diff --git a/doc/sphinx/Pacemaker_Remote/kvm-tutorial.rst b/doc/sphinx/Pacemaker_Remote/kvm-tutorial.rst index 4c2eca73c0..8ef197bbe3 100644 --- a/doc/sphinx/Pacemaker_Remote/kvm-tutorial.rst +++ b/doc/sphinx/Pacemaker_Remote/kvm-tutorial.rst @@ -1,636 +1,577 @@ .. index:: single: guest node; walk-through Guest Node Walk-through ----------------------- **What this tutorial is:** An in-depth walk-through of how to get Pacemaker to manage a KVM guest instance and integrate that guest into the cluster as a guest node. **What this tutorial is not:** A realistic deployment scenario. The steps shown here are meant to get users familiar with the concept of guest nodes as quickly as possible. Configure Cluster Nodes ####################### This walk-through assumes you already have a Pacemaker cluster configured. For examples, we will use a cluster with two cluster nodes named pcmk-1 and pcmk-2. You can substitute whatever your node names are, for however many nodes you have. If you are not familiar with setting up basic Pacemaker clusters, follow the walk-through in the Clusters From Scratch document before attempting this one. Install Virtualization Software _______________________________ On each node within your cluster, install virt-install, libvirt, and qemu-kvm. Start and enable libvirtd. .. code-block:: none # yum install -y virt-install libvirt qemu-kvm # systemctl start libvirtd # systemctl enable libvirtd Reboot the host. .. NOTE:: While KVM is used in this example, any virtualization platform with a Pacemaker resource agent can be used to create a guest node. The resource agent needs only to support usual commands (start, stop, etc.); Pacemaker implements the **remote-node** meta-attribute, independent of the agent. Configure the KVM guest ####################### Create Guest ____________ Create a KVM guest to use as a guest node. Be sure to configure the guest with a hostname and a static IP address (as an example here, we will use guest1 and 192.168.122.10). Here's an example way to create a guest: * Download an .iso file from the `CentOS Mirrors List `_ into a directory on your cluster node. * Run the following command, using your own path for the **location** flag: .. code-block:: none # virt-install \ --name vm-guest1 \ --ram 1024 \ --disk path=./vm-guest1.qcow2,size=1 \ --vcpus 2 \ --os-type linux \ --os-variant centos-stream8\ --network bridge=virbr0 \ --graphics none \ --console pty,target_type=serial \ --location \ --extra-args 'console=ttyS0,115200n8 serial' .. index:: single: guest node; firewall Configure Firewall on Guest ___________________________ On each guest, allow cluster-related services through the local firewall. If you're using ``firewalld``, run the following commands. .. code-block:: none [root@guest1 ~]# firewall-cmd --permanent --add-service=high-availability success [root@guest1 ~]# firewall-cmd --reload success .. NOTE:: If you are using some other firewall solution besides firewalld, simply open the following ports, which can be used by various clustering components: TCP ports 2224, 3121, and 21064. If you run into any problems during testing, you might want to disable the firewall and SELinux entirely until you have everything working. This may create significant security issues and should not be performed on machines that will be exposed to the outside world, but may be appropriate during development and testing on a protected host. To disable security measures: .. code-block:: none [root@guest1 ~]# setenforce 0 [root@guest1 ~]# sed -i.bak "s/SELINUX=enforcing/SELINUX=permissive/g" \ /etc/selinux/config [root@guest1 ~]# systemctl mask firewalld.service [root@guest1 ~]# systemctl stop firewalld.service Configure ``/etc/hosts`` ________________________ You will need to add the remote node's hostname (we're using **guest1** in this tutorial) to the cluster nodes' ``/etc/hosts`` files if you haven't already. This is required unless you have DNS set up in a way where guest1's address can be discovered. For each guest, execute the following on each cluster node and on the guests, replacing the IP address with the actual IP address of the guest node. .. code-block:: none # cat << END >> /etc/hosts 192.168.122.10 guest1 END Also add entries for each cluster node to the ``/etc/hosts`` file on each guest. For example: .. code-block:: none # cat << END >> /etc/hosts 192.168.122.101 pcmk-1 192.168.122.102 pcmk-2 END Verify Connectivity ___________________ At this point, you should be able to ping and ssh into guests from hosts, and vice versa. Configure pacemaker_remote on Guest Node ________________________________________ Install the pacemaker_remote daemon on the guest node. We'll also install the ``pacemaker`` package. It isn't required for a guest node to run, but it provides the ``crm_attribute`` tool, which many resource agents use. .. code-block:: none # yum install -y pacemaker-remote resource-agents pcs pacemaker Integrate Guest into Cluster ############################ Now the fun part, integrating the virtual machine you've just created into the cluster. It is incredibly simple. Start the Cluster _________________ On the host, start Pacemaker if it's not already running. .. code-block:: none # pcs cluster start Create a ``VirtualDomain`` Resource for the Guest VM ____________________________________________________ For this simple walk-through, we have created the VM and made its disk available only on node ``pcmk-1``, so that's the only node where the VM is capable of running. In a more realistic scenario, you'll probably want to have multiple nodes that are capable of running the VM. Next we'll assign an attribute to node 1 that denotes its eligibility to host ``vm-guest1``. If other nodes are capable of hosting your guest VM, then add the attribute to each of those nodes as well. .. code-block:: none [root@pcmk-1 ~]# pcs node attribute pcmk-1 can-host-vm-guest1=1 Then we'll create a ``VirtualDomain`` resource so that Pacemaker can manage ``vm-guest1``. Be sure to replace the XML file path below with your own if it differs. We'll also create a rule to prevent Pacemaker from trying to start the resource or probe its status on any node that isn't capable of running the VM. We'll save the CIB to a file, make both of these edits, and push them simultaneously. .. code-block:: none [root@pcmk-1 ~]# pcs cluster cib vm_cfg [root@pcmk-1 ~]# pcs -f vm_cfg resource create vm-guest1 VirtualDomain \ hypervisor="qemu:///system" config="/etc/libvirt/qemu/vm-guest1.xml" Assumed agent name 'ocf:heartbeat:VirtualDomain' (deduced from 'VirtualDomain') [root@pcmk-1 ~]# pcs -f vm_cfg constraint location vm-guest1 rule \ resource-discovery=never score=-INFINITY can-host-vm-guest1 ne 1 [root@pcmk-1 ~]# pcs cluster cib-push --config vm_cfg --wait .. NOTE:: If all nodes in your cluster are capable of hosting the VM that you've created, then you can skip the ``pcs node attribute`` and ``pcs constraint location`` commands. .. NOTE:: The ID of the resource managing the virtual machine (``vm-guest1`` in the above example) **must** be different from the virtual machine's node name (``guest1`` in the above example). Pacemaker will create an implicit internal resource for the Pacemaker Remote connection to the guest. This implicit resource will be named with the value of the ``VirtualDomain`` resource's ``remote-node`` meta attribute, which will be set by ``pcs`` to the guest node's node name. Therefore, that value cannot be used as the name of any other resource. Now we can confirm that the ``VirtualDomain`` resource is running on ``pcmk-1``. .. code-block:: none [root@pcmk-1 ~]# pcs resource status * vm-guest1 (ocf:heartbeat:VirtualDomain): Started pcmk-1 Prepare ``pcsd`` ________________ Now we need to prepare ``pcsd`` on the guest so that we can use ``pcs`` commands to communicate with it. Start and enable the ``pcsd`` daemon on the guest. .. code-block:: none [root@guest1 ~]# systemctl start pcsd [root@guest1 ~]# systemctl enable pcsd Created symlink /etc/systemd/system/multi-user.target.wants/pcsd.service → /usr/lib/systemd/system/pcsd.service. Next, set a password for the ``hacluster`` user on the guest. .. code-block:: none [root@guest1 ~]# echo MyPassword | passwd --stdin hacluster Changing password for user hacluster. passwd: all authentication tokens updated successfully. Now authenticate the existing cluster nodes to ``pcsd`` on the guest. The below command only needs to be run from one cluster node. .. code-block:: none [root@pcmk-1 ~]# pcs host auth guest1 -u hacluster Password: guest1: Authorized Integrate Guest Node into Cluster _________________________________ We're finally ready to integrate the VM into the cluster as a guest node. Run the following command, which will create a guest node from the ``VirtualDomain`` resource and take care of all the remaining steps. Note that the format