Chapter 3. The pcs command-line interface
Chapter 3. The pcs command-line interface The pcs command-line interface controls and configures cluster services such as corosync , pacemaker , booth , and sbd by providing an easier interface to their configuration files. Note that you should not edit the cib.xml configuration file directly. In most cases, Pacemaker will reject a directly modified cib.xml file. 3.1. pcs help display You use the -h option of pcs to display the parameters of a pcs command and a description of those parameters. The following command displays the parameters of the pcs resource command. 3.2. Viewing the raw cluster configuration Although you should not edit the cluster configuration file directly, you can view the raw cluster configuration with the pcs cluster cib command. You can save the raw cluster configuration to a specified file with the pcs cluster cib filename command. If you have previously configured a cluster and there is already an active CIB, you use the following command to save the raw xml file. For example, the following command saves the raw xml from the CIB into a file named testfile . 3.3. Saving a configuration change to a working file When configuring a cluster, you can save configuration changes to a specified file without affecting the active CIB. This allows you to specify configuration updates without immediately updating the currently running cluster configuration with each individual update. For information about saving the CIB to a file, see Viewing the raw cluster configuration . Once you have created that file, you can save configuration changes to that file rather than to the active CIB by using the -f option of the pcs command. When you have completed the changes and are ready to update the active CIB file, you can push those file updates with the pcs cluster cib-push command. Procedure The following is the recommended procedure for pushing changes to the CIB file. This procedure creates a copy of the original saved CIB file and makes changes to that copy. When pushing those changes to the active CIB, this procedure specifies the diff-against option of the pcs cluster cib-push command so that only the changes between the original file and the updated file are pushed to the CIB. This allows users to make changes in parallel that do not overwrite each other, and it reduces the load on Pacemaker which does not need to parse the entire configuration file. Save the active CIB to a file. This example saves the CIB to a file named original.xml . Copy the saved file to the working file you will be using for the configuration updates. Update your configuration as needed. The following command creates a resource in the file updated.xml but does not add that resource to the currently running cluster configuration. Push the updated file to the active CIB, specifying that you are pushing only the changes you have made to the original file. Alternately, you can push the entire current content of a CIB file with the following command. When pushing the entire CIB file, Pacemaker checks the version and does not allow you to push a CIB file which is older than the one already in a cluster. If you need to update the entire CIB file with a version that is older than the one currently in the cluster, you can use the --config option of the pcs cluster cib-push command. 3.4. Displaying cluster status There are a variety of commands you can use to display the status of a cluster and its components. You can display the status of the cluster and the cluster resources with the following command. You can display the status of a particular cluster component with the commands parameter of the pcs status command, specifying resources , cluster , nodes , or pcsd . For example, the following command displays the status of the cluster resources. The following command displays the status of the cluster, but not the cluster resources. If you run the pcs status command before Pacemaker has completed any actions required by changes to the CIB, the cluster state at that time might not match the desired status. As of RHEL Hat Enterprixe Linux 9.5, you can ensure that Pacemaker does not need to take any further actions by running the pcs status wait command. The pcs status wait command waits until the cluster has completed all current actions before returning a value. If any actions unrelated to your recent changes are in progress, the command waits until those are completed. The pcs status wait command returns a value of 0 as soon as Pacemaker completes pending actions. You can specify a period of time to wait. If the current actions have not completed after that time period, the command prints an error and returns a value of 1. The following command waits until Pacemaker has applied configuration changes. The following command waits up to one minute until Pacemaker has applied configuration changes. 3.5. Displaying the full cluster configuration Use the following command to display the full current cluster configuration. 3.6. Displaying resource status In a complex cluster setup, you might need to determine the status of an individual resource in a cluster before performing a cluster or resource action. As of Red Hat Enterprise Linux 9.5, you can query various attributes of a single resource in a cluster with the pcs status query resource commands. You can use these commands for pcs-based scripting because there is no need to parse plain text outputs. The pcs status query resource commands query the following attributes: the existence of the resource the type of the resource the state of the resource various information about the members of a collective resource on which nodes the resource is running The following command queries whether a resource has started. For example, the following command queries whether the resource resource1 has started. For a full list of the pcs status query resource commands, see the pcs (8) man page on your system. 3.7. Modifying the corosync.conf file with the pcs command You can use the pcs command to modify the parameters in the corosync.conf file. The following command modifies the parameters in the corosync.conf file. The following example command udates the knet_pmtud_interval transport value and the token and join totem values. Additional resources For information about adding and removing nodes from an existing cluster, see Managing cluster nodes . For information about adding and modifying links in an existing cluster, see Adding and modifying links in an existing cluster . For information about modifyng quorum options and managing the quorum device settings in a cluster, see Configuring cluster quorum and Configuring quorum devices . 3.8. Displaying the corosync.conf file with the pcs command The following command displays the contents of the corosync.conf cluster configuration file. You can print the contents of the corosync.conf file in a human-readable format with the pcs cluster config command, as in the following example. The output for this command includes the UUID for the cluster if the cluster was created in RHEL 9.1 or later, or if the UUID was added manually as described in Identifying clusters by UUID . You can run the pcs cluster config show command with the --output-format=cmd option to display the pcs configuration commands that can be used to recreate the existing corosync.conf file, as in the following example.
pcs resource -h pcs cluster cib filename pcs cluster cib testfile pcs cluster cib original.xml cp original.xml updated.xml pcs -f updated.xml resource create VirtualIP ocf:heartbeat:IPaddr2 ip=192.168.0.120 op monitor interval=30s pcs cluster cib-push updated.xml diff-against=original.xml pcs cluster cib-push filename pcs cluster cib-push --config filename pcs status pcs status commands pcs status resources pcs cluster status pcs status wait Waiting for the cluster to apply configuration changes pcs status wait 1min Waiting for the cluster to apply configuration changes (timeout: 60 seconds) pcs config pcs status query resource RESOURCE_ID is-state started pcs status query resource resource1 is-state started True pcs cluster config update [transport pass:quotes[ transport options ]] [compression pass:quotes[ compression options ]] [crypto pass:quotes[ crypto options ]] [totem pass:quotes[ totem options ]] [--corosync_conf pass:quotes[ path ]] pcs cluster config update transport knet_pmtud_interval=35 totem token=10000 join=100 pcs cluster corosync pcs cluster config Cluster Name: HACluster Cluster UUID: ad4ae07dcafe4066b01f1cc9391f54f5 Transport: knet Nodes: r8-node-01: Link 0 address: r8-node-01 Link 1 address: 192.168.122.121 nodeid: 1 r8-node-02: Link 0 address: r8-node-02 Link 1 address: 192.168.122.122 nodeid: 2 Links: Link 1: linknumber: 1 ping_interval: 1000 ping_timeout: 2000 pong_count: 5 Compression Options: level: 9 model: zlib threshold: 150 Crypto Options: cipher: aes256 hash: sha256 Totem Options: downcheck: 2000 join: 50 token: 10000 Quorum Device: net Options: sync_timeout: 2000 timeout: 3000 Model Options: algorithm: lms host: r8-node-03 Heuristics: exec_ping: ping -c 1 127.0.0.1 pcs cluster config show --output-format=cmd pcs cluster setup HACluster r8-node-01 addr=r8-node-01 addr=192.168.122.121 r8-node-02 addr=r8-node-02 addr=192.168.122.122 transport knet link linknumber=1 ping_interval=1000 ping_timeout=2000 pong_count=5 compression level=9 model=zlib threshold=150 crypto cipher=aes256 hash=sha256 totem downcheck=2000 join=50 token=10000