Using the df Command
The df command is used to report file system disk space usage.
It's a useful tool for checking available storage on your system.
All examples below use a hypothetical output for demonstration:
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda1 20480000 1024000 19456000 5% /
tmpfs 4096000 0 4096000 0% /dev/shm
/dev/sdb1 10240000 512000 9728000 5% /mnt/dataUnderstanding the Output
The df command output consists of several columns, each representing different aspects of the file system's disk usage:
- Filesystem : The name of the file system.
- 1K-blocks : Total size of the file system in 1K blocks.
- Used : Amount of space used.
- Available : Amount of space available for use.
- Use% : Percentage of space used.
- Mounted on : Directory where the file system is mounted.
Basic Usage
To display disk space usage, use df :
Example: Basic Usage
df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda1 20480000 1024000 19456000 5% /
tmpfs 4096000 0 4096000 0% /dev/shm
/dev/sdb1 10240000 512000 9728000 5% /mnt/dataOptions
The df command has options to change how it works:
- -h - Show sizes in human-readable format (e.g., KB, MB)
- -a - Show all file systems, even empty ones
- -T - Show the type of file system
- -i - Show inode usage
- -P - Use POSIX output format
Show Sizes in Human-Readable Format
The -h option allows you to show sizes in human-readable format.
Example: Show Sizes in Human-Readable Format
df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 20G 1.0G 19G 5% /
tmpfs 4.0G 0 4.0G 0% /dev/shm
/dev/sdb1 10G 500M 9.5G 5% /mnt/dataShow All File Systems
The -a option allows you to show all file systems, even empty ones.
Example: Show All File Systems
df -a
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda1 20480000 1024000 19456000 5% /
tmpfs 4096000 0 4096000 0% /dev/shm
/dev/sdb1 10240000 512000 9728000 5% /mnt/data
none 0 0 0 - /proc/sys/fs/binfmt_miscShow File System Type
The -T option allows you to show the type of file system.
Example: Show File System Type
df -T
Filesystem Type 1K-blocks Used Available Use% Mounted on
/dev/sda1 ext4 20480000 1024000 19456000 5% /
tmpfs tmpfs 4096000 0 4096000 0% /dev/shm
/dev/sdb1 ext4 10240000 512000 9728000 5% /mnt/dataFile System Type: This indicates the format and structure used to store and organize data on a disk.
Common file system types include ext4 , ntfs , and vfat .
Each type has its own features, limitations, and compatibility with operating systems.
Show Inode Usage
The -i option allows you to show inode usage.
Example: Show Inode Usage
df -i
Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/sda1 1310720 2560 1308160 1% /
tmpfs 1048576 1 1048575 1% /dev/shm
/dev/sdb1 655360 100 655260 1% /mnt/dataInodes: Inodes are data structures used by many file systems to store information about files and directories, such as their size, owner, permissions, and timestamps.
Each file or directory has a unique inode. The df -i command shows inode usage, which can be important for systems with many small files.
Use POSIX Output Format
The -P option allows you to use the POSIX output format.
Example: Use POSIX Output Format
df -P
Filesystem 1024-blocks Used Available Capacity Mounted on
/dev/sda1 20480000 1024000 19456000 5% /
tmpfs 4096000 0 4096000 0% /dev/shm
/dev/sdb1 10240000 512000 9728000 5% /mnt/dataPOSIX: POSIX (Portable Operating System Interface) is a set of standards specified by the IEEE for maintaining compatibility between operating systems.
The df -P option provides output in a POSIX-compliant format, ensuring consistency across different environments and systems.
Combining Options
Options can be combined to provide more detailed output.
For example, df -hT shows sizes in human-readable format along with the file system type.
Example: Combine Options
df -hT
Filesystem Type Size Used Avail Use% Mounted on
/dev/sda1 ext4 20G 1.0G 19G 5% /
tmpfs tmpfs 4.0G 0 4.0G 0% /dev/shm
/dev/sdb1 ext4 10G 500M 9.5G 5% /mnt/data