How to Mount and Unmount Filesystems in Linux?

In Linux, everything (pictures, binary files, text files, directories, etc.) is treated as a file. Understanding how to organize and access files efficiently is crucial for system administration. The mount and umount commands are essential tools for this purpose.

In this article, we will explore these two commands in detail. The mount command allows us to attach a filesystem to a directory in the filesystem hierarchy, while the umount command detaches it. These operations can be performed on hard disks, USB drives, and other storage devices. Important: All mount and unmount operations require sudo or root privileges.

Listing Storage Devices

Before mounting or unmounting filesystems, we need to identify available storage devices in the Linux system.

Using fdisk Command

sudo fdisk -l

[sudo] password for user:
Disk /dev/sda: 298.1 GiB, 320072933376 bytes, 625142448 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x0002d5a1

Device     Boot     Start       End   Sectors   Size Id Type
/dev/sda1  *         2048 620969983 620967936 296.1G 83 Linux
/dev/sda2       620972030 625141759   4169730     2G  5 Extended
/dev/sda5       620972032 625141759   4169728     2G 82 Linux swap / Solaris

Partition 2 does not start on physical sector boundary.

Using lsblk Command

lsblk

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0 298.1G  0 disk
??sda2   8:2    0     1K  0 part
??sda5   8:5    0     2G  0 part [SWAP]
??sda1   8:1    0 296.1G  0 part /

Viewing Currently Mounted Filesystems

The mount command without arguments displays all currently mounted filesystems:

mount

sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
udev on /dev type devtmpfs (rw,nosuid,relatime,size=985120k,nr_inodes=246280,mode=755)
/dev/sda1 on / type ext4 (rw,relatime,errors=remount-ro,data=ordered)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
...

Alternatively, you can view mount information using:

cat /proc/mounts

Understanding the mount output format:

/dev/sda1 on / type ext4 (rw,relatime,errors=remount-ro,data=ordered)

• /dev/sda1 Device/filesystem name

• on / Mount point (directory where filesystem is attached)

• type ext4 Filesystem type

• Options in parentheses Mount options (read-write, etc.)

Filtering Specific Filesystem Types

Use the -t option to display information about specific filesystem types:

mount -t ext4

/dev/sda1 on / type ext4 (rw,relatime,errors=remount-ro,data=ordered)

Mounting a Filesystem

To mount a filesystem, follow these steps:

1. Create a mount point directory:

   sudo mkdir /mnt/mydisk
   

2. Mount the filesystem:

   sudo mount -t filesystem_type device_name mount_point
   

   Example:

   sudo mount -t ext4 /dev/sdb1 /mnt/mydisk
   

For USB drives and other removable media, the process is identical. Once mounted, you can access the filesystem contents through the mount point directory.

Unmounting a Filesystem

The umount command detaches a mounted filesystem. You can specify either the device name or mount point:

sudo umount /dev/sdb1

Or:

sudo umount /mnt/mydisk

After unmounting, files in the mount point directory are no longer accessible.

Unmounting Multiple Filesystems

You can unmount multiple filesystems simultaneously:

sudo umount /dev/sdb1 /dev/sdc1

Lazy Unmount

Use the -l (lazy) option when you're unsure if read/write operations are ongoing:

sudo umount -l /dev/sdb1

This option detaches the filesystem immediately but cleans up references later, waiting for ongoing operations to complete.

Force Unmount

The -f (force) option forcefully unmounts a filesystem even during active operations:

sudo umount -f /dev/sdb1

Warning: Force unmounting can cause data loss. Use this option primarily for unreachable network shares or when the system is unresponsive.

Common Mount Options

Conclusion

The mount and umount commands are fundamental tools for Linux filesystem management. Understanding these commands enables efficient handling of storage devices, from permanent hard drives to temporary USB media. Always ensure proper unmounting to prevent data corruption and maintain system integrity.