Find free space linux

Linux / Unix – Checking Free Disk Space

Tutorial details
Difficulty level	Easy
Root privileges	No
Requirements	None
Est. reading time	1m

(a) df command : Report file system disk space usage.

(b) du command : Estimate file space usage.

df command examples to check free disk space

Type df -h or df -k to list free disk space:
$ df -h
OR
$ df -k
Sample outputs that show disk space utilization:

The df utility displays statistics about the amount of free disk space on the specified file system or on the file system of which file is a part. Values are displayed in 512-byte per block counts. The -H option is called as “Human-readable” output. It use unit suffixes: Byte, Kilobyte, Megabyte, Gigabyte, Terabyte and Petabyte in order to reduce the number of digits to four or fewer using base 10 for sizes i.e. you see 30G (30 Gigabyte).

How to check free disk space in Linux

To see the file system’s complete disk usage pass the -a option:
df -a
Find out disk usage and filesystem type by passing the -T option:
df -T
Want to get used and free inodes information on Linux? Try:
df -i

du command examples for checking free and used disk space

The du command shows how much space one ore more files or directories is using, enter:
$ du -sh
Sample outputs:

Fig.01: Unix df and du command outputs from my FreeBSD server

Say hello to ncdu command

ncdu (NCurses Disk Usage) is a curses-based version of the well-known ‘du’, and provides a fast way to see what directories are using your disk space. One can install with the following apt command/apt-get command:
sudo apt install ncdu
For RHEL/CentOS, first enable EPEL repo (see CentOS 8 turn on EPEL repo and RHEL 8 enable epel repo) and type the following yum command:
sudo yum install ncdu
Now just type:
ncdu
ncdu [dir] ncdu /etc/

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GUI program

Above programs are good if GUI is not installed or you are working with remote system over the ssh based session. Linux and UNIX-like oses comes with KDE and Gnome desktop system. You will find Free Disk Space Applet located under GUI menus. Here is a sample from Fedora Linux version 22 system:

Conclusion

You learned how to keep track of disk utilization, and disk space with various Linux and Unix commands.

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Linux Check Disk Space Command To View System Disk Usage

Linux commands to check disk space using:

1. df command – Shows the amount of disk space used and available on Linux file systems.
2. du command – Display the amount of disk space used by the specified files and for each subdirectory.
3. btrfs fi df /device/ – Show disk space usage information for a btrfs based mount point/file system.

Linux check disk space with df command

1. Open the terminal and type the following command to check disk space.
2. The basic syntax for df is:
   df [options] [devices]
   Type:
3. df
4. df -H

Fig.01: df command in action

See information about specific filesystem

You can give a device or mount point as an argument, and df report data only for the filesystem physically residing on that device. For example, the following command provides information only for the partition /dev/sda:
$ df /dev/sda
$ df -h /dev/sdc1
$ df /data/
Sample outputs:

Understanding df command output

The valid fields are as follows:

Display name	Valid field name (for —output option)	Description
Filesystem	source	The source of the mount point, usually a device.
1K-blocks	size	Total number of blocks.
Used	used	Number of used blocks.
Available	avail	Number of available blocks.
Use%	pcent	Percentage of USED divided by SIZE.
Mounted on	target	The mount point.

You can pass the output format defined by ‘valid field name’ as follows:
$ df —output=field1,field2.
$ df —output=source,used,avail /data/
Sample outputs:

You can print all available fields, enter:
$ df —o
Sample outputs:

Express df output in human readable form

Pass the -h option to see output in human readable format. You will device size in gigabytes or terabytes or megabytes:
$ df -h ### Human format
$ df -m ### Show output size in one-megabyte
$ df -k ### Show output size in one-kilobyte blocks (default)

Display output using inode usage instead of block usage

An inode is a data structure on a Linux file system that stores all information about file. To list inode information, enter:
$ df -i
$ df -i -h
Sample outputs:

Find out the type of each file system displayed

Pass the -T option to display the type of each filesystems listed such as ext4, btrfs, ext2, nfs4, fuse, cgroup, cputset, and more:
$ df -T
$ df -T -h
$ df -T -h /data/
Sample outputs:

Limit listing to file systems of given type

The syntax is:
$ df -t ext3 #Only see ext3 file system
$ df -t ext4 #Only see ext4 file system
$ df -t btrfs #Only see btrfs file system

Exclude given file system type

To list all but exclude ext2 filesystem pass the -x TYPE option, enter:
$ df -x ext2

Show all file system

Pass the -a or —all option to the df command to include in its output filesystems that have a size of zero blocks, run:
$ df -a

These file systems omitted by default.

