Heh. I still have a pre systemd machine around. It uses 300 M of RAM for the OS and a few services I use in my home.

I recently set up a "modern" systemd based Ubuntu server in a VM and it used closer to 1 G before I installed any service.

Why compare a "full-featured", do-everything OS like Ubuntu with something pre-systemd when you're concerned about memory consumption?

I just checked a random debian 12 system (with systemd) running a bunch of services at home, and here's what I see:

$ free -m

total used free shared buff/cache available

Mem: 3791 320 2235 1 1313 3471

Swap: 99 0 99

Seems like usage is pretty much on par with your expectation. The largest consumers are systemd-journal which is storing logs in RAM, and filebeat which is relatively wasteful w/ memory. systemd itself (without the journal buffer log) consumes maybe 20-30 MB.

I have checked three smaller machines.

On one (coreelec) systemd has 7M of resident data, of which 5.5M are shared libraries; by comparison, the numbers for sshd are respectively 6M and 3.5M.

On an OpenWRT machine without systemd (it's using procd) there are 700k of resident data. So the "cost" of systemd seems to be ~5M. Certainly I wouldn't run systemd on an old router with 16MB of RAM, but the cost is two orders of magnitude less than 1G-300M.

Is systemd using 700MB?