Createuser: could not connect to database postgres: FATAL: role "tom" does not exist

I'm trying to set up Postgres for the first time, and I need to create a user with permissions to read and create databases. However, when I use:

createuser username

in my terminal I get the following message:

createuser: could not connect to database postgres: FATAL: role "tom" does not exist

Tom is my Ubuntu user account that I'm logged into right now. I'm trying to create a username of "postgres" then do a psql -U psql template1 so I can create a database and assign an owner to it for my Rails app.

Solution 1:

You mentioned Ubuntu so I'm going to guess you installed the PostgreSQL packages from Ubuntu through apt.

If so, the postgres PostgreSQL user account already exists and is configured to be accessible via peer authentication for unix sockets in pg_hba.conf. You get to it by running commands as the postgres unix user, eg:

sudo -u postgres createuser owning_user
sudo -u postgres createdb -O owning_user dbname

This is all in the Ubuntu PostgreSQL documentation that's the first Google hit for "Ubuntu PostgreSQL" and is covered in numerous Stack Overflow questions.

(You've made this question a lot harder to answer by omitting details like the OS and version you're on, how you installed PostgreSQL, etc.)

Solution 2:

See git gist with instructions here

Run this:

 sudo -u postgres psql

OR

psql -U postgres

in your terminal to get into postgres

NB: If you're on a Mac and both of the commands above failed jump to the section about Mac below

postgres=#

Run

CREATE USER new_username;

Note: Replace new_username with the user you want to create, in your case that will be tom.

postgres=# CREATE USER new_username;
CREATE ROLE

Since you want that user to be able to create a DB, you need to alter the role to superuser

postgres=# ALTER USER new_username SUPERUSER CREATEDB;
ALTER ROLE

To confirm, everything was successful,

postgres=# \du
                         List of roles
 Role name |                   Attributes                   | Member of 
-----------+------------------------------------------------+-----------
new_username     | Superuser, Create DB                           | {}
postgres         | Superuser, Create role, Create DB, Replication | {}
root             | Superuser, Create role, Create DB              | {}

postgres=# 

Update/Modification (For Mac):

I recently encountered a similar error on my Mac:

psql: FATAL: role "postgres" does not exist

This was because my installation was setup with a database superuser whose role name is the same as your login (short) name.

But some linux scripts assume the superuser has the traditional role name of postgres

How did I resolve this?

If you installed with homebrew run:

/usr/local/opt/postgres/bin/createuser -s postgres

If you're using a specific version of postgres, say 10.5 then run:

/usr/local/Cellar/postgresql/10.5/bin/createuser -s postgres

OR:

/usr/local/Cellar/postgresql/10.5/bin/createuser -s new_username

OR:

/usr/local/opt/postgresql@11/bin/createuser -s postgres

If you installed with postgres.app for Mac run:

/Applications/Postgres.app/Contents/Versions/10.5/bin/createuser -s postgres

P.S: replace 10.5 with your PostgreSQL version

Solution 3:

sudo -u postgres createuser -s tom 

this should help you as this will happen if the administrator has not created a PostgreSQL user account for you. It could also be that you were assigned a PostgreSQL user name that is different from your operating system user name, in that case you need to use the -U switch.

Solution 4:

1- Login as default PostgreSQL user (postgres)

sudo -u postgres -i

2- As postgres user. Add a new database user using the createuser command

[postgres]$ createuser --interactive

3-exit

[postgres]$ exit