A short note on inode number – Linux/Unix
Inode number in Linux. It’s simply a reference (index) about the file and directory on the System.
This is an entry in Inode table. This data structure uses to represent a file system object, this can be one of the various things such as file or directory. It’s a unique number for files and directories under a disk block/partition.
The file system attributes include metadata like access time, modification time etc; as well as ownership and permission details of files and directories.
What are the important attributes included in inode?
The below mentioned keys are the different attributes in Unix file system and are included in inode.
- File type.
- File permission.
- Ownership and group.
- Access, change and modification time.
- Deletion time.
- Number of links.
How do I check the inode details of a file or directory?
Do you have a shell access to your server? If so, yes, you can simply check the inode number by using the following commands:
- ls -i
See the sample outputs
1. By using ls command.
The switch “i” uses with ls command to find out the inode number of a file or directory. See the sample output pasted below:
[email protected]:~$ touch inode.check [email protected]:~$ ls -i inode.check 1179765 inode.check
Here the inode for the file “inode.check” is 1179765.
2. By using stat command.
The “stat” command will display the inode number along with a lot of other attributes. See the output:
[email protected]:~$ stat inode.check File: 'inode.check' Size: 0 Blocks: 0 IO Block: 4096 regular empty file Device: 806h/2054d Inode: 1179765 Links: 1 Access: (0664/-rw-rw-r--) Uid: ( 1000/ arunlal) Gid: ( 1000/ arunlal) Access: 2016-11-15 20:00:07.548968280 +0530 Modify: 2016-11-15 20:00:07.548968280 +0530 Change: 2016-11-15 20:00:07.548968280 +0530 Birth: -
In this output you can see a lot of attributes of the file “inode.check.”
Top command has an important role in Unix/Linux system/server administration side. The command “top” displays a dynamic view of process that are currently running under the system. Here I’m explaining some of the useful usage of top command for my Admin friends.
You can also use these commands to check the details of directories. See one example pasted below:
[email protected]:~$ mkdir inode.check.dir [email protected]:~$ stat inode.check.dir File: 'inode.check.dir' Size: 4096 Blocks: 8 IO Block: 4096 directory Device: 806h/2054d Inode: 1314947 Links: 2 Access: (0775/drwxrwxr-x) Uid: ( 1000/ arunlal) Gid: ( 1000/ arunlal) Access: 2016-11-15 20:09:21.734325138 +0530 Modify: 2016-11-15 20:09:21.734325138 +0530 Change: 2016-11-15 20:09:21.734325138 +0530 Birth: -
Total inode usage on the Linux machine can be calculated from the ”df” command along with the usage of switch “i.” Please see the details pasted below:
$ df -i Filesystem Inodes IUsed IFree IUse% Mounted on udev 489347 557 488790 1% /dev tmpfs 494198 802 493396 1% /run /dev/sda6 3932160 238966 3693194 7% / tmpfs 494198 150 494048 1% /dev/shm
That’s it! Try it and add comments if you have any other ideas on it.