How to Force‑Unmount a Busy NFS Share on Linux: Step‑by‑Step Guide

When an NFS mount reports “device is busy”, you must identify and stop the processes using the mount point before forcing an unmount.

Using lsof

The lsof command lists all open files on a specific filesystem, revealing which processes are accessing the NFS directory. # lsof /mnt/nfs/linoxide_srv/ Typical output shows processes such as bash and vim with their PIDs. After confirming that the user has saved work, you can terminate the processes:

# kill -9 24098

# kill -9 24125

Using fuser

The fuser command identifies processes that prevent unmounting. Use the -m option to specify the mount point and -v for a verbose listing. # fuser -mv /mnt/nfs/linoxide_srv/ Output displays the user, PID, access mode, and command. To kill all processes accessing the mount point, add the -k option:

# fuser -kmv /mnt/nfs/linoxide_srv/

Standard unmount

After terminating the interfering processes, attempt a normal unmount: # umount /mnt/nfs/linoxide_srv/ If successful, df -h will no longer list the mount point.

Lazy (delayed) unmount

If the mount remains busy, you can perform a lazy unmount with the -l flag. This removes the mount from the namespace while allowing existing references to continue until they close. # umount -l /mnt/nfs/linoxide_srv/ Check the exit status ( echo $?) – a zero indicates success. Verify the mount point is gone with df -h.

Using lsof and fuser to locate and terminate blocking processes, followed by a regular or lazy unmount, reliably resolves "device is busy" errors on NFS mounts.