Chapter 10. Configuring fencing in a Red Hat High Availability cluster
Chapter 10. Configuring fencing in a Red Hat High Availability cluster A node that is unresponsive may still be accessing data. The only way to be certain that your data is safe is to fence the node using STONITH. STONITH is an acronym for "Shoot The Other Node In The Head" and it protects your data from being corrupted by rogue nodes or concurrent access. Using STONITH, you can be certain that a node is truly offline before allowing the data to be accessed from another node. STONITH also has a role to play in the event that a clustered service cannot be stopped. In this case, the cluster uses STONITH to force the whole node offline, thereby making it safe to start the service elsewhere. For more general information about fencing and its importance in a Red Hat High Availability cluster, see the Red Hat Knowledgebase solution Fencing in a Red Hat High Availability Cluster . You implement STONITH in a Pacemaker cluster by configuring fence devices for the nodes of the cluster. 10.1. Displaying available fence agents and their options The following commands can be used to view available fencing agents and the available options for specific fencing agents. Note Your system's hardware determines the type of fencing device to use for your cluster. For information about supported platforms and architectures and the different fencing devices, see the Cluster Platforms and Architectures section of the article Support Policies for RHEL High Availability Clusters . Run the following command to list all available fencing agents. When you specify a filter, this command displays only the fencing agents that match the filter. Run the following command to display the options for the specified fencing agent. For example, the following command displays the options for the fence agent for APC over telnet/SSH. Warning For fence agents that provide a method option, with the exception of the fence_sbd agent a value of cycle is unsupported and should not be specified, as it may cause data corruption. Even for fence_sbd , however. you should not specify a method and instead use the default value. 10.2. Creating a fence device The format for the command to create a fence device is as follows. For a listing of the available fence device creation options, see the pcs stonith -h display. The following command creates a single fencing device for a single node. Some fence devices can fence only a single node, while other devices can fence multiple nodes. The parameters you specify when you create a fencing device depend on what your fencing device supports and requires. Some fence devices can automatically determine what nodes they can fence. You can use the pcmk_host_list parameter when creating a fencing device to specify all of the machines that are controlled by that fencing device. Some fence devices require a mapping of host names to the specifications that the fence device understands. You can map host names with the pcmk_host_map parameter when creating a fencing device. For information about the pcmk_host_list and pcmk_host_map parameters, see General properties of fencing devices . After configuring a fence device, it is imperative that you test the device to ensure that it is working correctly. For information about testing a fence device, see Testing a fence device . 10.3. General properties of fencing devices There are many general properties you can set for fencing devices, as well as various cluster properties that determine fencing behavior. Any cluster node can fence any other cluster node with any fence device, regardless of whether the fence resource is started or stopped. Whether the resource is started controls only the recurring monitor for the device, not whether it can be used, with the following exceptions: You can disable a fencing device by running the pcs stonith disable stonith_id command. This will prevent any node from using that device. To prevent a specific node from using a fencing device, you can configure location constraints for the fencing resource with the pcs constraint location ... avoids command. Configuring stonith-enabled=false will disable fencing altogether. Note, however, that Red Hat does not support clusters when fencing is disabled, as it is not suitable for a production environment. The following table describes the general properties you can set for fencing devices. Table 10.1. General Properties of Fencing Devices Field Type Default Description pcmk_host_map string A mapping of host names to port numbers for devices that do not support host names. For example: node1:1;node2:2,3 tells the cluster to use port 1 for node1 and ports 2 and 3 for node2. As of RHEL 8.7, the pcmk_host_map property supports special characters inside pcmk_host_map values using a backslash in front of the value. For example, you can specify pcmk_host_map="node3:plug\ 1" to include a space in the host alias. pcmk_host_list string A list of machines controlled by this device (Optional unless pcmk_host_check=static-list ). pcmk_host_check string * static-list if either pcmk_host_list or pcmk_host_map is set * Otherwise, dynamic-list if the fence device supports the list action * Otherwise, status if the fence device supports the status action *Otherwise, none . How to determine which machines are controlled by the device. Allowed values: dynamic-list (query the device), static-list (check the pcmk_host_list attribute), none (assume every device can fence every machine) The