The lsblk command in Linux and what it does

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This post was originally published on my personal blog mariadcampbell.com.

Table of Contents

• lsblk introduction
• What is the lsblk command and what does it do?
• Installing util-linux if your distro does not have it by default
• lsblk syntax
• Running the lsblk command
• Footnotes
• Related Resources

lsblk introduction

The lsblk command comes as part of the util-linux package, which is a
package comprised of essential utilities for Linux systems. It provides
a wide range of functionality including tools for managing files, disks,
and system resources. util-linux comes installed with Linux Mint, for
example. According to the Linux Mint community,

(util-linux) contains a number of important utilities, most of which are
oriented towards maintenance of your system. Some of the more important
utilities included in this package allow you to view kernel messages, create
new filesystems, view block device information, interface with real time
clock, etc.

What is the lsblk command and what does it do?

The lsblk command stands for list block devices, and it provides detailed
information about block devices such as hard drives, solid state drives,
and other storage related devices that are connected to the computer. It
queries the /sys virtual filesystem and
udev db [^1] to obtain the information that it displays.

Installing util-linux if your distro does not have it by default

If by any chance you are not using Linux Mint, or Ubuntu or an
Ubuntu derivate for example, and your Linux distro does not contain the
util-linux package, you can install it:

# Debian/Ubuntu
sudo apt-get install util-linux
# in Linux Mint, I have installed my packages doing sudo apt install packagename. But util-linus is already installed in Linux Mint anyway.

lsblk syntax

The syntax for the lsblk command is the following:

lsblk [options] [device]

[options] refers to the flags available to the lsblk command. [device]
refers to the specific block devices that we want to list. If no device
is specified, lsblk will list all block devices.

Running the lsblk command

If I run lsblk in Terminal, it returns the following:

NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda      8:0    0   50G  0 disk
├─sda1   8:1    0    1M  0 part
├─sda2   8:2    0  513M  0 part /boot/efi
└─sda3   8:3    0 49.5G  0 part /
sr0     11:0    1 50.4M  0 rom  /media/maria/VBox_GAs_7.0.18

If I want to get all block devices including empty ones, I would run the
following:

lsblk -a

Which for me returns:

NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
loop0    7:0    0    0B  0 loop
loop1    7:1    0    0B  0 loop
loop2    7:2    0    0B  0 loop
loop3    7:3    0    0B  0 loop
loop4    7:4    0    0B  0 loop
loop5    7:5    0    0B  0 loop
loop6    7:6    0    0B  0 loop
loop7    7:7    0    0B  0 loop
sda      8:0    0   50G  0 disk
├─sda1   8:1    0    1M  0 part
├─sda2   8:2    0  513M  0 part /boot/efi
└─sda3   8:3    0 49.5G  0 part /
sr0     11:0    1 50.4M  0 rom  /media/maria/VBox_GAs_7.0.18

If I want to print out the information in list format, I would run the
following:

lsblk -l

Which for me returns:

NAME MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda    8:0    0   50G  0 disk
sda1   8:1    0    1M  0 part
sda2   8:2    0  513M  0 part /boot/efi
sda3   8:3    0 49.5G  0 part /
sr0   11:0    1 50.4M  0 rom  /media/maria/VBox_GAs_7.0.18

Now devices are listed without showing which ones are related to
each other like with the lsblk command.

If I run the following command in Terminal:

lsblk -p

For me, it returns the following:

NAME        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
/dev/sda      8:0    0   50G  0 disk
├─/dev/sda1   8:1    0    1M  0 part
├─/dev/sda2   8:2    0  513M  0 part /boot/efi
└─/dev/sda3   8:3    0 49.5G  0 part /
/dev/sr0     11:0    1 50.4M  0 rom  /media/maria/VBox_GAs_7.0.18

The -p flag produces output in key value pairs. The big difference here
is the absolute path to the device as well as the relationships between
related devices is also displayed. To learn more about lsblk, run
man lsblk in Terminal.

Footnotes

[^1]: udev (db) or
user /dev is systemd's device manager for the Linux kernel. It manages device
nodes in /dev and handles all user space actions when adding or removing
devices.

According to man udev, udev supplies the system software with device events,
manages permissions of device nodes and may create additional symlinks in the
/dev/ directory, or renames network interfaces. The kernel usually just assigns
unpredictable device names based on the order of discovery. Meaningful symlinks
or network device names provide a way to reliably identify devices based on
their properties or current configuration.

The udev daemon,
systemd-udevd.service(8),
receives device uevents directly from the kernel whenever a device is added or
removed from the system, or it changes its state. When udev receives a device
event, it matches its configured set of rules against various device attributes
to identify the device. Rules that match may provide additional device
information to be stored in the udev database or to be used to create meaningful
symlink names.

All device information udev processes is stored in the udev database and sent
out to possible event subscribers. Access to all stored data and the event
sources is provided by the library libudev.

Related Resources

• The Linux Filesystem Hierarchy: mariadcampbell.com
• How to List All Block Devices in Linux | lsblk Command: Geeks for Geeks