How to check the NFS version for a mounted export

Checking the NFS version on the client confirms which protocol version the kernel actually negotiated for a mounted export. This matters when a mount was expected to use NFSv4.2, when an application depends on NFSv4 behavior, or when a server-side change may have left an older NFSv3 mount active.

Linux records active mount details in the kernel mount table. findmnt can target the exact path and print the filesystem type plus options, where vers= or nfsvers= shows the version used by that mount; an nfs4 filesystem type confirms the NFSv4 family but does not by itself identify the minor version.

Run the check on the client that owns the mount and use the mounted path, not just a path copied from /etc/fstab or an automount map. If a service mounted the export with different options than expected, the live mount table is the proof surface, and saved configuration should be reviewed only after the active version is known.

Steps to check the NFS version for a mounted export:

Open a terminal on the Linux client that has the export mounted.
Check the target path with findmnt and print only the columns needed to identify the live NFS version.
```
$ findmnt --target /mnt/projects --types nfs,nfs4 --output TARGET,FSTYPE,OPTIONS
TARGET        FSTYPE OPTIONS
/mnt/projects nfs4   rw,relatime,vers=4.2,rsize=1048576,wsize=1048576,proto=tcp
```
Replace /mnt/projects with the mounted export path on the client. The vers=4.2 option is the negotiated protocol version for this active mount.
Read the FSTYPE and OPTIONS columns together.

nfs usually indicates an NFSv3 style mount, while nfs4 indicates the NFSv4 family. Use the explicit vers= or nfsvers= option when it is present because it can show the minor version, such as 4.1 or 4.2.

If findmnt returns no row, the path is not currently mounted as NFS in that client namespace. Check the actual mount point before changing /etc/fstab or server export settings.

List all mounted NFS exports when the exact mount point is uncertain.

$ findmnt --types nfs,nfs4 --output TARGET,SOURCE,FSTYPE,OPTIONS
TARGET        SOURCE                              FSTYPE OPTIONS
/mnt/projects files.example.net:/srv/nfs/projects nfs4   rw,relatime,vers=4.2,rsize=1048576,wsize=1048576,proto=tcp
/mnt/archive  files.example.net:/srv/nfs/archive  nfs    rw,relatime,vers=3,rsize=1048576,wsize=1048576,proto=tcp

Use the row whose TARGET matches the application path or mount point being checked.

Cross-check the same mount with nfsstat when the client utility package is available.
```
$ nfsstat --mounts
/mnt/projects from files.example.net:/srv/nfs/projects
 Flags: rw,vers=4.2,rsize=1048576,wsize=1048576,proto=tcp,sec=sys,clientaddr=192.0.2.10,addr=192.0.2.40
```
On Ubuntu and Debian clients, nfsstat is installed with nfs-common. On RHEL, CentOS Stream, Fedora, and compatible systems, it is installed with nfs-utils.

Related: How to install an NFS client on Ubuntu
Related: How to install an NFS client on CentOS Stream, RHEL, and Fedora
Compare the live version with the version you expected.

A mismatch means the mounted export should be remounted with the intended options or the server should be checked for version policy, but do not treat a saved /etc/fstab entry as proof until the live mount table shows the expected vers= value.

Related: How to manually mount an NFS export on Linux
Related: How to configure an NFSv4-only server