following table summarizes additional properties you can set for fencing devices. Note that these properties are for advanced use only. Table 10.2. Advanced Properties of Fencing Devices Field Type Default Description pcmk_host_argument string port An alternate parameter to supply instead of port. Some devices do not support the standard port parameter or may provide additional ones. Use this to specify an alternate, device-specific parameter that should indicate the machine to be fenced. A value of none can be used to tell the cluster not to supply any additional parameters. pcmk_reboot_action string reboot An alternate command to run instead of reboot . Some devices do not support the standard commands or may provide additional ones. Use this to specify an alternate, device-specific, command that implements the reboot action. pcmk_reboot_timeout time 60s Specify an alternate timeout to use for reboot actions instead of stonith-timeout . Some devices need much more/less time to complete than normal. Use this to specify an alternate, device-specific, timeout for reboot actions. pcmk_reboot_retries integer 2 The maximum number of times to retry the reboot command within the timeout period. Some devices do not support multiple connections. Operations may fail if the device is busy with another task so Pacemaker will automatically retry the operation, if there is time remaining. Use this option to alter the number of times Pacemaker retries reboot actions before giving up. pcmk_off_action string off An alternate command to run instead of off . Some devices do not support the standard commands or may provide additional ones. Use this to specify an alternate, device-specific, command that implements the off action. pcmk_off_timeout time 60s Specify an alternate timeout to use for off actions instead of stonith-timeout . Some devices need much more or much less time to complete than normal. Use this to specify an alternate, device-specific, timeout for off actions. pcmk_off_retries integer 2 The maximum number of times to retry the off command within the timeout period. Some devices do not support multiple connections. Operations may fail if the device is busy with another task so Pacemaker will automatically retry the operation, if there is time remaining. Use this option to alter the number of times Pacemaker retries off actions before giving up. pcmk_list_action string list An alternate command to run instead of list . Some devices do not support the standard commands or may provide additional ones. Use this to specify an alternate, device-specific, command that implements the list action. pcmk_list_timeout time 60s Specify an alternate timeout to use for list actions. Some devices need much more or much less time to complete than normal. Use this to specify an alternate, device-specific, timeout for list actions. pcmk_list_retries integer 2 The maximum number of times to retry the list command within the timeout period. Some devices do not support multiple connections. Operations may fail if the device is busy with another task so Pacemaker will automatically retry the operation, if there is time remaining. Use this option to alter the number of times Pacemaker retries list actions before giving up. pcmk_monitor_action string monitor An alternate command to run instead of monitor . Some devices do not support the standard commands or may provide additional ones. Use this to specify an alternate, device-specific, command that implements the monitor action. pcmk_monitor_timeout time 60s Specify an alternate timeout to use for monitor actions instead of stonith-timeout . Some devices need much more or much less time to complete than normal. Use this to specify an alternate, device-specific, timeout for monitor actions. pcmk_monitor_retries integer 2 The maximum number of times to retry the monitor command within the timeout period. Some devices do not support multiple connections. Operations may fail if the device is busy with another task so Pacemaker will automatically retry the operation, if there is time remaining. Use this option to alter the number of times Pacemaker retries monitor actions before giving up. pcmk_status_action string status An alternate command to run instead of status . Some devices do not support the standard commands or may provide additional ones. Use this to specify an alternate, device-specific, command that implements the status action. pcmk_status_timeout time 60s Specify an alternate timeout to use for status actions instead of stonith-timeout . Some devices need much more or much less time to complete than normal. Use this to specify an alternate, device-specific, timeout for status actions. pcmk_status_retries integer 2 The maximum number of times to retry the status command within the timeout period. Some devices do not support multiple connections. Operations may fail if the device is busy with another task so Pacemaker will automatically retry the operation, if there is time remaining. Use this option to alter the number of times Pacemaker retries status actions before giving up. pcmk_delay_base string 0s Enables a base delay for fencing actions and specifies a base delay value. As of Red Hat Enterprise Linux 8.6, you can specify different values for different nodes with the pcmk_delay_base parameter. For general information about fencing delay parameters and their interactions, see Fencing delays . pcmk_delay_max time 0s Enables a random delay for fencing actions and specifies the maximum delay, which