Most Linux systems comes with a program called df, that stands for “disk free”. It displays the disk usage and available space for each disk that you have mounted in your system.

Example:

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/nvme0n1p2  453G   19G  412G   5% /
/dev/nvme0n1p1  511M   51M  461M  10% /boot/efi

Option -h here means human-readable format. When you use it, the results are displayed in megabytes (M), gigabytes (G), etc. instead of bytes.

If you like to check only one partition, like the root partition (/), you can specify it as an argument:

$ df -h /
Filesystem      Size  Used Avail Use% Mounted on
/dev/nvme0n1p2  453G   19G  412G   5% /

For modifying the output, you can use –output option and provide column names to be included as a comma-separated list.

$ df --output=target,avail /
Mounted on     Avail
/          431122336

Valid column names are: source, fstype, itotal, iused, iavail, ipcent, size, used, avail, pcent, file and target.