mkosi: Make sure persistent journal storage is enabled

We ship with empty /var, so /var/log/journal does not exist, which
means journald does not do persistent logging. Let's fix that by
setting the config to explicitly enable persistent logging.

diff --git a/mkosi.presets/20-final/mkosi.extra/usr/lib/systemd/journald.conf.d/50-persistent.conf b/mkosi.presets/20-final/mkosi.extra/usr/lib/systemd/journald.conf.d/50-persistent.conf
new file mode 100644 (file)
index 0000000..2f95329
--- /dev/null
+++ b/mkosi.presets/20-final/mkosi.extra/usr/lib/systemd/journald.conf.d/50-persistent.conf
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+# We only ship /usr in the image so /var/log/journal won't exist on boot which means systemd-journald won't
+# persist any logs as the default Storage= setting is "auto". We can't create /var/log/journal using tmpfiles
+# as systemd-journal-flush.service runs before systemd-tmpfiles-setup.service so instead we explicitly set
+# Storage= to persistent to have systemd-journald create /var/log/journal itself.
+[Journal]
+Storage=persistent