Netplan/Systemd/Cloud-init/Dbus Race

This bug was originally filed in Launchpad as [LP: #1997124](https://bugs.launchpad.net/cloud-init/+bug/1997124)

Launchpad details

affected_projects = ['netplan', 'systemd (Ubuntu)']

assignee = falcojr

assignee_name = James Falcon

date_closed = None

date_created = 2022-11-18T23:07:12.002484+00:00

date_fix_committed = None

date_fix_released = None

id = 1997124

importance = high

is_complete = False

lp_url = https://bugs.launchpad.net/cloud-init/+bug/1997124

milestone = None

owner = holmanb

owner_name = Brett Holman

private = False

status = in_progress

submitter = holmanb

submitter_name = Brett Holman

tags = []

duplicates = []

_Launchpad user **Brett Holman(holmanb)** wrote on 2022-11-18T23:07:12.002484+00:00_

Cloud-init is seeing intermittent failures while running `netplan apply`, which appears to be caused by a missing resource at the time of call.

The symptom in cloud-init logs looks like:

Running ['netplan', 'apply'] resulted in stderr output: Failed to connect system bus: No such file or directory

I think that this error[1] is likely caused by cloud-init running netplan apply too early in boot process (before dbus is active).

Today I stumbled upon this error which was hit in MAAS[2]. We have also hit it intermittently during tests (we didn't have a reproducer).

Realizing that this may not be a cloud-init error, but possibly a dependency bug between dbus/systemd we decided to file this bug for broader visibility to other projects.

I will follow up this initial report with some comments from our discussion earlier.

[1] https://github.com/canonical/netplan/blob/main/src/dbus.c#L801
[2] https://discourse.maas.io/t/latest-ubuntu-20-04-image-causing-netplan-error/5970

Start with the cloud-init path that runs `netplan apply`, then inspect the referenced `netplan/src/dbus.c` location and the reported `Failed to connect system bus` log output. Determine the dependency or boot-order cause of the intermittent failure and confirm completion with a reproducible test or failure-free run.

Written by the indexing model from the issue text.