Interesting. I haven't rechecked but I had problems when /tmp wasn't mounted in /etc/fstab as tmpfs. What made me try that was the original blog post that you refer to. In his /etc/fstab is a line for /tmp, but he doesn't mention it in the text.
I use minibian jessie, so it is not the full raspbian distro. Don't know if that could make a difference.
I think I have solved my samba problem with an ugly hack.
I copied everything in /var/lib/samba to a backup-folder.
THen I put a symlink to /tmp so /var/lib/samba is found there.
Then I put a line in rc.local that copies the content of my backed up /var/lib/samba back (which now points to /tmp
and another line starting smbd
Now I can connect to my shares in my read only filesystem.
Of course I copy only the needed files, but this was the quich and dirty version 
I have disabled nmbd, but it should work too now I guess.
To not make unsuccessful appempts to start smbd before doing the copy I also disabled sbd with update-rc.d
Hello
Thank you very much for a very helpful tutorial!
I have one comment and one question.
I think you should mention that you also have to mount /tmp as tmpfs in /etc/fstab
After doing that it works like a charm.
But I also want samba to serve some files from my rpi. I find samba hard to handle here since it seems to need to write to some files in /var/lib/samba. When I boot with writable / it works, but not if I remount as writable after boot. If I make it writable after boot, it seems like smbd starts, but I cannot connect to the shares. What I think I have to do is create some files in /tmp at boot time maybe with tdbtool, but I don't know yet what files and if it will work. I will continue to investigate, but any time saving tips is highly appreciated :-).
