5.9.6.2.2. Terminating Access With umount

Next, all access to the disk drive must be terminated. For partitions with active file systems on them, this is done using the umount command. If a swap partition exists on the disk drive, it must be either be deactivated with the swapoff command, or the system should be rebooted.
Unmounting partitions with the umount command requires you to specify either the device file name, or the partition's mount point:
 umount /dev/hda2 umount /home 
A partition can only be unmounted if it is not currently in use. If the partition cannot be unmounted while at the normal runlevel, boot into rescue mode and remove the partition's /etc/fstab entry.
When using swapoff to disable swapping to a partition, you must specify the device file name representing the swap partition:
 swapoff /dev/hda4 
If swapping to a swap partition cannot be disabled using swapoff, boot into rescue mode and remove the partition's /etc/fstab entry.