===== Change password for user =====

<code bash>
sudo -u user_name psql db_name
</code>

<code sql>
ALTER USER user_name WITH PASSWORD 'new_password';
</code>

===== Update password auth method to SCRAM =====

Edit ''%%/etc/postgresql/16/main/postgresql.conf%%''.

<code bash>
password_encryption = scram-sha-256
</code>

Restart postgresql.service.

At this point, any services using the old MD5 auth method will fail to connect to their PostgreSQL databases.

Update the settings in ''%%/etc/postgresql/16/main/pg_hba.conf%%''.

<code bash>
TYPE    DATABASE        USER            ADDRESS         METHOD
local   all             mastodon                        scram-sha-256
local   all             synapse_user                    scram-sha-256
</code>

Enter a psql shell and determine who needs to upgrade their auth method.

<code sql>
SELECT rolname, rolpassword ~ '^SCRAM-SHA-256\$' AS has_upgraded FROM pg_authid WHERE rolcanlogin;

\password username
</code>

Restart postgresql.service and all services using a PostgreSQL database.