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

pmount, short for “policy mount”, is a command-line utility that allows normal users to mount hotpluggable devices without requiring superuser privileges. This command is particularly useful for mounting devices like USB drives and external hard disks that are often connected and disconnected from systems. The flexibility provided by pmount ensures that users can manage these devices more conveniently without compromising system security.

Use case 1: Mount a device below /media/ (using device as mount point)

Code:

pmount /dev/to/block/device

Motivation:

As computers become more portable and versatile, the need for plugging in devices such as USB drives, SD cards, and external hard drives increases. pmount simplifies this process, allowing users to quickly and easily access the contents of these devices without dealing with complex mount options or needing superuser credentials. This is particularly useful in multi-user environments, where granting superuser access to all users is not ideal.

Explanation:

• /dev/to/block/device: This represents the block device you want to mount. Generally, devices are located under /dev/, and their names follow a standard pattern such as /dev/sda1 for the first partition on the first SCSI disk. When using pmount, this is the only required parameter if you wish to mount using the default settings.

Example output:

Mounted /dev/to/block/device at /media/device

This indicates that the block device has been successfully mounted at the default location in /media/.

Use case 2: Mount a device with a specific filesystem type to /media/label

Code:

pmount --type filesystem /dev/to/block/device label

Motivation:

Different devices may use different filesystems, such as FAT32, NTFS, ext4, or exFAT. Specifying the filesystem type ensures that pmount uses the correct driver to interact with the device, which can optimize performance and prevent corruption or errors. Assigning a label also provides a user-friendly name for the mount point, making it easier for users to identify the mounted device in the /media directory.

Explanation:

• --type filesystem: This option specifies the type of the filesystem on the device. For example, it could be vfat, ext4, ntfs, etc. It’s important for ensuring the system handles the mounted device appropriately.
• /dev/to/block/device: As before, this is the path to the device you want to mount.
• label: The desired name for the directory created in /media/, making this mount point instantly recognizable to users.

Example output:

Mounted /dev/to/block/device at /media/label

This confirms the block device was mounted at the specified label path.

Use case 3: Mount a CD-ROM (filesystem type ISO9660) in read-only mode

Code:

pmount --type iso9660 --read-only /dev/cdrom

Motivation:

CD-ROMs and DVDs typically use the ISO9660 filesystem and are read-only by nature. This example highlights how pmount can accommodate such devices while keeping the integrity of the data intact by preventing any write operations. It’s crucial for archival purposes, software installations, and other situations where data must remain unchanged.

Explanation:

• --type iso9660: Specifies the ISO9660 filesystem, which is standard for optical media like CDs and DVDs.
• --read-only: Ensures the device is mounted in a mode where no write operations are possible, thereby maintaining the read-only nature of optical media.
• /dev/cdrom: The typical device file for a CD-ROM drive, though it may vary depending on system configuration.

Example output:

Mounted /dev/cdrom at /media/cdrom (read-only)

This shows successful mounting with read permissions only, ensuring data is protected.

Use case 4: Mount an NTFS-formatted disk, forcing read-write access

Code:

pmount --type ntfs --read-write /dev/sdX

Motivation:

When dealing with devices formatted with NTFS – a common filesystem for Windows – it is often necessary to write data to them from Linux systems. pmount allows users to force this read-write operation, enhancing interoperability between different operating systems and improving workflow efficiency when collaborating across multiple devices.

Explanation:

• --type ntfs: Indicates that the device uses the NTFS filesystem, which is prevalent for Windows-based systems.
• --read-write: Allows modifications to the data on the device while it’s mounted, an essential feature for NTFS devices on systems that support read-write NTFS operations.
• /dev/sdX: Refers to the appropriate NTFS storage device you’d like to mount.

Example output:

Mounted /dev/sdX at /media/sdX (read-write)

This resulting message confirms that the NTFS device was successfully mounted with read-write permissions.

Use case 5: Display all mounted removable devices

Code:

pmount

Motivation:

A straightforward way to list all currently mounted removable devices is essential for managing and verifying device states. This command assists in providing an overview of all user-specific mounted resources, aiding in quick diagnostics and system operations without requiring deep technical insights into the mounting hierarchy.

Explanation:

Here, pmount is used without additional arguments simply to list devices. This makes it an easy call for everyday checks and balances by users who frequently work with varied portable storage.

Example output:

/dev/sdb1 on /media/sdb1
/dev/sdc1 on /media/sddrive

This output lists each mounted device and their respective directories, facilitating quick access and checks.

Conclusion:

The pmount command serves as a convenient tool for managing hotpluggable devices by regular users, enhancing system accessibility without granting unnecessary superuser privileges. It supports various use cases, from mounting different filesystems to viewing all mounted devices, tailored to improve user experience in multi-user and cross-platform environments. Through the demonstrated examples, users can effectively employ pmount to suit their specific mounting needs, ensuring seamless data interaction and transfer across various devices.