systemd breaks upgrade with useless error if /var is not owned by root

[Darxus]

I just upgraded from 16.04 to 18.04. The upgrade broke. The error, from systemd, was:

"Unsafe symlinks encountered in /var/log/journal, refusing."

That directory was empty. The fix was "chmod root:root /var". Yes, it's weird that my /var wasn't owned by root, but upgrade breaking errors should say something useful.

panic:~# chown darxus:darxus /var
panic:~# dpkg-reconfigure systemd
Unsafe symlinks encountered in /var/spool/rsyslog, refusing.
Unsafe symlinks encountered in /var/lib/colord, refusing.
Unsafe symlinks encountered in /var/lib/colord/icc, refusing.
Unsafe symlinks encountered in /var/cache/man, refusing.
Unsafe symlinks encountered in /var/run/opendkim, refusing.
Unsafe symlinks encountered in /var/lib/systemd, refusing.
Unsafe symlinks encountered in /var/lib/systemd/coredump, refusing.
Unsafe symlinks encountered in /var/log/wtmp, refusing.
Unsafe symlinks encountered in /var/log/btmp, refusing.
Unsafe symlinks encountered in /var/log/lastlog, refusing.
Unsafe symlinks encountered in /var/log, refusing.
Unsafe symlinks encountered in /var/log/auth.log, refusing.
Unsafe symlinks encountered in /var/log/mail.err, refusing.
Unsafe symlinks encountered in /var/log/mail.log, refusing.
Unsafe symlinks encountered in /var/log/kern.log, refusing.
Unsafe symlinks encountered in /var/log/syslog, refusing.
Unsafe symlinks encountered in /var/log/journal, refusing.
Unsafe symlinks encountered in /var/log/journal, refusing.
Unsafe symlinks encountered in /var/log/journal, refusing.
Unsafe symlinks encountered in /var/log/journal, refusing.
Unsafe symlinks encountered in /var/log/journal/6118992be5f52430d74ed66e4cc8d590, refusing.
Unsafe symlinks encountered in /var/log/journal/6118992be5f52430d74ed66e4cc8d590, refusing.
Unsafe symlinks encountered in /var/log/journal/6118992be5f52430d74ed66e4cc8d590, refusing.
Unsafe symlinks encountered in /var/log/journal/6118992be5f52430d74ed66e4cc8d590, refusing.
Unsafe symlinks encountered in /var/log/journal/6118992be5f52430d74ed66e4cc8d590/system.journal, refusing.
Unsafe symlinks encountered in /var/log/journal/6118992be5f52430d74ed66e4cc8d590/system.journal, refusing.
panic:~# chown root:root /var
panic:~# dpkg-reconfigure systemd

I found the fix here: https://askubuntu.com/a/1095796
Showing that I'm not the only one encountering this.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: systemd 237-3ubuntu10.42
Uname: Linux 5.6.14-x86_64-linode135 x86_64
ApportVersion: 2.20.9-0ubuntu7.16
Architecture: i386
Date: Wed Aug 12 15:58:33 2020
Lsusb: Error: command ['lsusb'] failed with exit code 1:
MachineType: QEMU Standard PC (Q35 + ICH9, 2009)
ProcKernelCmdLine: root=/dev/sda console=tty1 console=ttyS0 ro devtmpfs.mount=1
ProcModules:

SourcePackage: systemd
UpgradeStatus: Upgraded to bionic on 2020-08-12 (0 days ago)
dmi.bios.date: 04/01/2014
dmi.bios.vendor: SeaBIOS
dmi.bios.version: rel-1.12.0-0-ga698c8995f-prebuilt.qemu.org
dmi.chassis.type: 1
dmi.chassis.vendor: QEMU
dmi.chassis.version: pc-q35-3.1
dmi.modalias: dmi:bvnSeaBIOS:bvrrel-1.12.0-0-ga698c8995f-prebuilt.qemu.org:bd04/01/2014:svnQEMU:pnStandardPC(Q35+ICH9,2009):pvrpc-q35-3.1:cvnQEMU:ct1:cvrpc-q35-3.1:
dmi.product.name: Standard PC (Q35 + ICH9, 2009)
dmi.product.version: pc-q35-3.1
dmi.sys.vendor: QEMU

[Steve Langasek (vorlon)]

If your /var is not owned by root, your system is insecure. Why was /var not owned by root?

[Balint Reczey (rbalint)]

Who owned /var?

[Dan Streetman (ddstreet)]

seems to require 7f0704da9454d36d19920e033ddadf06c9c6441e

[Darxus (darxus)]

Var was owned by the user I usually log in as. I don't know why, yes it's weird, I fixed it. I don't think that justifies this package's upgrade braking behavior.

[Launchpad Janitor (janitor)]

[Expired for systemd (Ubuntu) because there has been no activity for 60 days.]

[Dan Streetman (ddstreet)]

I can reproduce the warning messages, but they don't actually cause the package upgrades to fail. If your release upgrade failed, it seems like it's due to some other problem.