Merge pull request #32834 from hshiina/machineconfig-kdump

Author: Bob Furu

modules/investigating-kernel-crashes.adoc

@@ -27,7 +27,7 @@ Perform the following steps to enable `kdump` on {op-system}.
 # rpm-ostree kargs --append='crashkernel=256M'
 ----
 
-. Optional: To write the crash dump over the network or to some other location, rather than to the default local `/var/crash` location, edit the `/etc/kdump.conf` configuration file. 
+. Optional: To write the crash dump over the network or to some other location, rather than to the default local `/var/crash` location, edit the `/etc/kdump.conf` configuration file.
 +
 [NOTE]
 ====
@@ -65,6 +65,82 @@ The `kdump` service is intended to be enabled per node to debug kernel problems.
 
 If you are aware of the downsides and trade-offs of having the `kdump` service enabled, it is possible to enable `kdump` in a cluster-wide fashion. Although machine-specific machine configs are not yet supported, you can perform the previous steps through a `systemd` unit in a `MachineConfig` object on day-1 and have kdump enabled on all nodes in the cluster. You can create a `MachineConfig` object and inject that object into the set of manifest files used by Ignition during cluster setup. See "Customizing nodes" in the _Installing -> Installation configuration_ section for more information and examples on how to use Ignition configs.
 
+.Procedure
+
+Create a `MachineConfig` object for cluster-wide configuration:
+
+. Optional: If you change the `/etc/kdump.conf` configuration from the default, you can encode it into base64 format to include its content in your `MachineConfig` object:
++
+[source,terminal]
+----
+$ cat << EOF | base64
+path /var/crash
+core_collector makedumpfile -l --message-level 7 -d 31
+EOF
+----
+
+. Optional: Create a content of the `/etc/sysconfig/kdump` file and encode it as base64 if you change the configuration from the default:
++
+[source,terminal]
+----
+$ cat << EOF | base64
+KDUMP_COMMANDLINE_REMOVE="hugepages hugepagesz slub_debug quiet log_buf_len swiotlb"
+KDUMP_COMMANDLINE_APPEND="irqpoll nr_cpus=1 reset_devices cgroup_disable=memory mce=off numa=off udev.children-max=2 panic=10 rootflags=nofail acpi_no_memhotplug transparent_hugepage=never nokaslr novmcoredd hest_disable"
+KEXEC_ARGS="-s"
+KDUMP_IMG="vmlinuz"
+EOF
+----
+
+. Create the `MachineConfig` object file:
++
+[source,terminal]
+----
+$ cat << EOF > ./99-master-kdump-configuration.yaml
+apiVersion: machineconfiguration.openshift.io/v1
+kind: MachineConfig
+metadata:
+  labels:
+    machineconfiguration.openshift.io/role: master <1>
+  name: 99-master-kdump-configuration
+spec:
+  kernelArguments:
+    - 'crashkernel=256M' <2>
+  config:
+    ignition:
+      version: 3.2.0
+    storage:
+      files:
+        - contents:
+            source: data:text/plain;charset=utf-8;base64,ICAgIHBhdGggL3Zhci9jcmFzaAogICAgY2...  <3>
+          mode: 420
+          overwrite: true
+          path: /etc/kdump.conf
+        - contents:
+            source: data:text/plain;charset=utf-8;base64,S0RVTVBfQ09NTUFORExJTkVfUkVNT1ZFPS...  <4>
+          mode: 420
+          overwrite: true
+          path: /etc/sysconfig/kdump
+    systemd:
+      units:
+        - enabled: true
+          name: kdump.service
+EOF
+----
++
+<1> Replace `master` with `worker` for creating a `MachineConfig` object for the `worker` role.
+<2> Provide kernel arguments to reserve memory for the crash kernel. You can add other kernel arguments if necessary.
+<3> Replace the base64 content with the one you created for `/etc/kdump.conf`.
+<4> Replace the base64 content with the one you created for `/etc/sysconfig/kdump`.
++
+
+. Put the YAML file into manifests during cluster setup. You can also create this `MachineConfig` object after cluster setup with the YAML file:
+
++
+[source,terminal]
+----
+ $ oc create -f ./99-master-kdump-configuration.yaml
+----
+
 == Testing the kdump configuration
 
 ifdef::openshift-enterprise[]