is the maximum value of the combined base delay and random delay. For example, if the base delay is 3 and pcmk_delay_max is 10, the random delay will be between 3 and 10. For general information about fencing delay parameters and their interactions, see Fencing delays . pcmk_action_limit integer 1 The maximum number of actions that can be performed in parallel on this device. The cluster property concurrent-fencing=true needs to be configured first (this is the default value for RHEL 8.1 and later). A value of -1 is unlimited. pcmk_on_action string on For advanced use only: An alternate command to run instead of on . Some devices do not support the standard commands or may provide additional ones. Use this to specify an alternate, device-specific, command that implements the on action. pcmk_on_timeout time 60s For advanced use only: Specify an alternate timeout to use for on actions instead of stonith-timeout . Some devices need much more or much less time to complete than normal. Use this to specify an alternate, device-specific, timeout for on actions. pcmk_on_retries integer 2 For advanced use only: The maximum number of times to retry the on command within the timeout period. Some devices do not support multiple connections. Operations may fail if the device is busy with another task so Pacemaker will automatically retry the operation, if there is time remaining. Use this option to alter the number of times Pacemaker retries on actions before giving up. In addition to the properties you can set for individual fence devices, there are also cluster properties you can set that determine fencing behavior, as described in the following table. Table 10.3. Cluster Properties that Determine Fencing Behavior Option Default Description stonith-enabled true Indicates that failed nodes and nodes with resources that cannot be stopped should be fenced. Protecting your data requires that you set this true . If true , or unset, the cluster will refuse to start resources unless one or more STONITH resources have been configured also. Red Hat only supports clusters with this value set to true . stonith-action reboot Action to send to fencing device. Allowed values: reboot , off . The value poweroff is also allowed, but is only used for legacy devices. stonith-timeout 60s How long to wait for a STONITH action to complete. stonith-max-attempts 10 How many times fencing can fail for a target before the cluster will no longer immediately re-attempt it. stonith-watchdog-timeout The maximum time to wait until a node can be assumed to have been killed by the hardware watchdog. It is recommended that this value be set to twice the value of the hardware watchdog timeout. This option is needed only if watchdog-only SBD configuration is used for fencing. concurrent-fencing true (RHEL 8.1 and later) Allow fencing operations to be performed in parallel. fence-reaction stop (Red Hat Enterprise Linux 8.2 and later) Determines how a cluster node should react if notified of its own fencing. A cluster node may receive notification of its own fencing if fencing is misconfigured, or if fabric fencing is in use that does not cut cluster communication. Allowed values are stop to attempt to immediately stop Pacemaker and stay stopped, or panic to attempt to immediately reboot the local node, falling back to stop on failure. Although the default value for this property is stop , the safest choice for this value is panic , which attempts to immediately reboot the local node. If you prefer the stop behavior, as is most likely to be the case in conjunction with fabric fencing, it is recommended that you set this explicitly. priority-fencing-delay 0 (disabled) (RHEL 8.3 and later) Sets a fencing delay that allows you to configure a two-node cluster so that in a split-brain situation the node with the fewest or least important resources running is the node that gets fenced. For general information about fencing delay parameters and their interactions, see Fencing delays . For information about setting cluster properties, see Setting and removing cluster properties . 10.4. Fencing delays When cluster communication is lost in a two-node cluster, one node may detect this first and fence the other node. If both nodes detect this at the same time, however, each node may be able to initiate fencing of the other, leaving both nodes powered down or reset. By setting a fencing delay, you can decrease the likelihood of both cluster nodes fencing each other. You can set delays in a cluster with more than two nodes, but this is generally not of any benefit because only a partition with quorum will initiate fencing. You can set different types of fencing delays, depending on your system requirements. static fencing delays A static fencing delay is a fixed, predetermined delay. Setting a static delay on one node makes that node more likely to be fenced because it increases the chances that the other node will initiate fencing first after detecting lost communication. In an active/passive cluster, setting a delay on a passive node makes it more likely that the passive node will be fenced when communication breaks down. You configure a static delay by using the pcs_delay_base cluster property. You can set this property when a separate fence device is used for each node or, as of RHEL 8.6, when a single fence device is used for all nodes. dynamic fencing delays A dynamic fencing delay is random. It can vary and is determined at the time fencing is needed. You configure a random delay and