postgres: upgrade a user to be a superuser?

ALTER USER myuser WITH SUPERUSER;

You can read more at the Documentation

---

To expand on the above and make a quick reference:

To make a user a SuperUser: ALTER USER username WITH SUPERUSER;

To make a user no longer a SuperUser: ALTER USER username WITH NOSUPERUSER;

To just allow the user to create a database: ALTER USER username CREATEDB;

You can also use CREATEROLE and CREATEUSER to allow a user privileges without making them a superuser.

Documentation

---

$ su - postgres
$ psql
$ \du; for see the user on db
select the user that do you want be superuser and:
$ ALTER USER "user" with superuser;

---

May be sometimes upgrading to a superuser might not be a good option. So apart from super user there are lot of other options which you can use. Open your terminal and type the following:

$ sudo su - postgres
[sudo] password for user: (type your password here)
$ psql
postgres@user:~$ psql
psql (10.5 (Ubuntu 10.5-1.pgdg18.04+1))
Type "help" for help.

postgres=# ALTER USER my_user WITH option

Also listing the list of options

SUPERUSER | NOSUPERUSER | CREATEDB | NOCREATEDB  | CREATEROLE | NOCREATEROLE |
CREATEUSER | NOCREATEUSER | INHERIT | NOINHERIT | LOGIN | NOLOGIN | REPLICATION|
NOREPLICATION | BYPASSRLS | NOBYPASSRLS | CONNECTION LIMIT connlimit | 
[ ENCRYPTED | UNENCRYPTED ] PASSWORD 'password' | VALID UNTIL 'timestamp'

So in command line it will look like

postgres=# ALTER USER my_user WITH  LOGIN

OR use an encrypted password.

postgres=# ALTER USER my_user  WITH ENCRYPTED PASSWORD '5d41402abc4b2a76b9719d911017c592';

OR revoke permissions after a specific time.

postgres=# ALTER USER my_user  WITH VALID UNTIL '2019-12-29 19:09:00';

---

Run this Command

alter user myuser with superuser;

If you want to see the permission to a user run following command

\du

---

You can create a SUPERUSER or promote USER, so for your case

$ sudo -u postgres psql -c "ALTER USER myuser WITH SUPERUSER;"

or rollback

$ sudo -u postgres psql -c "ALTER USER myuser WITH NOSUPERUSER;"

To prevent a command from logging when you set password, insert a whitespace in front of it, but check that your system supports this option.

$  sudo -u postgres psql -c "CREATE USER my_user WITH PASSWORD 'my_pass';"
$  sudo -u postgres psql -c "CREATE USER my_user WITH SUPERUSER PASSWORD 'my_pass';"

---

alter user username superuser;

---

If you reached this because you're using Amazon Redshift you CANNOT assign SUPERUSER

ALTER USER <username> SUPERUSER;

Instead assign CREATEUSER:

ALTER USER <username> CREATEUSER;

Apparently, SUPERUSER isn't an available user assignment in Amazon Redshift clusters. I am utterly confused by this.

https://docs.aws.amazon.com/redshift/latest/dg/r_superusers.html

Screenshots showing this:

https://i.stack.imgur.com/uyWXt.png

https://i.stack.imgur.com/ycbeL.png

---