How to find a list of block devices information

The lsblk command is used to display a list of information about all available block devices in Linux systems. However, it does not list information about RAM disks by default. Examples of block devices include hard disks, flash drives, and CD-ROM drives. This article explains how to find and display block device information on Linux machines.

Installing lsblk

For Fedora and CentOS systems, use the following command −

$ sudo yum install util-linux-ng

For Ubuntu and Linux Mint systems, use the following command −

$ sudo apt-get install util-linux -y

Basic Usage

To find the default list of all block devices, use the following command −

$ lsblk

The sample output should be like this −

NAME                             MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda                                8:0   0  931.5G  0 disk
??sda1                             8:1   0    500M  0 part /boot/efi
??sda2                             8:2   0     40M  0 part
??sda3                             8:3   0    128M  0 part
??sda4                             8:4   0    750M  0 part
??sda5                             8:5   0  462.1G  0 part
??sda6                             8:6   0  452.1G  0 part /
??sda7                             8:7   0      8G  0 part
? ??vol_grp1-logical_vol1 (dm-0) 252:0   0    100M  0 lvm
??sda8                             8:8   0    7.9G  0 part [SWAP]
sr0

Understanding the Output

The output columns provide the following information −

• NAME − Indicates the device name.

• MAJ:MIN − Shows the major and minor device number information.

• RM − Shows whether the device is removable (1) or not (0).

• SIZE − Displays the size of the device.

• RO − Indicates whether a device is read-only (1) or not (0).

• TYPE − Shows whether the block device is a disk, partition (part), or other type like LVM.

• MOUNTPOINT − Indicates the mount point where the device is mounted.

Common lsblk Options

Display All Devices Including Empty Ones

To show a list of all devices including empty devices and RAM disks, use the following command −

$ lsblk -a

This will display additional devices like loop devices and RAM disks that are normally hidden.

Display Ownership and Permissions

To display information related to the owner, group, and mode of the block device, use the following command −

$ lsblk -m

The sample output includes ownership details −

NAME                       SIZE OWNER GROUP    MODE
sda                      931.5G root  disk     brw-rw----
??sda1                     500M root  disk     brw-rw----
??sda2                      40M root  disk     brw-rw----
??sda6                   452.1G root  disk     brw-rw----
??sda8                     7.9G root  disk     brw-rw----

Display Size in Bytes

To find the size of devices in bytes rather than human-readable format, use the following command −

$ lsblk -b

Hide Slave/Holder Information

If you do not want to display slave devices or partition information, use the following command −

$ lsblk -d

The sample output shows only top-level devices −

NAME MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda    8:0   0 931.5G  0 disk
sr0   11:0   1  1024M  0 rom

Comparison of Key Options

Conclusion

The lsblk command is an essential tool for displaying block device information in Linux systems. Its various options allow you to customize the output to show device hierarchies, ownership details, exact sizes, or simplified device lists depending on your specific needs.