Advanced File Permissions in Linux (Sticky Bit)

Advanced File Permissions in Linux

There are 3 special attributes other than the common read/write/execute.

1. Sticky bit

2. Set User ID (SUID)

3. Set Group ID (SGID)

Example:

drwxrwxrwt - Sticky Bits - chmod  1777

drwsrwxrwx - SUID set -   chmod  4777

drwxrwsrwx - SGID set -   chmod  2777

Here we will discuss about Sticky bit

Sticky bit

Sticky bits are mainly set on directories. If the sticky bit is set for a directory, only the owner of that directory or the owner of a file can delete or rename a file within that directory.

PRACTICAL STEPS TO UNDERSTAND STICKY BIT

Create a directory

[root@localhost]# mkdir /test

Check permissions of this directory

[root@localhost]#ls -la /

Now change permissions of this directory

[root@localhost]# chmod 777 /test

(This gives permissions for all the users to read, write and execute)

Check again permissions of this directory

[root@localhost]#ls -la /

Set Sticky Bit of this directory

[root@localhost]# chmod +t /test

Now only owner of directory or owner of file can rename or delete files in this directory

Check again permissions of this directory


[root@localhost]#ls -la /

Open a new terminal

login u1 user

[u1@localhost]$ 

create a file named file1 in /test 

[u1@localhost]$ vim file1 /test

Note: only owner of directory (root) or u1 can rename or delete file1

Open a new terminal

login u2 user

[u2@localhost]$ 

create a file named file2 in /test 

[u2@localhost]$ vim file2 /test

Note: only owner of directory (root) or u2 can rename or delete file2. u2 can not rename or delete file1 of u1.