Checking Filesystem Information with `lsblk`

Exploring Your Linux Filesystem with the `lsblk` Command

When managing a Linux system, it's essential to have a grasp of your disk drives and their respective partitions – not just for regular maintenance, but also for performing tasks like troubleshooting, system monitoring, or even when planning upgrades. One of the simplest and most effective tools for this purpose is the lsblk command, which stands for "list block devices."

What is `lsblk`?

lsblk is a utility in Linux used to display information about all available or the specified block devices. It reads the sysfs filesystem and udev db to gather information. Block devices, in Linux terms, are storage devices that can be used for storing data, such as hard drives, solid state drives, and USB drives. This tool provides a neatly-formatted overview of these devices, their partitions, sizes, and where they are mounted in the filesystem.

Basic Usage of `lsblk`

To begin with, simply open your terminal and type lsblk and press Enter. This will display a list of all the block devices, along with their major and minor device numbers, their size, the type of device, and where they are mounted:

$ lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0   100G  0 disk 
├─sda1   8:1    0    96G  0 part /
├─sda2   8:2    0     1K  0 part 
└─sda5   8:5    0     4G  0 part [SWAP]
sdb      8:16   0   500G  0 disk 
├─sdb1   8:17   0   500G  0 part /data

In the output above, the device names (sda, sdb) are listed with their partitions (sda1, sdb1), sizes, and mount points. The RM column shows whether the device is removable. The RO column tells if the device is read-only. The TYPE column shows whether the device is a disk or a partition (part).

Advanced Options

Show Filesystem Details

For more detailed output, including the filesystem type, you can combine lsblk with the -f option:

$ lsblk -f
NAME   FSTYPE LABEL UUID                                 MOUNTPOINT
sda                                                     
├─sda1 ext4         7f49265f-8c08-4503-8844-6239db85ed1e /
├─sda2                                                   
└─sda5 swap         d6f6bb73-d6b7-4a1f-93d0-7869cb10f010 [SWAP]
sdb                                                     
├─sdb1 xfs          d8325f76-fbc4-4f55-b256-407ea3b0113e /data

This output now includes the filesystem type (FSTYPE), and may also show a label (LABEL) and UUID if available, which are useful for identifying and mounting file systems.

Exclude Loop Devices

On systems with many loop devices, for instance when using Docker, Cloudbase, or when mounting image files, output might get cluttered. To exclude them, use the -e option:

$ lsblk -e 7

This usage of -e filters out devices with a major number of 7, which are loop devices.

JSON and Tree View Outputs

For scripting purposes, a JSON output can be very useful. lsblk offers a JSON formatted output which can be parsed by tools like jq:

$ lsblk -J

For human-readable insights, especially during presentations or for better clarity, you can use the tree (-T) output:

$ lsblk -T

Conclusion

Whether you're a seasoned system administrator or a curious Linux beginner, understanding and using lsblk is crucial for managing and inspecting your filesystems and block devices. Its full power is seen when combined with other commands and options, tailored to suit specific information needs. Get comfortable with lsblkk – it’s a tool that pairs simplicity with profound capabilities, helping you to navigate the storage architecture of your Linux systems efficiently.

Exploring Your Linux Filesystem with the lsblk Command

What is lsblk?

Basic Usage of lsblk