pg_restore and users

Dear all,
I normally don't do a lot of pg_dump and pg_restore. And it is not easy
to experiment with this.
Just trying to clarify something.

While I was using a user name that have rights to createdb, createuser
to restore the database

pg_restore -d mydb mydb.tar

the program exited with error message: user abs does not exist.

then I created that user with the command createuser abc.
the restore can be finished (actually I have a few users, I have to do
all of them).

1. Do I have such problem if I use the super user POSTGRES?
2. Is the database intended to store a lot of users or only a few? If
you have a lot users and you forgot about them, it could be very
difficult to restore the database.

Anyone can tell me about the normal way of dealing with this. Or I am
doing something wrong.

Kemin

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