Note:

This tutorial is available in an Oracle-provided free lab environment.
It uses example values for Oracle Cloud Infrastructure credentials, tenancy, and compartments. When completing your lab, substitute these values with ones specific to your cloud environment.

Use ReaR to Perform an Oracle Linux Backup

Introduction

Relax-and-Recover (ReaR) was born in 2006 by Gratien D’haese and Schlomo Schapiro as part of a complete rewrite of an earlier Linux Disaster Recovery project mkCDrec. ReaR is an Open Source bare metal disaster recovery solution that Oracle Linux (OL) provides natively. It produces a bootable image that can recreate the system’s original storage layout and restore from the backup.

ReaR is directly available from the Application Streams repository in Oracle Linux 8 or later and is simple to deploy and configure.

This tutorial guides users on installing and configuring ReaR to backup and restore Oracle Linux using NFS storage.

Objectives

At the end of this tutorial, you should be able to do the following:

Install the ReaR package
Configure ReaR to exclude specific filesystems, mount points, and Logical Volumes that are not needed
Perform a ReaR backup using NFS storage as a backup repository
Verify the ReaR client backup on the NFS storage
Perform a ReaR recovery

Prerequisites

An Oracle Linux system as the ReaR client
An NFS server as the backup storage location
Another system for the recovery

The free lab environment uses KVM to provide virtual machines for the three required systems.

See the Create VMs with KVM on Oracle Linux tutorial for details on installing KVM on Oracle Linux.

Verify Virtual Machine Creation

Note: When using the free lab environment, see Oracle Linux Lab Basics for connection and other usage instructions.

Information: The free lab deploys a running Oracle Linux KVM environment with two VMs. The deployment takes approximately 10 minutes to finish after launch. Therefore, you might want to step away while this runs and promptly return to complete the lab.

Open a terminal and connect via ssh to the ol-kvm node.
```
ssh oracle@<hostname or IP address>
```

Get a list of running VMs.

sudo virsh list

Example Output:

[oracle@ol-vbox ~]$ sudo virsh list
 Id   Name         State
----------------------------
 1    ol9-nfs      running
 2    ol9-client   running

Get the IP address of the ol9-nfs VM.

sudo virsh net-dhcp-leases default

Example Output:

[oracle@ol-vbox ~]$ sudo virsh net-dhcp-leases default
 Expiry Time           MAC address         Protocol   IP address           Hostname     Client ID or DUID
--------------------------------------------------------------------------------------------------------------
 2023-05-28 19:56:44   52:54:00:6d:c7:e0   ipv4       192.168.122.37/24    ol9-client   01:52:54:00:6d:c7:e0
 2023-05-28 19:55:50   52:54:00:78:7c:eb   ipv4       192.168.122.181/24   ol9-nfs      01:52:54:00:78:7c:eb

Another way to get the IP address of a VM is using sudo virsh domifaddr <vm_name>.

Upgrade the ol9-nfs VM to the current release.
```
ssh opc@$(sudo virsh -q domifaddr ol9-nfs | awk '{ print $4 }' | cut -d "/" -f 1) sudo dnf upgrade -y
ssh opc@$(sudo virsh -q domifaddr ol9-nfs | awk '{ print $4 }' | cut -d "/" -f 1) sudo reboot
```
The embedded command above retrieves the IP address and passes it directly to ssh, after trimming out the headers (-q) and other data using awk and cut. Then ssh remotely runs the command to upgrade the system and reboot.

Repeat the upgrade steps for the ol9-client VM.

ssh opc@$(sudo virsh -q domifaddr ol9-client | awk '{ print $4 }' | cut -d "/" -f 1) sudo dnf upgrade -y
ssh opc@$(sudo virsh -q domifaddr ol9-client | awk '{ print $4 }' | cut -d "/" -f 1) sudo reboot  

Install and Configure NFS

Using the ol9-nfs VM, install and configure the NFS server.

