therefore looks like:

melbourne-fs3:/server      /server    nfs     defaults  0 2
melbourne-fs3:/server/volumes/vol2      /server/volumes/vol2     nfs     
defaults  0 2
melbourne-fs3:/server/volumes/vol1      /server/volumes/vol1     nfs     
defaults  0 2
melbourne-fs3:/server/volumes/vol0      /server/volumes/vol0     nfs     
defaults  0 2


The clients  then have  a link from /Staff  --> /server/Staff which in 
it self is a link to /server/volumes/vol0/Staff
i.e. /Staff (link on client's root)  --> /server/Staff (link on nfs 
mount) --> /server/volumes/vol0/Staff (Real NFS exported directory)

This works fine most of the time and allows us to  move data between 
disks without having to change links of the clients. It also allows us 
to add new disks an easily bring them into use.

However on occasion we have noticed that the /server/Staff link just 
disappears for some SuSE9.2 clients and the user no longer has access to 
there home directory. All other clients still have the link available 
and they are fine.

It appears that the client looses the /server/Staff  symbolic link out 
of its NFS cache and forgets about it until the cache expires and does a 
readdirplus on the /server directory.   All other accesses to the 
/server director on the NFS client prior to the cache update  only check 
the attibutes of the /server directory and it contents (excluding the 
/server/Staff link) and as nothing has changed, uses the cached data.

I am at a loss as to how I can debug this NFS problem  further.  I have 
done copious amounts of searching on google and have not found a similar 
issue.

Server and client particulars are:

Both SuSE 9.2
Server 'uname -a': Linux melbourne-fs3 2.6.8-24.14-default #1 Tue Mar 29 
09:27:43 UTC 2005 i686 athlon i386 GNU/Linux
Kernel based NFS server

Client 'uname -a': Linux cockatoo 2.6.8-24-default #1 Wed Oct 6 09:16:23 
UTC 2004 i686 athlon i386 GNU/Linux



Any assistance as to how I should go about debuging such a beast would 
be greatly appreciated, especially as it only happens 1 a fortnight 
further componding being able to resolve it

David









-------------------------------------------------------
This SF.Net email is sponsored by: NEC IT Guy Games.
Get your fingers limbered up and give it your best shot. 4 great events, 4
opportunities to win big! Highest score wins.NEC IT Guy Games. Play to
win an NEC 61 plasma display. Visit http://www.necitguy.com/?r=20
_______________________________________________
NFS maillist  -  NFS@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/nfs