How To Change Linux File and Directory Permissions?

Linux is a secure operating system that uses file and directory permissions to allow and deny different access types. In general, a file or directory has 3 operations named read , write and execute . These operations permissions can be set according to the different users or user groups. The chmod command is used to change file and directory permissions. The chmod command name comes from change mod .

chmod Command Syntax

The chmod command has the following syntax

chmod PERMISSION FILE_DIRECTORY
  • PERMISSION is the permission we want to set to the FILE_DIRECTORY.
  • FILE_DIRECTORY is a file or directory in which permissions are changed.

Permissions

Linux provides the following permissions.

Numeric ValueCharacer ValuePermissionDescription
None
1eExecute
2wWrite
3ewExecute and Write
4rRead
5reRead and Execute
6rwRead and Write
7rweRead, Write and Execute

Change Owner User Permissions

The u character is used to change the file or directory permission for the owner user. Every file and directory has an owner user and the permission can be changed like below.

Add User Execute Permission

$ chmod u+x file.txt

Remove User Execute Permission

$ chmod u-x file.txt

Add User Write Permission

$ chmod u+w file.txt

Remove User Write Permission

$ chmod u-x file.txt

Add User Read Permission

$ chmod u+r file.txt

Remove User Remove Permission

$ chmod u-r file.txt

Add User Read and Write Permission

$ chmod u+rw file.txt

Remove User Read and Write Permission

$ chmod u-rw file.txt

Change Group Permissions

Files and directories also have group ownership where the ownership group has provided permissions. Group ownership is used to provide a group of users to the files and directories. User permissions for files and directories can be changed like below.

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Add Group Execute Permission

$ chmod g+x file.txt

Remove Group Execute Permission

$ chmod g-x file.txt

Add Group Write Permission

$ chmod g+w file.txt

Remove Group Write Permission

$ chmod g-x file.txt

Add Group Read Permission

$ chmod g+r file.txt

Remove Group Remove Permission

$ chmod g-r file.txt

Add Group Read and Write Permission

$ chmod g+rw file.txt

Remove Group Read and Write Permission

$ chmod g-rw file.txt

Change Other Permissions

The other is used to specify all users except the owner user and owner group which is described in the previous parts. Generally removing all permissions for the other is a secure implementation.

Add Other Execute Permission

$ chmod o+x file.txt

Remove Other Execute Permission

$ chmod o-x file.txt

Add Other Write Permission

$ chmod o+w file.txt

Remove Other Write Permission

$ chmod o-x file.txt

Add Other Read Permission

$ chmod o+r file.txt

Remove Other Remove Permission

$ chmod o-r file.txt

Add Other Read and Write Permission

$ chmod o+rw file.txt

Remove Other Read and Write Permission

$ chmod o-rw file.txt

Change All Permissions

The chmod command also provides the a to set permission for all user types like user, group and others.

Add All Execute Permission

$ chmod a+x file.txt

Remove All Execute Permission

$ chmod a-x file.txt

Add All Write Permission

$ chmod a+w file.txt

Remove All Write Permission

$ chmod a-x file.txt

Add All Read Permission

$ chmod a+r file.txt

Remove All Remove Permission

$ chmod a-r file.txt

Add All Read and Write Permission

$ chmod a+rw file.txt

Remove All Read and Write Permission

$ chmod a-rw file.txt

Change Permission Recursively

In order to change directories and child content permissions, we should specify the -R recursive option for the usermod .

$ chmod u+rw mybackups

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