Stable support for Ubuntu from 17.04 to 18.04 LTS +

[stickgrinder]

Changes in this MR:

• User doesn't need to explicitely select different installers for OS versions anymore, Ansible does it for you.
• All ubuntu versions from 17.04 upwards now ditch dnsmasq and resolvconf which both create edge-cases with loops that push CPU to 100%. Even in normal situations laptop has been reported to almost double battery life getting rid of concurring resolvers. We now just use systemd-resolved.
• Documentation has been updated and official docker repository support to bionic beaver has been checked so we don't need to rely on tricks to apt-get docker-ce anymore.

NOTE: This MR can be merged but requires real-world testing. I planned to test it in virtualbox but still didn't do this. We can ask someone in Spark to test it against 18.04 maybe?

[grota]

LGTM

[Pinolo]

Something was wrong trying to use the new installer on an upgraded 18.04:

• docker repository is wrong
• linux-image-extra for the current kernel is not available
• docker package is now called "docker-engine"

Here's a diff I used to get through (linux-image-extra was already installed in my system, but does not match my kernel version)

diff --git a/ansible/ubuntu/ubuntu18.yml b/ansible/ubuntu/ubuntu18.yml
index 25f80e1..288d1f2 100644
--- a/ansible/ubuntu/ubuntu18.yml
+++ b/ansible/ubuntu/ubuntu18.yml
@@ -5,7 +5,7 @@
   become_user: root

   vars:
-    apt_repository: deb [arch=amd64] https://download.docker.com/linux/ubuntu {{ ansible_lsb.id|lower }}-{{ ansible_lsb.codename|lower }} stable
+    apt_repository: deb [arch=amd64] https://download.docker.com/linux/ubuntu {{ ansible_lsb.codename|lower }} stable
     docker_compose_version: 1.21.0
     dnsdock_image: aacebedo/dnsdock:v1.16.4-amd64

@@ -30,11 +30,10 @@
     - name: Install the base required dependencies and suggested packages
       apt:
         pkg:
-          - "linux-image-extra-{{ ansible_kernel }}"
           - linux-image-extra-virtual
           - apt-transport-https
           - ca-certificates
-          - docker-ce
+          - docker-engine
           - git
         state: latest
         update_cache: yes
@@ -70,4 +69,4 @@
       become: no

     - name: Restart systemd-resolved
-      service: name=systemd-resolved state=restarted
\ No newline at end of file
+      service: name=systemd-resolved state=restarted

[stickgrinder]

You're right for the package, it has been removed by 18.04. It used to work during beta thou... (at least, in my memory :D)

For the other changes:

• While bionic beta we had to rely on artful repos. Obviously official ones changes things again :P I'm upgrading the reference, thanks.
• You managed to install docker-engine but I'm pretty sure you ended up installing the 18.04 standard repo package, since no package with that name seems to appear in offical repo... I'm making sure of this, @MarianoFranzese managed to install the docker.io package after fetching the correct bionic repo.

Let me check it twice and I'll add the right reference to the playbook. Thanks for the test!

[stickgrinder]

@Pinolo @MarianoFranzese here is the problem: https://github.com/docker/for-linux/issues/290

Now the repository is there but the package is not. I'm changing the repo to test channel so we can learn if RC1 is working. We can still use artful repo instead if you experience any issue. June will see stable 18.05 release and we'll switch the repo back to stable.

I'm also updating the docs to reflect this.

[stickgrinder]

OK, this PR has been tested on two PCs now and it seems to work (or at least it doesn't harm).

I'm going to merge it to develop and if it needs refinement, we'll add them with other PRs.