Understanding UMASK value in Linux
UMASK (User Mask) is the default permission given when another file or directory is created on a Linux machine. At the point when user create a file or directory under Linux or UNIX, It create with a default set of permissions.Most of the Linux distros give 022 (0022) as default UMASK. In other words, it is a system default permissions for newly created files/folders in the machine.
Default umask:
Umask value is set for different reason with different value like files, directories, home directory for any user. The user file creation mode mask (umask) is use to decide the file permission for recently created files. It can be used to control the default file permission for new files. The default umask value 002 used for normal users and umask value 022 used for root user.
Explain Octal umask Mode
As I said before, if the default settings are not changed, file are created with the access mode 666 and directories with 777.
| umask Octal Value | File Permissions | Directory Permissions |
| 0 | rw- | rwx |
| 1 | rw- | rw- |
| 2 | r– | r-x |
| 3 | r– | r– |
| 4 | -w- | -wx |
| 5 | -w- | -w- |
| 6 | –x | –x |
| 7 | — (none) | — (none) |
Check UMASK Value
To check the umask value run the following command.
# umask
Change UMASK Value for New User
For CentOS/RHEL
The UMASK value can be set on /etc/profile file for all new users.
# vim /etc/profile
Find below lines and replace the values:
if [ $UID -gt 199 ] && [ "`id -gn`" = "`id -un`" ]; then
umask 002
else
umask 022
fi
For Ubuntu/Debain
# vim /etc/pam.d/common-session # vim /etc/pam.d/common-session-noninteractive
Find below lines in both files:
session optional pam_umask.so
Changed the value as below:
session optional pam_umask.so umask=0023
Change UMASK Value for Existing User
For existing users you can edit ~/.bashrc file in their home directory.
# vim ~/.bashrc
Add below line at the end of file:
umask 033
Change UMASK Value Temporary
If you change the umask temporary then when system will reboot value will be change and set default value. To change the umask temporary run the following command:
# umask 033
Enjoy it!
