Chapter 6. Configuring an active/passive NFS server in a Red Hat High Availability cluster

Procedure

1. On both nodes of the cluster, perform the following steps to set the value for the LVM system ID to the value of the uname identifier for the system. The LVM system ID will be used to ensure that only the cluster is capable of activating the volume group.

   1. Set the system_id_source configuration option in the /etc/lvm/lvm.conf configuration file to uname.

      # Configuration option global/system_id_source.
      system_id_source = "uname"

   2. Verify that the LVM system ID on the node matches the uname for the node.

      # lvm systemid
        system ID: z1.example.com
      # uname -n
        z1.example.com

2. Create the LVM volume and create an ext4 file system on that volume. Since the /dev/sdb1 partition is storage that is shared, you perform this part of the procedure on one node only.

   Note

   If your LVM volume group contains one or more physical volumes that reside on remote block storage, such as an iSCSI target, Red Hat recommends that you ensure that the service starts before Pacemaker starts. For information on configuring startup order for a remote physical volume used by a Pacemaker cluster, see Configuring startup order for resource dependencies not managed by Pacemaker.

   1. Create an LVM physical volume on partition /dev/sdb1.

      # pvcreate /dev/sdb1
        Physical volume "/dev/sdb1" successfully created

   2. Create the volume group my_vg that consists of the physical volume /dev/sdb1.

      For RHEL 8.5 and later, specify the --setautoactivation n flag to ensure that volume groups managed by Pacemaker in a cluster will not be automatically activated on startup. If you are using an existing volume group for the LVM volume you are creating, you can reset this flag with the vgchange --setautoactivation n command for the volume group.

      # vgcreate --setautoactivation n my_vg /dev/sdb1
        Volume group "my_vg" successfully created

      For RHEL 8.4 and earlier, create the volume group with the following command.

      # vgcreate my_vg /dev/sdb1
        Volume group "my_vg" successfully created

      For information on ensuring that volume groups managed by Pacemaker in a cluster will not be automatically activated on startup for RHEL 8.4 and earlier, see Ensuring a volume group is not activated on multiple cluster nodes.

   3. Verify that the new volume group has the system ID of the node on which you are running and from which you created the volume group.

      # vgs -o+systemid
        VG    #PV #LV #SN Attr   VSize  VFree  System ID
        my_vg   1   0   0 wz--n- <1.82t <1.82t z1.example.com

   4. Create a logical volume using the volume group my_vg.

      # lvcreate -L450 -n my_lv my_vg
        Rounding up size to full physical extent 452.00 MiB
        Logical volume "my_lv" created

      You can use the lvs command to display the logical volume.

      # lvs
        LV      VG      Attr      LSize   Pool Origin Data%  Move Log Copy%  Convert
        my_lv   my_vg   -wi-a---- 452.00m
        ...

   5. Create an ext4 file system on the logical volume my_lv.

      # mkfs.ext4 /dev/my_vg/my_lv
      mke2fs 1.44.3 (10-July-2018)
      Creating filesystem with 462848 1k blocks and 115824 inodes
      ...

1. 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

2. Add the volume groups other than my_vg (the volume group you have just defined for the cluster) as entries to auto_activation_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 auto_activation_volume_list line of the lvm.conf file and add these volume groups as entries to auto_activation_volume_list as follows. Note that the volume group you have just defined for the cluster (my_vg in this example) is not in this list.

   auto_activation_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 auto_activation_volume_list entry as auto_activation_volume_list = [].

3. 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)

4. 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.

5. 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

Procedure

1. On both nodes in the cluster, create the /nfsshare directory.

   # mkdir /nfsshare

2. On one node in the cluster, perform the following procedure.

   1. Ensure that the logical volume you you created in Configuring an LVM volume with an ext4 file system. is activated, then mount the file system you created on the logical volume on the /nfsshare directory.

      [root@z1 ~]# lvchange -ay my_vg/my_lv
      [root@z1 ~]# mount /dev/my_vg/my_lv /nfsshare

   2. Create an exports directory tree on the /nfsshare directory.

      [root@z1 ~]# mkdir -p /nfsshare/exports
      [root@z1 ~]# mkdir -p /nfsshare/exports/export1
      [root@z1 ~]# mkdir -p /nfsshare/exports/export2

   3. Place files in the exports directory for the NFS clients to access. For this example, we are creating test files named clientdatafile1 and clientdatafile2.

      [root@z1 ~]# touch /nfsshare/exports/export1/clientdatafile1
      [root@z1 ~]# touch /nfsshare/exports/export2/clientdatafile2

   4. Unmount the ext4 file system and deactivate the LVM volume group.

      [root@z1 ~]# umount /dev/my_vg/my_lv
      [root@z1 ~]# vgchange -an my_vg

1. Create the LVM-activate resource named my_lvm. Because the resource group nfsgroup does not yet exist, this command creates the resource group.

   Warning

   Do not configure more than one LVM-activate resource that uses the same LVM volume group in an active/passive HA configuration, as this risks data corruption. Additionally, do not configure an LVM-activate resource as a clone resource in an active/passive HA configuration.

