Ubuntu – How to permanently enable compressed ram swap? What version to use

Like Sergey "Shnatsel" Davidoff was quoted in that blog post, this package installs a script to run it as a service. The script automatically configures itself and the service starts up automatically. There is no further configuration needed. The service can be manually controlled via:

sudo service zramswap start|stop|status|restart|reload|force-reload

If you open the deb package with file roller you can see that only two files are installed:

/etc/init/zramswap.conf
/etc/init.d/zramswap

Along with some documentation files. The DEBIAN directory contains package meta data and commands to initialize the service. Thats all there is in the package. The corresponding devices are named after this scheme: /dev/zram[0-9]

Have you installed it via PPA? I recommend doing that.

Ubuntu 20.04 kills a process.

I noticed it myself on a new GCE 20.04 server: I got a notification one of our instances was acting up and before I could log into it Ubuntu had already killed one of 9 MySQL processes. After some investigation it was the one consuming more than 70% of the memory of the server.

This will give you information about "killes processes":

journalctl -a | grep -i "killed process"

dmesg and syslog will also show notifications from oom-kill

kernel: [{timestamp}] Out of memory: Killed process {id} ({name}) {process information} oom_score_adj:{number}

I did not see that happen in 18.04 or older versions. The server would just stay slow until I killed a process myself. This works on processes, not when you hibernate/suspend: that will require swap and if there is not hibernate/suspend won't work

Story on out of memory killer:

Whenever your server/process is out of memory, Linux has two ways to handle that, the first one is an OS(Linux) crash and your whole system is down, and the second one is to kill the process (application) making the system run out of memory. The best bet for the second option is to kill the process and save the OS from crashing. In short, the Out-Of-Memory Killer is the process which is responsible for terminating the application to save the kernel from crashing, as it only kills the application and saves the entire OS from crashing. Let’s first discuss how OOM and works and how to control that, and later we will discuss how OOM Killer decides which application to kill.

Personal comment: "as it only kills the application" is probably wrong. I noticed it killed a process and not restart the mysql service.