An inode or Index Node is a data structure within a Linux system that provides metadata about a file-system object. A file system object in Linux can be a file or a directory.
It contains metadata about the file or directory. An inode is assigned to a file system object when a file or a directory gets created. Each of the inodes is identified by an integer data type.
An inode contains the below information.
- Access Mode(Read/write/execute permissioms)
- Owner(UID{User Identifier } and GID{Group Identifier} )
- File Type
- File Size
- Group
- Number of Links
- Created time
- ACL (Acess Control List)
- Blocks list.
There is a file system such as ext3(Third Extended File System) that creates an inode every time a file is created. But a file system like xfs creates inode when needed.
To see the inode for the file under directory we can use ls il command.
root@5c8d55b982b8:/usr/tutorials# ls -il
total 3404
6294749 -rw-r--r-- 1 root root 576000 Sep 3 19:49 cars_data.csv
6294778 drwxr-xr-x 2 root root 4096 Sep 3 19:49 file1
6294790 drwxr-xr-x 2 root root 4096 Sep 3 19:49 file2
6294796 drwxr-xr-x 2 root root 4096 Sep 3 19:50 file3
6294821 -rw-r--r-- 1 root root 2893177 Sep 3 19:50 movies_data.csv