   [root@z1 ~]# pcs resource create my_lvm ocf:heartbeat:LVM-activate vgname=my_vg vg_access_mode=system_id --group nfsgroup

2. Check the status of the cluster to verify that the resource is running.

   root@z1 ~]#  pcs status
   Cluster name: my_cluster
   Last updated: Thu Jan  8 11:13:17 2015
   Last change: Thu Jan  8 11:13:08 2015
   Stack: corosync
   Current DC: z2.example.com (2) - partition with quorum
   Version: 1.1.12-a14efad
   2 Nodes configured
   3 Resources configured
   
   Online: [ z1.example.com z2.example.com ]
   
   Full list of resources:
    myapc  (stonith:fence_apc_snmp):       Started z1.example.com
    Resource Group: nfsgroup
        my_lvm     (ocf::heartbeat:LVM-activate):   Started z1.example.com
   
   PCSD Status:
     z1.example.com: Online
     z2.example.com: Online
   
   Daemon Status:
     corosync: active/enabled
     pacemaker: active/enabled
     pcsd: active/enabled

3. Configure a Filesystem resource for the cluster.

   The following command configures an ext4 Filesystem resource named nfsshare as part of the nfsgroup resource group. This file system uses the LVM volume group and ext4 file system you created in Configuring an LVM volume with an ext4 file system and will be mounted on the /nfsshare directory you created in Configuring an NFS share.

   [root@z1 ~]# pcs resource create nfsshare Filesystem device=/dev/my_vg/my_lv directory=/nfsshare fstype=ext4 --group nfsgroup

   You can specify mount options as part of the resource configuration for a Filesystem resource with the options=options parameter. Run the pcs resource describe Filesystem command for full configuration options.

4. Verify that the my_lvm and nfsshare resources are running.

   [root@z1 ~]# pcs status
   ...
   Full list of resources:
    myapc  (stonith:fence_apc_snmp):       Started z1.example.com
    Resource Group: nfsgroup
        my_lvm     (ocf::heartbeat:LVM-activate):   Started z1.example.com
        nfsshare   (ocf::heartbeat:Filesystem):    Started z1.example.com
   ...

5. Create the nfsserver resource named nfs-daemon as part of the resource group nfsgroup.

   Note

   The nfsserver resource allows you to specify an nfs_shared_infodir parameter, which is a directory that NFS servers use to store NFS-related stateful information.

   It is recommended that this attribute be set to a subdirectory of one of the Filesystem resources you created in this collection of exports. This ensures that the NFS servers are storing their stateful information on a device that will become available to another node if this resource group needs to relocate. In this example;

   • /nfsshare is the shared-storage directory managed by the Filesystem resource
   • /nfsshare/exports/export1 and /nfsshare/exports/export2 are the export directories
   • /nfsshare/nfsinfo is the shared-information directory for the nfsserver resource

   [root@z1 ~]# pcs resource create nfs-daemon nfsserver nfs_shared_infodir=/nfsshare/nfsinfo nfs_no_notify=true --group nfsgroup
   
   [root@z1 ~]# pcs status
   ...

6. Add the exportfs resources to export the /nfsshare/exports directory. These resources are part of the resource group nfsgroup. This builds a virtual directory for NFSv4 clients. NFSv3 clients can access these exports as well.

   Note

   The fsid=0 option is required only if you want to create a virtual directory for NFSv4 clients. For more information, see How do I configure the fsid option in an NFS server’s /etc/exports file?.

   [root@z1 ~]# pcs resource create nfs-root exportfs clientspec=192.168.122.0/255.255.255.0 options=rw,sync,no_root_squash directory=/nfsshare/exports fsid=0 --group nfsgroup
   
   [root@z1 ~]# pcs resource create nfs-export1 exportfs clientspec=192.168.122.0/255.255.255.0 options=rw,sync,no_root_squash directory=/nfsshare/exports/export1 fsid=1 --group nfsgroup
   
   [root@z1 ~]# pcs resource create nfs-export2 exportfs clientspec=192.168.122.0/255.255.255.0 options=rw,sync,no_root_squash directory=/nfsshare/exports/export2 fsid=2 --group nfsgroup

7. Add the floating IP address resource that NFS clients will use to access the NFS share. This resource is part of the resource group nfsgroup. For this example deployment, we are using 192.168.122.200 as the floating IP address.

   [root@z1 ~]# pcs resource create nfs_ip IPaddr2 ip=192.168.122.200 cidr_netmask=24 --group nfsgroup

8. Add an nfsnotify resource for sending NFSv3 reboot notifications once the entire NFS deployment has initialized. This resource is part of the resource group nfsgroup.

   Note

   For the NFS notification to be processed correctly, the floating IP address must have a host name associated with it that is consistent on both the NFS servers and the NFS client.

   [root@z1 ~]# pcs resource create nfs-notify nfsnotify source_host=192.168.122.200 --group nfsgroup

9. After creating the resources and the resource constraints, you can check the status of the cluster. Note that all resources are running on the same node.

   [root@z1 ~]# pcs status
   ...
   Full list of resources:
    myapc  (stonith:fence_apc_snmp):       Started z1.example.com
    Resource Group: nfsgroup
        my_lvm     (ocf::heartbeat:LVM-activate):   Started z1.example.com
        nfsshare   (ocf::heartbeat:Filesystem):    Started z1.example.com
        nfs-daemon (ocf::heartbeat:nfsserver):     Started z1.example.com
        nfs-root   (ocf::heartbeat:exportfs):      Started z1.example.com
        nfs-export1        (ocf::heartbeat:exportfs):      Started z1.example.com
        nfs-export2        (ocf::heartbeat:exportfs):      Started z1.example.com
        nfs_ip     (ocf::heartbeat:IPaddr2):       Started  z1.example.com
        nfs-notify (ocf::heartbeat:nfsnotify):     Started z1.example.com
   ...