psql: FATAL: role "postgres" does not exist

I'm a postgres novice.

I installed the postgres.app for mac. I was playing around with the psql commands and I accidentally dropped the postgres database. I don't know what was in it.

I'm currently working on a tutorial: http://www.rosslaird.com/blog/building-a-project-with-mezzanine/

And I'm stuck at sudo -u postgres psql postgres

ERROR MESSAGE: psql: FATAL: role "postgres" does not exist

$ which psql

/Applications/Postgres.app/Contents/MacOS/bin/psql

This is what prints out of psql -l

                                List of databases
    Name    |   Owner    | Encoding | Collate | Ctype |     Access privileges     
------------+------------+----------+---------+-------+---------------------------
 user       | user       | UTF8     | en_US   | en_US | 
 template0  | user       | UTF8     | en_US   | en_US | =c/user                  +
            |            |          |         |       | user      =CTc/user      
 template1  | user       | UTF8     | en_US   | en_US | =c/user                  +
            |            |          |         |       | user      =CTc/user      
(3 rows)

So what are the steps I should take? Delete an everything related to psql and reinstall everything?

Thanks for the help guys!

NOTE: If you installed postgres using homebrew, see the comment from @user3402754 below.

Note that the error message does NOT talk about a missing database, it talks about a missing role. Later in the login process it might also stumble over the missing database.

But the first step is to check the missing role: What is the output within psql of the command \du ? On my Ubuntu system the relevant line looks like this:

                              List of roles
 Role name |            Attributes             | Member of 
-----------+-----------------------------------+-----------
 postgres  | Superuser, Create role, Create DB | {}        

If there is not at least one role with superuser, then you have a problem :-)

If there is one, you can use that to login. And looking at the output of your \l command: The permissions for user on the template0 and template1 databases are the same as on my Ubuntu system for the superuser postgres. So I think your setup simple uses user as the superuser. So you could try this command to login:

sudo -u user psql user

If user is really the DB superuser you can create another DB superuser and a private, empty database for him:

CREATE USER postgres SUPERUSER;
CREATE DATABASE postgres WITH OWNER postgres;

But since your postgres.app setup does not seem to do this, you also should not. Simple adapt the tutorial.

The key is "I installed the postgres.app for mac." This application sets up the local PostgreSQL installation with a database superuser whose role name is the same as your login (short) name.

When Postgres.app first starts up, it creates the $USER database, which is the default database for psql when none is specified. The default user is $USER, with no password.

Some scripts (e.g., a database backup created with pgdump on a Linux systsem) and tutorials will assume the superuser has the traditional role name of postgres.

You can make your local install look a bit more traditional and avoid these problems by doing a one time:

/Applications/Postgres.app/Contents/Versions/9.*/bin/createuser -s postgres

which will make those FATAL: role "postgres" does not exist go away.

For MAC:

1. Install Homebrew
2. brew install postgres
3. initdb /usr/local/var/postgres
4. /usr/local/Cellar/postgresql/<version>/bin/createuser -s postgres or /usr/local/opt/postgres/bin/createuser -s postgres which will just use the latest version.
5. start postgres server manually: pg_ctl -D /usr/local/var/postgres start

To start server at startup

• mkdir -p ~/Library/LaunchAgents
• ln -sfv /usr/local/opt/postgresql/*.plist ~/Library/LaunchAgents
• launchctl load ~/Library/LaunchAgents/homebrew.mxcl.postgresql.plist

Now, it is set up, login using psql -U postgres -h localhost or use PgAdmin for GUI.

By default user postgres will not have any login password.

Check this site for more articles like this: https://medium.com/@Nithanaroy/installing-postgres-on-mac-18f017c5d3f7

createuser postgres --interactive

or make a superuser postgresl just with

createuser postgres -s

This happens when you run initdb with a user whose ID is not postgres, without specifying the postgres username with --username=postgres or -U postgres.

The database cluster is then created with the system's user account that you used to run initdb, and it is given superuser permissions.

To fix it, simply create a new user named postgres with the option --superuser using the createuser utility that comes with Postgres. The utility can be found in the Postgres' bin directory. e.g.

createuser --superuser postgres

If you have a custom hostname or port then be sure to set the appropriate options.

Don't forget to delete the other user account that was created for you by initdb.