Permission handling in Linux

In this post we are going to see(Permission handling in Linux) how to set permission for files and directories in linux/unix.

Before set/unset permission we should check the existing permission for a file usinf ll <filename> command like below.

[[email protected] ~]# ll abu
-rwxrwxrwx. 1 abu root 113 Dec 11 20:22 abu

We can assign permission based on below categories and same has been display while executing ll or ls –l command.

User:    u

Group:  g

Others:  o

Numeric values used for changing/identifying the permissions:

Read:       4, r

Write:      2, w

Execute:  1, x

Command used for changing file permission:

#Chmod 655 <filename>

Example:

Command to set permission:

We are going to set permission for file abu from 777 to 755 using below command. 755 will have full permission for user, read and execute for group and others.

[[email protected] ~]# chmod 755 abu
[[email protected] ~]# ll abu
-rwxr-xr-x. 1 abu root 113 Dec 11 20:22 abu

Also will set the permissions usings characters like below.

Read:        r

Write:       w

Execute:  x

Example:

Command to set permission using characters:

In the below example going to set execute permission alone to others

[[email protected] ~]# ll abu1
-rwxr-xr--. 1 root abu 0 Dec 11 20:17 abu1
[[email protected] ~]# chmod o+x abu1
[[email protected] ~]# ll abu1
-rwxr-xr-x. 1 root abu 0 Dec 11 20:17 abu1

Changing ownership of a file or directory:

#Chwon user:group <filename>

example:

In below example going to change owner of the directory as lbcuser for lbc directory. User has been created already.

Note: Existing owner and group will be root.

before changing owhership:

[[email protected] ~]# mkdir lbc
[[email protected] ~]# ll | grep lbc
drwxr-xr-x. 2 root root 6 Dec 16 20:33 lbc

after changing ownership:

[[email protected] ~]# chown lbcuser lbc
[[email protected] ~]# ll | grep lbc
drwxr-xr-x. 2 lbcuser root 6 Dec 16 20:33 lbc

using chown command will change group as well like below.

Going to change group as finance.

[[email protected] ~]# chown :finance lbc
[[email protected] ~]# ll | grep lbc
drwxr-xr-x. 2 lbcuser finance 6 Dec 16 20:33 lbc

Will change the group alone using chgrp command:

[[email protected] ~]# mkdir lbc1
[[email protected] ~]# chgrp finance lbc1
[[email protected] ~]# ll | grep lbc1
drwxr-xr-x. 2 root finance 6 Dec 16 20:47 lbc1

 

Reference: RedHat Document

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