The inode is a data structure in the Unix-like file system and which stores information about the file except for its name and the path of the file. An inode is always said to be metadata of data. A file in the Unix-like system is stored in two places on the disk – data block and inodes. The contents of the file stored in the data block and the inode contain the information about the data. The inode contains the following information:
1) Mode/permission (protection)
2) Owner ID
3) Group ID
4) Size of file
5) Number of hard links to the file
6) Time last accessed
7) Time last modified
8) Time inode last modified
To list the inode of files on a directory, we can use the following command.
# cd /
# ls -lai
total 132
2 drwxr-xr-x 24 root root 4096 Feb 26 13:31 .
2 drwxr-xr-x 24 root root 4096 Feb 26 13:31 ..
2637825 drwxr-xr-x 2 root root 4096 Jan 14 19:02 bin
196609 drwxr-xr-x 3 root root 4096 Feb 24 10:41 boot
3 drwxr-xr-x 16 root root 4460 Mar 5 09:35 dev
983041 drwxr-xr-x 206 root root 12288 Mar 5 07:45 etc
2 drwxr-xr-x 14 root root 4096 Dec 29 09:24 home
One of the major issues on the server-side is the disk space issues and high load average issues. Most likely you got this message “No space left on device” or “disk is full” despite having enough space free on your server. If you ever face this trouble, most likely it’s because your server exceeds the available inodes. Let’s discuss the solution for this problem;
Solution
1) The first step is for it to check whether your server has enough free disk space. Use the below-given command for checking the available disk space on the server.
# df -h
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/xvda 33030016 10407780 22622236 32% /
tmpfs 368748 0 368748 0% /lib/init/rw
varrun 368748 56 368692 1% /var/run
varlock 368748 0 368748 0% /var/lock
udev 368748 108 368640 1% /dev
tmpfs 368748 0 368748 0% /dev/shm
2) The second step is to check the available inodes on your server. For that use below command to check the available inodes on the server.
# df -i
Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/xvda 2080768 2080768 0 100% /
tmpfs 92187 3 92184 1% /lib/init/rw
varrun 92187 38 92149 1% /var/run
varlock 92187 4 92183 1% /var/lock
udev 92187 4404 87783 5% /dev
tmpfs 92187 1 92186 1% /dev/shm
If the result has 100% or near IUse% value, then a large number of files is the reason for this issue.
3) The next step is to find those files. For that, we can use a small script that will list the directories and the number of files on them.
# for i in /*; do echo $i; find $i |wc -l; done
From the output, you can see the directory which uses a large number of files, then repeat this script for that directory like below. Repeat it until you see the suspected directory.
# for i in /home/*; do echo $i; find $i |wc -l; done
4) When you find the suspected directory with a large number of unwanted files. Just delete the unwanted files on that directory and free up some inode space by the following command.
# rm -rf /home/bad_user/directory_with_lots_of_empty_files
You have successfully solved the problem. Check the inode usage now with the df -i command again, you can see the difference like this.
# df -i
Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/xvda 2080768 284431 1796337 14% /
tmpfs 92187 3 92184 1% /lib/init/rw
varrun 92187 38 92149 1% /var/run
varlock 92187 4 92183 1% /var/lock
udev 92187 4404 87783 5% /dev
tmpfs 92187 1 92186 1% /dev/shm
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