Relax-and-Recover (ReaR)

RHEL 7.9 (Maipo)

Setting up NFS server

・ Configuring NFS Server on Linux

Installing ReaR

~]# yum install rear nfs-utils

・ Configuring Yum Repositories

Configuring ReaR

ReaR is configured in the /etc/rear/local.conf file.

~]# cat >> /etc/rear/local.conf << EOF
OUTPUT=ISO
OUTPUT_URL=nfs://192.168.3.112/nfs
BACKUP=NETFS
BACKUP_URL=nfs://192.168.3.112/nfs
BACKUP_PROG_EXCLUDE=("${BACKUP_PROG_EXCLUDE[@]}" '/media' '/var/tmp' '/var/crash')
NETFS_KEEP_OLD_BACKUP_COPY=
EOF

On a UEFI system, RHEL bootloaders need to be used by ReaR.

~]# [ /sys/firmware/efi ] && echo UEFI || echo BIOS
UEFI

~]# yum -y install grub2-efi-x64-modules

~]# cat >> /etc/rear/local.conf << EOF
UEFI_BOOTLOADER=/boot/efi/EFI/redhat/grubx64.efi
SECURE_BOOT_BOOTLOADER=/boot/efi/EFI/redhat/shimx64.efi
EOF

Ensure that NFS traffic is allowed through.

~]# firewall-cmd --permanent --add-service=nfs
~]# firewall-cmd --reload

Creating Rescue Media and Backup System

~]# rear -d -v mkbackup
Relax-and-Recover 2.4 / Git
Using log file: /var/log/rear/rear-localhost.log
Using backup archive '/tmp/rear.tidkk4ynvLutuCB/outputfs/localhost/backup.tar.gz'
Creating disk layout
Using guessed bootloader 'GRUB' (found in first bytes on /dev/sda)
Creating root filesystem layout
Handling network interface 'ens192'
ens192 is a physical device
Handled network interface 'ens192'
To log into the recovery system via ssh set up /root/.ssh/authorized_keys or specify SSH_ROOT_PASSWORD
Copying logfile /var/log/rear/rear-localhost.log into initramfs as '/tmp/rear-localhost-partial-2026-05-19T15:35:39+0800.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 (273231843 bytes) in 38 seconds
Making ISO image
Wrote ISO image: /var/lib/rear/output/rear-localhost.iso (270M)
Copying resulting files to nfs location
Saving /var/log/rear/rear-localhost.log as rear-localhost.log to nfs location
Creating tar archive '/tmp/rear.tidkk4ynvLutuCB/outputfs/localhost/backup.tar.gz'
Archived 870 MiB [avg 6606 KiB/sec] OK
Archived 870 MiB in 136 seconds [avg 6557 KiB/sec]
Exiting rear mkbackup (PID 17951) and its descendant processes
Running exit tasks
You should also rm -Rf /tmp/rear.tidkk4ynvLutuCB

# On nfs server:
~]$ sudo ls -l /nfs/localhost/
total 1328764
-rw------- 1 root root 698335232 May 19 15:38 backup.tar.gz
-rw------- 1 root root       202 May 19 15:36 README
-rw------- 1 root root 282212352 May 19 15:36 rear-localhost.iso
-rw------- 1 root root    754860 May 19 15:36 rear-localhost.log
-rw------- 1 root root       278 May 19 15:36 VERSION

The localhost is hostname.

Scheduling ReaR

~]# contab -e
0 22 * * 1-5 root /usr/sbin/rear mkbackup

Performing Restore System

1. Burn the bootable ISO image to a CD or DVD.

2. Boot the server from the recovery medium.

3. Select Recover . Here, the hostname is the client system's hostname.

4. Login as root without password.

5. Run the following command to restore the backup to this server:

~]# rear -d -v recover

6. Reboot the server and start from the local hard disk.

Reference

・ What is Relax and Recover(ReaR) and how to use it for disaster recovery?