Why centos server won't boot?

Question

CentOS

Due to lack of memory, the server knocks out lowmem (it kills swap and RAM, I looked at top).
After the reboot, the server cannot boot, in technical assistance they again say that it does not have enough memory for this and it hangs.
Tell me where to start, how to find out what is eating up memory if I can't load the server?

Answer 1

Add memory and see =)))
PS run in debug mode.

Answer 2

Run on 1 runlevel and remove everything from startup. True, for this you need a remote direct console