How do I set the run target and turn off services on a non running installation ?

[linux guy]

I have a non booting installation that I need to get running.  I would like
to know how to change the run target to the command line and disable
several services that are causing issues during the boot process.

How does one manually change the run target on a non booting installation
?  What do I edit ?  Because my installation doesn't boot, I can't run
systemctl, so I must edit the link manually.

How does one manually disable services so they don't start during the boot
process ?  Because my installation doesn't boot, I can't run systemctl, so
I must edit the configuration manually.

Thanks