RELAX-AND-RECOVER (REAR)

When a software or hardware failure breaks the system, the system administrator faces three tasks to restore it to the fully functioning state on a new hardware environment:

 

1. Booting a rescue system on the new hardware

2. Replicating the original storage layout

3. Restoring user and system files

 

Most backup software solves only the third problem. To solve the first and second problems, use Relax-and-Recover (ReaR), a disaster recovery and system migration utility.

 

Backup software creates backups. ReaR complements backup software by creating a rescue system. Booting the rescue system on a new hardware allows you to issue the rear recover command, which starts the recovery process. During this process, ReaR replicates the partition layout and filesystems, prompts for restoring user and system files from the backup created by backup software, and finally installs the boot loader. By default, the rescue system created by ReaR only restores the storage layout and the boot loader, but not the actual user and system files.

 

Create NFS Server to store the backup image:

1. Installing NFS

[root@cdn01 ~]# yum install nfs-utils

 

2. Create folder to store the backup.

[root@cdn01 ~]#mkdir /var/nfs-share

 

3. Change the permission for folder.

[root@cdn01 ~]##chmod -R 755 /var/nfs-share/

 

4. Update the NFS configiration file.

[root@cdn01 ~]# vi /etc/exports

/var/nfs-share  *(fsid=0,rw,sync,no_root_squash,no_subtree_check,crossmnt)

[root@cdn01 ~]#

 

5. Restart the NFS Server.

[root@cdn01 ~]#systemctl restart nfs-server

 

6. Open NFS port on firewall. 

[root@cdn01 ~]#firewall-cmd --permanent --add-service=nfs

[root@cdn01 ~]#firewall-cmd --add-service=nfs

 

7. Installing ReaR package on client system

[root@cap01 ~]# yum install rear

 

8. Configuring ReaR

ReaR is configured in the /etc/rear/local.conf file. Specify the rescue system configuration by adding these lines:

 

[root@cap01 ~]# vi /etc/rear/local.conf

OUTPUT=ISO

OUTPUT_URL=nfs://cdn01/var/nfs-share

BACKUP=NETFS

BACKUP_URL=nfs://cdn01/var/nfs-share

NETFS_KEEP_OLD_BACKUP_COPY=2

[root@cap01 ~]#

 

9. Creating a backup of System

The following example shows how to create a rescue system with verbose output:

 

[root@cap01 ~]# rear -d -v mkbackup

Relax-and-Recover 2.4 / Git

Using log file: /var/log/rear/rear-cap01.log

Using backup archive '/tmp/rear.IcOaa604mQChxcF/outputfs/cap01/backup.tar.gz'

Creating disk layout

Using guessed bootloader 'GRUB' (found in first bytes on /dev/sda)

Creating root filesystem layout

Handling network interface 'ens33'

ens33 is a physical device

Handled network interface 'ens33'

Copying logfile /var/log/rear/rear-cap01.log into initramfs as '/tmp/rear-cap01-partial-2019-11-04T17:14:03+0530.log'

Copying files and directories

Copying binaries and libraries

Copying kernel modules

Copying all files in /lib*/firmware/

Creating recovery/rescue system initramfs/initrd initrd.cgz with gzip default compression

Created initrd.cgz with gzip default compression (230799147 bytes) in 34 seconds

Making ISO image

Wrote ISO image: /var/lib/rear/output/rear-cap01.iso (229M)

Copying resulting files to nfs location

Saving /var/log/rear/rear-cap01.log as rear-cap01.log to nfs location

Creating tar archive '/tmp/rear.IcOaa604mQChxcF/outputfs/cap01/backup.tar.gz'

Archived 551 MiB [avg 4243 KiB/sec] OK

Archived 551 MiB in 134 seconds [avg 4212 KiB/sec]

Exiting rear mkbackup (PID 2148) and its descendant processes

Running exit tasks

You should also rm -Rf /tmp/rear.IcOaa604mQChxcF

[root@cap01 ~]#

 

10. Download the iso image for below location and keep it on your desktop for booting the system.

 

Location of ISO image stored on client system

[root@cap01 ~]# ls -l /var/lib/rear/output/rear-cap01.iso

-rw-------. 1 root root 238555136 Nov  4 20:13 /var/lib/rear/output/rear-cap01.iso

[root@cap01 ~]

 

Location of ISO Image stored in nfs servers. 

[root@cdn01 cap01]# ls -l /var/nfs-share/cap01/rear-cap01.iso

-rw-------. 1 root root 239697920 Nov  4 17:15 /var/nfs-share/cap01/rear-cap01.iso

[root@cdn01 cap01]#

 

 Performing a System Restore.

 

To perform a restore :

 

1. Boot the with ISO image 

2. In the console interface, select the "Recover" option:

3. You are taken to the prompt:

4. Run the rear recover command to perform the restore 

5. Ensure that SELinux relabels the files on the next boot:

     # touch /mnt/local/.autorelabel

Otherwise you may be unable to log in the system, because the /etc/passwd file may have the incorrect SELinux context.

6. Reboot the server. 

For more details refer to below link.

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/system_administrators_guide/ch-relax-and-recover_rear