An issue with Emu cropped up a few weeks ago that was seemingly caused by upgrading from Ubuntu 16.04 to 18.04.

However, the problems only seemed related to using Emu via the GUI; users could still use Emu as a headless computer via SSH.

Today, I was upgrading some packages and noticed two things:

1. When initially logging in to Emu.

   
   sam@swoose:~$ ssh emu
   Welcome to Ubuntu 16.04.5 LTS (GNU/Linux 4.4.0-57-generic x86_64)
   
   * Documentation:  https://help.ubuntu.com
   * Management:     https://landscape.canonical.com
   * Support:        https://ubuntu.com/advantage
   
   0 packages can be updated.
   0 updates are security updates.
   
   New release '18.04.1 LTS' available.
   Run 'do-release-upgrade' to upgrade to it.
   
   You have mail.
   Last login: Tue Oct  2 07:30:32 2018 from 128.95.149.75
   

   This is showing that Emu is still running Ubuntu 16.04, not 18.04 as presumed!

2. An error in the GRUB config generation process when upgrading packages.

run-parts: executing /etc/kernel/postrm.d/zz-update-grub 4.4.0-134-generic /boot/vmlinuz-4.4.0-134-generic
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-4.4.0-137-generic
Found initrd image: /boot/initrd.img-4.4.0-137-generic
Found linux image: /boot/vmlinuz-4.4.0-135-generic
Found initrd image: /boot/initrd.img-4.4.0-135-generic
Found linux image: /boot/vmlinuz-4.4.0-57-generic
Found initrd image: /boot/initrd.img-4.4.0-57-generic
Found linux image: /boot/vmlinuz-4.4.0-53-generic
Found initrd image: /boot/initrd.img-4.4.0-53-generic
error: syntax error.
error: Incorrect command.
error: syntax error.
Syntax error at line 98
Syntax errors are detected in generated GRUB config file.
Ensure that there are no errors in /etc/default/grub
and /etc/grub.d/* files or please file a bug report with
/boot/grub/grub.cfg.new file attached.
done
Processing triggers for libc-bin (2.23-0ubuntu10) ...

These two bits of information led me to believe the problem wasn’t that the system upgrade to 18.04 was incompatible with these old Apple Xserve hardware (since the upgrade didn’t actually get implemented) and instead was that the upgrade might have been initiated, but aborted, which modified the GRUB configuration file(s), breaking the GUI; much like the problem I previously addressed earlier this summer.

When I fixed the display/GUI issues with Emu and Roadrunner earlier this summer, I noted that the /etc/default/grub files on each of the computers were slightly different, despite the fact that these two computers should be identical. So, I replaced the /etc/default/grub file on Emu with the file from Roadrunner and rebooted Emu.

Contents of /etc/default/grub file on Emu/Roadrunner, for future reference:

# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
# For full documentation of the options in this file, see:
#   info -f grub -n 'Simple configuration'

GRUB_DEFAULT=0
#GRUB_HIDDEN_TIMEOUT=0
GRUB_HIDDEN_TIMEOUT_QUIET=true
GRUB_TIMEOUT=10
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX=""

# Uncomment to enable BadRAM filtering, modify to suit your needs
# This works with Linux (no patch required) and with any kernel that obtains
# the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...)
#GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef"

# Uncomment to disable graphical terminal (grub-pc only)
#GRUB_TERMINAL=console

# The resolution used on graphical terminal
# note that you can use only modes which your graphic card supports via VBE
# you can see them in real GRUB with the command `vbeinfo'
#GRUB_GFXMODE=640x480

# Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux
#GRUB_DISABLE_LINUX_UUID=true

# Uncomment to disable generation of recovery mode menu entries
#GRUB_DISABLE_RECOVERY="true"

# Uncomment to get a beep at grub start
#GRUB_INIT_TUNE="480 440 1"

Voila! Emu now has a functional display/GUI again!