OK, my problem is all better now. I could not create users or groups. Went through the vaious software fixes proposed in similar posts, and none of them seemed to apply. Problem went away with a complete poweroff and blowing out dust. I can now create users and groups, and mysql-server installed without any trouble.

I have one install that has mysql-server for one app that needs it for its database. It only gets used from localhost, and it works fine. I just upgraded it after many months, and it still works.

I just tried to install mysql-server on my main box, and it's failing with this error message:

dpkg: error processing archive /var/cache/apt/archives/mysql-server-5.5_5.5.55-0+deb8u1_amd64.deb (--unpack):
 subprocess new pre-installation script returned error exit status 1

Attempting to add the group manually:

groupadd -g 121 mysql
groupadd: failure while writing changes to /etc/group

This is strange. I got the same error a few days ago trying to install something, but that was in a chroot, and I needed to make the bind-mounts with sys, dev and proc. Right now, I'm not in a chroot. I'm installing directly on hardware in the running system. If someone else wants to try, you can let me know if the problem is just with my setup.

I don't think it's a file permission problem:

-rw-r--r-- 1 root root 904 Mar  8 18:38 /etc/group

When you start synaptic from the menu, you should get a window that asks for a password. If you set up the system to use a root account, use the root password, and if you set it up for sudo, use your password. If you're not getting the pop-up window for authentication, the start it from a terminal like you did until that issue is solved.

For the grub problem. You're right. Editing the config on devuan won't help if debian is in charge of boot. I can think of three ways to fix it.
1. Boot into Devuan and reinstall grub-efi-amd64
2. Boot into Devuan and run 'sudo grub-install' in a terminal. (no device name needed with uefi)
    - optional for 2: run 'sudo grub-install --bootloader-id=some-name'

In either of those cases above, grub will create a bootloader and I expect it will put itself first in the list of bootloaders. Then you'll need to run update-grub to get debian in the boot menu. WARNING: I don't know this for a fact. UEFI implementations vary from manufacturer to manufacturer, so your system might not act like mine. COMMENT: I would try #2 with the bootloader-id first, and use an id name that is something other than debian, devuan or boot. Then you will know for sure that it's the one you just made.

In my system, Debian's bootloader is in /boot/efi/EFI/debian and Devuan's is in /boot/efi/EFI/devuan. There is a /boot/efi/EFI/boot/, too. I forget where that came from, and I don't use it. Whenever I install a linux and allow grub to install, it becomes first. If I change the order of the bootloaders using efibootmgr, it shows me that the boot order has changed, and then it reverts to the previous order as soon as I reboot. Yours may act differently.

3. Boot into Debian and copy the menuentry for Devuan from /boot/grub/grub.cfg into /etc/grub.d/40_custom, add nomodeset to the linux line, and run update-grub. There will be an extra entry for Devuan in the boot menu, and that one will have nomodeset in the boot command. The entry starts with the word, menuentry and ends with a closing curly brace `}' 

Read this if you haven't, re-read it if you have: http://www.rodsbooks.com/efi-bootloaders/index.html

1. Graphics card or driver. Whichever one you want to blame. You could try the proprietary driver, but if it's working ok, there's no need.

2. Yes. Add nomodeset to /etc/default/grub and then run update-grub to generate a new menu. Then you don't have to edit at boot every time.

GRUB_CMDLINE_LINUX_DEFAULT="quiet nomodeset"

At the boot menu, press 'e' to edit the boot entry. Use the arrow keys to navigate to the linux line and add the word, nomodeset to the line. Then ctrl-x to boot.

No, I haven't seen that except when I was trying to boot to console. You should not need to log in to the desktop - it should happen automatically.
It's an isohybrid image, so anything that just copies it bit by bit to the whole device should work. I don't know what Mint or Rufus does, but if Rufus needs to know that it's for uefi, then it's probably doing something about that, and it should not. If you have a running linux, you can just use dd.

Please check the following commands:

tty          #which tty are you connected to?
ps ax |grep slim       # is the display manager running?
sudo runlevel
cat .xsession-errors
sudo less /var/log/Xorg.0.log    # look for lines starting with EE

Try ctrl-alt-F7 (maybe F8 or F9) to see if that gets you to the desktop.

If slim is not running, try starting it:

sudo service slim start

Check the sha256sum to make sure the download was good.

$ sha256sum devuan_jessie_1.0.0-RC2_amd64_uefi-live.iso
ac38f0c7d983f8ce93f7b261274fef30823022707b96fc1c09f6b9a1b0c3709d  devuan_jessie_1.0.0-RC2_amd64_uefi-live.iso

You'll get that if root is logged in on console or in a root terminal or if you're running some app as root.

