What is the equivalent of oradim on Linux? Does Oracle even provide anything like that for Linux?
There is not alternate command for oradim. On linux simply manualy create new enviroment for new instance.
On Linux (and Unix) there are no Services (at least not as on Windows), but only processes, and these processes are automatically activated when the instance is started, and removed when the instance is shut down.
To start a new instance, say newsid, you create an initnewsid.ora file, then
$ export ORACLE_SID=newsid $ sqlplus / as sysdba
SQL*Plus: Release 10.2.0.1.0 - Production on Tue Sep 5 16:38:30 2006
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to an idle instance.
SYS@newsid SQL> startup nomount pfile=
If you are running RedHat (or CentOS), you could copy and change one of the scripts in /etc/init.d and add it to your service list by using chkconfig. This can help you with automagically starting your database after a reboot of the machine.
It does seem that you are fairly new to the linux platform though, so please ask an administrator to help you with those scripts (nofi).