How to Use the Command 'lsblk' (with examples)

The ’lsblk’ command in Linux is a powerful utility used to list information about all available or specified block devices. It produces a detailed, hierarchical view of storage devices, their partitions, sizes, and, optionally, their filesystem types and mount points. This tool is essential for systems administrators and developers who need to assess and manage disk resources on a Linux system efficiently. The command can display information in various formats and levels of detail, making it flexible for different use cases.

Use case 1: List all storage devices in a tree-like format

Code:

lsblk

Motivation:

The primary use of lsblk without any options is to get a quick overview of all connected block storage devices in a system. This tree-like visualization is straightforward, making it easy to identify the device hierarchy, which includes disks and their respective partitions or logical volumes.

Explanation:

• lsblk: This base command lists all block devices connected to the system in a format that shows parent-child relationships.

Example output:

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0 931.5G  0 disk
├─sda1   8:1    0   512M  0 part /boot
└─sda2   8:2    0 931G  0 part /
sdb      8:16   0 223.6G  0 disk
└─sdb1   8:17   0 223.6G  0 part

Use case 2: Also list empty devices

Code:

lsblk -a

Motivation:

Sometimes, it’s important to see devices that may not be currently used or mounted. Listing all devices, including empty ones, helps identify unused or uninitialized disks that can be repurposed or configured.

Explanation:

• -a: This option ensures that all devices, including those not in use or empty, are displayed in the output. It’s vital when managing or auditing all hardware resources.

Example output:

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0 931.5G  0 disk
├─sda1   8:1    0   512M  0 part /boot
└─sda2   8:2    0 931G  0 part /
sdb      8:16   0 223.6G  0 disk
└─sdb1   8:17   0 223.6G  0 part
sdc      8:32   1     0B  1 disk

Use case 3: Print the SIZE column in bytes rather than in a human-readable format

Code:

lsblk -b

Motivation:

Displaying sizes in bytes can be crucial for certain technical scenarios, such as scripting, because it provides precision without any conversion involved. This accuracy helps in programmatically processing or comparing device sizes.

Explanation:

• -b: This option displays the sizes of devices in bytes, ensuring that there is no ambiguity or need for human-related size conversion.

Example output:

NAME   MAJ:MIN RM         SIZE RO TYPE MOUNTPOINT
sda      8:0    0 1000204886016  0 disk
├─sda1   8:1    0     536870912  0 part /boot
└─sda2   8:2    0  999667488768  0 part /
sdb      8:16   0  240057409536  0 disk
└─sdb1   8:17   0  240057409536  0 part

Use case 4: Output info about filesystems

Code:

lsblk -f

Motivation:

Seeing the filesystem types assigned to each partition helps when determining the purpose of each disk or identifying unauthorized and erroneous configurations. This is fundamental for system administration and storage management.

Explanation:

• -f: Outputs the filesystem type for each block device, providing additional context for understanding the current use and configuration of disk storage.

Example output:

NAME   FSTYPE LABEL  UUID                                 MOUNTPOINT
sda
├─sda1 ext4          1d2e471e-7c68-4d3e-9a55-1d4c37f9a611 /boot
└─sda2 ext4          3c965a7c-bd94-4cc9-bb29-2d4081c21131 /
sdb
└─sdb1 ext4          5d7c17b2-8d14-4f92-b3f9-0eaf20c8a42e

Use case 5: Use ASCII characters for tree formatting

Code:

lsblk -i

Motivation:

When working in environments where the display terminal may not support special or graphical characters, using ASCII can prevent rendering issues while still delivering readable and structured output.

Explanation:

• -i: This flag changes the tree formatting to use only ASCII characters, ensuring compatibility with legacy terminals or console-only access.

Example output:

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0 931.5G  0 disk
|--sda1   8:1    0   512M  0 part /boot
`--sda2   8:2    0 931G  0 part /
sdb      8:16   0 223.6G  0 disk
`--sdb1   8:17   0 223.6G  0 part

Use case 6: Output info about block-device topology

Code:

lsblk -t

Motivation:

Understanding the topology of block devices is useful for performance tuning and system architecture planning. It allows users to see the relationship between physical and logical volumes and how they are layered.

Explanation:

• -t: This flag outputs detailed information about the block-device topology, including the hierarchical structure and relationships between devices and partitions.

Example output:

NAME   ALIGNMENT MIN-IO OPT-IO PHY-SEC LOG-SEC ROTA SCHED     RQ-SIZE  RA WSAME
sda           0    512      0     512     512    1 deadline      128 128    0B
├─sda1        0    512      0     512     512    1 deadline      128 128    0B
└─sda2        0    512      0     512     512    1 deadline      128 128    0B
sdb           0    512      0     512     512    1 deadline      128 128    0B
└─sdb1        0    512      0     512     512    1 deadline      128 128    0B

Use case 7: Exclude the devices specified by the comma-separated list of major device numbers

Code:

lsblk -e 1,7

Motivation:

In some situations, you might want to exclude certain devices from the output to focus on the devices you’re managing directly. This exclusion is useful for filtering out irrelevant devices like virtual file systems or loop devices.

Explanation:

• -e 1,7: This option excludes devices whose major device numbers are in the comma-separated list 1,7. It helps tailor the output, removing devices deemed unnecessary for the current task.

Example output:

NAME MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda    8:0    0 931.5G  0 disk
├─sda1 8:1    0   512M  0 part /boot
└─sda2 8:2    0 931G    0 part /
sdb    8:16   0 223.6G  0 disk
└─sdb1 8:17   0 223.6G  0 part

Use case 8: Display a customized summary using a comma-separated list of columns

Code:

lsblk --output NAME,SERIAL,MODEL,TRAN,TYPE,SIZE,FSTYPE,MOUNTPOINT

Motivation:

Customizing the columns to display allows you to focus on specific characteristics of devices that are pertinent to your task. Whether it’s for documentation or troubleshooting, having just the relevant details avoids clutter.

Explanation:

• --output NAME,SERIAL,MODEL,TRAN,TYPE,SIZE,FSTYPE,MOUNTPOINT: This option specifies a custom list of columns to be shown, providing only the essential information required for the current context.

Example output:

NAME SERIAL            MODEL      TRAN   TYPE SIZE FSTYPE MOUNTPOINT
sda  S1Z8J9AH304349T   MZ7LN512HMTP-000L1 sata   disk  500G
├─sda1                partition  500M ext4   /boot
└─sda2                partition  499G ext4   /
sdb  WD-WX61EA5RJ5C3   WDC WD10EZEX sata   disk  1T
└─sdb1                partition  1T   ntfs

Conclusion:

The lsblk command offers a variety of options to list block devices and their properties in Linux, accommodating different needs from basic listings to complex use cases involving filtering and formatting. By understanding and utilizing these options, users can effectively manage their system’s disk resources, ensuring that they maintain control and can extract the necessary information with precision and ease.