How to upgrade in place from 16.10 unity to 17.04 gnome

[Marius Gedminas]

On Thu, Apr 20, 2017 at 02:17:26PM +1000, Brian Burch wrote:
> On 17/04/17 18:10, Pander wrote:
> > To remove Unity, I simply use dpkg -P packagenames. When that list
> > becomes long from many dependencies, I put the output of that
> > through grep to get all the depending packages and cat those to a
> > file. Edit the file (vim and a lot of Shift-j) and put dpkg -P at
> > the beginning. I use the same trick for ouput of dpkg -l|grep -v ^ii
> > 
> > Of course, check if those lists of package names are okay to purge
> > before doing bulk purges. Some packages are tricky, see my post a
> > while back on Unity dependencies.
> 
> Thanks for your suggestion, Pander. I did something fairly similar to that
> in the past. If I decide to go ahead this time, then I will follow your plan
> because it seems simpler than what I did before.
> 
> However, I was hoping to receive advice that would be attractive and useful
> to people who are not as confident as us with these low-level tools.
> 
> Am I correct in thinking the "old method" of installing gnome-desktop
> alongside unity has become too complex to be worth trying?

Have you tried it?

I did that a long time ago and it worked for me.  I haven't had the
chance to try it lately.

Installing the gnome metapackage and removing the unity metapackage
ought to suffice, IMHO.  You might need to hunt down some other packages
that differ between Unity and GNOME (e.g. the bootsplash theme).

If I weren't a lazy person, I'd install both in two virtual machines,
then compare the lists of installed packages (e.g. dpkg -l) so I would
know which ones to install and remove to turn one into the other.

> I tried "sudo dpkg --purge --dry-run unity" (-P is the same as --purge) on
> my xenial system "just for fun", but it bombed out with a "too many
> dependencies" error. However, it didn't list ANY of them!

dpkg is too low-level for this; don't use it.  apt purge exists these
days, and it deals with dependencies correctly.

(AFAIU the only reason to remove/purge Unit packages is in case they
install some system-wide gsettings override files that change some GNOME
settings defaults to Unity defaults.  )

> Perhaps I should just wait for the next ubuntu release and hope there will
> be a more straightforward conversion path?

A full reinstall is always a good way to test your backup completeness
;)

Marius Gedminas
-- 
I read I forget; I see I remember; I teach I understand.