for visitors from the future:

i was able to solve this with the help of fsmithred (thanks!) and a good amount of trial & error.  the details are in the above posts but to summarize there are 2 ways that we tried to install Devuan ASCII 2.1 to existing Btrfs subvolumes.  for both cases in another shell/vt the encrypted partition must be opened first with cryptsetup and the Btrfs subvolume(s) then mounted before starting the installation.

• with the netinst/Debian installer: set the Btrfs default subvolume to be the desired one on which to install /, perform the installation to the Btrfs partition, then copy /home, etc. to their desired subvolumes after installation

• with the live/refractainstaller from the command line: edit the refractainstaller script to add the correct --options subvol= to the mount commands for the / and /home partitions, which are given as the /dev/mapper/XXXX

in both cases after the installation is completed some additional steps need to be performed in a chroot, preferably before rebooting:

• apt update && apt upgrade

• edit /etc/fstab and /etc/crypttab appropriately for the subvolumes

• set CRYPTSETUP=y in /etc/cryptsetup-initramfs/conf-hook

• if using encryption and the installer did not take care of it, set GRUB_ENABLE_CRYPTODISK=y and  GRUB_CMDLINE_LINUX_DEFAULT= in /etc/default/grub

• update-grub

• updateinitramfs

there may be some small steps that i missed but the details are in the above threads.  i ended using the refractainstaller as the steps were all laid out in the script that is well documented and easy to follow, making it simple to perform the above mentioned edits.  good luck!

way to go!  unfortunately after doing the same edits as you described above with the live refractainstaller i find myself in a similar position: i enter the encryption password to GRUB (my /boot is in the encrypted Btrfs partition) and can start booting.  however after the line "loading the initial ramdisk" i get tons of the following messages mdadm: No arrays found in config file or automatically then Gave up waiting for root file system device before finally dropping me to an initramfs prompt like you, complaining about the UUID not existing.

strangely enough the first time that i booted the fresh install and this occurred, in the initramfs shell i was able to use cryptsetup to open the LUKS partition, then exit and the shell and continue booting.  however on every consecutive reboot since then the cryptsetup command is no longer available in the initramfs shell thus i cannot get any further?!  the one time that i was able to use cryptsetup and continue booting, while i could not log in via slim i did run an apt upgrade in a terminal, perhaps that removed cryptsetup somehow?  or maybe this points to the problem: the crypt stuff is not getting loaded during boot and thus the initramfs cannot be found in the unopened encrypted partition.  however i see the crypt insmod in the GRUB config.

i tried your fix by changing the root= kernel command line argument to use the /dev/mapper/storage value but ended up with the same thing i.e. stuck in the initramfs shell with no cryptsetup.

at this point i feel like i have hit a dead end.  i may try the netinst method to see if at least that gives me a booting system, though the refractainstaller is refreshingly simple and straightforward.

thanks as always, let me know if you make any progress.

peace, w

i assume that you mean netinst by "installer" and "regular installer"?  i tried what you said with netinst expert mode:

• in the "Partition disks" step at first i only saw the sda3 LUKS1 encrypted partition (the Btrfs partition is inside the encrypted container)

• i was able to open the encrypted /sda3 in a separate shell using cryptsetup (after doing something (maybe selecting "Configure encrypted volumes"?) that made the cryptsetup command available in the shell, as it initially was not?)

• at that point after exiting and re-entering the "Partition disks" step i now see the Btrfs partition under a new heading "Encrypted volume".  and while i can select it for installation without formatting, unfortunately i still cannot see/select the subvolumes as installation targets.  in addition i could not add the mount options for selecting the subvolume

this is an improvement as maybe i can just set the root subvolume as the default subvolume for this Btrfs partition which would install the system at least to a single subvolume. then copy over home afterwards?  however, it still would be nice to have the installer set up correctly the fstab, cryptab, and GRUB paths.

  just in case i also tried with the desktop-live installer i.e. refractainstaller but could not find a way to even see unlocked Btrfs partition (again in a separate shell via cryptsetup) as above.  maybe because you most likely meant the netinst in the first place

thanks for testing this out.  i have set up full disk encryption (i.e. with encrypted /boot) with a single encrypted partition containing Btrfs and subvolumes with other distros using GRUB (LUKS1 only).  one thing that always got me was that GRUB does not understand Btrfs subvolumes so you need to use the full paths to each subvolume in the config.  maybe that is tripping you up?

  OK, let me know if you have any other ideas and thanks again!

peace, w

adding some more info here after discussion on IRC regarding the existing Btrfs subvolumes to which i am trying to install Devuan:

• the btrfs mount commands:

  mount -o subvol=/shares/home /dev/mapper/storage /mnt/home/
  mount -o subvol=/systems/Devuan/root /dev/mapper/storage /mnt/Devuan/root/

• output of mount with Btrfs subvolumes mounted:

  root@devuan:~# mount
  sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
  proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
  udev on /dev type devtmpfs (rw,nosuid,relatime,size=1978076k,nr_inodes=494519,mode=755)
  devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
  tmpfs on /run type tmpfs (rw,nosuid,noexec,relatime,size=399652k,mode=755)
  /dev/shm on /lib/live/mount/medium type tmpfs (rw,relatime,size=1084164k)
  /dev/loop0 on /lib/live/mount/rootfs/filesystem.squashfs type squashfs (ro,noatime)
  tmpfs on /lib/live/mount/overlay type tmpfs (rw,relatime)
  overlay on / type overlay (rw,noatime,lowerdir=//filesystem.squashfs/,upperdir=/live/overlay//rw,workdir=/live/overlay//work)
  tmpfs on /run/lock type tmpfs (rw,nosuid,nodev,noexec,relatime,size=5120k)
  pstore on /sys/fs/pstore type pstore (rw,relatime)
  tmpfs on /run/shm type tmpfs (rw,nosuid,nodev,noexec,relatime,size=799300k)
  tmpfs on /tmp type tmpfs (rw,nosuid,nodev,relatime)
  rpc_pipefs on /run/rpc_pipefs type rpc_pipefs (rw,relatime)
  tmpfs on /sys/fs/cgroup type tmpfs (rw,nosuid,nodev,noexec,mode=755)
  cgroup on /sys/fs/cgroup/elogind type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/usr/lib/elogind/elogind-cgroups-agent,name=elogind)
  tmpfs on /run/user/1000 type tmpfs (rw,nosuid,nodev,relatime,size=399648k,mode=700,uid=1000,gid=1000)
  /dev/mapper/storage on /mnt/home type btrfs (rw,relatime,space_cache,subvolid=257,subvol=/shares/home)
  /dev/mapper/storage on /mnt/Devuan/root type btrfs (rw,relatime,space_cache,subvolid=259,subvol=/systems/Devuan/root)

ahoy specing,

  thanks for the detailed tutorial on getting Btrfs+subvolumes installed.  i am trying to use an existing Btrfs partition and subvolumes (described in more detail here https://dev1galaxy.org/viewtopic.php?pid=19401#p19401) but am having problems with the step

when i get to the partitioning step in the netinst expert mode installer, i cannot find a way to select a root partition that allows that step to complete without (seemingly) the installer overwriting my Btrfs partition.  my disk only has 2 partitions:

/dev/sda1    GRUB BIOS boot partition (for booting GPT disk with BIOS)
/dev/sda2    LUKS1 dm encrypted Btrfs partition (remainder of disk)

  thus has something changed in the latest installer for ASCII stable 2.1 that changes your instructions?  or am i missing some simple step implied in your tutorial (this is my first experience with the Debian/Devuan installer)?

thanks again for your help, w