On 22/11/2018 18:21, Roger Leigh wrote:
> Before I follow up on any of the points you (and others) made in 
> response, let me begin with some history you may be unaware of.  It 
> actually predates systemd, and is largely unrelated to systemd.
I just rediscovered
   
https://wiki.debian.org/ReleaseGoals/MountUsrInInitramfs
which has some additional details.  Though it actually contains less 
detail overall than my email yesterday, but there are some additional 
small bits of information there.  It never got fully updated after 
completion of the goal.  But it might be of general interest.
   
https://wiki.debian.org/UsrMerge
Looking at the details of the /usr merge in more detail, if you're 
currently running with a separate /usr, this shouldn't have any impact 
on booting via the initramfs with initramfs-tools.  The only 
consideration would be that you would need to have sufficient disc space 
under /usr for the files being moved over from the rootfs.
So if you're insistent upon retaining a separate /usr, that shouldn't be 
a problem.  Though it will definitely break booting of / without an 
initramfs; you won't be able to do a direct boot of the rootfs since all 
the binaries will be missing.
Regards,
Roger