NFS: mount.nfs: Protocol not supported

Question

I want to mount the NFS share of a Zyxel NSA310s NAS. Showmount, called on the client machine, shows the share:

$ showmount 10.0.0.100 -e
Export list for 10.0.0.100:
/i-data/7fd943bf/nfs/zyxelNFS *

The client's /etc/fstab contains the line:

10.0.0.100:/i-data/7fd943bf/nfs/zyxelNFS /media/nasNFS nfs rw  0 0

But mounting does not work:

sudo mount /media/nasNFS/ -v
mount.nfs: timeout set for Mon May 25 17:34:46 2015
mount.nfs: trying text-based options 'vers=4,addr=10.0.0.100,clientaddr=10.0.0.2'
mount.nfs: mount(2): Protocol not supported
mount.nfs: trying text-based options 'addr=10.0.0.100'
mount.nfs: prog 100003, trying vers=3, prot=6
mount.nfs: trying 10.0.0.100 prog 100003 vers 3 prot TCP port 2049
mount.nfs: portmap query retrying: RPC: Program/version mismatch
mount.nfs: prog 100003, trying vers=3, prot=17
mount.nfs: trying 10.0.0.100 prog 100003 vers 3 prot UDP port 2049
mount.nfs: portmap query failed: RPC: Program/version mismatch
mount.nfs: Protocol not supported

nfs-common is installed. What else can be missing?

Kevin · Answer

[root@sousvide mnt]# mount projects/
mount.nfs: Protocol not supported

The solution to this error in my case was adjusting the Freenas (BSD) settings "Authorized Hosts and IP Addresses" to allow the target machine in question access...
/etc/fstab had an entry like
x.x.x.x:/mnt/media/projects /mnt/projects nfs defaults,timeo=900,retrans=5,_netdev,noauto 0 0

Swiss Frank · Answer

I'm getting this error on Fedora 31.  It turns out the drive is already mounted...

Martin Konrad · Answer

I ran into the "Protocol not supported" error as well. In my case the root cause turned out to be a subtle issue with a DNS reverse entry.

Background: I was using NFSv4 and had the following entries in /etc/exports:

/srv/nfs      *.example.com(ro,fsid=root,insecure,no_subtree_check,async,root_squash)
/srv/nfs/data myhost.example.com(rw,sync,no_subtree_check)

Instead of the FQDN, running host 1.2.3.4 returned pointers to both "myhost." and "myhost.example.com.". My NFS server seemed to look at the first PTR entry in the DNS response only which didn't match the wildcard in /etc/exports and as a consequence it blocked NFSv4 from this host. So if you use rules based on host names in /etc/exports double-check that DNS reverse lookups work correctly for your clients.

Lambert · Answer

To summarize the steps taken to get to the answer:

According to the output given the NFS server does not like NFSv4 nor UDP. To see the capabilities of the NFS server you can use rpcinfo 10.0.0.100 (you might extend the command to filter for nfs by: |egrep "service|nfs")

Apparently the only version supported by the server is version 2:

rpcinfo 10.0.0.100 |egrep "service|nfs"
program version netid     address                service    owner
100003  2       udp       0.0.0.0.8.1            nfs        unknown
100003  2       tcp       0.0.0.0.8.1            nfs        unknown

Solution to mount the export is to use mount option vers=2 either on the commandline:

mount -o rw,vers=2 10.0.0.100:/i-data/7fd943bf/nfs/zyxelNFS /media/nasNFS

or by editing the /etc/fstab:

10.0.0.100:/i-data/7fd943bf/nfs/zyxelNFS /media/nasNFS nfs rw,vers=2  0 0

Another approach may be to change the NFS server to support version 3 (or even 4).

daniel · Answer

try to use this option

....   nfs    rsize=8192,wsize=8192,timeo=14,intr 0 0

NFS: mount.nfs: Protocol not supported

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