specify a maximum value for the combined base delay and random delay with the pcs_delay_max cluster property. When the fencing delay for each node is random, which node is fenced is also random. You may find this feature useful if your cluster is configured with a single fence device for all nodes in an active/active design. priority fencing delays A priority fencing delay is based on active resource priorities. If all resources have the same priority, the node with the fewest resources running is the node that gets fenced. In most cases, you use only one delay-related parameter, but it is possible to combine them. Combining delay-related parameters adds the priority values for the resources together to create a total delay. You configure a priority fencing delay with the priority-fencing-delay cluster property. You may find this feature useful in an active/active cluster design because it can make the node running the fewest resources more likely to be fenced when communication between the nodes is lost. The pcmk_delay_base cluster property Setting the pcmk_delay_base cluster property enables a base delay for fencing and specifies a base delay value. When you set the pcmk_delay_max cluster property in addition to the pcmk_delay_base property, the overall delay is derived from a random delay value added to this static delay so that the sum is kept below the maximum delay. When you set pcmk_delay_base but do not set pcmk_delay_max , there is no random component to the delay and it will be the value of pcmk_delay_base . As of Red Hat Enterprise Linux 8.6, you can specify different values for different nodes with the pcmk_delay_base parameter. This allows a single fence device to be used in a two-node cluster, with a different delay for each node. You do not need to configure two separate devices to use separate delays. To specify different values for different nodes, you map the host names to the delay value for that node using a similar syntax to pcmk_host_map . For example, node1:0;node2:10s would use no delay when fencing node1 and a 10-second delay when fencing node2 . The pcmk_delay_max cluster property Setting the pcmk_delay_max cluster property enables a random delay for fencing actions and specifies the maximum delay, which is the maximum value of the combined base delay and random delay. For example, if the base delay is 3 and pcmk_delay_max is 10, the random delay will be between 3 and 10. When you set the pcmk_delay_base cluster property in addition to the pcmk_delay_max property, the overall delay is derived from a random delay value added to this static delay so that the sum is kept below the maximum delay. When you set pcmk_delay_max but do not set pcmk_delay_base there is no static component to the delay. The priority-fencing-delay cluster property (RHEL 8.3 and later) Setting the priority-fencing-delay cluster property allows you to configure a two-node cluster so that in a split-brain situation the node with the fewest or least important resources running is the node that gets fenced. The priority-fencing-delay property can be set to a time duration. The default value for this property is 0 (disabled). If this property is set to a non-zero value, and the priority meta-attribute is configured for at least one resource, then in a split-brain situation the node with the highest combined priority of all resources running on it will be more likely to remain operational. For example, if you set pcs resource defaults update priority=1 and pcs property set priority-fencing-delay=15s and no other priorities are set, then the node running the most resources will be more likely to remain operational because the other node will wait 15 seconds before initiating fencing. If a particular resource is more important than the rest, you can give it a higher priority. The node running the master role of a promotable clone gets an extra 1 point if a priority has been configured for that clone. Interaction of fencing delays Setting more than one type of fencing delay yields the following results: Any delay set with the priority-fencing-delay property is added to any delay from the pcmk_delay_base and pcmk_delay_max fence device properties. This behavior allows some delay when both nodes have equal priority, or both nodes need to be fenced for some reason other than node loss, as when on-fail=fencing is set for a resource monitor operation. When setting these delays in combination, set the priority-fencing-delay property to a value that is significantly greater than the maximum delay from pcmk_delay_base and pcmk_delay_max to be sure the prioritized node is preferred. Setting this property to twice this value is always safe. Only fencing scheduled by Pacemaker itself observes fencing delays. Fencing scheduled by external code such as dlm_controld and fencing implemented by the pcs stonith fence command do not provide the necessary information to the fence device. Some individual fence agents implement a delay parameter, with a name determined by the agent and which is independent of delays configured with a pcmk_delay_ * property. If both of these delays are configured, they are added together and would generally not be used in conjunction. 