Getting more help about the df command

Pass the —help option see a brief help message:
$ df —help
Or read its man page by typing the following command:
$ man df

Linux check disk space with the du command

The NA command is very useful to track down disk space hogs. It is useful to find out the names of directories and files that consume large amounts of space on a disk. The basic syntax is:
du
du /path/do/dir
du [options] [directories and/or files]
To see the names and space consumption of each of the directories including all subdirectories in the directory tree, enter:
$ du
Sample outputs:

The first column is expressed in kilobytes (file size) and the second column is the filename or directory name.

See du output in human readable format

Pass the -h option to display size in K (kilobytes), M (megabytes), G (gigabytes) instead of the default kilobytes:
$ du -h
Sample outputs:

Finding information about any directory trees or files

To find out /etc/ directory space usage, enter:
# du /etc/
# du -h /etc/
The following will report the sizes of the thee files named hdparm, iptunnel and ifconfig that are located in the /sbin directory:
$ du /sbin/hdparm /sbin/iptunnel /sbin/ifconfig
$ du -h /sbin/hdparm /sbin/iptunnel /sbin/ifconfig
Sample outputs:

How do I summarize disk usage for given directory name?

Pass the -s option to the du command. In this example, ask du command to report only the total disk space occupied by a directory tree and to suppress subdirectories:
# du -s /etc/
# du -sh /etc/
Sample outputs:

Pass the -a (all) option to see all files, not just directories:
# du -a /etc/
# du -a -h /etc/
Sample outputs:

You can also use star ( * ) wildcard, which will match any character. For example, to see the size of each png file in the current directory, enter:
$ du -ch *.png

The -c option tells du to display grand total.

Putting it all together

To list top 10 directories eating disk space in /etc/, enter:
# du -a /etc/ | sort -n -r | head -n 10
Sample outputs:

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For more information on the du command, type:
$ man du
$ du —help

Dealing with btrfs file system

For btrfs filesystem use the btrfs fi df command to see space usage information for a mount point. The syntax is:

Examples

# btrfs fi df /data/
# btrfs fi df -h /data/
Sample outputs:

To see raw numbers in bytes, run:
# btrfs fi df -b /data/
OR
# btrfs fi df -k /data/ ### show sizes in KiB ##
# btrfs fi df -m /data/ ### show sizes in MiB ##
# btrfs fi df -g /data/ ### show sizes in GiB ##
# btrfs fi df -t /data/ ### show sizes in TiB ##

Conclusion

Here is quick summary for Linux check disk space commands. Use the du command when you need to estimate file space usage. To report Linux file system disk space usage use the df command. The btrfs df command must be used when using btrfs file system. Fore more info see GNU coreutils page here.

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Category	List of Unix and Linux commands
Documentation	help • mandb • man • pinfo
Disk space analyzers	df • duf • ncdu • pydf
File Management	cat • cp • less • mkdir • more • tree
Firewall	Alpine Awall • CentOS 8 • OpenSUSE • RHEL 8 • Ubuntu 16.04 • Ubuntu 18.04 • Ubuntu 20.04
Linux Desktop Apps	Skype • Spotify • VLC 3
Modern utilities	bat • exa
Network Utilities	NetHogs • dig • host • ip • nmap
OpenVPN	CentOS 7 • CentOS 8 • Debian 10 • Debian 8/9 • Ubuntu 18.04 • Ubuntu 20.04
Package Manager	apk • apt
Processes Management	bg • chroot • cron • disown • fg • glances • gtop • jobs • killall • kill • pidof • pstree • pwdx • time • vtop
Searching	ag • grep • whereis • which
Shell builtins	compgen • echo • printf
Text processing	cut • rev
User Information	groups • id • lastcomm • last • lid/libuser-lid • logname • members • users • whoami • who • w
WireGuard VPN	Alpine • CentOS 8 • Debian 10 • Firewall • Ubuntu 20.04

Comments on this entry are closed.

