psql: error: connection to server on socket "/var/run/postgresql/.s.PGSQL.5432" failed: FATAL: Peer authentication failed for user "postgres" (Ubuntu)

Peer authentication means that the connection is only allowed if the name of the database user is the same as the name of the operating system user.

So if you run psql -U postgres as operating system user root or jimmy, it won't work.

You can specify a mapping between operating system users and database users in pg_ident.conf.

You can edit your .conf files with privileges using an editor, for my case it is nano.

$sudo nano /etc/postgresql/14/main/pg_ident.conf

Map your user by adding this line

# MAPNAME       SYSTEM-USERNAME         PG-USERNAME
user1             <computer-username>               postgres

Replace the <computer-username> with the System-Username, which can be found using the whoami command. Type in your terminal:

$whoami

Then go ahead to the pg_hba.conf

$sudo nano /etc/postgresql/14/main/pg_hba.conf

Add your postgre user, with method=peer, as shown below:

# TYPE  DATABASE        USER            ADDRESS                 METHOD
local   all             postgres                                peer

This worked for me.

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