10.5. Testing a fence device Fencing is a fundamental part of the Red Hat Cluster infrastructure and it is important to validate or test that fencing is working properly. Procedure Use the following procedure to test a fence device. Use ssh, telnet, HTTP, or whatever remote protocol is used to connect to the device to manually log in and test the fence device or see what output is given. For example, if you will be configuring fencing for an IPMI-enabled device,then try to log in remotely with ipmitool . Take note of the options used when logging in manually because those options might be needed when using the fencing agent. If you are unable to log in to the fence device, verify that the device is pingable, there is nothing such as a firewall configuration that is preventing access to the fence device, remote access is enabled on the fencing device, and the credentials are correct. Run the fence agent manually, using the fence agent script. This does not require that the cluster services are running, so you can perform this step before the device is configured in the cluster. This can ensure that the fence device is responding properly before proceeding. Note These examples use the fence_ipmilan fence agent script for an iLO device. The actual fence agent you will use and the command that calls that agent will depend on your server hardware. You should consult the man page for the fence agent you are using to determine which options to specify. You will usually need to know the login and password for the fence device and other information related to the fence device. The following example shows the format you would use to run the fence_ipmilan fence agent script with -o status parameter to check the status of the fence device interface on another node without actually fencing it. This allows you to test the device and get it working before attempting to reboot the node. When running this command, you specify the name and password of an iLO user that has power on and off permissions for the iLO device. The following example shows the format you would use to run the fence_ipmilan fence agent script with the -o reboot parameter. Running this command on one node reboots the node managed by this iLO device. If the fence agent failed to properly do a status, off, on, or reboot action, you should check the hardware, the configuration of the fence device, and the syntax of your commands. In addition, you can run the fence agent script with the debug output enabled. The debug output is useful for some fencing agents to see where in the sequence of events the fencing agent script is failing when logging into the fence device. When diagnosing a failure that has occurred, you should ensure that the options you specified when manually logging in to the fence device are identical to what you passed on to the fence agent with the fence agent script. For fence agents that support an encrypted connection, you may see an error due to certificate validation failing, requiring that you trust the host or that you use the fence agent's ssl-insecure parameter. Similarly, if SSL/TLS is disabled on the target device, you may need to account for this when setting the SSL parameters for the fence agent. Note If the fence agent that is being tested is a fence_drac , fence_ilo , or some other fencing agent for a systems management device that continues to fail, then fall back to trying fence_ipmilan . Most systems management cards support IPMI remote login and the only supported fencing agent is fence_ipmilan . Once the fence device has been configured in the cluster with the same options that worked manually and the cluster has been started, test fencing with the pcs stonith fence command from any node (or even multiple times from different nodes), as in the following example. The pcs stonith fence command reads the cluster configuration from the CIB and calls the fence agent as configured to execute the fence action. This verifies that the cluster configuration is correct. If the pcs stonith fence command works properly, that means the fencing configuration for the cluster should work when a fence event occurs. If the command fails, it means that cluster management cannot invoke the fence device through the configuration it has retrieved. Check for the following issues and update your cluster configuration as needed. Check your fence configuration. For example, if you have used a host map you should ensure that the system can find the node using the host name you have provided. Check whether the password and user name for the device include any special characters that could be misinterpreted by the bash shell. Making sure that you enter passwords and user names surrounded by quotation marks could address this issue. Check whether you can connect to the device using the exact IP address or host name you specified in the pcs stonith command. For example, if you give the host name in the stonith command but test by using the IP address, that is not a valid test. If the protocol that your fence device uses is accessible to you, use that protocol to try to connect to the device. For example many agents use ssh or telnet. You should try to connect to the device with the credentials you provided when configuring the device, to see if you get a valid prompt and can log in to the device. If you determine that all your parameters are appropriate but you still have trouble connecting to your fence device, you can check the logging on the fence device itself, if the device provides that, which will show if the user has connected and what command the user issued. You can also search through the /var/log/messages file for instances of stonith and error, which could give some idea of what is transpiring, but some agents can provide additional information. Once the fence