useradd

Useradd is a command-line utility on Unix-like operating systems used to create a new user account. It is a low-level tool in the system’s user management toolkit and typically updates the user and group databases, such as /etc/passwd, /etc/shadow, and related files. Because it operates at a low level, it is usually used by administrators or within scripts rather than by regular users. After creating a user, a password is typically set separately to enable login.

The command accepts a range of options that configure the new account. Common options include -c for a comment or full name, -d to specify the home directory, -m to create the home directory from the skeleton directory, -s to set the login shell, -g to define the primary group, and -G to add supplementary groups. It also supports -u to assign a specific user identifier, -r to create a system account, -e to set an expiration date, -f to specify the number of days after password expiry before the account is locked, and -p to provide an encrypted password (though supplying passwords on the command line is discouraged in favor of an interactive password or other secure methods). Some implementations offer -k to specify a skeleton directory, and -M to avoid creating a home directory.

On many distributions, a friendlier front end such as adduser provides a guided creation process while delegating to the underlying useradd logic. Administrators should consult the local man page, as options and defaults vary between distributions and system configurations. See also usermod and userdel for modifying and removing accounts.