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Mounting and unmounting

The commands mount and umount both mount and unmount a filesystem. They cannot survive reboot, if you want to make permanent changes you must add fields in /etc/fstab. This guide will go over the basics of mount, umount and /etc/fstab

mount

mount command mounts a storage device or filesystem, making it accessible. This command does not permanently mount a filesystem or device.

Common Uses

mount -o option There are several other options you can put into a mount. The most common ones are remount, rw (mount as read write), and ro (read only)

mount -a This will mount all points that are mentioned in /etc/fstab

mount /dev/location /path/to/mount - This will mount the device location to the mount point.

Examples of mount

  1. Lets say you have a usb drive that you want to mount and you want to mount it to /media/usb. You used lsblk and see that it's device /sdd1

mkdir /media/usb
mount /dev/sdd1 /media/usb
  1. Lets say you have a drive /dev/sdd1/ and it's currently mounted to /mnt/dev1/. It is read-only but you want to change to it read-write so you can change some files.

mount -o remount,rw /dev/sdd1 /mnt/dev1

Note how this is useful only if a filesystem is already mounted.

  1. Now lets say you have a drive /dev/sdd1/ and it's currently mounted to /mnt/dev1/. It is read-write but now you want to change to it read-only so other's can't write on it.

mount -o remount,ro /dev/sdd1 /mnt/dev1
  1. Mount /dev/sde to /mnt/dev2 but have it read-only

mount -o ro  /dev/sde /mnt/dev2
  1. Mount /dev/sde to /mnt/dev2 but have it read-write

mount -o rw  /dev/sde /mnt/dev2
  1. You made some changes to /etc/fstab. Now you want to access the mount point.

mount -a

umount

umount unmounts filesystem or disk .

Common Options

-f Forcefully unmounts filesystem or disk.

-l Lazy unmount: Detaches the filesystem and cleans up filesystem when it's not busy anymore.

Examples of umount

  1. Lets say you want to unmount /mnt/dev1 point
umount /mnt/dev1
  1. Lets say you used umount onf /mnt/dev1 and it says umount: /mnt/dev1: device is busy.You want to forcefully unmount it.

umount -f /mnt/dev1
  1. Now lets say you used umount -f /mnt/dev1 and it still doesn't work. You still want to unmount it.

umount -l /mnt/dev1

/etc/fstab

/etc/fstab file can be used to define how disk partitions, various other block devices, or remote filesystems should be mounted into the filesystem.

Line Syntax :

device        dir        type        options        dump fsck

The device can be the /dev/device or block UUID which could be found using


blkid -no UUID /device/path

Examples of /etc/fstab

  1. This is an example of how a fstab would look
#device        dir        type        options        dump fsck

/dev/mapper/centos-swap swap  swap  defaults  0 0
/swapfile swap  swap  defaults  0 0
/dev/sda1 /mnt/dev1 ext4  defaults  0 0
UUID=5fcca3995-7dd7-4d9b-bc4d-db6ea2594cb5  swap  swap  defaults  0 0

Notice the differences between swap partitions, UUID , swapfile, and mount points look.

  1. Add swap partition for /dev/sdd1 to /etc/fstab

2a. Get the UUID and append to /etc/fstab



lsblk -no UUID /dev/sdd1 >> /etc/fstab

2b. Find the UUID number on last line and add to it.


UUID=5fcca3995-7dd7-4d9b-bc4d-db6ea2594cb5  swap  swap  defaults  0 0

Note: Dont forget to add the UUID= at the beginning of the line.

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