[SOLVED] Rollback mono 4.0.1 to 3.12.0

Issue

So, our mono was updated from 3.12.0 to 4.0.1 and caused a bunch of problems with nunit as seen here: New SIGABRT after upgrading to Mono 4 running NUnit tests While upgrading to 4.1.0 snapshot fixes these issues, it hasn't been officially released and we would not like to use it. Instead we'd like to downgrade back to 3.12.0 but it seems that I can't even do that. Running apt-cache showpkg mono-complete gives me only the following options

matt@matt-T420:~/vw3$ apt-cache showpkg mono-complete
Package: mono-complete
Versions: 
4.0.1-0xamarin4 (/var/lib/apt/lists/download.mono-project.com_repo_debian_dists_wheezy_main_binary-amd64_Packages)
 Description Language: 
                 File: /var/lib/apt/lists/ca.archive.ubuntu.com_ubuntu_dists_vivid_universe_binary-amd64_Packages
                  MD5: dacc30c6a4347277b44c68a99c998d5f
 Description Language: en
                 File: /var/lib/apt/lists/ca.archive.ubuntu.com_ubuntu_dists_vivid_universe_i18n_Translation-en
                  MD5: dacc30c6a4347277b44c68a99c998d5f

3.2.8+dfsg-4ubuntu4 (/var/lib/apt/lists/ca.archive.ubuntu.com_ubuntu_dists_vivid_universe_binary-amd64_Packages)
 Description Language: 
                 File: /var/lib/apt/lists/ca.archive.ubuntu.com_ubuntu_dists_vivid_universe_binary-amd64_Packages
                  MD5: dacc30c6a4347277b44c68a99c998d5f
 Description Language: en
                 File: /var/lib/apt/lists/ca.archive.ubuntu.com_ubuntu_dists_vivid_universe_i18n_Translation-en
                  MD5: dacc30c6a4347277b44c68a99c998d5f

However if I browse to http://origin-download.mono-project.com/repo/debian/dists/wheezy/snapshots/3.12.0/ I can see the package but I'm not sure how to add it to my list of repos. I don't know how to modify echo "deb http://download.mono-project.com/repo/debian wheezy main" | sudo tee /etc/apt/sources.list.d/mono-xamarin.list to pint to that 3.12.0 folder.

I basically just want to blow away mono-4.0, reinstall 3.12.0 and then pin/hold it at that version. Can someone please help?

Solution

First remove mono 4.0.1

sudo apt-get remove mono-complete

sudo apt-get purge mono-complete

sudo apt-get autoremove

After a few attempts, I have modified my repo like this, which seems to have worked:

echo "deb http://download.mono-project.com/repo/debian wheezy/snapshots/3.12.0 main" | sudo tee /etc/apt/sources.list.d/mono-xamarin.list

then ran:

sudo apt-get update

sudo apt-get install mono-complete

mono --version

I am now running 3.12

Answered By - scastbur