lsblk — List Block Devices

lsblk prints a tree view of your disks, partitions, and mount points. Use it before you mount/unmount a volume, resize a disk, or troubleshoot "disk full" incidents so you know exactly which device backs /, /var/www, /var/lib/mysql, or /mnt/backups. The -p flag is especially useful because it prints full device paths (for copy/paste safety).

Quick Summary

Run lsblk -p -f to see full device paths plus filesystem type and UUID, then confirm your WordPress paths with df -h /var/www/html and findmnt -T /var/www/html.

Mental Model

block-device-tree.txt

/dev/sda (disk)
  └─/dev/sda1 (partition) -> mounted at /
/dev/sdb (disk)
  └─/dev/sdb1 (partition) -> mounted at /mnt/backups

Prerequisites

lsblk is provided by the util-linux package and is installed by default on most Linux servers.

Verify it exists:

verify-lsblk-installed.sh

which lsblk
lsblk --version

Core Syntax

lsblk-syntax.sh

lsblk [OPTIONS] [DEVICE...]

• If you omit DEVICE, lsblk lists all block devices.
• Use -p to print /dev/... paths (recommended for operational work).

Key Options

Option	What it does	Example	WordPress / VPS use case
-p	Print full device paths	lsblk -p	Copy/paste safe device names
-f	Show filesystem info (type, UUID)	lsblk -f	Prepare /etc/fstab entries
-o COLS	Choose output columns	lsblk -o NAME,SIZE,TYPE,MOUNTPOINTS	Cleaner troubleshooting view
-a	Include empty devices	lsblk -a	See devices even if not mounted
-r	Raw output (no tree)	lsblk -r	Grep/parse-friendly output
-n	No header	lsblk -n -o NAME,SIZE	Script output without headings
-J	JSON output	lsblk -J -o NAME,SIZE,MOUNTPOINTS	Programmatic parsing
-P	KEY="VALUE" output	lsblk -P -o NAME,SIZE,MOUNTPOINTS	Shell parsing with awk/xargs

Examples (Commands + Expected Output)

Output varies

Device names and sizes are examples. Your VPS may use vda (VirtIO) instead of sda.

List all disks and partitions

lsblk-basic.sh

lsblk

Expected output:

example-output-lsblk-basic.txt

NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda      8:0    0   50G  0 disk
└─sda1   8:1    0   50G  0 part /
sdb      8:16   0  200G  0 disk
└─sdb1   8:17   0  200G  0 part /mnt/backups

Use case: Get a quick map of storage and mounts.

Print full device paths (recommended)

lsblk-print-full-paths.sh

lsblk -p

Expected output:

example-output-lsblk-p.txt

NAME        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
/dev/sda      8:0    0   50G  0 disk
└─/dev/sda1   8:1    0   50G  0 part /

Use case: Avoid ambiguity when you run commands like mount /dev/sdb1 /mnt/backups.

Show filesystem type and UUID (great for fstab)

lsblk-filesystem-info.sh

lsblk -p -f

Expected output:

example-output-lsblk-f.txt

NAME        FSTYPE FSVER LABEL UUID                                 FSAVAIL FSUSE% MOUNTPOINTS
/dev/sda1   ext4   1.0         11111111-2222-3333-4444-555555555555   40G    20%   /
/dev/sdb1   ext4   1.0  BACKUP 66666666-7777-8888-9999-000000000000  150G    25%   /mnt/backups

Use case: Copy the UUID into /etc/fstab to mount reliably across reboots.

Focus on a single disk

lsblk-single-device.sh

lsblk -p /dev/sdb

Expected output:

example-output-lsblk-single-disk.txt

NAME        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
/dev/sdb     8:16   0  200G  0 disk
└─/dev/sdb1  8:17   0  200G  0 part /mnt/backups

Use case: Validate the disk you plan to format/mount.

Show only the columns you care about

lsblk-custom-columns.sh

lsblk -p -o NAME,SIZE,FSTYPE,UUID,MOUNTPOINTS

Expected output:

example-output-lsblk-custom-columns.txt

NAME        SIZE FSTYPE UUID                                 MOUNTPOINTS
/dev/sda1    50G ext4   11111111-2222-3333-4444-555555555555 /
/dev/sdb1   200G ext4   66666666-7777-8888-9999-000000000000 /mnt/backups

Use case: A clean view for runbooks and incident notes.

JSON output for automation

lsblk-json-output.sh

lsblk -J -o NAME,SIZE,TYPE,MOUNTPOINTS

Expected output:

example-output-lsblk-json.txt

{"blockdevices":[{"name":"sda","size":"50G","type":"disk","mountpoints":[null]},{"name":"sda1","size":"50G","type":"part","mountpoints":["/"]}]}

Use case: Parse block device information in scripts.

WordPress VPS Use Cases

Situation	What you need to know	Command	Why it helps
Disk is filling up	Which device backs /	lsblk -p -f	Tells you which disk/partition to resize
Backups failing	Backup mount device and size	lsblk -p -f	Confirms backup volume is present and mounted
Moving uploads to another disk	Target device + filesystem	lsblk -p -f	Prevents mounting the wrong partition
Editing /etc/fstab	UUID and filesystem type	lsblk -p -f	Stable mounts across reboots

Troubleshooting

Problem	Likely cause	Fix
A disk is not listed	Not attached or not recognized	Verify in your provider panel; rescan or reboot
MOUNTPOINTS is empty	Partition is not mounted	Use mount or findmnt to confirm, then mount it
UUID missing	No filesystem on the partition	Format the partition (carefully) before mounting
You see loop devices	Snap packages / loop mounts	Usually normal; filter with custom columns

Best Practices

• Use lsblk -p when you plan to copy/paste device names.
• Use lsblk -p -f before touching /etc/fstab.
• Confirm mounts with findmnt -T PATH before assuming where data lives.

Cheat Sheet

lsblk-cheat-sheet.sh

lsblk
lsblk -p
lsblk -p -f
lsblk -p -o NAME,SIZE,FSTYPE,UUID,MOUNTPOINTS
lsblk -J -o NAME,SIZE,TYPE,MOUNTPOINTS
lsblk -p /dev/sdb

What's Next

• blkid — Show Device UUID and Labels
• findmnt — List Mount Points
• mount — Mount a Filesystem
• df — Disk Free & Filesystem Usage