Archive:RHEV en

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REAR on RedHat RHEV Environments

Deutsche Version: REAR in RedHat RHEV-Umgebungen

This page describes both backup and restore of several Virtual Machines for disaster recovery purposes. The process has been tested SEP sesam 4.2.2.18 and later.

Saving the machine settings

For all shown cases it is necessary to take notes of the VM configuration (including settings about CPU/Memory assignment, Size of attached harddrives, network settings etc). We recommend to do this before starting to configure the backup for this is essentially important to do a successful restore.


Backing up

The procedure in this section creates a backup of the guest operating systems on the RedHat Enterprise Virtualization Environment.


RedHat Enterprise Linux 5 and 6, CentOS 6

syslinux package on RHEL 6

Please note that the package syslinux has to be installed on RedHat Enterprise Linux 6 in order to create the bootable *.iso file.

Requirements for a working Bare System Recover backup are:

The following procedure requires a working SEP sesam setup of the client, meaning that the ability to make backups has to be given.


  • Backup task creation

As on windows server operating systems, two backup tasks have to be created using the GUI:

One task using the Linux BSR option

Rhel5-b bsr.jpg


and one using the complete filesystem option

Rhel5-b all.jpg


  • Start the backup tasks

The two backup tasks "rhel5-bsrguide_all" and "rhel5-bsrguide_bsr" can either be started using the GUI or by assigning them to a schedule in the SEPuler. For further information on the schedule, see Sesam Quick Install Guide - Step 5 Schedules.

After the two backup jobs have completed, a complete system backup is present.

Don't forget to create the bootable media!

The bootable, client-specific *.iso file for the disaster recovery environment is stored in /var/opt/sesam/var/lib/rear/var/lib/rear/output/rear-[hostname].iso on the client. Please store it in a safe location to have the media required for the restore process.




Restoring

RedHat Enterprise Linux 5 and 6, CentOS 6

  • When the RHEV environment has failed, a complete restore has to be done. After setting up the new hypervisor, upload the SEP sesam rear *.iso file to the environment using the command:
[root@rhevm ~]# rhevm-iso-uploader --iso-domain=ISO_DOMAIN upload /path/to/rear-hostname.iso 
  • Re-create the virtual machine you want to restore. Therefor, use the original configuration values recorded before starting the backup.

Rhel5-r vmcreation-1 en.jpg

  • In the start options, choose the virtual CD drive to be the first boot option and attach the *.iso image.

Rhel5-r vmcreation-2 en.jpg

  • Re-create the virtual hard drive(s):

Rhel5-r vmcreation-disk en.jpg

  • Power on the VM and enter its console. You should now see the following:

Rear restore 1.jpg

Networking

During bootup the system will provide you with a selection of network interfaces. Choose the right network interface which is needed to ensure connectivity with your backup server. The IP configuration of the original system will be used:


Rear restore 2.jpg


Login to the disaster recovery console

After the system has finished booting you can login to the disaster recovery console with the username "root" and no password. The disaster recovery console is also reachable via SSH, in case you have to login remotely. The recovery process can be started with the command "rear recover" just as shown in this screenshot:


Rear restore 3.jpg


Restoring disk information

The disk restore wizard will suggest a local disk to be partitioned, select the appropriate disk to be used:


Rear restore 4.jpg


Confirm the disk layout configuration:


Rear restore 5.jpg


Start the recovery and let the recovery console create the filesystems and partitions:


Rear restore 6.jpg


Rear restore 7.jpg


The recovery routine processed so far creates a mountpoint "/mnt/local". This will be the restore target for the next step: The restore of the filesystem backup.

Restoring the original filesystem

In the SEP sesam GUI, create a new Restore Task for the client that has to be restored. For most szenarios, all options (excepting the last page) can be left at the default values.

Rhel5-r all step2.jpg

Select the filesystem backup you want to restore and check "complete restore of selected task":

Rhel5-r all step3.jpg

Restore target must be set to /mnt/local/

The restore target must be changed from the default value "all" to the new target "/mnt/local/" on the recovery console

Rhel5-r all step4.jpg


When the Restore Task has completed, exit the rear recovery procedure on the client typing "exit" into the console and shutdown the appliance afterwards.


It is now necessary to remove the bootable media from the VM's drive and set the virtual HDD as first boot option:

Rhev vm startoptions en.jpg


Power on the appliance after saving the changes. The restore is now officially done, the system is going to boot to the state of the backup.

Necessary adjustments on RedHat Enterprise Linux 6 or CentOS 6

When using one of the above mentioned operating systems, there is a possibility of the machine failing to boot after recovery. This occurs when SELinux was set to 'enforcing' during the system backup. So on RHEL6 and CentOS, follow these steps after rebooting from the REAR recover:

  • Press a key when prompted by the boot loader (GRUB):

Rhelcentos grub1.jpg


  • Select the appropriate boot loader entry:

Rhelcentos grub2.jpg


  • Press 'e' to edit the commands for the selected entry:

Rhelcentos grub3.jpg


  • Add 'selinux=0' to the commands:

Rhelcentos grub4.jpg


  • Press 'Enter' to confirm the changes and 'b' to boot up the machine with SELinux disabled.

When having access to the system, change the option SELINUX of /etc/selinux/config to the following:

SELINUX=permissive

Afterwards, reboot the system and feel free to set the SELINUX value back to 'enforcing' if needed.




Troubleshooting

If the following "ERROR: SMS0004: The specified device does not exist." occurs on a Windows operating system, please reinstall the software package "CBMR x.x SEP Sesam Version".

Known Issues

Sesam client will not start on RHEL6/CentOS6 based recovery images

The Sesam client will not automatically start on RHEL6 based Recovery images as the file "/etc/init.d/functions" is missing within the recovery image. The client can be started manually via:

/opt/sesam/bin/sesam/sm_main start

Further documentation

  • For further information about Relax and Recover see here