feat: implement zwar swap (implements ND-2005)

files/usr/local/lib/systemd/system/zramswap.service

+[Unit]
+Description=Swap with zram
+After=multi-user.target
+
+[Service]
+Type=oneshot
+RemainAfterExit=true
+ExecStartPre=/sbin/mkswap /dev/zram0
+ExecStart=/sbin/swapon /dev/zram0
+ExecStop=/sbin/swapoff /dev/zram0
+
+[Install]
+WantedBy=multi-user.target

handlers/main.yml

@@ -64,5 +64,11 @@
   when: ansible_os_family == "Debian"
   changed_when: false
 
+- name: restart zramswap
+  ansible.builtin.systemd:
+    name: "zramswap.service"
+    state: restarted
+    daemon_reload: true
+
 - name: udev-Regel bekannt machen
   ansible.builtin.command: "udevadm control --reload"

tasks/configure_swap.yml

 ---
-- name: check if swap is active
-  ansible.builtin.command: swapon -s
-  register: swap_active
-  changed_when: false
+- name: configure zram based swap (Debian)
+  block:
+    - name: install zram
+      ansible.builtin.package:
+        name: "zram-tools"
+        state: latest
+    - name: configure zram
+      ansible.builtin.blockinfile:
+        path: "/etc/default/zramswap"
+        block: |
+          ALGO=lz4
+          PERCENT=50
+      notify: restart zramswap
+  when: ansible_os_family == "Debian"
 
-# https://docs.ansible.com/ansible/latest/user_guide/playbooks_tests.html#testing-strings
-- name: switch off swap (immediate result for running server, not reboot persistent)
-  ansible.builtin.command: swapoff -va
-  when:
-    - ansible_hostname is not search("validate")
-    - swap_active.stdout | length == 0
-  register: disable_swap
-  changed_when: disable_swap.stdout not in "swapoff LABEL=swap"
+# RHEL part is based on https://www.techrepublic.com/article/how-to-enable-zram-rocky-linux/
+#   Note: all that udev stuff from that guide doesn't work. We'll use CLI commands.
+# More docu on zram at https://www.kernel.org/doc/html/latest/admin-guide/blockdev/zram.html
+- name: configure zram based swap (RedHat)
+  block:
+    - name: disable swapping first, otherwise zram will not work
+      ansible.builtin.command: "swapoff -a"
+      changed_when: false
+    - name: switch off swap (no result for running server, reboot persistent)
+      ansible.posix.mount:
+        path: "none"
+        fstype: "swap"
+        state: "absent"
 
-- name: switch off swap (no result for running server, reboot persistent)
-  ansible.posix.mount:
-    path: "none"
-    fstype: "swap"
-    state: "absent"
-  when:
-    - ansible_hostname is not search("validate")
-    - swap_active.stdout | length == 0
+    - name: load zram Kernel module
+      ansible.builtin.lineinfile:
+        path: "/etc/modules-load.d/zram.conf"
+        create: true
+        line: "zram"
+        mode: "0644"
+    # Use `zramctl -f` to show available zram devices.
+    - name: configure zram Kernel module. This will create a zram device.
+      ansible.builtin.lineinfile:
+        path: "/etc/modprobe.d/zram.conf"
+        create: true
+        line: "options zram num_devices=1"
+        mode: "0644"
+    - name: find out if zram Kernel module has been loaded already
+      ansible.builtin.command: "lsmod"
+      register: kernel_modules
+      changed_when: false
+    - name: load zram Kernel module
+      ansible.builtin.command: "modprobe zram"
+      when: "not 'zram' in kernel_modules.stdout"
+    - name: find existing zram devices
+      ansible.builtin.command: "zramctl --noheadings"
+      register: "zram_devices"
+      changed_when: false
+    - name: setup zram device
+      ansible.builtin.command: "zramctl -a lzo -s {{ ( ansible_facts.memtotal_mb / 2 ) | round | int }}M /dev/zram0"
+      changed_when: false
+    - name: create SystemD unit directory
+      ansible.builtin.file:
+        path: "/usr/local/lib/systemd/system/"
+        state: directory
+        mode: "0755"
+    - name: create Systemd unit for zram
+      ansible.builtin.copy:
+        src: "usr/local/lib/systemd/system/zramswap.service"
+        dest: "/usr/local/lib/systemd/system/zramswap.service"
+        mode: "0644"
+      notify: restart zramswap
+  when: ansible_os_family == "RedHat"
+
+- name: configure zram based swap (common)
+  block:
+    - name: start zram service
+      ansible.builtin.systemd:
+        name: "zramswap.service"
+        state: started
+        enabled: true

tasks/main.yml

@@ -112,9 +112,8 @@
   import_tasks: configure_sudoers.yml
   tags: [sudo]
 
-- name: Disable swap
+- name: Configure swap
   import_tasks: configure_swap.yml
-  when: ansible_hostname != "sdvlzavalidate"
   tags: [swap, vm]
 
 - name: sar konfigurieren