So recently I was tasked with resurrecting a few old Sun machines from a closet. And of course once they were dug out, no one could remember the root or LOM passwords and the since the machine was set to boot from the disk, I had no way in. But as they say, physical access trumps all. Here are the few steps I went through to gain access to the machine and re-install them.
Recover the ALOM password
Insert the installation disk and pull out the hard-drive.
Power-on the machine, this will eventually dump you to the ok> prompt where you can give it boot cdrom -s to get single user mode.
After the machine eventually boots you into single user mode, you can issue /usr/platform/`uname -i`/rsc/rscadm show/showuser to see the admin account.
Then /usr/platform/`uname -i`/rsc/rscadm userpassword <username> and enter the new password twice.
Boot from CDROM when boot order is set to boot from disk:
From the ALOM, issue poweron and then quickly issue console. This will start the machine and then switch you to the console terminal.
Once in the console terminal, give it a break command. I was able to do this with CTRL-BREAK on the keyboard.
This will dump you to the ok> prompt where you can then boot cdrom.