Comment 3 for bug 1636912

On Wed, Oct 26, 2016 at 6:41 PM, Steve Langasek <
<email address hidden>> wrote:

> Note that the systemd dependencies shown for cloud-init in xenial (on
> which Ubuntu Core 16 is based) don't match those listed in the bug
> description. Instead, xenial currently has:
>
> After=cloud-init-local.service networking.service
> Before=network-online.target sshd.service sshd-keygen.service
> systemd-user-sessions.service
> Requires=networking.service
> Wants=local-fs.target cloud-init-local.service sshd.service
> sshd-keygen.service
>
> That's certainly an easier target for fixing the ordering on.
>

We're preparing an SRU for Xenial, but the issue is related to
systemd-resolved which is NOT in Xenial, so the
failing behavior of a 120 second timeout for resolving hosts when dbus
isn't up yet doesn't materialize on Xenial, only yakkety.

 https://bugs.launchpad.net/ubuntu/+source/cloud-init/+bug/1629797

>
> I'm surprised that cloud-init is being ordered before dbus in 16.10+.
> This appears to have been done in response to bug #1629797. This change
> to ordering on account of nss-resolve does not give me the warm fuzzies.
> There's feedback in the end of that bug that cloud-init should *not* be
> using Before=basic.target / Before=dbus.socket, but instead use
> Before=sysinit.target. That seems like a change we should be making. But
> I also didn't understand that we would be using nss-resolve - I missed a
> nuance in <https://lists.ubuntu.com/archives/ubuntu-devel/2016-
> June/039406.html>, I thought that once resolved supported DNS, we would
> use that /instead of/ the NSS module. Is there really a benefit to using
> both?
>

systemd-resolved doesn't runs soon enough where cloud-init needs to resolve
metadata service end points, like in GCE.

I don't know enough to say if resolved and NSS are 100% swappable; but at a
min, resolved would need to be able to run as early as NSS runs to allow
cloud-init to resolve metadata service URLS very early in boot.

>
> Regardless, none of that seems to account for the specific problem
> reported here, on Ubuntu Core 16; because Ubuntu Core 16 does contain
> libnss-resolve, but does *not* contain the cloud-init with the
> DefaultDependencies=no.
>

We're specifically introducing a newer cloud-init which adds support for
snap create-user support which also includes the change in Unit
dependencies from upstream cloud-init.
Those changes to unit dependencies will also be SRU to Xenial.

>
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> report.
> https://bugs.launchpad.net/bugs/1636912
>
> Title:
> systemd-networkd runs too late for cloud-init.service (net)
>
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