Experiences with Ubuntu Core 14.04

The theory behind Ubuntu Core is that it's a stripped, very light-weight version of Ubuntu for the cloud or server installations. It's a nice theory, but I found the practise a little less idyllic.

  • https://wiki.ubuntu.com/Core (page shows latest release as 14.04, but there's a 15.04 release that's smaller than the 14.04 release)
  • 15.04 amd64 tarball (gzip) is 47MB
  • note: tarball, not bootable installer: the install process is rather ugly
  • I used a gparted live ISO in VirtualBox to do the drive set-up
  • then following these instructions: http://askubuntu.com/questions/67001/what-commands-are-needed-to-install-ubuntu-core (the instructions on the "Core" page are pretty weak)
  • the gparted live CD balked at the chroot command
  • tried it with Debian netinst disk in Rescue mode ... chroot worked
  • interesting problem: the instructions at askubuntu.com say to use the command apt-get install linux-{headers,image}-generic: this doesn't work in the Debian rescue environment as the shell is unable to expand the "{headers,image}" construct, so I ran the command twice, once with "linux-headers-generic" and once with "linux-image-generic"
  • the headers used a lot of space
  • the kernel ("linux-image-generic") downloaded 99MB including not only the kernel but a huge number of deps, which then expanded to ~360MB on disk
  • by which time "Core" is no longer looking like a lightweight choice
  • after rebooting, the system boots ... but I couldn't log in: /etc/shadow shows root's password as "*", so I had to use a boot disk to change that from "*" to ""
  • reboot, login as root with no password as it's been set to blank
  • but I couldn't use passwd to change root's password because / was mounted ro
  • fixed with mount -o remount,rw /
  • this may be because I've managed to create a bizarro hybrid of Ubuntu with a Debian GRUB (presumably because I was using a Debian rescue environment
  • grub-install /dev/sda in an attempt to get the Ubuntu version of GRUB going on
  • reboot
  • lots of errors during boot (appeared to be the same as previously), but the system comes up okay
  • df -h: "df: cannot read table of mounted file systems: No such file or directory"
  • that's right, there's no /etc/mtab
  • grep -v rootfs /proc/mounts > /etc/mtab (nifty - one of those little fixes you can find on the internet)
  • didn't work first try because the FS is again mounted ro - fixed as above, rerun
  • df now works as expected
  • / is 779M
  • apt-get clean gets us to / being 663M
  • at this point though, the .VDI file is already 1008MB in size: I can make a usable (and better equipped and less error-prone) Debian system more easily: it's slightly larger, but it works and is much easier to deal with
  • and so ends the Ubuntu Core experiment