sudo -u postgres psql postgres
# login as postgres user

\conninfo
# get the current connection infomation

alter user "user" with superuser;
# change user "user" to superuser

# ======
# Config remote login

show hba_file;
# find where is the config file of postgresql
# Allow remote access
# 1. change pg_hba.conf
# eg.
host all all 192.168.1.0 255.255.255.0 trust
# 2. change postgresql.conf
# change listen_addresses
tcpip_socket = true
listen_addresses = '*' # if the firewall block other ports, it's okay to do so
                       # otherwise, may be bind to certain address so it is more safe
# 3. You might need to change firewall rules to allow traffic
# eg show firewall status (ubuntu)
sudo ufw status verbose
# eg
sudo ufw allow from 192.168.1.0/24 to 74.86.26.69 port 443 proto tcp

# ======
# Basic commands
\du # show all users info
\l # list db
\c dbname # connect to db
\d # show db info