Vol. I · No. 46The command line sectionSat, 10 Oct 2026
Linux · disks & space

lsblk

what disks are attached

lsblk — list block devices — shows every disk and the partitions on it, with sizes and mount points. It is the command to run before touching a disk, to be sure which device is which.

Before any command that writes to a disk, lsblk tells you its real name.

Shows
Disks and partitions
as a tree
Names
sda, nvme0n1
partitions add a number
Needs root
No
it only reads
More detail
-f
filesystem, label, UUID

At the terminal

Read the session first, then the notes: each numbered line in the output is answered by the note with the same number.

user@netflow — bashutil-linux
$ lsblk
1NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
2sda 8:0 0 100G 0 disk
├─sda1 8:1 0 1.1G 0 part /boot/efi
3└─sda2 8:2 0 98.9G 0 part /
4sdb 8:16 1 14.9G 0 disk
└─sdb1 8:17 1 14.9G 0 part
Illustrative session · names, sizes and dates are examples, and every address is from a documentation or private range
Reading the output

What the numbered lines are telling you

1
The columns

RM is 1 for removable media, RO is 1 for read-only, TYPE says disk or partition, and MOUNTPOINTS is where it appears in the tree.

2
A whole disk

sda is the first disk, 100 GB. The lines drawn beneath it are its partitions.

3
A mounted partition

sda2 holds the root filesystem. Its contents are what you see at /.

4
A USB stick, not mounted

RM is 1 and the size is 14.9G: removable. The empty MOUNTPOINTS column means its files are not yet reachable.

Switches

A switch changes how the command behaves. These are the ones used day to day; man lsblk lists the rest. Single-letter switches can usually be joined, so -l -a may be written -la.

-f
Show filesystem type, label, UUID and mount point.
-o COLUMNS
Choose the columns, such as NAME,SIZE,MODEL.
-d
List whole disks only, not partitions.
-p
Print full device paths: /dev/sda1.
-b
Print sizes in bytes.
-J
Print JSON, for scripts.

Variations worth knowing

The same tool, pointed at a narrower question. These four cover most of what it is reached for day to day.

lsblk -f

Adds the filesystem type, label and UUID of each partition.

lsblk -o NAME,SIZE,MODEL,SERIAL

Chooses the columns — here, to identify the physical drives.

lsblk -d

Lists whole disks only, without their partitions.

sudo blkid

Prints the UUID and type of every partition, for use in /etc/fstab.

In cybersecurity

Most disk disasters are the right command run on the wrong device.

Confirm the device first

Names such as sdb are handed out in the order disks are found and can change between boots. Check size and model with lsblk before dd, mkfs or fdisk.

Unexpected devices

A disk or USB device nobody recalls attaching is worth explaining — on a server, removable media should be rare.

Look for encryption

A partition of type crypt is encrypted with LUKS. A laptop whose data partition is not is readable by whoever takes the disk out.

Filed under

Disks & space

Read alongside

dfShows how much space each mounted filesystem has: its size, how much is used, and how much is free.mountAttaches a filesystem — a partition, USB stick or network share — to a directory in the tree.