How to use the 'mountpoint' command (with examples)

The ‘mountpoint’ command is a simple yet powerful tool used in Linux environments to determine whether a specific directory is a mountpoint. In the context of filesystems, a mountpoint is a directory where a particular filesystem is mounted, making its files accessible. The ‘mountpoint’ command helps system administrators and users verify and manage filesystem mounts with ease. Moreover, it offers options to check without displaying output or to reveal more technical information such as major/minor numbers of the filesystem.

Use case 1: Check if a directory is a mountpoint

Code:

mountpoint path/to/directory

Motivation: In system administration, it is often necessary to verify whether a particular directory is serving as a mountpoint for a filesystem. This operation is essential when managing disk partitions, troubleshooting filesystem-related issues, or ensuring that backup and data storage operations are performed as intended. By confirming a directory’s status as a mountpoint, users can prevent data loss from improperly mounted filesystems.

Explanation: The command consists of ‘mountpoint’ followed by the path to the target directory. Here:

• mountpoint: This is the command that checks if a directory is a mountpoint.
• path/to/directory: This is a placeholder for the actual path of the directory you want to test. Replace it with the actual directory path you are interested in.

Example Output:

path/to/directory is a mountpoint

or

path/to/directory is not a mountpoint

This output clearly indicates whether the specified directory is a mountpoint, helping you quickly ascertain the configuration of your filesystem without delving into deeper command output or complex configurations.

Use case 2: Check if a directory is a mountpoint without showing any output

Code:

mountpoint -q path/to/directory

Motivation: In scenarios where scripts automate system checks or configuration validations, it may not be desirable to generate console output. This use case allows silent verification of a directory’s mountpoint status, which is particularly useful for automated monitoring systems or scripts that log errors or status checks without direct user interaction.

Explanation: This command uses the ‘-q’ option:

• -q: This option stands for “quiet” mode. It makes the ‘mountpoint’ command execute without producing output unless an error occurs.
• path/to/directory: As before, this is the directory path you wish to verify as a mountpoint.

Example Output: There will be no output if the command executes successfully. If an error occurs, that error will be displayed. Silent success is often desirable in automation tasks where only failures are recorded, allowing needless log noise to be avoided.

Use case 3: Show major/minor numbers of a mountpoint’s filesystem

Code:

mountpoint --fs-devno path/to/directory

Motivation: Understanding the major and minor device numbers of a filesystem can provide valuable technical insights, particularly during deep system diagnostics, performance tuning, and when mapping filesystems to their physical storage devices. These numbers help in identifying the particular filesystem on a device node, which is crucial for advanced troubleshooting and configuration tasks in Linux systems.

Explanation: The command includes the ‘–fs-devno’ flag:

• --fs-devno: This option prompts the command to display the major/minor numbers associated with the filesystem mounted at the specified directory. These numbers correlate to the device numbers in the system’s device hierarchy.
• path/to/directory: This is the directory whose mountpoint’s major/minor numbers you wish to discover.

Example Output:

major: 8; minor: 1

This output shows the major and minor device numbers, providing a clear perspective of the filesystem’s underlying block device, assisting you in correlating logical filesystems with physical devices for further analysis.

Conclusion

The ‘mountpoint’ command is an essential administrative tool that allows users to quickly check filesystem mount status and delve deeper into filesystem attributes with major and minor device numbers. Through its various options, users can employ it for simple status queries, silent checks, and advanced information retrieval, making it a versatile addition to any Linux user’s toolkit.