How to Check Disk Space and Usage in Linux

Managing disk space is a critical responsibility for Linux system administrators and users. A full disk can degrade system performance, cause services to fail, and can even prevent users from logging in or accessing essential directories. Whether you manage a local machine, a bare metal server, or a cloud server such as a Vultr Compute Instance, understanding disk usage helps ensure system stability and avoid unexpected outages.

This article explains how to check disk space and usage on a Linux system using built-in command-line tools. You will learn how to identify large files, analyze mounted file systems, and troubleshoot disk-related issues efficiently.

Commands to Check Disk Space and Usage

Linux includes several essential command-line tools that help monitor and manage disk space efficiently. These tools offer insight into the amount of storage used, available space, and which files or directories are consuming the most disk space. Regular use of these tools helps prevent system slowdowns, service interruptions, and data loss due to full partitions.

Common Disk Related Commands

How to Check Disk Space

The df command provides a quick overview of disk usage across all mounted file systems. Use it to identify partitions with low free space and act before system performance is degraded.

df Command Syntax

The basic syntax for the df command is as follows:

df [OPTION]... [FILE]...

Within the command:

• [OPTION]: Represents the options or flags passed to the df command.
• [FILE]: Specifies a file or directory. If not provided, df will display the disk space for all mounted file systems.

Common df Command Options

Examples of Using the df Command

• To display the disk usage of all mounted file systems in a human-readable format.

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  $ df -h

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  Your output should be similar to the one below:

  Filesystem      Size  Used Avail Use% Mounted on
  ...
  /dev/vda2       150G   12G  132G   9% /
  /dev/vda1       260M  7.1M  253M   3% /boot/efi
  tmpfs           768M  4.0K  768M   1% /run/user/1000
  /dev/vdb1        40G  1.1G   37G   3% /mnt
  /dev/vdc1        40G  375M   40G   1% /home

  In the above output you have:

  • Filesystem: The name of the file system or the device (for example, partition, virtual file system).
  • Size: The total size of the file system or partition.
  • Used: The amount of disk space currently in use on the file system.
  • Avail: The amount of free (available) disk space on the file system.
  • Use%: The percentage of disk space that is currently used.
  • Mounted on: The directory where the file system is mounted.

• To check disk usage of a specific mount point such as /mnt, use the below command.

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  $ df -h /mnt

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  Your output should be similar to the one below:

  Filesystem      Size  Used Avail Use% Mounted on
  /dev/vdb1        40G  1.1G   37G   3% /mnt

  This command displays the disk space information of /dev/vdb1 partition mounted on /mnt directory.

• To check the disk space information for a specific file system type, such as ext.

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  $ df -h -t ext4

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  This command displays disk usage only for file systems of type ext4 in a human-readable format.

  Your output should be similar to the one below:

  Filesystem      Size  Used Avail Use% Mounted on
  /dev/vda2       150G   12G  132G   9% /
  /dev/vdb1        40G  1.1G   37G   3% /mnt

  In the above output, both /dev/vda2 and /dev/vdb1 are ext4 partitions. The Size, Used, and Avail columns help monitor disk usage for these specific file systems.

• To exclude certain file system types, such as tmpfs, from the output.

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  $ df -h -x tmpfs

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  Your output should be similar to the one below:

  Filesystem      Size  Used Avail Use% Mounted on
  ...
  /dev/vda2       150G   12G  132G   9% /
  /dev/vda1       260M  7.1M  253M   3% /boot/efi
  /dev/vdb1        40G  1.1G   37G   3% /mnt
  /dev/vdc1        40G  375M   40G   1% /home

• To include the type of each file system in the output.

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  $ df -hT

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  This command displays disk space information along with the type of each file system, helping identify the file system format used for each mount point.

