How to mount and unmount a filesystem in Linux

Mount a filesystem now, or make it permanent in /etc/fstab. Run as root.

Unmounting a filesystem a process or database is using will fail, or if forced can cause errors, so check it with fuser/lsof first. Add it to /etc/fstab only when the entry is correct: a bad fstab can stop the system booting.

# Mount an existing filesystem to a directory
sudo mount /dev/sdb1 /data

# Mount everything defined in /etc/fstab
sudo mount -a

# Unmount
sudo umount /data

# If it is busy, see who is using it first
sudo fuser -vm /data

# Lazy unmount (detach once no longer busy)
sudo umount -l /data

# Persistent: add a line to /etc/fstab, then test with: sudo mount -a
#   UUID=<uuid>  /data  xfs  defaults  0 0