I've installed postgresql server via ubuntu repository and the service is active. When I try to add a user this is the result:
sudo -u postgres createuser -D -A -P myuser
Enter password for new role:
Enter it again:
createuser: could not connect to database postgres: could not connect to server: No such file or directory
Is the server running locally and accepting
connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
Why?

Here the line of listen address in postgresql.conf
listen_addresses = '*'


Here the pg_hba.conf:

Database administrative login by Unix domain socket

local all postgres peer
TYPE DATABASE USER ADDRESS METHOD
"local" is for Unix domain socket connections only

local all all peer
IPv4 local connections:

host all all 127.0.0.1/32 md5
IPv6 local connections:

host all all ::1/128 md5
Allow replication connections from localhost, by a user with the
replication privilege.

#local replication postgres peer
#host replication postgres 127.0.0.1/32 md5
#host replication postgres ::1/128 md5
host all all 10.0.0.0 255.255.255.0 md5