device tests are working and the cluster is up and running, test an actual failure. To do this, take an action in the cluster that should initiate a token loss. Take down a network. How you take a network depends on your specific configuration. In many cases, you can physically pull the network or power cables out of the host. For information about simulating a network failure, see the Red Hat Knowledgebase solution What is the proper way to simulate a network failure on a RHEL Cluster? . Note Disabling the network interface on the local host rather than physically disconnecting the network or power cables is not recommended as a test of fencing because it does not accurately simulate a typical real-world failure. Block corosync traffic both inbound and outbound using the local firewall. The following example blocks corosync, assuming the default corosync port is used, firewalld is used as the local firewall, and the network interface used by corosync is in the default firewall zone: Simulate a crash and panic your machine with sysrq-trigger . Note, however, that triggering a kernel panic can cause data loss; it is recommended that you disable your cluster resources first. 10.6. Configuring fencing levels Pacemaker supports fencing nodes with multiple devices through a feature called fencing topologies. To implement topologies, create the individual devices as you normally would and then define one or more fencing levels in the fencing topology section in the configuration. Pacemaker processes fencing levels as follows: Each level is attempted in ascending numeric order, starting at 1. If a device fails, processing terminates for the current level. No further devices in that level are exercised and the level is attempted instead. If all devices are successfully fenced, then that level has succeeded and no other levels are tried. The operation is finished when a level has passed (success), or all levels have been attempted (failed). Use the following command to add a fencing level to a node. The devices are given as a comma-separated list of stonith ids, which are attempted for the node at that level. The following command lists all of the fencing levels that are currently configured. In the following example, there are two fence devices configured for node rh7-2 : an ilo fence device called my_ilo and an apc fence device called my_apc . These commands set up fence levels so that if the device my_ilo fails and is unable to fence the node, then Pacemaker will attempt to use the device my_apc . This example also shows the output of the pcs stonith level command after the levels are configured. The following command removes the fence level for the specified node and devices. If no nodes or devices are specified then the fence level you specify is removed from all nodes. The following command clears the fence levels on the specified node or stonith id. If you do not specify a node or stonith id, all fence levels are cleared. If you specify more than one stonith id, they must be separated by a comma and no spaces, as in the following example. The following command verifies that all fence devices and nodes specified in fence levels exist. You can specify nodes in fencing topology by a regular expression applied on a node name and by a node attribute and its value. For example, the following commands configure nodes node1 , node2 , and node3 to use fence devices apc1 and apc2 , and nodes node4 , node5 , and node6 to use fence devices apc3 and apc4 . The following commands yield the same results by using node attribute matching. 10.7. Configuring fencing for redundant power supplies When configuring fencing for redundant power supplies, the cluster must ensure that when attempting to reboot a host, both power supplies are turned off before either power supply is turned back on. If the node never completely loses power, the node may not release its resources. This opens up the possibility of nodes accessing these resources simultaneously and corrupting them. You need to define each device only once and to specify that both are required to fence the node, as in the following example. 10.8. Displaying configured fence devices The following command shows all currently configured fence devices. If a stonith_id is specified, the command shows the options for that configured fencing device only. If the --full option is specified, all configured fencing options are displayed. 10.9. Exporting fence devices as pcs commands As of Red Hat Enterprise Linux 8.7, you can display the pcs commands that can be used to re-create configured fence devices on a different system using the --output-format=cmd option of the pcs stonith config command. The following commands create a fence_apc_snmp fence device and display the pcs command you can use to re-create the device. 10.10. Modifying and deleting fence devices Modify or add options to a currently configured fencing device with the following command. Updating a SCSI fencing device with the pcs stonith update command causes a restart of all resources running on the same node where the fencing resource was running. As of RHEL 8.5, you can use either version of the following command to update SCSI devices without causing a restart of other cluster resources. As of RHEL 8.7, SCSI fencing devices can be configured as multipath devices. Use the following command to remove a fencing device from the current configuration. 