This document discusses basic file permissions in Linux/Unix. It covers the different file attributes seen in the ls -l command output including permissions, owner, group, size and date. It describes the rwx permissions for owner, group and others. It also explains how to modify permissions using chmod with absolute and symbolic modes, and how to change file ownership with chown.

1. Basic File Permissions
Basic File Permissions

2. File and Directory Attributes
-Unix/Linux files have 8 attributes that can be seen with ls –l command.
-rw-r—r-- 1 root root 1229 Aug 20 6:20 reports
si
Note: only the owner or the root can change the permissions.
root@powerpc# ls –l reports
Type
permissions
links owner
Owner’s
primary
group
Date
File
namesSize

3. Access Levels
- rwx rwx rwx
- File
d Directory
l links
Owner
Primary
Group
Others

4. Access Modes
Permission
Absolute Mode
4 2 1
Symbolic Mode
rwx

5. Access Modes
Access Mode File Directory
r 4 To display the content of the file To list the contents of the
directory
w 2 To modify or append to the file To create or remove files of
directories
x 1 To execute the file To enter into the directory

6. Default Permission
File Directory
Created
by root
rw-r—r-- 644 rwxr-xr-x 755
Created
by user
rw-rw-r-- 664 rwxrwxr-x 775

7. Modifying the Permission
Modifying the Permission
[root@power_pc]# chmod <permission/weight> <file/dir>
Options:
Category u(owner) g(group) o(others)
Operators + - =
Permissions r w x
Weight 4 2 1

8. Example of Permission: Absolute
Applying permission to owner(u), group(g) and others(o) on file reports
[root@power_pc]# chmod 754 reports

9. Example of Permission: symbolic
Applying permission to owner(u), group(g) and others(o) on file reports
[root@power_pc]# chmod u=rwx, g=rx o=r reports

10. Changing Ownership
Changing ownership of a file or directory
[root@power_pc]# chown <user name/group name> <file/dir name>