The debootstrap command left me without a kernel or bootloader, so it was necessary to mount those things (didn't really need /dev/pts) and chroot into the target to install grub and linux-image. While there, I also created a root password. There's no way I could have rebooted to do those things in the installed system.

Refracta isos have included devuan debootstrap since some early version of devuan debootstrap. I just re-tested it with a current refracta iso. I did not give it a URL, and it pulls from packages.devuan.org. I stopped at "I: Base system installed successfully" (haven't chrooted in and installed bootloader yet.) Looks to me like it works as it should.

Download a refracta live-iso and boot it from CD or USB on the computer you want to install. Instructions almost identical to what's below are in /home/user/debootstrap_devuan
https://sourceforge.net/projects/refrac … isohybrid/

Create partition
Format partition
Mount the partition and run debootstrap. You might be more lenient with the excludes. Just excluding systemd-sysv should be equivalent to using one of the devuan_jessie installer isos.

mount /dev/sdb1 /mnt   # replace sdb1 with correct drive and partition
debootstrap --arch i386(or amd64) --exclude systemd,libpamsystemd,systemd-sysv,libsystemd0 jessie /mnt

If you have custom configs or other special files, you can copy files to the new system.
(example:   cp /boot/grub/splash.png /mnt/boot/grub/)

Mount some things so you can install the grub bootloader.

mount --bind /proc /mnt/proc
mount --bind /sys /mnt/sys
mount --bind /dev /mnt/dev
mount --bind /dev/pts /mnt/dev/pts

Chroot into the installed system.

chroot /mnt

Install software, edit configs, *create root password*, create user, install a kernel.

Still in chroot, install the bootloader and create the boot menu, then exit the chroot.

grub-install  /dev/sdb   # replace sdb with correct drive
update-grub
exit

Unmount stuff.

umount -l /mnt/dev/pts
umount -l /mnt/dev/
umount -l /mnt/sys
umount -l /mnt/proc
umount -l /mnt

That's all. Reboot.

Maybe yes, maybe no. You can install them, but sometimes getting them to work without a reboot is difficult. And of course, if you reboot the live session, you lose any changes. I didn't know you could install debs with synaptic. Thanks for that.

The regular installer isos have the wireless firmware, and you can choose to install it or not. That didn't work in beta2, but it's fixed in RC. The desktop-live and minimal-live don't have any wireless firmware installed or available, unless you have a network connection already. (catch-22). There's a good chance the final live isos will have wireless firmware. I don't know what the best way to do it is.

Here's a list of the wireless firmware packages that I pack in the Refracta isos. It's all of the ones I could find, but I haven't checked lately to see if there are more. I was able to install all of them in devuan without having to agree to a EULA with the exception of one - the ipw2x00.

b43-fwcutter_1%3a019-2_amd64.deb
b43-fwcutter_1%3a019-2_i386.deb
firmware-atheros_0.43_all.deb
firmware-b43-installer_1%3a019-2_all.deb
firmware-b43legacy-installer_1%3a019-2_all.deb
firmware-bnx2_0.43_all.deb
firmware-bnx2x_0.43_all.deb
firmware-brcm80211_0.43_all.deb
firmware-intelwimax_0.43_all.deb
firmware-ipw2x00_0.43_all.deb
firmware-iwlwifi_0.43_all.deb
firmware-libertas_0.43_all.deb
firmware-linux-nonfree_0.43_all.deb
firmware-myricom_0.43_all.deb
firmware-netxen_0.43_all.deb
firmware-qlogic_0.43_all.deb
firmware-ralink_0.43_all.deb
firmware-realtek_0.43_all.deb
firmware-ti-connectivity_0.43_all.deb
firmware-zd1211_3.0.0.56-3_all.deb

And here are the package names for installing with apt.

b43-fwcutter firmware-atheros firmware-b43-installer firmware-b43legacy-installer firmware-bnx2 firmware-bnx2x firmware-brcm80211 firmware-intelwimax firmware-ipw2x00 firmware-iwlwifi firmware-libertas firmware-linux-nonfree firmware-myricom firmware-netxen firmware-qlogic firmware-ralink firmware-realtek firmware-ti-connectivity firmware-zd1211

WOW! Code boxes that don't break my line. Nice. Thanks to whoever did that.

Edit: I would guess that the most common ones are atheros, iwlwifi, realtek and broadcom (all the ones that start with b). The ralink is another realtek. I have one of those on a pci card.

Some of them are from udev, and yeah, they will be there on a fresh install.