blkid Command Linux: Complete Guide to Display Block Device Information

The blkid command is an essential Linux utility that displays information about block devices, including file system types, UUIDs, labels, and other metadata. Whether you’re a system administrator managing multiple storage devices or a developer working with file systems, understanding blkid is crucial for effective Linux system management.

What is the blkid Command?

The blkid (block identifier) command is a command-line utility that locates and prints block device attributes. It can identify file system types, retrieve UUIDs (Universally Unique Identifiers), display volume labels, and show various other properties of storage devices and partitions.

This command is particularly useful for:

• Identifying file system types on partitions
• Retrieving UUIDs for mounting devices
• Displaying volume labels and metadata
• Troubleshooting storage-related issues
• Creating automated scripts for system administration

Basic Syntax and Installation

The basic syntax of the blkid command is:

blkid [options] [device...]

The blkid command is typically pre-installed on most Linux distributions as part of the util-linux package. If it’s not available, you can install it using your distribution’s package manager:

# Ubuntu/Debian
sudo apt-get install util-linux

# CentOS/RHEL/Fedora
sudo yum install util-linux
# or
sudo dnf install util-linux

Basic Usage Examples

Display All Block Devices

To display information about all available block devices, simply run blkid without any arguments:

$ blkid

Example output:

/dev/sda1: UUID="a1b2c3d4-e5f6-7890-abcd-ef1234567890" TYPE="ext4" PARTUUID="12345678-01"
/dev/sda2: UUID="f9e8d7c6-b5a4-3210-9876-543210fedcba" TYPE="swap" PARTUUID="12345678-02"
/dev/sdb1: LABEL="DATA" UUID="11223344-5566-7788-99aa-bbccddeeff00" TYPE="ntfs" PARTUUID="87654321-01"
/dev/sr0: UUID="2023-08-15-14-30-00-00" LABEL="Ubuntu 22.04 LTS amd64" TYPE="iso9660"

Display Information for Specific Device

To get information about a specific device, specify the device path:

$ blkid /dev/sda1

Example output:

/dev/sda1: UUID="a1b2c3d4-e5f6-7890-abcd-ef1234567890" TYPE="ext4" PARTUUID="12345678-01"

Important Command Options

Show Specific Attributes (-s option)

Use the -s option to display only specific attributes:

# Show only UUID
$ blkid -s UUID /dev/sda1
/dev/sda1: UUID="a1b2c3d4-e5f6-7890-abcd-ef1234567890"

# Show only file system type
$ blkid -s TYPE /dev/sda1
/dev/sda1: TYPE="ext4"

# Show only label
$ blkid -s LABEL /dev/sdb1
/dev/sdb1: LABEL="DATA"

Output Only Values (-o option)

The -o option controls the output format:

# Output only the value (useful for scripting)
$ blkid -s UUID -o value /dev/sda1
a1b2c3d4-e5f6-7890-abcd-ef1234567890

# Output in key=value format
$ blkid -o export /dev/sda1
DEVNAME=/dev/sda1
UUID=a1b2c3d4-e5f6-7890-abcd-ef1234567890
TYPE=ext4
PARTUUID=12345678-01

List All Devices (-l option)

Use the -l option to list all devices with a specific attribute:

# List all ext4 file systems
$ blkid -l -t TYPE=ext4
/dev/sda1: UUID="a1b2c3d4-e5f6-7890-abcd-ef1234567890" TYPE="ext4" PARTUUID="12345678-01"

# List all devices with a specific UUID
$ blkid -l -t UUID="a1b2c3d4-e5f6-7890-abcd-ef1234567890"
/dev/sda1: UUID="a1b2c3d4-e5f6-7890-abcd-ef1234567890" TYPE="ext4" PARTUUID="12345678-01"

Advanced Usage Examples

Finding Devices by Label

You can search for devices using their labels:

# Find device with specific label
$ blkid -L "DATA"
/dev/sdb1

# List all devices with labels
$ blkid -s LABEL -o device

Finding Devices by UUID

Locate devices using their UUID:

# Find device with specific UUID
$ blkid -U "a1b2c3d4-e5f6-7890-abcd-ef1234567890"
/dev/sda1

Probe Specific File System

Use the -p option for low-level probing:

$ blkid -p /dev/sda1

Example output:

/dev/sda1: UUID="a1b2c3d4-e5f6-7890-abcd-ef1234567890" VERSION="1.0" TYPE="ext4" MINIMUM_IO_SIZE="512" PHYSICAL_SECTOR_SIZE="512" LOGICAL_SECTOR_SIZE="512"

Working with Different File Systems

Common File System Types

The blkid command can identify various file system types:

Example: Identifying USB Drive

When you connect a USB drive, you can identify its file system:

$ blkid /dev/sdc1
/dev/sdc1: LABEL="USB_DRIVE" UUID="1234-5678" TYPE="vfat" PARTUUID="abcdef12-01"

Practical Use Cases

1. Creating fstab Entries

Use blkid to get UUIDs for /etc/fstab entries:

# Get UUID for fstab
$ blkid -s UUID -o value /dev/sda1
a1b2c3d4-e5f6-7890-abcd-ef1234567890

# Use in fstab
UUID=a1b2c3d4-e5f6-7890-abcd-ef1234567890 / ext4 defaults 0 1

2. Scripting Example

Here’s a bash script that checks if a specific file system type exists:

#!/bin/bash

# Check if any ext4 partitions exist
if blkid -t TYPE=ext4 &>/dev/null; then
    echo "ext4 partitions found:"
    blkid -t TYPE=ext4
else
    echo "No ext4 partitions found"
fi

3. System Information Gathering

Create a comprehensive storage report:

#!/bin/bash

echo "=== Storage Device Information ==="
echo
echo "All block devices:"
blkid
echo
echo "File system summary:"
blkid -s TYPE -o device,value | sort -k2

Troubleshooting Common Issues

Permission Denied Errors

If you encounter permission errors, run the command with sudo:

$ sudo blkid /dev/sda1

Device Not Found

If a device is not found, verify it exists:

# List all block devices
$ lsblk

# Check if device exists
$ ls -l /dev/sda1

No Output for New Devices

For newly created file systems, you might need to force a probe:

$ sudo blkid -p /dev/sda1

Security Considerations

When using blkid in scripts or automation:

• Always validate device paths before using them
• Use UUIDs instead of device names for mounting (more reliable)
• Be cautious when parsing output in scripts
• Consider using the -o export format for reliable parsing

Integration with Other Commands

Combining with lsblk

# Show block devices with file system info
$ lsblk -f

Combining with mount

# Mount by UUID
$ sudo mount UUID="a1b2c3d4-e5f6-7890-abcd-ef1234567890" /mnt/data

Combining with findmnt

# Show mounted file systems with UUIDs
$ findmnt -D

Best Practices

1. Use UUIDs for mounting: UUIDs remain constant even if device names change
2. Script-friendly output: Use -o value when you need only the value in scripts
3. Regular monitoring: Include blkid in system monitoring scripts
4. Backup important data: Always backup data before manipulating block devices
5. Verify changes: Use blkid to verify file system changes after formatting

Conclusion

The blkid command is an indispensable tool for Linux system administrators and users who need to work with block devices and file systems. From identifying file system types to retrieving UUIDs for reliable mounting, blkid provides essential functionality for storage management tasks.

By mastering the various options and use cases covered in this guide, you’ll be well-equipped to handle storage-related tasks efficiently and reliably. Remember to always verify device information before making changes, and consider using UUIDs for persistent device identification in your scripts and configuration files.

Whether you’re setting up automated backups, configuring system mounts, or troubleshooting storage issues, the blkid command will prove to be an invaluable addition to your Linux command-line toolkit.