is ``pcs cluster node add-guest ``. .. code-block:: none [root@pcmk-1 ~]# pcs cluster node add-guest guest1 vm-guest1 No addresses specified for host 'guest1', using 'guest1' Sending 'pacemaker authkey' to 'guest1' guest1: successful distribution of the file 'pacemaker authkey' Requesting 'pacemaker_remote enable', 'pacemaker_remote start' on 'guest1' guest1: successful run of 'pacemaker_remote enable' guest1: successful run of 'pacemaker_remote start' You should soon see ``guest1`` appear in the ``pcs status`` output as a node. The output should look something like this: .. code-block:: none # pcs status Cluster name: mycluster Cluster Summary: * Stack: corosync * Current DC: pcmk-1 (version 2.0.5-8.el8-ba59be7122) - partition with quorum * Last updated: Wed Mar 17 08:37:37 2021 * Last change: Wed Mar 17 08:31:01 2021 by root via cibadmin on pcmk-1 * 3 nodes configured * 2 resource instances configured Node List: * Online: [ pcmk-1 pcmk-2 ] * GuestOnline: [ guest1@pcmk-1 ] Full List of Resources: * vm-guest1 (ocf::heartbeat:VirtualDomain): pcmk-1 Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled The resulting configuration should look something like the following: .. code-block:: none [root@pcmk-1 ~]# pcs resource config Resource: vm-guest1 (class=ocf provider=heartbeat type=VirtualDomain) Attributes: config=/etc/libvirt/qemu/vm-guest1.xml hypervisor=qemu:///system Meta Attrs: remote-addr=guest1 remote-node=guest1 Operations: migrate_from interval=0s timeout=60s (vm-guest1-migrate_from-interval-0s) migrate_to interval=0s timeout=120s (vm-guest1-migrate_to-interval-0s) monitor interval=10s timeout=30s (vm-guest1-monitor-interval-10s) start interval=0s timeout=90s (vm-guest1-start-interval-0s) stop interval=0s timeout=90s (vm-guest1-stop-interval-0s) How pcs Configures the Guest ____________________________ Let's take a closer look at what the ``pcs cluster node add-guest`` command is doing. There is no need to run any of the commands in this section. First, ``pcs`` copies the Pacemaker authkey file to the VM that will become the guest. If an authkey is not already present on the cluster nodes, this command creates one and distributes it to the existing nodes and to the guest. If you want to do this manually, you can run a command like the following to generate an authkey in ``/etc/pacemaker/authkey``, and then distribute the key to the rest of the nodes and to the new guest. .. code-block:: none [root@pcmk-1 ~]# dd if=/dev/urandom of=/etc/pacemaker/authkey bs=4096 count=1 Then ``pcs`` starts and enables the ``pacemaker_remote`` service on the guest. If you want to do this manually, run the following commands. .. code-block:: none [root@guest1 ~]# systemctl start pacemaker_remote [root@guest1 ~]# systemctl enable pacemaker_remote Finally, ``pcs`` creates a guest node from the ``VirtualDomain`` resource by adding ``remote-addr`` and ``remote-node`` meta attributes to the resource. If you want to do this manually, you can run the following command if you're using ``pcs``. Alternativately, run an equivalent command if you're using another cluster shell, or edit the CIB manually. .. code-block:: none [root@pcmk-1 ~]# pcs resource update vm-guest1 meta remote-addr='guest1' \ remote-node='guest1' --force Starting Resources on KVM Guest ############################### The following example demonstrates that resources can be run on the guest node in the exact same way as on the cluster nodes. Create a few ``Dummy`` resources. A ``Dummy`` resource is a real resource that actually executes operations on its assigned node. However, these operations are trivial (creating, deleting, or checking the existence of an empty or small file), so ``Dummy`` resources are ideal for testing purposes. ``Dummy`` resources use the ``ocf:heartbeat:Dummy`` or ``ocf:pacemaker:Dummy`` resource agent. .. code-block:: none # for i in {1..5}; do pcs resource create FAKE${i} ocf:heartbeat:Dummy; done Now check your ``pcs status`` output. In the resource section, you should see something like the following, where some of the resources started on the cluster nodes, and some started on the guest node. .. code-block:: none Full List of Resources: * vm-guest1 (ocf::heartbeat:VirtualDomain): Started pcmk-1 * FAKE1 (ocf::heartbeat:Dummy): Started guest1 * FAKE2 (ocf::heartbeat:Dummy): Started guest1 * FAKE3 (ocf::heartbeat:Dummy): Started pcmk-1 * FAKE4 (ocf::heartbeat:Dummy): Started guest1 * FAKE5 (ocf::heartbeat:Dummy): Started pcmk-1 The guest node, **guest1**, behaves just like any other node in the cluster with respect to resources. For example, choose a resource that is running on one of your cluster nodes. We'll choose ``FAKE3`` from the output above. It's currently running on ``pcmk-1``. We can force ``FAKE3`` to run on ``guest1`` in the exact same way as we could force it to run on any particular cluster node. We do this by creating a location constraint: .. code-block:: none # pcs constraint location FAKE3 prefers guest1 Now, looking at the bottom of the `pcs status` output you'll see FAKE3 is on **guest1**. .. code-block:: none Full List of Resources: * vm-guest1 (ocf::heartbeat:VirtualDomain): Started pcmk-1 * FAKE1 (ocf::heartbeat:Dummy): Started guest1 * FAKE2 (ocf::heartbeat:Dummy): Started guest1 * FAKE3 (ocf::heartbeat:Dummy): Started guest1 * FAKE4 (ocf::heartbeat:Dummy): Started pcmk-1 * FAKE5 (ocf::heartbeat:Dummy): Started pcmk-1 Testing Recovery and Fencing ############################ Pacemaker's scheduler is smart enough to know fencing guest nodes associated with a virtual machine means shutting off/rebooting the virtual machine. No special configuration is necessary to make this happen. If you are interested in testing this functionality out, trying stopping the guest's pacemaker_remote daemon. This would be equivalent of abruptly terminating a cluster node's corosync membership without properly shutting it down. ssh into the guest and run this command. .. code-block:: none # kill -9 $(pidof pacemaker-remoted) Within a few seconds, your ``pcs status`` output will show a monitor failure, and the **guest1** node will not be shown while it is being recovered. .. code-block:: none # pcs status Cluster name: mycluster Cluster Summary: * Stack: corosync * Current DC: pcmk-1 (version 2.0.5-8.el8-ba59be7122) - partition with quorum * Last updated: Wed Mar 17 08:37:37 2021 * Last change: Wed Mar 17 08:31:01 2021 by root via cibadmin on pcmk-1 * 3 nodes configured * 7 resource instances configured Node List: * Online: [ pcmk-1 pcmk-2 ] Full List of Resources: * vm-guest1 (ocf::heartbeat:VirtualDomain): FAILED pcmk-1 * FAKE1 (ocf::heartbeat:Dummy): FAILED guest1 * FAKE2 (ocf::heartbeat:Dummy): FAILED guest1 * FAKE3 (ocf::heartbeat:Dummy): FAILED guest1 * FAKE4 (ocf::heartbeat:Dummy): Started pcmk-1 * FAKE5 (ocf::heartbeat:Dummy): Started pcmk-1 Failed Actions: * guest1_monitor_30000 on pcmk-1 'unknown error' (1): call=8, status=Error, exitreason='none', last-rc-change='Wed Mar 17 08:32:01 2021', queued=0ms, exec=0ms Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled .. NOTE:: A guest node involves two resources: an explicitly configured resource that you create, which manages the virtual machine (the ``VirtualDomain`` resource in our example); and an implicit resource that Pacemaker creates, which manages the ``pacemaker-remoted`` connection to the guest. The implicit resource's name is the value of the explicit resource's ``remote-node`` meta attribute. When we killed ``pacemaker-remoted``, the **implicit** resource is what failed. That's why the failed action starts with ``guest1`` and not ``vm-guest1``. Once recovery of the guest is complete, you'll see it automatically get re-integrated into the cluster. The final ``pcs status`` output should look something like this. .. code-block:: none # pcs status Cluster name: mycluster Cluster Summary: * Stack: corosync * Current DC: pcmk-1 (version 2.0.5-8.el8-ba59be7122) - partition with quorum * Last updated: Wed Mar 17 08:37:37 2021 * Last change: Wed Mar 17 08:31:01 2021 by root via cibadmin on pcmk-1 * 3 nodes configured * 7 resource instances configured Node List: * Online: [ pcmk-1 pcmk-2 ] * GuestOnline: [ guest1@pcmk-1 ] Full List of Resources: * vm-guest1 (ocf::heartbeat:VirtualDomain): pcmk-1 * FAKE1 (ocf::heartbeat:Dummy): Stopped * FAKE2 (ocf::heartbeat:Dummy): Stopped * FAKE3 (ocf::heartbeat:Dummy): Stopped * FAKE4 (ocf::heartbeat:Dummy): Started pcmk-1 * FAKE5 (ocf::heartbeat:Dummy): Started pcmk-1 Failed Actions: * guest1_monitor_30000 on pcmk-1 'unknown error' (1): call=8, status=Error, exitreason='none', last-rc-change='Fri Jan 12 18:08:29 2018', queued=0ms, exec=0ms Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled Normally, once you've investigated and addressed a failed action, you can clear the failure. However Pacemaker does not yet support cleanup