I have a trouble with NFS client-side attribute caching. I'm using some servers, one is an NFS server and the others are NFS client servers.
All servers are Debian(lenny, 2.6.26-2-amd64 of Linux) and versions are following.
% dpkg -l | grep nfs
ii libnfsidmap2 0.20-1 An nfs idmapping library
ii nfs-common 1:1.1.2-6lenny1 NFS support files common to client and server
ii nfs-kernel-server 1:1.1.2-6lenny1 support for NFS kernel server
In the NFS server, /etc/exports is written as following:
/export-path 192.168.0.0/255.255.255.0(async,rw,no_subtree_check)
In the NFS clients, /etc/fstab is written as following:
server:/export-path /mountpoint nfs rw,hard,intr,rsize=8192,async 0 0
As you can see, "async" option is used for multi-clients access performance. However, sometimes this can cause false-caching errors.
Since I am maintaining many servers (and I have not so strong permission to change the mount options), I don't want to modify /etc/exports nor /etc/fstab. I think it is sufficient if I have a command-line tool that "cleans" NFS client-side attribute cache with a user permission.
Please let me know if there such commands.
Thanks,
(Appended)
I mean by "false-caching errors",
% ls -l /data/1/kabe/foo
ls: cannot access /data/1/kabe/foo: No such file or directory
% ssh another-server 'touch /data/1/kabe/foo'
% ls -l /data/1/kabe/foo
ls: cannot access /data/1/kabe/foo: No such file or directory
Sometimes such cases happen. The problem is not a file content but file attributes(=dentries information) since NFS says it guarantees Close-to-Open consistency.
Answer
Depending on what you mean by "false-caching errors", running sync may get you what you need. This will flush all filesystem buffers.
If needed, you can also clear out the VM caches in the kernel using /proc/sys/vm/drop_caches.
# To free pagecache
echo 1 > /proc/sys/vm/drop_caches
# To free dentries and inodes
echo 2 > /proc/sys/vm/drop_caches
# To free pagecache, dentries and inodes
echo 3 > /proc/sys/vm/drop_caches