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104-the-lsblk-command.md

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The lsblk command

Summary

The lsblk command displays the block and loop devices on the system. It is especially useful when you want to format disks, write filesystems, check the filesystem and know the mount point of a device.

Examples

  1. Basic usage is fairly simple - just execute 'lsblk' sans any option.
lsblk
  1. Make lsblk display empty devices as well
lsblk -a
  1. Make lsblk print size info in bytes
lsblk -b
  1. Make lsblk print zone model for each device
lsblk -z
  1. Make lsblk skip entries for slaves
lsblk -d
  1. Make lsblk use ascii characters for tree formatting
lsblk -i
  1. Make lsblk display info about device owner, group, and mode
lsblk -m
  1. Make lsblk output select columns
lsblk -o NAME,SIZE

Syntax

lsblk [options] [<device> ...]

Reading information given by lsblk

On running lsblk with no flags or command-line arguments, it writes general disk information to the STDOUT. Here is a table that interpretes that information:

Column Name Meaning Interpretation
NAME Name of the device. Shows name of the device.
RM Removable. Shows 1 if the device is removable, 0 if not.
SIZE Size of the device. Shows size of the device.
RO Read-Only. Shows 1 if read-only, 0 if not.
TYPE The type of block or loop device. Shows disk for entire disk and part for partitions.
MOUNTPOINTS Where the device is mounted. Shows where the device is mounted. Empty if not mounted.

Reading information of a specific device

lsblk can display information of a specific device when the device's absolute path is passed to it. For example, lsblk command for displaying the information of the sda disk is:

lsblk /dev/sda

Useful flags for lsblk

Here is a table that show some of the useful flags that can be used with lsblk

Short Flag Long Flag Description
-a --all lsblk does not list empty devices by default. This option disables this restriction.
-b --bytes Print the SIZE column in bytes rather than in human-readable format.
-d --nodeps Don't print device holders or slaves.
-D --discard Print information about the discard (TRIM, UNMAP) capabilities for each device.
-E --dedup column Use column as a de-duplication key to de-duplicate output tree. If the key is not available for the device, or the device is a partition and parental whole-disk device provides the same key than the device is always printed.
-e --exclude list xclude the devices specified by a comma-separated list of major device numbers. Note that RAM disks (major=1) are excluded by default. The filter is applied to the top-level devices only.
-f --fs Displays information about filesystem.
-h --help Print a help text and exit.
-l --include list Displays all the information in List Format.
-J --json Displays all the information in JSON Format.
-l --list Displays all the information in List Format.
-m --perms Displays info about device owner, group and mode.
-M --merge Group parents of sub-trees to provide more readable output for RAIDs and Multi-path devices. The tree-like output is required.
-n --noheadings Do not print a header line.
-o --output list Specify which output columns to print. Use --help to get a list of all supported columns.
-O --output-all Displays all available columns.
-p --paths Displays absolute device paths.
-P --pairs Use key="value" output format. All potentially unsafe characters are hex-escaped (\x)
-r --raw Use the raw output format. All potentially unsafe characters are hex-escaped (\x) in NAME, KNAME, LABEL, PARTLABEL and MOUNTPOINT columns.
-S --scsi Output info about SCSI devices only. All partitions, slaves and holder devices are ignored.
-s --inverse Print dependencies in inverse order.
-t --topology Output info about block device topology. This option is equivalent to "-o NAME,ALIGNMENT,MIN-IO,OPT-IO,PHY-SEC,LOG-SEC,ROTA,SCHED,RQ-SIZE".
-T --tree[=column] Displays all the information in Tree Format.
-V --version Output version information and exit.
-w --width pecifies output width as a number of characters. The default is the number of the terminal columns, and if not executed ona terminal, then output width is not restricted at all by default.
-x --sort [column] Sort output lines by column. This option enables --list output format by default. It is possible to use the option --tree to force tree-like output and than the tree branches are sorted by the column.
-z --zoned Print the zone model for each device.
- --sysroot directory Gather data for a Linux instance other than the instance from which the lsblk command is issued. The specified directory is the system root of the Linux instance to be inspected.

Exit Codes

Like every Unix / Linux Program, lslbk returns an exit code to the environment. Here is a table of all the exit codes.

Exit Code Meaning
0 Exit with success.
1 Exit with failure.
32 Specified device(s) not found.
64 Some of the specified devices were found while some not.