Chapter 9. Recovering and restoring a system
To recover and restore a system using an existing backup, Red Hat Enterprise Linux provides the Relax-and-Recover (ReaR) utility.
You can use the utility as a disaster recovery solution and also for system migration.
The utility enables you to perform the following tasks:
- Produce a bootable image and restore the system from an existing backup, using the image.
- Replicate the original storage layout.
- Restore user and system files.
- Restore the system to a different hardware.
Additionally, for disaster recovery, you can also integrate certain backup software with ReaR.
Setting up ReaR involves the following high-level steps:
- Install ReaR.
- Modify ReaR configuration file, to add backup method details.
- Create rescue system.
- Generate backup files.
9.1. Setting up ReaR
Use the following steps to install the package for using the Relax-and-Recover (ReaR) utility, create a rescue system, configure and generate a backup.
Necessary configurations as per the backup restore plan are ready.
Note that you can use the
NETFSbackup method, a fully-integrated and built-in method with ReaR.
Install the ReaR utility by running the following command:
# yum install rear
Modify the ReaR configuration file in an editor of your choice, for example:
# vi /etc/rear/local.conf
Add the backup setting details to
/etc/rear/local.conf. For example, in the case of the
NETFSbackup method, add the following lines:
Replace backup.location by the URL of your backup location.
To configure ReaR to keep the previous backup archive when the new one is created, also add the following line to the configuration file:
To make the backups incremental, meaning that only the changed files are backed up on each run, add the following line:
Create a rescue system:
# rear mkrescue
Take a backup as per the restore plan. For example, in the case of the
NETFSbackup method, run the following command:
# rear mkbackuponly
Alternatively, you can create the rescue system and the backup in a single step by running the following command:
# rear mkbackup
This command combines the functionality of the
9.2. Using a ReaR rescue image on the 64-bit IBM Z architecture
Basic Relax and Recover (ReaR) functionality is now available on the 64-bit IBM Z architecture as a Technology Preview. You can create a ReaR rescue image on IBM Z only in the z/VM environment. Backing up and recovering logical partitions (LPARs) has not been tested.
ReaR on the 64-bit IBM Z architecture is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process. For more information about the support scope of Red Hat Technology Preview features, see https://access.redhat.com/support/offerings/techpreview.
The only output method currently available is Initial Program Load (IPL). IPL produces a kernel and an initial ramdisk (initrd) that can be used with the
ReaR is installed.
To install ReaR, run the
yum install rearcommand
- To install ReaR, run the
Add the following variables to the
/etc/rear/local.conf to configure ReaR for producing a rescue image on the 64-bit IBM Z architecture:
To configure the
IPLoutput method, add
To configure the backup method and destination, add
BACKUP_URLvariables. For example:
BACKUP=NETFS BACKUP_URL=nfs://<nfsserver name>/<share path>Important
The local backup storage is currently not supported on the 64-bit IBM Z architecture.
Optionally, you can also configure the
OUTPUT_URLvariable to save the kernel and
initrdfiles. By default, the
OUTPUT_URLis aligned with
To perform backup and rescue image creation:
This creates the kernel and initrd files at the location specified by the
OUTPUT_URL(if set) variable, and a backup using the specified backup method.
To recover the system, use the ReaR kernel and initrd files created in step 3, and boot from a Direct Attached Storage Device (DASD) or a Fibre Channel Protocol (FCP)-attached SCSI device prepared with the
ziplboot loader, kernel, and
initrd. For more information, see Using a Prepared DASD.
When the rescue kernel and
initrdget booted, it starts the ReaR rescue environment. Proceed with system recovery.
Currently, the rescue process reformats all the DASDs (Direct Attached Storage Devices) connected to the system. Do not attempt a system recovery if there is any valuable data present on the system storage devices. This also includes the device prepared with the zipl bootloader, ReaR kernel, and initrd that were used to boot into the rescue environment. Ensure to keep a copy.