We are evaluating a scenario where we want to run raspbian os on minimal possible memory. I am fine with custom building it. Can someone throw some light on this?
Without a GUI running, it should be okay with ~50 MiB. It will start up at around 25 MiB however, so that doesn't leave you with much.
> free total used free Mem: 448376 401792 46584 -/+ buffers/cache: 55896 392480 ^^^^^
That's a B+ running pidora, but raspbian is the same. It's been on four or five days. The largest userland process is actually
dhclient, which manages DHCP for internet service, then
rsyslogd (which is optional on pidora, but required on raspbian sans systemd), then
systemd (on raspbian, that would be
init). The init setup is reduced from stock (e.g., I don't use NetworkManager), but not drastically.
free and other tools don't report the memory used by the kernel, which is probably about 5-10 MiB.
You will get much better performance if you do leave a decent amount of free memory due to file caching.
You can of course also use a swapfile (raspbian does by default), but using significant disk swap will slow the system down.