Default permissions for files and directories

Whenever a user creates a file, the system assigned permissions are -rw-rw-rw- that is 666 in octal notation and for a directory it is drwxr-xr-x that is 777 in octal notations. But there is an environment variable UMASK which comes into the picture. That stands for users mask which will have a default value 022 and it is subtracted from the default permissions. For a file 666 - 022 yields 644. That will make the file -rw-r-r-. To a directory 777 - 022 yields 755. That will make the directory drwxr-xr-x.

Commonly the umask value assigned to users through default is 022 that grant permissions to newly created files or directory. Through modifying the value of umask the permissions granted to a file or directory could be controlled on creation.

After modifying the value of the umask from the command line or in the .profile file the user must logout from the present session and again login into the system in order to make the umask settings effectual