  Your output should be similar to the one below:

  Filesystem     Type      Size  Used Avail Use% Mounted on
  ...
  tmpfs          tmpfs     1.5G   29M  1.5G   2% /run
  /dev/vda2      ext4      150G   12G  132G   9% /
  /dev/vda1      vfat      260M  7.1M  253M   3% /boot/efi
  /dev/vdb1      ext4       40G  1.1G   37G   3% /mnt
  /dev/vdc1      xfs        40G  375M   40G   1% /home

• To display inode usage, which is useful for monitoring the number of files and directories.

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  $ df -i

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  Your output should be similar to the one below:

  Filesystem       Inodes  IUsed    IFree IUse% Mounted on
  ...
  /dev/vda2      41611680 123735 41487945    1% /
  /dev/vdb1       2621440     12  2621428    1% /mnt
  /dev/vdc1      20971008   2755 20968253    1% /home

  In the above output:

  • Inodes: The total number of inodes available in the file system (an inode is a data structure that stores metadata about files and directories).
  • IUsed: The number of inodes that are being used.
  • IFree: The number of free inodes available for new files or directories.
  • IUse%: The percentage of inodes that are being used.

How to Check Disk Usage

The du (disk usage) command in Linux is used to estimate and display the disk space used by files and directories. It's an essential tool for monitoring disk usage, helping you identify large files or directories that may need to be cleaned up to free space.

du Command Syntax

The basic syntax for the du command is as follows:

du [OPTION]... [FILE]...

Within the command:

• [OPTION]: Represents the options or flags passed to the du command.
• [FILE]: Specifies the file or directory for which disk usage is calculated. If not provided, du shows the usage of the current directory.

du Command Options

Examples of Using the du Command

• To check the disk usage information of a specific directory in a human-readable format, use the -sh options.

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  $ sudo du -sh /path/to/directory  

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  It's recommended to use sudo with this command, as some files or directories may require elevated permissions.

  In the above command:

  • -s: Shows only the total disk usage (summary).
  • -h: Prints sizes in a human-readable format.

• To include hidden files (those starting with a dot) in the disk usage report, use the -a option.

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  $ sudo du -ah /path/to/directory

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  In this command:

  • -a: Includes all files, not just directories, in the output.

  This is useful for identifying the disk usage of all files, including configuration files that are typically hidden.

• To exclude certain files or directories from the disk usage calculation, use the --exclude option.

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  $ sudo du -ah --exclude='*.log' /path/to/directory

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  In this command:

  • --exclude='*.log': Excludes all files with the .log extension from the report.

  This is useful for ignoring temporary or log files that are not relevant to the analysis.

• To list the disk usage of all subdirectories within a specific directory (for example, /var), use the --max-depth=1 flag. This limits the display to the top-level subdirectories.

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  $ sudo du -h --max-depth=1 /var

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  Your output should be similar to the one below:

  ...
  22M     /var/log
  97M     /var/lib
  4.0K    /var/yp
  4.0K    /var/preserve
  216M    /var

• To sort the directories by disk usage, use the sort command in combination with du. For example, to sort the subdirectories of /var from largest to smallest.

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  $ sudo du -h --max-depth=1 /var | sort -rh

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  Your output should be similar to the one below:

  216M    /var
  97M     /var/lib
  97M     /var/cache
  22M     /var/log
  ...

  In this output, the directories are sorted in descending order by their disk usage, with the largest directory listed first.

• Use the find command along with du to locate large files in a directory. For example, to find all files larger than 50MB within the /var directory.

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  $ sudo find /var -type f -size +50M -exec ls -lh {} \;

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  Your output should be similar to the one below:

  -rw-r--r--. 1 root root 65M May  6 20:29 /var/lib/rpm/rpmdb.sqlite

  This command lists all files in /var larger than 50 MB. The output shows the file size, permissions, and last modification date of each file.

Conclusion

You have now learned how to effectively manage disk space on your Linux system using essential command-line tools like df, du, and find. By monitoring disk usage, you can identify large files, analyze mounted file systems, and prevent potential system slowdowns or outages due to full disks. With the commands and examples provided in this article, you are equipped to keep your system running and avoid disk-related issues.