How to fix Cannot be run as root in PostgreSQL

The safest and most common approach is to switch to the postgres user before running any PostgreSQL commands. Use the su command with the - flag to get a login shell with the postgres user's environment:

su - postgres

Now you can run PostgreSQL commands without sudo:

pg_ctl start -D /var/lib/postgresql/14/main
initdb -D /path/to/data/directory

You can verify you're running as the correct user with whoami.

If you need to run PostgreSQL commands from a non-root user account, use sudo -u postgres to execute them as the postgres user without an interactive shell:

sudo -u postgres pg_ctl start -D /var/lib/postgresql/14/main
sudo -u postgres initdb -D /path/to/data/directory
sudo -u postgres psql

This approach is convenient for one-off commands or scripts.

To connect to a running PostgreSQL server, use the postgres user directly:

sudo -u postgres psql

Alternatively, if you're already logged in as another user, specify the user with the -U flag:

psql -U postgres

Do NOT attempt to connect as the root user—PostgreSQL won't recognize a root role unless explicitly created, which is extremely unusual.

If you're running PostgreSQL in a Docker container and hitting this error, update your Dockerfile or docker-compose.yml to ensure the postgres user is used. Example Dockerfile:

USER postgres
CMD ["postgres", "-D", "/var/lib/postgresql/data"]

For docker-compose.yml, ensure the container is not running as root:

services:
  postgres:
    image: postgres:15
    environment:
      POSTGRES_PASSWORD: password
    user: "999:999"  # postgres UID:GID

Always verify the official postgres Docker image documentation for best practices.