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3.4. Exclusive Activation of a Volume Group in a Cluster

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The following procedure configures the LVM volume group in a way that will ensure that only the cluster is capable of activating the volume group, and that the volume group will not be activated outside of the cluster on startup. If the volume group is activated by a system outside of the cluster, there is a risk of corrupting the volume group's metadata.
This procedure modifies the volume_list entry in the /etc/lvm/lvm.conf configuration file. Volume groups listed in the volume_list entry are allowed to automatically activate on the local node outside of the cluster manager's control. Volume groups related to the node's local root and home directories should be included in this list. All volume groups managed by the cluster manager must be excluded from the volume_list entry. Note that this procedure does not require the use of clvmd.
Perform the following procedure on each node in the cluster.
  1. Execute the following command to ensure that locking_type is set to 1 and that use_lvmetad is set to 0 in the /etc/lvm/lvm.conf file. This command also disables and stops any lvmetad processes immediately. 
    # lvmconf --enable-halvm --services --startstopservices
  2. Determine which volume groups are currently configured on your local storage with the following command. This will output a list of the currently-configured volume groups. If you have space allocated in separate volume groups for root and for your home directory on this node, you will see those volumes in the output, as in this example. 
    # vgs --noheadings -o vg_name
  my_vg        
  rhel_home
  rhel_root
  3. Add the volume groups other than my_vg (the volume group you have just defined for the cluster) as entries to volume_list in the /etc/lvm/lvm.conf configuration file. For example, if you have space allocated in separate volume groups for root and for your home directory, you would uncomment the volume_list line of the lvm.conf file and add these volume groups as entries to volume_list as follows: 
    volume_list = [ "rhel_root", "rhel_home" ]

    Note

    If no local volume groups are present on a node to be activated outside of the cluster manager, you must still initialize the volume_list entry as volume_list = [].
  4. Rebuild the initramfs boot image to guarantee that the boot image will not try to activate a volume group controlled by the cluster. Update the initramfs device with the following command. This command may take up to a minute to complete. 
    # dracut -H -f /boot/initramfs-$(uname -r).img $(uname -r)
  5. Reboot the node.

    Note

    If you have installed a new Linux kernel since booting the node on which you created the boot image, the new initrd image will be for the kernel that was running when you created it and not for the new kernel that is running when you reboot the node. You can ensure that the correct initrd device is in use by running the uname -r command before and after the reboot to determine the kernel release that is running. If the releases are not the same, update the initrd file after rebooting with the new kernel and then reboot the node.
  6. When the node has rebooted, check whether the cluster services have started up again on that node by executing the pcs cluster status command on that node. If this yields the message Error: cluster is not currently running on this node then enter the following command. 
    # pcs cluster start
    Alternately, you can wait until you have rebooted each node in the cluster and start cluster services on all of the nodes in the cluster with the following command. 
    # pcs cluster start --all
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