How to check total space and available space in Linux using the terminal?

In Linux/Unix systems, the df (disk free) command is the primary tool for checking storage details and disk space usage. It displays total space, used space, and available space for mounted file systems through the terminal.

df (disk free) command

The df command reports file system disk space usage in the Linux system. By default, it shows space usage in 1K blocks, but various options make the output more readable and useful for different purposes.

Syntax

The general syntax of the df command is as follows:

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

Common Options

Basic Usage

To check basic disk space usage, run the df command without any options:

$ df

Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/sda1       20960256 8234567  11718888  42% /
/dev/sda5        1048576  524288    495616  52% /home
tmpfs            2097152       0   2097152   0% /tmp

The default output shows space in 1K blocks, which can be difficult to interpret. The numbers represent kilobytes but lack clear units.

Human-Readable Format

To display output in an easily understandable format, use the -h option:

$ df -h

Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1        21G  8.1G   12G  42% /
/dev/sda5      1024M  512M  485M  52% /home
tmpfs           2.1G     0  2.1G   0% /tmp

This format uses familiar units like G (gigabytes), M (megabytes), and K (kilobytes) in powers of 1024.

SI Units Format

To display storage in powers of 1000 (decimal), use the -H option:

$ df -H

Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1        22G  8.4G   12G  42% /
/dev/sda5       1.1G  537M  507M  52% /home
tmpfs           2.2G     0  2.2G   0% /tmp

File System Type Information

To include file system types in the output, combine -h with -T:

$ df -hT

Filesystem     Type      Size  Used Avail Use% Mounted on
/dev/sda1      ext4       21G  8.1G   12G  42% /
/dev/sda5      ext4     1024M  512M  485M  52% /home
tmpfs          tmpfs     2.1G     0  2.1G   0% /tmp

Key Points

• The -h option is most commonly used for readable output in binary units (1024-based).

• The -H option displays decimal units (1000-based), similar to storage manufacturer specifications.

• The Use% column shows the percentage of used space, helping identify full partitions quickly.

• The Mounted on column indicates where each file system is mounted in the directory tree.

Conclusion

The df command is essential for monitoring disk space usage in Linux systems. Using the -h option provides human-readable output, making it easy to quickly assess available storage space and identify partitions that may need attention.