If you come from the Windows world, you may not be familiar with the concept of inode. This is not something you are exposed to until you journey into the Unix world.
Even if you use Unix, you may or may not encounter an inode. It depends on how much you care about the systems internals of the Unix world. If you do care, keep reading because it is going to get very interesting.
Inode (index node) is a data structure in a Unix-style file system such as Linux, Solaris, MacOS, and FreeBSD that describes a filesystem object such as a file or directory. Each inode stores the following information
- Permission such as read, write and execute
- Owner ID
- Group ID
- Size of the file
- Number of hard link relative to an inode
- Time of last change
- Time of last access
- Time of last modified
- Link to location of the file
What is stored in a Unix file?
A Unix file is stored in two different parts of the disk – the data blocks and the inodes. The data blocks contain the contents of the file. The information of the file is contained in the inode.
How to check the inode?
To list the inodes of a file, use the “ls -i” command.
$ cd /
$ ls -i
16777217 bin 1048577 lib 5505025 var
2 boot 54001665 lib64 36175873 sbin
1025 dev 53870593 media 42860545 srv
42729473 etc 32243713 mnt 58720257 tmp
27525121 home 25690113 opt By using the -i option, you can see the inode number before the filename.
Display file system information
Another way to view the inode of a file is by using the stat command. Unlike the previous command, this option gives you information about the times of last changed, accessed and modified of a file.
$ stat hello.txt
File: hello.txt
Size: 6 Blocks: 8 IO Block: 4096 regular file
Device: fe00h/65024d Inode: 27534469 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 1000/ root) Gid: ( 1000/ root)
Access: 2020-06-04 06:23:12.213401430 -0700
Modify: 2020-06-04 06:20:27.907562714 -0700
Change: 2020-06-04 06:20:27.927563425 -0700
Birth: -You also see a lot of other information about the file such as ownership and permissions.
