21.2.2. Adding a User

To add a user to the system:

Issue the useradd command to create a locked user account:
```
useradd <username> 
```
Unlock the account by issuing the passwd command to assign a password and set password aging guidelines:
```
passwd <username> 
```

Command line options for useradd are detailed in Table 21.1, “ useradd Command Line Options”.

Option	Description
`-c` '`<comment>`'	`<comment>` can be replaced with any string. This option is generally used to specify the full name of a user.
`-d` `<home-dir>`	Home directory to be used instead of default `/home/<username>/`
`-e` `<date>`	Date for the account to be disabled in the format YYYY-MM-DD
`-f` `<days>`	Number of days after the password expires until the account is disabled. If `0` is specified, the account is disabled immediately after the password expires. If `-1` is specified, the account is not be disabled after the password expires.
`-g` `<group-name>`	Group name or group number for the user's default group. The group must exist prior to being specified here.
`-G` `<group-list>`	List of additional (other than default) group names or group numbers, separated by commas, of which the user is a member. The groups must exist prior to being specified here.
`-m`	Create the home directory if it does not exist.
`-M`	Do not create the home directory.
`-n`	Do not create a user private group for the user.
`-r`	Create a system account with a UID less than 500 and without a home directory
`-p` `<password>`	The password encrypted with `crypt`
`-s`	User's login shell, which defaults to `/bin/bash`
`-u` `<uid>`	User ID for the user, which must be unique and greater than 499