Cap the systemd journal at 512M on disk, 128M in memory and two weeks in the common role

common/defaults/main.yml

@@ -6,3 +6,9 @@ disk_maintenance:
   fstrim_on_calendar:
   # Cron "minute hour" of the monthly ZFS trim and scrub from zfsutils-linux; unset keeps 00:24.
   zfs_cron_time:
+
+# journald.conf [Journal] settings of a drop-in, in this order; null leaves journald untouched.
+journald_size_cap:
+  SystemMaxUse: 512M
+  RuntimeMaxUse: 128M
+  MaxRetentionSec: 2week

common/handlers/main.yml

@@ -1,2 +1,7 @@
 - name: reload_sysctl
   command: sysctl --system
+
+- name: restart_journald
+  systemd:
+    name: systemd-journald
+    state: restarted

common/tasks/journald.yml

@@ -0,0 +1,17 @@
+- name: Cap the journal size
+  when: journald_size_cap | default(none) is not none
+  block:
+    - name: Create the journald drop-in directory
+      file:
+        path: /etc/systemd/journald.conf.d
+        state: directory
+
+    - name: Set the journal size cap
+      copy:
+        dest: /etc/systemd/journald.conf.d/10-size-cap.conf
+        content: |
+          [Journal]
+          {% for key, value in journald_size_cap.items() %}
+          {{ key }}={{ value }}
+          {% endfor %}
+      notify: restart_journald

common/tasks/main.yml

@@ -11,3 +11,6 @@
 - import_tasks: ./networking.yml
 
 - import_tasks: ./disk_maintenance.yml
+
+- import_tasks: ./journald.yml
+  tags: journald