What is UMASK?

UMASK is User file creation mask, which is used to set default permissions for newly created files and directories.

The default maximum permissions for file is 666 because file doesn’t have execute permissions by default and the maximum permissions for directory is 777.

Check current UMASK

 To check current umask value,  just enter the umask command on terminal.

 

   Here, 0022 is the current umask value set on the system.

   These 4 values are as below:

0	Special Permissions
0	Owner Permissions
2	Group Permissions
2	Other User’s Permissions

   Now, we will calculate how newly files get default permissions.

Default file permissions – UMASK = Newly created files permissions

0666 - 0022 = 0644 (Here UMASK value is 0022 so newly created files get 0644 permissions)

Default Directory permissions – UMASK = Newly created files permissions

0777 – 0022 = 0755 (Here, UMASK value is 0022, so newly created directory get 0755 permissions)

 

How to change UMASK temporarily?  
To change umask temporarily use the below command.

 

Here, We have set 0044 as umask value.

Now, newly created files and directories will get the permissions as below

0666 - 0044 = 0622 (So 0622 should be default permissions for file)

0777 - 0044 = 0733 (So 0733 should be default permissions for directory)

Now, When ever you create new files and directories and check, you will see 622 (rw--w--w-) permissions for file and 733 (rwx-wx-wx) to directories. Check below example.

Note: You will need to open new terminal to see new umask.

Examples:

[root@p ~]# umask 0044 [root@p ~]# touch test [root@p ~]# ls -l test -rw--w--w-. 1 root root 0 Jul 25 19:01 test [root@p ~]# mkdir new [root@p ~]# ls -ld new drwx-wx-wx. 2 root root 4096 Jul 25 19:02 new [root@p ~]#

 

How to change UMASK permanently?

You will need to open the file .bash_profile which is present in home directory of user.

Once you open the file you will need to add the entry of umask value which you want to set.

Now, we have permanently set umask value to 0044.

Note: You will need to manually add umask 0044 in .bash_profile file.

Finally, we can say that umask is used to set the default permissions for newly created files and directories. You will get the newly permissions by subtracting default maximum permissions with umask value.