Identify Block Device Attributes with Blkid

The blkid command in Linux is a powerful utility used to locate and print attributes of block devices. It's essential for system administrators and developers who need to identify storage devices, retrieve their unique identifiers like UUIDs (Universally Unique Identifiers), and understand their types, including support for encrypted volumes like LUKS (Linux Unified Key Setup).

Understanding Blkid Output

blkid can display a wealth of information about your disks and partitions. By default, it shows the device path, UUID, LABEL, and TYPE. This information is crucial for tasks such as configuring file systems, setting up RAID arrays, or managing encrypted storage. Understanding these attributes helps in reliably referencing devices, especially when device names might change across reboots.

Common Blkid Usage Examples

Here are some practical examples of how to use the blkid command:

# Display attributes of all block devices
blkid

# Display attributes of a specific block device
blkid /dev/sdX

# Display only the UUID of a specific device, outputting just the value
blkid -s UUID -o value /dev/sdX

# Check if a device is a LUKS encrypted volume
blkid -s TYPE -o value /dev/sdX | grep -q 'crypto_LUKS' && echo "LUKS device"

# Format output using udev-style key-value pairs
blkid -p -o udev /dev/sdX

# Display all available attributes in a full format
blkid -o full /dev/sdX

# Utilize a cache file for faster results (or specify /dev/null to disable caching)
blkid -c /dev/null /dev/sdX

# Cache the results to a file and update the cache
blkid -c /etc/blkid.tab /dev/sdX

Advanced Blkid Options and LUKS Identification

The blkid command offers various options to tailor its output. The -s option allows you to select specific tags (attributes) to display, such as UUID or TYPE. The -o option controls the output format, with options like value for plain output, full for all details, and udev for a format compatible with udev rules. When dealing with encrypted storage, checking the TYPE attribute for crypto_LUKS is a standard method to confirm if a device is prepared for LUKS encryption.

External Resources for Block Device Management

• Blkid man page - Official documentation for the blkid command.
• Kernel Parameters Documentation - Understanding how kernel parameters relate to block devices.
• Universally Unique Identifier (UUID) on Wikipedia - Learn more about UUIDs.
• Cryptsetup Project - The primary tool for managing LUKS encrypted devices.