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Nfs administration commands

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Update Exported Shares

After editing /etc/exports run
exportfs -a

List Exported Shares

# showmount -e
Export list for myserver:
/export/home       10.1.0.0/24
#

List Mounts on NFS-Server

# showmount 
Hosts on myserver:
10.1.0.15
#

List active Protocols/Services

To list local services run:
# rpcinfo -p
   program vers proto   port  service
    100000    4   tcp    111  portmapper
    100000    3   tcp    111  portmapper
    100000    2   tcp    111  portmapper
    100000    4   udp    111  portmapper
    100000    3   udp    111  portmapper
    100000    2   udp    111  portmapper
    100024    1   udp  48555  status
    100024    1   tcp  49225  status
    100003    2   tcp   2049  nfs
    100003    3   tcp   2049  nfs
    100003    4   tcp   2049  nfs
    100227    2   tcp   2049
    100227    3   tcp   2049
    100003    2   udp   2049  nfs
    100003    3   udp   2049  nfs
    100003    4   udp   2049  nfs
    100227    2   udp   2049
    100227    3   udp   2049
    100021    1   udp  51841  nlockmgr
    100021    3   udp  51841  nlockmgr
    100021    4   udp  51841  nlockmgr
    100021    1   tcp  37319  nlockmgr
    100021    3   tcp  37319  nlockmgr
    100021    4   tcp  37319  nlockmgr
    100005    1   udp  57376  mountd
    100005    1   tcp  37565  mountd
    100005    2   udp  36255  mountd
    100005    2   tcp  36682  mountd
    100005    3   udp  54897  mountd
    100005    3   tcp  51122  mountd
Above output is from an NFS server. You can also run it for remote servers by passing an IP. NFS clients usually just run status and portmapper:
# rpcinfo -p 10.1.0.15
   program vers proto   port  service
    100000    4   tcp    111  portmapper
    100000    3   tcp    111  portmapper
    100000    2   tcp    111  portmapper
    100000    4   udp    111  portmapper
    100000    3   udp    111  portmapper
    100000    2   udp    111  portmapper
    100024    1   udp  44152  status
    100024    1   tcp  53182  status

Mounting NFSv4 Shares

The difference in mounting is that you need to provide "nfs4" and transport and port options like this:
mount -t nfs4 -o proto=tcp,port=2049 server:/export/home /mnt

Ensure NFSv4 Id Mapper Running

When using NFSv4 share ensure to have the id mapper running on all clients. On Debian you need to explicitely start it:
service idmapd start

Configure NFSv4 User Mappings

You might want to set useful NFSv4 default mappings and some explicit mappings for unknown users:
#cat /etc/idmapd.conf
[...]
[Mapping]
Nobody-User = nobody
Nobody-Group = nogroup

[Static]
someuser@otherserver = localuser

Tuning NFS Client Mount Options

Try the following client mount option changes:
  • Use "hard" instead of "soft"
  • Add "intr" to allow for dead server and killable client programs
  • Increase "mtu" to maximum
  • Increase "rsize" and "wsize" to maximum supported by clients and server
  • Remove "sync"
After changing and remounting check for effective options using "nfsstat -m" which will give you a list like this:
$ nfsstat -m
/data from 10.1.0.16:/data
 Flags:	rw,relatime,vers=4.0,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,port=0,timeo=600,retrans=2,sec=sys,clientaddr=10.1.0.16,local_lock=none,addr=10.1.0.15
$

Tuning NFS Server

For the exported filesystem mount options:
  • Use "noatime"
  • Use "async" if you can (risk of data corruption)
  • Use "no_subtree_check"
Other than that:
  • Use CFQ I/O scheduler
  • Increase /sys/block/sda/device/block/sda/queue/max_sectors_kb
  • Check /sys/block/sda/device/block/sda/queue/read_ahead_kb
  • Increase number of nfsd threads

Getting NFS Statistics

Use "nfsstat" for detailed NFS statistics! The options are "-c" for client and "-s" for server statistics. On the server caching statistics are most interesting,
# nfsstat -o rc
Server reply cache:
hits       misses     nocache
0          63619      885550  
#
on the client probably errors and retries. Also note that you can get live per-interval results when running with "--sleep=<interval>". For example
# nfsstat -o fh --sleep=2