is it the same password as admin,root?
i am setting up a forum and cant get into the database with the password for admin,root
so the result is that i cant install unless i use /usr/bin/mysqladmin -u root password 123456789
But then i cant log in to my database and create a new 
Never and I mean really never change your MySQL root password, this is used internally in the SME Server.
If you login at your server you can access the mysql client with the root account without a password, this account only works locally. With this account you can create a new account with the proper privileges to access your server (see the mysql manual for this).
If this user has to login from a remote machine you will have to change your mysql configuration to have it accept connections at a port as it is default configured to use a socket. I don't know to do this by heart, but it has been explained on the forums several times, please use the search funtion.