Linux commands to create users

To create a user and the home directory automatically, use the -m option:

Check if the directory exists with the ls command:

The directory contains initialization files copied from the /etc/skel directory.

Adding a User with a Specific Home Directory

To add a user in Linux with a specific home directory, use the -m option with -d and provide the directory path:

The useradd command warns that the directory already exists and doesn’t copy files from /etc/skel. Use this option to create a custom or shared home directory.

Adding a User without Home Directory

If the /etc/login.defs configuration CREATE_HOME variable value is yes , the useradd command automatically creates a home directory.

To override the default settings and add a user without a home directory, use the -M option:

The command adds the user without creating a home directory, overriding the default settings.

Adding a User with Specific User ID

To add a user with a specific user ID, use the -u tag and provide the UID:

If the UID is not unique, the terminal outputs a message and does not add the user. Check the UID with the id command:

Use a UID above 1000 to indicate a regular user.

Adding a User with Specific Group ID

To create a user and add them to a specific group, use the -g tag:

The group name or GID must exist. Otherwise, the command throws an error. Check the user’s GID with:

The output prints the user’s group ID.

Adding a User to Multiple Groups

Add a user to multiple groups with the -G option and list the group names or GIDs in a comma-separated list, followed by the username. For example:

Check the user’s groups with:

The groups must exist, and the list should not contain any spaces. The command doesn’t add the user if any groups do not exist.

Note: To add an existing user to a group, check out the following guide: How to Add User to a Group in Linux.

Adding a User with a Specific Login Shell

Each new user gets a default login shell (such as the Bourne shell or Bourne Again Shell). To explicitly define the user’s shell, add the -s tag and provide the shell’s path:

For example, to add a user and set Bash as the default login shell, run:

Check the /etc/passwd file to confirm the shell selection:

The final field shows the login shell for the new user.

Adding a User with a Specific Comment

To add a user with a specific comment, run:

To view the comment, check the /etc/passwd file and grep for the user:

The comment is for descriptive purposes only and has no actual functionality.

Adding a User with Account Expiry Date

Add a user with an account expiry date to automatically delete the account after provided date:

View the account’s expiry information with:

The output prints the account expiry date ( Account expires ). Use this option for temporary accounts.

Adding a User with a Deactivation Period

If a user has a password expiry set, the useradd command allows stating a period before the account deactivates after expiry. If an account expires, the expiry period will enable users to change their password and reactivate the account.

Use the -f command and add the number of days:

For example, to have an account deactivate three days after the password expires, run:

View the expiry information with:

The /etc/shadow file stores password information, including idle time (third to the last field).

Use this method to deactivate users who don’t change their password in the provided timeframe.

The deactivation period is a good security measure, and the recommended duration is 35 days. Business requirements dictate what’s the perfect duration before the account expires. If the value is too low, the consequences are costly for an administrator, whereas a high value impacts security.

Adding a System User

Programs and systems create system user accounts, which are different from regular users. Programs such as MySQL or Tomcat require a unique user account to work on the system, and daemons typically create system users during installation.

To create a system user, use the -r option:

Check the user’s information with:

The user has a UID lower than 1000, indicating it’s a system user.

The adduser Command

The adduser command is an alternative way to add users to a Linux system and acts as a simple interactive front end for useradd .

The command prints the user and group to the console.

Next, the command asks for the following:

• Password, which needs to be re-entered to continue.
• User information. The data acts as a comment (same as useradd -c command and option).

Press Y to complete the process. In case of a mistake, press N and reenter the correct information.

Check the parameters from the adduser command with:

The command adds all the values entered during the command execution and the Bash shell by default.

Add Multiple Users

The useradd and adduser commands do not support adding multiple users at once. To add multiple users, use a Bash for loop in a script or in the terminal directly to loop through a list of usernames.

Note: Learn what are the differences between useradd and adduser commands.

For example, to add ten users, do the following:

1. Create a text file using a text editor:

2. Append usernames to the file, entering each on a new line. For example:

Save the file and close nano (CTRL+X, Y, then Enter).

3. Use a for loop to list through the names in the file and run useradd on each:

for i in `cat ~/user_list.txt` ; do useradd $i ; done 

4. Show the created users with:

for i in `cat ~/user_list.txt` ; do id $i ; done

To add passwords, exchange the command in the do clause with passwd and enter the password for each user. Alternatively, use the expect command to automate the password creation process, especially if working with a large number of users.

After completing this guide, you know how to add new users to a Linux system with the useradd command.

Next, read about privileged access management and how it helps reduce security attacks and data breaches.

Источник