for the implicitly created connection resource while the explicit resource is active. If you want to clear the failed action from the status output, stop the guest resource before clearing it. For example: .. code-block:: none # pcs resource disable vm-guest1 --wait # pcs resource cleanup guest1 # pcs resource enable vm-guest1 Accessing Cluster Tools from Guest Node ####################################### Besides allowing the cluster to manage resources on a guest node, pacemaker_remote has one other trick. The pacemaker_remote daemon allows nearly all the pacemaker tools (``crm_resource``, ``crm_mon``, ``crm_attribute``, etc.) to work on guest nodes natively. Try it: Run ``crm_mon`` on the guest after pacemaker has integrated the guest node into the cluster. These tools just work. This means resource agents such as promotable resources (which need access to tools like ``crm_attribute``) work seamlessly on the guest nodes. Higher-level command shells such as ``pcs`` may have partial support on guest nodes, but it is recommended to run them from a cluster node. -Guest nodes will show up in ``crm_mon`` output as normal. For example, this is the -``crm_mon`` output after **guest1** is integrated into the cluster: - -.. code-block:: none - - Cluster name: mycluster - - Cluster Summary: - * Stack: corosync - * Current DC: pcmk-1 (version 2.0.5-8.el8-ba59be7122) - partition with quorum - * Last updated: Wed Mar 17 08:37:37 2021 - * Last change: Wed Mar 17 08:31:01 2021 by root via cibadmin on pcmk-1 - * 2 nodes configured - * 2 resource instances configured - - Node List: - * Online: [ pcmk-1 ] - * GuestOnline: [ guest1@pcmk-1 ] - - Full List of Resources: - * vm-guest1 (ocf::heartbeat:VirtualDomain): Started pcmk-1 - -Now, you could place a resource, such as a webserver, on **guest1**: - -.. code-block:: none - - # pcs resource create webserver apache params configfile=/etc/httpd/conf/httpd.conf op monitor interval=30s - # pcs constraint location webserver prefers guest1 - -Now, the crm_mon output would show: - -.. code-block:: none - - Cluster name: mycluster - - Cluster Summary: - * Stack: corosync - * Current DC: pcmk-1 (version 2.0.5-8.el8-ba59be7122) - partition with quorum - * Last updated: Wed Mar 17 08:38:37 2021 - * Last change: Wed Mar 17 08:35:01 2021 by root via cibadmin on pcmk-1 - * 2 nodes configured - * 3 resource instances configured - - Node List: - * Online: [ pcmk-1 ] - * GuestOnline: [ guest1@pcmk-1 ] - - Full List of Resources: - * vm-guest1 (ocf::heartbeat:VirtualDomain): Started pcmk-1 - * webserver (ocf::heartbeat::apache): Started guest1 - -It is worth noting that after **guest1** is integrated into the cluster, nearly all the -Pacemaker command-line tools immediately become available to the guest node. -This means things like ``crm_mon``, ``crm_resource``, and ``crm_attribute`` will work -natively on the guest node, as long as the connection between the guest node -and a cluster node exists. This is particularly important for any promotable -clone resources executing on the guest node that need access to -``crm_attribute`` to set promotion scores. - Troubleshooting a Remote Connection ################################### Note: This section should not be done when the guest is connected to the cluster. Should connectivity issues occur, it can be worth verifying that the cluster nodes can contact the remote node on port 3121. Here's a trick you can use. Connect using ssh from each of the cluster nodes. The connection will get destroyed, but how it is destroyed tells you whether it worked or not. If running the ssh command on one of the cluster nodes results in this output before disconnecting, the connection works: .. code-block:: none # ssh -p 3121 guest1 ssh_exchange_identification: read: Connection reset by peer If you see one of these, the connection is not working: .. code-block:: none # ssh -p 3121 guest1 ssh: connect to host guest1 port 3121: No route to host .. code-block:: none # ssh -p 3121 guest1 ssh: connect to host guest1 port 3121: Connection refused If you see this, then the connection is working, but port 3121 is attached to SSH, which it should not be. .. code-block:: none # ssh -p 3121 guest1 kex_exchange_identification: banner line contains invalid characters Once you can successfully connect to the guest from the host, you may shutdown the guest. Pacemaker will be managing the virtual machine from this point forward.