On Linux and other Unix-like operating systems, new files are created with a default set of permissions. Specifically, a new file’s permissions may be restricted in a specific way by applying a permissions “mask” called the umask. The umask command is used to set this mask, or to show you its current value.

What is masking a service in Linux?

Masking a service prevents the service from being started manually or automatically. For this example, systemctl is creating a symlink from /etc/systemd/system/sshd. service to /dev/null . Targets in /etc/systemd override those provided by packages in /lib/systemd .

What is unmask in Unix?

The umask (UNIX shorthand for “user file-creation mode mask“) is a four-digit octal number that UNIX uses to determine the file permission for newly created files. … The umask specifies the permissions you do not want given by default to newly created files and directories.