Nice article. What about “ncdu”
For graphical overview… 🙂

How do i format a 39TB drive with ext4?
web-a1

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How to Find Unallocated Space on Linux

Unallocated space is the unused space on the hard disk which has not been partitioned into a volume or drive. It is not a partition, just dead space. It can be made into a partition and formatted or it can be used to extend a current partition next to it.

In this tutorial, I will show you commands which can help to find unallocated space on your Linux system in order to extend existing partition or create a new disk.

What is unallocated space?

Don’t confuse free space and unallocated space. Unallocated space means that the operating system knows that there’s physical space on the hard drive, but it hasn’t been assigned (allocated) to a particular partition whereas free space means that the operating system knows you haven’t used up all of the allocated space on a particular drive or partition.

1) Display disk cylinders

With fdisk command, the start and end columns in your fdisk -l output are the start and end cylinders. From the header of your fdisk -l output, you can also see how many cylinders the disk has and how many bytes a cylinder represents. Normally, the cylinder’s values follow each other when all disk space is allocated. If there are some values that are missing, it means that we have unallocated disk space.

Consider the example below

You can see that /dev/sdf1 ends on sector ‘9766911’ but /dev/sdf2 doesn’t start directly on the next value but on sector ‘18032550’. It means that the range ‘9766912-18032549’ is missing so there is unallocated space on the disk. To calculate the unallocated space, you can do as below:

• missing sectors: 18032549 — 9766912 = 82656378265637
• calculate the size in bytes: 82656378265637 * 512 = 4232006144 bytes

Notice that /dev/sdf1 starts on sector ‘2048’ which is normal on some cases for the first default partition. It also means that before, there are few unallocated space.

2) Show numbering of on-disk partitions

It is possible to use partx command which asks the kernel to probe a given device and re-read the partition table. Given a device or disk-image, partx tries to parse the partition table and list its contents. You first need to take disk size information with fdisk -l command

Total space 12.9 GB . You can use partx -l command to list the partitions in order to find the used space and can subtract from total space. You shall notice that but all numbers are in 512-byte sectors.

#1 and #2 are the number of partitions. Remember that in Linux, when a disk space is ready to be initialized by the system, it is numbered as you can see on fdisk -l output. So my server has around 4.2 GB unallocated space.

Instead of -l option, you can use -s option to have more information detailed and size readable by human.

3) Use the partition manipulation program

Another option we have is to use parted command. You can use ‘free’ parameter to get unallocated space and also disk partition.

The keyword Free Space there doesn’t refer to the free space explained on the introduction but exactly to unallocated space which is the subject of this topic. You can see the first Free Space which refers to the unallocated space that I explained before for the first default partition. Also notice that unallocated space has no numbering.

In the following example, there is no partition on the hard disk and so it displays only unallocated space (free space). See that there is no numbering

When you execute parted command without any argument, by default it selects the first hard disk drive that is available on your system.

To print free space in specific units, for example to print in GB:

4) Display disk partition table

Another command we can use is cfdisk. It is a curses-based program for partitioning any hard disk drive. The partitions section always displays the current partition table. The command line is the place where commands and text are entered. The format of the partition table in the partitions section is, from left to right: Name, Flags, Partition Type, Filesystem Type, and Size.

You can see the first row shows Free Space . For more detail, you can choose ‘Print’, then ‘Sectors’ and validate to have the result below

Conclusion

In this tutorial, we have learned how to find unallocated disk space using Linux terminal commands. Among the command, I feel parted command is the simplest solution to find unallocated space.

Thanks for reading, please provide your suggestion in the below comment section.

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