Table of Contents
Overview
There are three components that are in the picture when it comes to managing the permissions of a file.
Permission Groups
- User – Abbreviated by ‘u’
- Group – Abbreviated by ‘g’
- Other– Abbreviated by ‘o’
- All – Abbreaviated by ‘a’
Permission Types
- Read Permission – Abbreviated by ‘r’
- Write Permission – Abbreviated by ‘w’
- Execute Permission – Abbreviated by ‘x’
Operations Definitions
- + is used to add a permission
- – is used to remove a permission
- = is used to set a permission
So o-w means taking away write permission from the other user
Before we see an example let’s see how file permissions are represented when you run ls command
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Below are some points about the above diagram
- The first character represents the file type. ‘-‘ means regular file and ‘d’ means directory
- The second to fourth character represents the Read, Write and Execute Permission for the owner.
- The fourth to seventh character represents the Read, Write and Execute Permissions for the group
- The eighth to the tenth character represents the Read, Write and Execute Permissions for the other user
Example
- Create a file temp.txt. Check its permissions.
ls -all | grep temp.txt
-rw-r--r-- 1 root root 0 Aug 9 14:50 temp.txt
Notice that the other user only has permission to only read
- Now run command to give write permission to the other user
chmod o+w temp.txt
ls -all | grep temp.txt
-rw-r--rw- 1 root root 0 Aug 9 14:50 temp.txt
See output above. Execute permission is also given to the other user.
- Now run command to take away write permission to the other user
chmod o-w temp.txt
ls -all | grep temp.txt
-rw-r--r-- 1 root root 0 Aug 9 14:50 temp.txt
Notice how write permission is taken away from the other user