testcases expect first kernel log line, but not always in logs

[Dan Streetman]

[impact]

boot-and-services and cmdline-upstart-boot expect the first(ish) kernel log line to be in the system logs, but that is not guaranteed to be in the logs.

[test case]

run autopkgtest on arm64 with the current kernel, whose kernel log size is too small for journald or rsyslogd to capture the first kernel log messages.

[regression potential]

low; testcase fix only.

[other info]

the specific cause of this currently is too-small kernel log buffer size on arm64, which is being fixed in bug 1824864, but increasing amounts of boot time logging may cause a failure again, or custom kernel configs with small log buffers.

[Dimitri John Ledkov (xnox)]

It's a critical but in the Ubuntu platform if the very first kernel log line is not available in the system logs.

And it is present on all arches, apart from the identified buggy arm64 which is in-flight being fixed (in eoan-proposed & disco-proposed with other releases to follow).

cmdline-upstart-boot is only present in xenial? and arm64-kvm testing only started to be done post xenial release. Hence systemd/arm64 autopkgtest status is currently "Always Failed" and doesn't block anything.

This is not applicable to devel series, nor should be applied in prior releases, instead kernel should be fixed.