Comment by ad404b8a372f2b9

Yes, the read-write disk partition also holds my files.

No docs I'm afraid and I set it up too long ago to remember the exact details. I used overlayroot, there are some really good resources on google to set it up like this. If I remember correctly it's just a matter of setting the overlayroot.conf file to:

  overlayroot_cfgdisk="disabled"  
  overlayroot="tmpfs:swap=1,recurse=0"  

And then a grub option to mount the base in read-only:

  linux /boot/vmlinuz-5.3.0-51-generic root=UUID=... ro  $vt_handoff

Then you add your mounts in fstab for persistent stuff.

I think this blog post describes it well: https://spin.atomicobject.com/2015/03/10/protecting-ubuntu-r...

For modifications to the base, installing or modifying software, etc I have a grub option to disable the overlay system and mount the base partition in read-write so it can be used normally. So I reboot into this option, do my changes, then reboot immediately in overlay mode.

  linux /boot/vmlinuz-5.3.0-51-generic root=UUID=... rw overlayroot=disabled  $vt_handoff  

It took me about a month to get used to it, sometimes I'd apt-get something then the next day I'd facepalm after realizing I had done it in overlay-mode and had to do it all over again. I haven't lost any personal files though, it's pretty easy to remember to avoid saving them to your home and instead go to the persistent partition.