blkid — Show Block Device UUIDs and Labels

blkid prints identifying metadata for block devices (filesystem type, UUID, label, PARTUUID). Use it when you need a stable identifier for /etc/fstab, when you are mounting a new backup disk, or when you're verifying that a partition really contains the filesystem you expect. On WordPress VPS servers, this is commonly used to mount /mnt/backups and to confirm where database storage lives.

Quick Summary

Use sudo blkid to list all known devices, then mount by UUID in /etc/fstab (preferred) instead of hardcoding /dev/sdb1.

Mental Model

uuid-to-mount.txt

/dev/sdb1  ->  UUID="6666-7777-..."  ->  /etc/fstab  ->  mounted at /mnt/backups

Prerequisites

blkid is provided by the util-linux package and is installed by default on most Linux distributions.

Verify it exists:

verify-blkid-installed.sh

which blkid
blkid --version

Core Syntax

blkid-syntax.sh

blkid [OPTIONS] [DEVICE...]

Most practical usage is either:

• List all devices: sudo blkid
• Query a single device: sudo blkid /dev/sdb1

Key Options

Option	What it does	Example	WordPress / VPS use case
-o <format>	Choose output format	sudo blkid -o full /dev/sdb1	Readable output with all tags
-o export	Export format for scripts	sudo blkid -o export /dev/sdb1	Easy parsing into env-like lines
-s <tag>	Print only specific tag(s)	sudo blkid -s UUID /dev/sdb1	Focus on UUID only
-t NAME=VALUE	Find device with a token	blkid -t LABEL=BACKUP	Find disks by label
-U <uuid>	Convert UUID to device	blkid -U 6666-...	Find device path after reboot
-L <label>	Convert LABEL to device	blkid -L BACKUP	Mount by label (less stable than UUID)
-p	Probe device (bypass cache)	sudo blkid -p /dev/sdb1	Refresh detection after changes
-c /dev/null	Disable cache	sudo blkid -c /dev/null /dev/sdb1	Avoid stale cache results

Examples (Commands + Expected Output)

Output varies

UUIDs and device names are examples. Always copy UUIDs from your own server.

List all block devices with filesystem signatures

blkid-list-all.sh

sudo blkid

Expected output:

example-output-blkid-list-all.txt

/dev/sda1: UUID="11111111-2222-3333-4444-555555555555" TYPE="ext4" PARTUUID="aaaa-bbbb"
/dev/sdb1: LABEL="BACKUP" UUID="66666666-7777-8888-9999-000000000000" TYPE="ext4" PARTUUID="cccc-dddd"

Use case: Identify the UUID of a new backup disk.

Query a single device

blkid-single-device.sh

sudo blkid /dev/sdb1

Expected output:

example-output-blkid-single-device.txt

/dev/sdb1: LABEL="BACKUP" UUID="66666666-7777-8888-9999-000000000000" TYPE="ext4" PARTUUID="cccc-dddd"

Use case: Confirm the filesystem type before you mount it.

Print only the UUID value (script-friendly)

blkid-uuid-only-value.sh

sudo blkid -s UUID -o value /dev/sdb1

Expected output:

example-output-blkid-uuid-only.txt

66666666-7777-8888-9999-000000000000

Use case: Paste only the UUID into /etc/fstab.

Find a device by UUID

blkid-find-device-by-uuid.sh

blkid -U 66666666-7777-8888-9999-000000000000

Expected output:

example-output-blkid-u.txt

/dev/sdb1

Use case: Map a UUID back to a device name after reboot.

Find a device by LABEL

blkid-find-device-by-label.sh

blkid -L BACKUP

Expected output:

example-output-blkid-l.txt

/dev/sdb1

Use case: Quick lookup when you label a dedicated backup disk.

Export output format for parsing

blkid-export-format.sh

sudo blkid -o export /dev/sdb1

Expected output:

example-output-blkid-export.txt

DEVNAME=/dev/sdb1
LABEL=BACKUP
UUID=66666666-7777-8888-9999-000000000000
TYPE=ext4
PARTUUID=cccc-dddd

Use case: Feed values into automation.

WordPress VPS Use Cases

Situation	What you need	Command	Why it helps
Add a backup disk mount	UUID and filesystem type	sudo blkid /dev/sdb1	Stable fstab entry and correct mount
Verify a DB volume	Mount device identity	sudo blkid /var/lib/mysql	Confirms where database storage lives
Repair mount failures	Confirm UUID did not change	sudo blkid	Detects formatting/replacement events

Troubleshooting

Problem	Likely cause	Fix
blkid prints nothing for a device	No filesystem signature exists	Format the partition (carefully) before mounting
Permission denied	Needs root to read block metadata	Use sudo blkid ...
UUID changed	Device was reformatted/replaced	Update /etc/fstab and any scripts using the old UUID
Results look stale	Cache is outdated	Use sudo blkid -p or sudo blkid -c /dev/null

Best Practices

• Prefer UUID-based mounts in /etc/fstab over raw /dev/sdX names.
• Use lsblk -p -f alongside blkid to see mount points and filesystem IDs together.

Cheat Sheet

blkid-cheat-sheet.sh

sudo blkid
sudo blkid /dev/sdb1
sudo blkid -s UUID -o value /dev/sdb1
blkid -U <uuid>
blkid -L <label>
sudo blkid -o export /dev/sdb1
sudo blkid -p /dev/sdb1

What's Next

• lsblk — List Block Devices
• findmnt — List Mount Points
• mount — Mount a Filesystem
• umount — Unmount a Filesystem