Comment 5 for bug 1673860

I just tested the zesty-proposed version and it works as expected.

% lxc launch ubuntu-daily:zesty z1
Creating z1
Starting z1

# confirm current version of systemd
% lxc exec z1 -- apt-cache policy systemd
systemd:
  Installed: 232-19
  Candidate: 232-19
  Version table:
 *** 232-19 500
        500 http://archive.ubuntu.com/ubuntu zesty/main amd64 Packages
        100 /var/lib/dpkg/status

# confirm that network-online.target is started before systemd-resolved
%3 lxc exec z1 -- journalctl --no-pager -o short-precise --unit systemd-resolved --unit network-online.target
-- Logs begin at Fri 2017-03-31 18:48:46 UTC, end at Fri 2017-03-31 18:48:54 UTC. --
Mar 31 18:48:51.485348 z1 systemd[1]: Reached target Network is Online.
Mar 31 18:48:51.519147 z1 systemd[1]: systemd-resolved.service: Failed to reset devices.list: Operation not permitted
Mar 31 18:48:51.526564 z1 systemd[1]: systemd-resolved.service: Failed to set invocation ID on control group /system.slice/systemd-resolved.service, ignoring: Operation not permitted
Mar 31 18:48:51.533523 z1 systemd[1]: Starting Network Name Resolution...
Mar 31 18:48:51.665835 z1 systemd-resolved[432]: Positive Trust Anchors:
Mar 31 18:48:51.670257 z1 systemd-resolved[432]: . IN DS 19036 8 2 49aac11d7b6f6446702e54a1607371607a1a41855200fd2ce1cdde32f24e8fb5
Mar 31 18:48:51.671291 z1 systemd-resolved[432]: . IN DS 20326 8 2 e06d44b80b8f1d39a95c0b0d7c65d08458e880409bbc683457104237c7f8ec8d
Mar 31 18:48:51.672004 z1 systemd-resolved[432]: Negative trust anchors: 10.in-addr.arpa 16.172.in-addr.arpa 17.172.in-addr.arpa 18.172.in-addr.arpa 19.172.in-addr.arpa 20.172.in-addr.arpa 21.172.in-addr.arpa 22.172.in-addr.arpa 23.172.in-addr.arpa 24.172.in-addr.arpa 25.172.in-addr.arpa 26.172.in-addr.arpa 27.172.in-addr.arpa 28.172.in-addr.arpa 29.172.in-addr.arpa 30.172.in-addr.arpa 31.172.in-addr.arpa 168.192.in-addr.arpa d.f.ip6.arpa corp home internal intranet lan local private test
Mar 31 18:48:51.673770 z1 systemd-resolved[432]: Using system hostname 'z1'.
Mar 31 18:48:51.696484 z1 systemd-resolved[432]: Switching to system DNS server 10.245.119.1.
Mar 31 18:48:51.807829 z1 systemd[1]: Started Network Name Resolution.

# enable proposed
% lxc exec z1 -- sh -c 'echo "deb http://us.archive.ubuntu.com/ubuntu/ zesty-proposed main restricted" > /etc/apt/sources.list.d/zesty-proposed.list; apt update'
Hit:1 http://security.ubuntu.com/ubuntu zesty-security InRelease
Get:2 http://us.archive.ubuntu.com/ubuntu zesty-proposed InRelease [240 kB]
Get:3 http://archive.ubuntu.com/ubuntu zesty InRelease [243 kB]
Get:4 http://us.archive.ubuntu.com/ubuntu zesty-proposed/main amd64 Packages [53.3 kB]
Get:5 http://us.archive.ubuntu.com/ubuntu zesty-proposed/main Translation-en [26.3 kB]
Hit:6 http://archive.ubuntu.com/ubuntu zesty-updates InRelease
Get:7 http://archive.ubuntu.com/ubuntu zesty-backports InRelease [92.0 kB]
Get:8 http://archive.ubuntu.com/ubuntu zesty/main Sources [911 kB]
Get:9 http://archive.ubuntu.com/ubuntu zesty/multiverse Sources [188 kB]
Get:10 http://archive.ubuntu.com/ubuntu zesty/universe Sources [8481 kB]
Get:11 http://archive.ubuntu.com/ubuntu zesty/restricted Sources [5076 B]
Get:12 http://archive.ubuntu.com/ubuntu zesty/main amd64 Packages [1234 kB]
Get:13 http://archive.ubuntu.com/ubuntu zesty/universe amd64 Packages [8096 kB]
Get:14 http://archive.ubuntu.com/ubuntu zesty/universe Translation-en [4680 kB]
Get:15 http://archive.ubuntu.com/ubuntu zesty/multiverse amd64 Packages [158 kB]
Get:16 http://archive.ubuntu.com/ubuntu zesty/multiverse Translation-en [111 kB]
Fetched 24.5 MB in 19s (1267 kB/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
43 packages can be upgraded. Run 'apt list --upgradable' to see them.