10.11. Manually fencing a cluster node You can fence a node manually with the following command. If you specify --off this will use the off API call to stonith which will turn the node off instead of rebooting it. In a situation where no fence device is able to fence a node even if it is no longer active, the cluster may not be able to recover the resources on the node. If this occurs, after manually ensuring that the node is powered down you can enter the following command to confirm to the cluster that the node is powered down and free its resources for recovery. Warning If the node you specify is not actually off, but running the cluster software or services normally controlled by the cluster, data corruption/cluster failure will occur. 10.12. Disabling a fence device To disable a fencing device/resource, run the pcs stonith disable command. The following command disables the fence device myapc . 10.13. Preventing a node from using a fencing device To prevent a specific node from using a fencing device, you can configure location constraints for the fencing resource. The following example prevents fence device node1-ipmi from running on node1 . 10.14. Configuring ACPI for use with integrated fence devices If your cluster uses integrated fence devices, you must configure ACPI (Advanced Configuration and Power Interface) to ensure immediate and complete fencing. If a cluster node is configured to be fenced by an integrated fence device, disable ACPI Soft-Off for that node. Disabling ACPI Soft-Off allows an integrated fence device to turn off a node immediately and completely rather than attempting a clean shutdown (for example, shutdown -h now ). Otherwise, if ACPI Soft-Off is enabled, an integrated fence device can take four or more seconds to turn off a node (see the note that follows). In addition, if ACPI Soft-Off is enabled and a node panics or freezes during shutdown, an integrated fence device may not be able to turn off the node. Under those circumstances, fencing is delayed or unsuccessful. Consequently, when a node is fenced with an integrated fence device and ACPI Soft-Off is enabled, a cluster recovers slowly or requires administrative intervention to recover. Note The amount of time required to fence a node depends on the integrated fence device used. Some integrated fence devices perform the equivalent of pressing and holding the power button; therefore, the fence device turns off the node in four to five seconds. Other integrated fence devices perform the equivalent of pressing the power button momentarily, relying on the operating system to turn off the node; therefore, the fence device turns off the node in a time span much longer than four to five seconds. The preferred way to disable ACPI Soft-Off is to change the BIOS setting to "instant-off" or an equivalent setting that turns off the node without delay, as described in "Disabling ACPI Soft-Off with the Bios" below. Disabling ACPI Soft-Off with the BIOS may not be possible with some systems. If disabling ACPI Soft-Off with the BIOS is not satisfactory for your cluster, you can disable ACPI Soft-Off with one of the following alternate methods: Setting HandlePowerKey=ignore in the /etc/systemd/logind.conf file and verifying that the node node turns off immediately when fenced, as described in "Disabling ACPI Soft-Off in the logind.conf file", below. This is the first alternate method of disabling ACPI Soft-Off. Appending acpi=off to the kernel boot command line, as described in Disabling ACPI completely in the GRUB file below. This is the second alternate method of disabling ACPI Soft-Off, if the preferred or the first alternate method is not available. Important This method completely disables ACPI; some computers do not boot correctly if ACPI is completely disabled. Use this method only if the other methods are not effective for your cluster. 10.14.1. Disabling ACPI Soft-Off with the BIOS You can disable ACPI Soft-Off by configuring the BIOS of each cluster node with the following procedure. Note The procedure for disabling ACPI Soft-Off with the BIOS may differ among server systems. You should verify this procedure with your hardware documentation. Procedure Reboot the node and start the BIOS CMOS Setup Utility program. Navigate to the Power menu (or equivalent power management menu). At the Power menu, set the Soft-Off by PWR-BTTN function (or equivalent) to Instant-Off (or the equivalent setting that turns off the node by means of the power button without delay). The BIOS CMOS Setup Utiliy example below shows a Power menu with ACPI Function set to Enabled and Soft-Off by PWR-BTTN set to Instant-Off . Note The equivalents to ACPI Function , Soft-Off by PWR-BTTN , and Instant-Off may vary among computers. However, the objective of this procedure is to configure the BIOS so that the computer is turned off by means of the power button without delay. Exit the BIOS CMOS Setup Utility program, saving the BIOS configuration. Verify that the node turns off immediately when fenced. For information about testing a fence device, see Testing a fence device . BIOS CMOS Setup Utility : This example shows ACPI Function set to Enabled , and Soft-Off by PWR-BTTN set to Instant-Off . 10.14.2. Disabling ACPI Soft-Off in the logind.conf file To disable power-key handing in the /etc/systemd/logind.conf file, use the following procedure. Procedure Define the following configuration in the /etc/systemd/logind.conf file: Restart the systemd-logind service: Verify that the node turns off immediately when fenced. For information about testing a fence device, see Testing a fence device . 10.14.3. Disabling ACPI completely in the GRUB file You can disable ACPI Soft-Off by appending acpi=off to the GRUB menu entry for a kernel. Important This method completely disables ACPI; some computers do not boot correctly if ACPI is completely disabled. Use this method only if the other methods are not effective for your cluster. Procedure Use the following procedure to disable ACPI in the GRUB file: Use the --args option in combination with the --update-kernel option of the grubby tool to change the grub.cfg file of each cluster node as follows: Reboot the node. Verify that the node turns off immediately when fenced. For information about testing a fence device, see Testing a fence device .
