For CentOS/RHEL 7 For accessing qcow2 disk image of guest on a CentOS/RHEL 7 KVM host, either use qemu-nbd or libguestfs. Using qemu-nbd Follow the below steps to mount the qcow2 image in CentOS/RHEL 7 using qemu-nbd. 1. Enable NBD kernel driver on the KVM host. # modprobe nbd 2. Connect the qcow2 image as network block device. # qemu-nbd --connect=/dev/nbd0 olseven.qcow2 -f qcow2 3. Find the partitions in the image using fdisk # fdisk /dev/nbd0 -l Disk /dev/nbd0: 32.2 GB, … [Read more...] about How to Mount Guest Qcow2 Virtual disk Image containing LVM on KVM Host Machine
Linux
“WARNING: Device for PV [] not found or rejected by a filter” – error on scanning LVM devices
The Problem Getting following error message after configuring lvm filter in CentOS/RHEL7. WARNING: Device for PV [] not found or rejected by a filter. Lvm filter configured as below. These filter settings gets change on reboot. filter = [ "a|/dev/emcpower.*|", "r|.*|" ] Can't scan lvm metadata from powerpath devices if lvm filter configured to accept all devices. LVM not accepting or scanning emcpower or third party multipath device names. The Solution When the lvmetad daemon is … [Read more...] about “WARNING: Device for PV [] not found or rejected by a filter” – error on scanning LVM devices
How to remove mirroring in Logical Volume and remove a PV
Question: We have a mirrored logical volume and need to remove one PV from the logical volume. --- Logical volume --- LV Name /dev/oravg/oralv VG Name oravg LV UUID oXzD0c-e7Tq-ZDAx-Uqdc-Xl8w-1Jxd-8e1awA LV Write Access read/write LV Status available # open 1 LV Size 29.90 GB [...] --- Physical volumes --- PV Name /dev/emcpowere PV UUID … [Read more...] about How to remove mirroring in Logical Volume and remove a PV
How to Configure Multiple Fencing-device Levels in Pacemaker Cluster
Configuring storage fencing Next, to configuring fencing to power-cycle a node (or to simply turn it off), fencing can also be configured to shut a faulty node off from shared storage. This is called storage fencing or SCSI fencing. SCSI fencing is implemented in the Red Hat Enterprise Linux High Availability Add-on using the fence_scsi fencing agent. When fence_scsi is used, whenever a cluster node starts it will create a SCSI reservation for itself using a key. Once one or more keys are … [Read more...] about How to Configure Multiple Fencing-device Levels in Pacemaker Cluster
Configuring Network Redundancy for PaceMaker Cluster Communication
What is Redundant Ring Protocol Redundant Ring Protocol (RRP) is a communication protocol where corosync can use two separate networks to establish connections between cluster nodes. When one network fails, communication can continue over the second network. RRP is not a replacement for network channel bonding; instead, bonded interfaces can be used to connect to the two rings for further redundancy. Where bonded interfaces protect against hardware failures (NIC, network cable, switch), RRP … [Read more...] about Configuring Network Redundancy for PaceMaker Cluster Communication
How to configure a GFS2 Pacemaker cluster resource
GFS2 cluster resources Global File System 2 (GFS2) file systems should not be mounted automatically at boot through the configuration of /etc/fstab. Instead, a Pacemaker resource group should be set up that automatically mounts the GFS2 resources on appropriate nodes when the supporting cluster infrastructure starts up. Using a Pacemaker cluster file system resource to manage GFS2 file systems allows Pacemaker to manage and control the GFS2 file system resource in the same way as other … [Read more...] about How to configure a GFS2 Pacemaker cluster resource
How to restore a volume group and its logical volumes in LVM after a disk (physical volume) is failed/corrupted
NOTE: These instructions should be used with extreme caution, and only if you are familiar with the implications of each command, the current layout of the volumes, the layout that you need to achieve, and the contents of the backup metadata file. These commands have the potential to corrupt data, and as such, it is recommended that you contact your Support Services for assistance in troubleshooting. This procedure requires a recent backup of the LVM configuration. This can be generated with … [Read more...] about How to restore a volume group and its logical volumes in LVM after a disk (physical volume) is failed/corrupted
LVM commands are not displaying the expected physical volume, volume group, or logical volume
Problems of this nature are most often caused by an incorrect filter in /etc/lvm/lvm.conf. The default filter scans any and all devices in /dev, so if a problem is encountered with devices not being found, it is often helpful to revert to this default filter: filter = [ "a/.*/" ] Now run the same commands again and see if the volume is found. If so, then modification to the filter may be needed to properly scan the appropriate physical volumes. If the filter is not causing the issue, and … [Read more...] about LVM commands are not displaying the expected physical volume, volume group, or logical volume
How to add a physical disk to a volume group to extend a logical volume using lvm
The following steps assume you have an existing system using the Logical Volume Manager (LVM). If a volume group has no more usable space then it is possible to increase the volume groups usable space by adding a physical volume to the volume group, which in turn will allow you to increase a logical volume. Check with the following commands to evaluate the physical volume free space: # pvs # pvdisplay Check with the following commands to evaluate the volume groups free space: # vgs # … [Read more...] about How to add a physical disk to a volume group to extend a logical volume using lvm
LVM : Need to prevent the activation of a volume group at boot
LVM volume group activation can be prevented by using the vgexport command. This command adds a tag to the LVM metadata that informs LVM to ignore the volume group. To remove the export tag, the vgimport command should be used. Then the volume group can be activated once again. 1. The logical volumes must be deactivated for the volume group to be exported. # vgchange -an testvg 0 logical volume(s) in volume group "testvg" now active 2. Export the volume group oncec it is … [Read more...] about LVM : Need to prevent the activation of a volume group at boot