Postgresql – postgres user cannot drop database

GRANTing ALL permissions for public to the database is mostly redundant (as public has connect, temporary by default, so you'd only be adding CREATE which you probably don't want to do). You probably expected a GRANT ALL on the database to result in a recursive GRANT ALL to contained schemas and tables. GRANT is not recursive, so this doesn't happen; a GRANT ALL on a database just grants CONNECT and TEMPORARY rights to the database, with no effect on contained schemas and tables.

The default GRANTs are, from the docs on GRANT:

PostgreSQL grants default privileges on some types of objects to PUBLIC. No privileges are granted to PUBLIC by default on tables, columns, schemas or tablespaces. For other types, the default privileges granted to PUBLIC are as follows: CONNECT and CREATE TEMP TABLE for databases; EXECUTE privilege for functions; and USAGE privilege for languages. The object owner can, of course, REVOKE both default and expressly granted privileges. (For maximum security, issue the REVOKE in the same transaction that creates the object; then there is no window in which another user can use the object.) Also, these initial default privilege settings can be changed using the ALTER DEFAULT PRIVILEGES command.

So you can see you don't need to GRANT anything on the database unless you want the user to be able to create schemas, etc. You need to:

• GRANT USAGE ON SCHEMA myschema TO theuser; for any schema other than public. CREATE can be granted if you want the user to be able to make tables, views, etc.
• GRANT SELECT, INSERT, UPDATE, DELETE ON TABLE sometable TO theuser; for tables. I've omitted the TRUNATE, REFERENCES and TRIGGER rights as you probably don't want to grant them.
• GRANT USAGE ON SEQUENCE sometable_somecolumn_seq TO theuser; for any sequences that are used in table defaults, either explicitly or via a SERIAL or BIGSERIAL column.

... etc. See the manual for GRANT linked above for full definitions of what the privileges do, which are available on which objects, etc. Take note of the wildcard ALL TABLES and ALL SEQUENCES options.

If this seems like too much hassle to do for each table, view, schema, sequence, etc, you can in Pg 9.1 and above use ALTER DEFAULT PRIVILEGES to change the default GRANTs on new objects.

• The manual for GRANT
• The manual for ALTER DEFAULT PRIVILEGES

postgres has no password after an automated install, it's expected to authenticate through the peer method. sudo su - postgres is the first step to it. The second step is to connect through the Unix local domain socket, but your command doesn't do that, it connects through TCP, that's why you're stuck with the password problem.

The installed pg_hba.conf file probably starts with these two rules, apart from comments:

# Database administrative login by Unix domain socket
local   all             postgres                                peer

# IPv4 local connections:
host    all             all             127.0.0.1/32            md5
[...]

When doing a TCP connection with -h localhost... the first rule doesn't match. The second rule matches and it triggers the demand for a password, but as none was set this can only fail (empty passwords are not allowed either).

The solution is to remove -h localhost from psql invocation, for the first rule to be taken instead. As it's on a Unix system, it will attempt a connection through the Unix domain socket.

Once logged to psql as the postgres user, you may set a password with the \password command or ALTER USER postgres PASSWORD 'foobar';

See also https://help.ubuntu.com/community/PostgreSQL
In the section Using pgAdmin III GUI , they suggest to change the pg_hba.conf first rule from auth peer to md5, after having set a password. Personally I don't quite get why. I'd rather leave that rule alone and run pgAdmin from my own Unix account, choosing localhost TCP connections.