pcs stonith list [ filter ] pcs stonith describe [ stonith_agent ] pcs stonith describe fence_apc Stonith options for: fence_apc ipaddr (required): IP Address or Hostname login (required): Login Name passwd: Login password or passphrase passwd_script: Script to retrieve password cmd_prompt: Force command prompt secure: SSH connection port (required): Physical plug number or name of virtual machine identity_file: Identity file for ssh switch: Physical switch number on device inet4_only: Forces agent to use IPv4 addresses only inet6_only: Forces agent to use IPv6 addresses only ipport: TCP port to use for connection with device action (required): Fencing Action verbose: Verbose mode debug: Write debug information to given file version: Display version information and exit help: Display help and exit separator: Separator for CSV created by operation list power_timeout: Test X seconds for status change after ON/OFF shell_timeout: Wait X seconds for cmd prompt after issuing command login_timeout: Wait X seconds for cmd prompt after login power_wait: Wait X seconds after issuing ON/OFF delay: Wait X seconds before fencing is started retry_on: Count of attempts to retry power on pcs stonith create stonith_id stonith_device_type [ stonith_device_options ] [op operation_action operation_options ] pcs stonith create MyStonith fence_virt pcmk_host_list=f1 op monitor interval=30s fence_ipmilan -a ipaddress -l username -p password -o status fence_ipmilan -a ipaddress -l username -p password -o reboot fence_ipmilan -a ipaddress -l username -p password -o status -D /tmp/USD(hostname)-fence_agent.debug pcs stonith fence node_name firewall-cmd --direct --add-rule ipv4 filter OUTPUT 2 -p udp --dport=5405 -j DROP firewall-cmd --add-rich-rule='rule family="ipv4" port port="5405" protocol="udp" drop echo c > /proc/sysrq-trigger pcs stonith level add level node devices pcs stonith level pcs stonith level add 1 rh7-2 my_ilo pcs stonith level add 2 rh7-2 my_apc pcs stonith level Node: rh7-2 Level 1 - my_ilo Level 2 - my_apc pcs stonith level remove level [ node_id ] [ stonith_id ] ... [ stonith_id ] pcs stonith level clear [ node ]| stonith_id (s)] pcs stonith level clear dev_a,dev_b pcs stonith level verify pcs stonith level add 1 "regexp%node[1-3]" apc1,apc2 pcs stonith level add 1 "regexp%node[4-6]" apc3,apc4 pcs node attribute node1 rack=1 pcs node attribute node2 rack=1 pcs node attribute node3 rack=1 pcs node attribute node4 rack=2 pcs node attribute node5 rack=2 pcs node attribute node6 rack=2 pcs stonith level add 1 attrib%rack=1 apc1,apc2 pcs stonith level add 1 attrib%rack=2 apc3,apc4 pcs stonith create apc1 fence_apc_snmp ipaddr=apc1.example.com login=user passwd='7a4D#1j!pz864' pcmk_host_map="node1.example.com:1;node2.example.com:2" pcs stonith create apc2 fence_apc_snmp ipaddr=apc2.example.com login=user passwd='7a4D#1j!pz864' pcmk_host_map="node1.example.com:1;node2.example.com:2" pcs stonith level add 1 node1.example.com apc1,apc2 pcs stonith level add 1 node2.example.com apc1,apc2 pcs stonith config [ stonith_id ] [--full] pcs stonith create myapc fence_apc_snmp ip="zapc.example.com" pcmk_host_map="z1.example.com:1;z2.example.com:2" username="apc" password="apc" pcs stonith config --output-format=cmd Warning: Only 'text' output format is supported for stonith levels pcs stonith create --no-default-ops --force -- myapc fence_apc_snmp ip=zapc.example.com password=apc 'pcmk_host_map=z1.example.com:1;z2.example.com:2' username=apc op monitor interval=60s id=myapc-monitor-interval-60s pcs stonith update stonith_id [ stonith_device_options ] pcs stonith update-scsi-devices stonith_id set device-path1 device-path2 pcs stonith update-scsi-devices stonith_id add device-path1 remove device-path2 pcs stonith delete stonith_id pcs stonith fence node [--off] pcs stonith confirm node pcs stonith disable myapc pcs constraint location node1-ipmi avoids node1 `Soft-Off by PWR-BTTN` set to `Instant-Off` +---------------------------------------------|-------------------+ | ACPI Function [Enabled] | Item Help | | ACPI Suspend Type [S1(POS)] |-------------------| | x Run VGABIOS if S3 Resume Auto | Menu Level * | | Suspend Mode [Disabled] | | | HDD Power Down [Disabled] | | | Soft-Off by PWR-BTTN [Instant-Off | | | CPU THRM-Throttling [50.0%] | | | Wake-Up by PCI card [Enabled] | | | Power On by Ring [Enabled] | | | Wake Up On LAN [Enabled] | | | x USB KB Wake-Up From S3 Disabled | | | Resume by Alarm [Disabled] | | | x Date(of Month) Alarm 0 | | | x Time(hh:mm:ss) Alarm 0 : 0 : | | | POWER ON Function [BUTTON ONLY | | | x KB Power ON Password Enter | | | x Hot Key Power ON Ctrl-F1 | | | | | | | | +---------------------------------------------|-------------------+ HandlePowerKey=ignore systemctl restart systemd-logind.service grubby --args=acpi=off --update-kernel=ALL