UMASK is user file-creation mode to determine permissions of newly created files. When any user creates a file or directory under Linux or UNIX, the default setting of the permissions was applied on the basis of UMASK mentioned in the config file. By default, UMASK id022 but you can change it complete system or for a particular user. Any files can have 3 types of permission read, write and execute, numeric representation is 777 for full permissions to a user, group and other users. When any user creates a file on the system with default UMASK 022 then files will get 755 permissions. 755 means read, write & execute to the user and read & execute to the group and other users. UMASK is a very crucial command to control file & directory security. The system administrator can control file access permissions using UMASK in an efficient manner.