# show new systemd package from proposed
% lxc exec z1 -- apt-cache policy systemd
systemd:
  Installed: 232-19
  Candidate: 232-21ubuntu2
  Version table:
     232-21ubuntu2 500
        500 http://us.archive.ubuntu.com/ubuntu zesty-proposed/main amd64 Packages
 *** 232-19 500
        500 http://archive.ubuntu.com/ubuntu zesty/main amd64 Packages
        100 /var/lib/dpkg/status

# upgrade systemd and reboot container
% lxc exec z1 -- sh -c 'apt -y install systemd && reboot'
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
  libnss-resolve libpam-systemd libsystemd0
Suggested packages:
  systemd-ui systemd-container
The following packages will be upgraded:
  libnss-resolve libpam-systemd libsystemd0 systemd
4 upgraded, 0 newly installed, 0 to remove and 39 not upgraded.
Need to get 2801 kB of archives.
After this operation, 6144 B disk space will be freed.
Get:1 http://us.archive.ubuntu.com/ubuntu zesty-proposed/main amd64 libnss-resolve amd64 232-21ubuntu2 [114 kB]
Get:2 http://us.archive.ubuntu.com/ubuntu zesty-proposed/main amd64 libpam-systemd amd64 232-21ubuntu2 [115 kB]
Get:3 http://us.archive.ubuntu.com/ubuntu zesty-proposed/main amd64 systemd amd64 232-21ubuntu2 [2362 kB]
Get:4 http://us.archive.ubuntu.com/ubuntu zesty-proposed/main amd64 libsystemd0 amd64 232-21ubuntu2 [210 kB]
Fetched 2801 kB in 1s (1415 kB/s)
(Reading database ... 26516 files and directories currently installed.)
Preparing to unpack .../libnss-resolve_232-21ubuntu2_amd64.deb ...
Unpacking libnss-resolve:amd64 (232-21ubuntu2) over (232-19) ...
Preparing to unpack .../libpam-systemd_232-21ubuntu2_amd64.deb ...
Unpacking libpam-systemd:amd64 (232-21ubuntu2) over (232-19) ...
Preparing to unpack .../systemd_232-21ubuntu2_amd64.deb ...
Unpacking systemd (232-21ubuntu2) over (232-19) ...
Preparing to unpack .../libsystemd0_232-21ubuntu2_amd64.deb ...
Unpacking libsystemd0:amd64 (232-21ubuntu2) over (232-19) ...
Setting up libsystemd0:amd64 (232-21ubuntu2) ...
Processing triggers for ureadahead (0.100.0-19) ...
Processing triggers for libc-bin (2.24-7ubuntu2) ...
Setting up systemd (232-21ubuntu2) ...
addgroup: The group `systemd-journal' already exists as a system group. Exiting.
Setting up libnss-resolve:amd64 (232-21ubuntu2) ...
Processing triggers for man-db (2.7.6.1-2) ...
Processing triggers for dbus (1.10.10-1ubuntu2) ...
Setting up libpam-systemd:amd64 (232-21ubuntu2) ...
Processing triggers for libc-bin (2.24-7ubuntu2) ...

# check installed version after reboot
% lxc exec z1 -- apt-cache policy systemd
systemd:
  Installed: 232-21ubuntu2
  Candidate: 232-21ubuntu2
  Version table:
 *** 232-21ubuntu2 500
        500 http://us.archive.ubuntu.com/ubuntu zesty-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     232-19 500
        500 http://archive.ubuntu.com/ubuntu zesty/main amd64 Packages

# check unit ordering
% lxc exec z1 -- journalctl --no-pager -o short-precise --unit systemd-resolved --unit network-online.target
-- Logs begin at Fri 2017-03-31 18:54:56 UTC, end at Fri 2017-03-31 18:54:59 UTC. --
Mar 31 18:54:57.949660 z1 systemd[1]: systemd-resolved.service: Failed to reset devices.list: Operation not permitted
Mar 31 18:54:57.951958 z1 systemd[1]: systemd-resolved.service: Failed to set invocation ID on control group /system.slice/systemd-resolved.service, ignoring: Operation not permitted
Mar 31 18:54:57.952719 z1 systemd[1]: Starting Network Name Resolution...
Mar 31 18:54:58.047708 z1 systemd-resolved[433]: Positive Trust Anchors:
Mar 31 18:54:58.047730 z1 systemd-resolved[433]: . IN DS 19036 8 2 49aac11d7b6f6446702e54a1607371607a1a41855200fd2ce1cdde32f24e8fb5
Mar 31 18:54:58.047738 z1 systemd-resolved[433]: . IN DS 20326 8 2 e06d44b80b8f1d39a95c0b0d7c65d08458e880409bbc683457104237c7f8ec8d
Mar 31 18:54:58.047780 z1 systemd-resolved[433]: Negative trust anchors: 10.in-addr.arpa 16.172.in-addr.arpa 17.172.in-addr.arpa 18.172.in-addr.arpa 19.172.in-addr.arpa 20.172.in-addr.arpa 21.172.in-addr.arpa 22.172.in-addr.arpa 23.172.in-addr.arpa 24.172.in-addr.arpa 25.172.in-addr.arpa 26.172.in-addr.arpa 27.172.in-addr.arpa 28.172.in-addr.arpa 29.172.in-addr.arpa 30.172.in-addr.arpa 31.172.in-addr.arpa 168.192.in-addr.arpa d.f.ip6.arpa corp home internal intranet lan local private test
Mar 31 18:54:58.048109 z1 systemd-resolved[433]: Using system hostname 'z1'.
Mar 31 18:54:58.049619 z1 systemd-resolved[433]: Switching to system DNS server 10.245.119.1.
Mar 31 18:54:58.168190 z1 systemd[1]: Started Network Name Resolution.
Mar 31 18:54:58.168593 z1 systemd[1]: Reached target Network is Online.