How to use the command `mount` (with examples)

The mount command in Linux is a powerful utility used for managing how and where operating system partitions are connected and accessed in a filesystem tree. By leveraging mount, users can attach filesystems from devices to directories, making their data accessible and organized efficiently. This is crucial for tasks such as accessing additional storage drives, utilizing external devices, or setting up network shares. The command also allows for fine-tuning filesystem access with options such as read-only or user-specific permissions.

By understanding and applying these use cases, system administrators and users can optimize filesystem management, enhance security, and improve user access experiences.

Use case 1: Show all mounted filesystems

Code:

mount

Motivation:
Examining all currently mounted filesystems can reveal vital information, such as where different devices and partitions are mounted, the type of filesystems they use, and the options they are mounted with. This insight is crucial for diagnosing system behavior, understanding filesystem layout, and managing resources effectively.

Explanation:
The command mount without any arguments lists all filesystems that are currently mounted. It provides a comprehensive snapshot of the system’s state in terms of storage device usage, allowing users to inspect mount points and filesystem types.

Example Output:
When executed, this command will produce output similar to:

/dev/sda1 on / type ext4 (rw,relatime)
tmpfs on /run type tmpfs (rw,nosuid,nodev,mode=755)
...

Use case 2: Mount a device to a directory

Code:

mount -t ext4 /dev/sdb1 /mnt/data

Motivation:
Mounting a device to a directory enables access to the device’s contents through the filesystem hierarchy. This is particularly useful for adding additional storage capacity or accessing files from external drives. It also aids in organizing storage solutions by attaching physical or virtual devices to a chosen directory.

Explanation:

• -t ext4: Specifies the filesystem type of the device. Here, it’s ext4, a common Linux filesystem.
• /dev/sdb1: Represents the device file to be mounted, typically found in the /dev directory.
• /mnt/data: The target directory where the device will be accessible. This directory acts as an entry point to the device’s contents.

Example Output:
If successful, the command does not return an output. Listing /mnt/data will show the contents of /dev/sdb1.

Use case 3: Create a specific directory if it does not exist and mount a device to it

Code:

mount --mkdir /dev/sdb1 /mnt/newdata

Motivation:
This use case is valuable for automation or scripting scenarios where the existence of the directory cannot be assumed. By instructing mount to create the target directory if it doesn’t exist, the process is streamlined, reducing the risk of errors and manual intervention.

Explanation:

• --mkdir: Instructs mount to create the specified directory (/mnt/newdata) if it doesn’t already exist.
• /dev/sdb1: The device file to be mounted.
• /mnt/newdata: The directory where the device will be mounted.

Example Output:
The command will not return any output upon success, but the directory /mnt/newdata will be created and the contents of /dev/sdb1 will be accessible from there.

Use case 4: Mount a device to a directory for a specific user

Code:

mount -o uid=1000,gid=1000 /dev/sdb1 /mnt/userdata

Motivation:
Mounting a device such that a specific user owns the mounted files can be essential in multi-user environments. It allows setting permissions directly when the device is mounted, ensuring that the designated user has the appropriate access, thus enhancing security and access control.

Explanation:

• -o uid=1000,gid=1000: Sets the user ID and group ID for the mount. Here, UID 1000 and GID 1000 usually correspond to the first non-root user in a freshly installed Linux system.
• /dev/sdb1: The device file to be accessed.
• /mnt/userdata: The directory where the device will be mounted.

Example Output:
No output will be shown if successful. The user with UID 1000 will have ownership permissions over the mounted files.

Use case 5: Mount a CD-ROM device (with the filetype ISO9660) to /cdrom (readonly)

Code:

mount -t iso9660 -o ro /dev/cdrom /cdrom

Motivation:
Optical media like CDs are typically mounted as read-only since they cannot be modified. This command is specifically designed for accessing data on a CD-ROM and ensures the filesystem is mounted appropriately with the correct type and permissions.

Explanation:

• -t iso9660: Specifies the filesystem type for the CD-ROM, which is ISO9660, a standard for optical disc filesystems.
• -o ro: Mounts the filesystem as read-only, which is suitable for optical media.
• /dev/cdrom: The device file representing the CD-ROM drive.
• /cdrom: The mount point for accessing the CD-ROM’s contents.

Example Output:
Upon mounting, no direct output is given. Accessing the /cdrom directory will list the files available on the CD-ROM.

Use case 6: Mount all the filesystems defined in /etc/fstab

Code:

mount -a

Motivation:
The fstab file lists all the available disks and partitions and indicates how they should be associated with the filesystem hierarchy. Using mount -a applies all these configurations, which is particularly useful for ensuring that all defined filesystems are active, especially after system boot or configuration changes.

Explanation:

• -a: An option that triggers the mounting of all filesystems mentioned in /etc/fstab that are not currently mounted.

Example Output:
There is typically no output unless errors occur. The command will ensure all mounts defined in /etc/fstab are active.

Use case 7: Mount a specific filesystem described in /etc/fstab

Code:

mount /my_drive

Motivation:
Mounting a specific filesystem from fstab allows for easy management without specifying the device or options manually. This is convenient in day-to-day use or script automation when repeatedly accessing specific devices.

Explanation:

• /my_drive: Refers to the mount point or device as defined in /etc/fstab. The system reads the appropriate line and mounts the device accordingly.

Example Output:
The command executes silently if successful, and /my_drive is populated with the specified device’s contents.

Use case 8: Mount a directory to another directory

Code:

mount --bind /var/www /home/user/www_backup

Motivation:
The concept of bind mounting allows a directory to be accessed from an alternative mount point, which is useful for backup, development, or virtualization purposes, where identical data is required in multiple locations of the filesystem hierarchy.

Explanation:

• --bind: Creates a second mount point for an already mounted filesystem.
• /var/www: The original directory to be mirrored.
• /home/user/www_backup: The new directory where /var/www will be accessible.

Example Output:
No output is generated. Upon checking /home/user/www_backup, it will mirror the contents of /var/www.

Conclusion:

The mount command is an indispensable tool for managing filesystems in a Linux environment, providing flexibility and fine control over how storage resources are accessed. By effectively utilizing these examples, users can enhance system robustness, streamline workflow processes, and ensure that storage management aligns with both personal and organizational needs. Understanding the mount command helps in achieving optimal performance and organization of filesystems across varying use cases and scenarios.