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Manually Adding User Accounts

Table of Contents

Adding Users Through /etc/passwd

Each line in the /etc/passwd file represents a user account.

You can add lines to this file to manually add user accounts to the system.

Add a new line for the user:

You'll need to open /etc/passwd to add a user manually: 

sudo vi /etc/passwd
The format of each line is as follows:
username:password:UID:GID:GECOS:home_directory:shell

  • username: The username for the new user.
  • password: The encrypted password for the user.
    • You can leave this field empty to disable password login.
    • You can also leave this empty and set the password manually with the passwd command.
  • UID: The user ID for the new user.
  • GID: The primary group ID for the new user.
  • GECOS: Additional information about the user (such as full name or description).
  • home_directory: The home directory for the new user.
  • shell: The login shell for the new user.
    • Set to /bin/bash to allow them to use bash on the system.

Save and close the file after adding the user information.

Create the user's home directory

If you specified a home directory for the new user, you may need to manually create it using the mkdir command. 

sudo mkdir /home/newuser

Set permissions for the home directory

After creating the home directory, make the new user the owner to allow the new user to access it. 

sudo chown newuser:newuser /home/newuser

Set the user's password

If you left the password field empty in the /etc/passwd file, set a password for the new user using the passwd command. 

sudo passwd newuser

Test the new user account

After completing those steps, you can test the new user account by logging in with the username and password (if applicable) and verifying that the user has access to the home directory.

Determining the UID and GID for a New User

Finding an Available UID

  • To find the next available UID, you can typically look at the highest UID used for existing users in the /etc/passwd file and increment it by 1.
    • Alternatively, you can use the id command to list existing user IDs and choose one that is not already in use.
  • You can use awk to list existing user IDs:
    awk -F: '{print $3}' /etc/passwd
    You could also sort them in numerical order:
    awk -F: '{print $3}' /etc/passwd | sort -n

Determining the GID (Group ID)

All the groups on the system live in the /etc/group file.

  • The GID will be automatically assigned when creaing a user with useradd, but if manually adding a user you need to pick one yourself.
    • You should choose a unique GID for the new user's primary group.
    • The GID is a numeric value that identifies the primary group to which the user belongs.
  • You can choose an existing group's GID or create a new group with a unique GID.
    • To find the next available GID, you can follow a similar approach as for finding the UID.
  • You can use awk to list existing group IDs:
    awk -F: '{print $4}' /etc/group

The GECOS Field (General Electric Comprehensive Operating System)

  • The GECOS field typically includes additional information about the user, such as the user's full name or description.
  • You can enter any descriptive information you like in the GECOS field, such as the user's full name or job title.
    • This field is optional, so you can leave it empty if you prefer.
  • For example, you can enter "John Smith,,," to indicate that the user's full name is "John Smith" and leave the other fields empty.