Ubuntu – Create system user without login

sudo groupadd --system prometheus
sudo useradd -s /sbin/nologin --system -g prometheus prometheus

To create a system user without login on Ubuntu (i.e., a user that cannot log in interactively, typically used for services), use the adduser command with the --system and --no-create-home options, or useradd with appropriate flags.

Recommended Method (using adduser – interactive and safer):

sudo adduser --system --no-create-home --group myserviceuser

• --system: Creates a system user (UID < 1000, no password, no home by default).
• --no-create-home: Prevents creating a home directory.
• --group: Creates a primary group with the same name (optional but common for system users).
• No password is set → cannot log in.

Alternative (using useradd – non-interactive):

sudo useradd -r -s /usr/sbin/nologin -M myserviceuser

• -r: System user.
• -s /usr/sbin/nologin: Sets shell to nologin (prevents interactive login).
• -M: Do not create home directory.

Note: On Ubuntu, /usr/sbin/nologin is preferred over /bin/false because it displays a polite message when login is attempted.

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Verify the user was created:

id myserviceuser
getent passwd myserviceuser

Example output:

myserviceuser:x:116:122::/nonexistent:/usr/sbin/nologin

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Optional: Disable password entirely (extra security)

sudo passwd -l myserviceuser

This locks the password field.

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Use Case Example (e.g., for a service like Nginx or a custom daemon):

sudo adduser --system --no-create-home --group nginx

Then run your service as this user:

sudo -u nginx your-command

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Summary:
Use sudo adduser --system --no-create-home --group <username> for a clean, login-disabled system user on Ubuntu.