Connect to the ol9-nfs VM.

ssh opc@$(sudo virsh -q domifaddr ol9-nfs | awk '{ print $4 }' | cut -d "/" -f 1)

Install the NFS Utilities package.
```
sudo dnf install -y nfs-utils
```
Create a directory for the NFS share.
```
sudo mkdir /storage
```

Create the NFS export.

sudo tee -a /etc/exports > /dev/null <<'EOF'
/storage *(rw,no_root_squash)
EOF

Add firewall rules to allow NFS traffic.

sudo firewall-cmd --permanent --add-service=nfs
sudo firewall-cmd --reload

Enable and start the NFS server.
```
sudo systemctl enable --now nfs-server
```
Show the NFS export options.
```
sudo exportfs -s
```
See the exports(5) manual page for details on these options. Using the showmount command with the latest versions of Oracle Linux is not recommended, as it defaults to using NFSv4. With NFSv4, the showmount command does not return any data.
Disconnect from the ol9-nfs VM.
```
exit
```

Install, Configure, and Run ReaR

Connect to the ol9-client VM.

ssh opc@$(sudo virsh -q domifaddr ol9-client | awk '{ print $4 }' | cut -d "/" -f 1)

Install the ReaR package.
```
sudo dnf install -y rear grub2-efi-x64-modules nfs-utils
```
This command installs the ReaR package and necessary dependencies. The grub2-efi-x64-modules is required on systems that use EFI, such as the free lab environment.
Configure ReaR.

This specific ReaR configuration file uses modifications based on the free lab environment. When running ReaR outside the free lab environment, users should modify this file using parameters suitable for their environment, including the IP address, NFS mount point, export name, backup directory exclusions, etc.

Important: Replace the xx in the IP address for both the OUTPUT_URL and BACKUP_URL with the last digits of the IP address of the free lab environments ol9-nfs VM.
```
sudo tee -a /etc/rear/local.conf > /dev/null <<'EOF'

OUTPUT=ISO
OUTPUT_URL=nfs://192.168.122.xx/storage
ISO_DEFAULT=manual
BACKUP=NETFS
BACKUP_URL=nfs://192.168.122.xx/storage
BACKUP_PROG_EXCLUDE=("${BACKUP_PROG_EXCLUDE[@]}" '/media' '/var/tmp' '/var/crash')
NETFS_KEEP_OLD_BACKUP_COPY=y
USE_DHCLIENT=y
EOF
```
Note: When adding paths to the BACKUP_PROG_EXCLUDE variable, be sure to keep the defaults by adding the ${BACKUP_PROG_EXCLUDE[@]} in the list. Omitting the defaults may cause the restored system not to boot.

ReaR documents the configuration variables in /usr/share/rear/conf/default.conf while documenting example templates in /usr/share/rear/conf/examples/. Do not modify these files directly, and instead overrule those variables needed by defining them in the /etc/rear/sites.conf or the /etc/rear/local.conf files.
Test the ReaR configuration syntax.

Users should treat the ReaR configuration files as Bash scripts, as the program sources the configuration files during runtime and breaks if any Bash syntax errors exist.
```
sudo bash -n /etc/rear/local.conf
```
If Bash reports any errors, fix the syntax and test again.

Perform the ReaR Backup.

sudo rear -d mkbackup

Wait for the backup to complete. The resulting output should look similar to the following:

Example Output:

[opc@ol9-client ~]$ sudo rear -d mkbackup
Relax-and-Recover 2.6 / 2020-06-17
Running rear mkbackup (PID 2696)
Using log file: /var/log/rear/rear-ol9-client.log
Running workflow mkbackup on the normal/original system
Using backup archive '/var/tmp/rear.10orO0oAXWuOgQf/outputfs/ol9-client/backup.tar.gz'
Using autodetected kernel '/boot/vmlinuz-5.15.0-3.60.5.1.el9uek.x86_64' as kernel in the recovery system
Creating disk layout
Using guessed bootloader 'GRUB' (found in first bytes on /dev/vda)
Verifying that the entries in /var/lib/rear/layout/disklayout.conf are correct ...
Creating recovery system root filesystem skeleton layout
Adding net.ifnames=0 to KERNEL_CMDLINE
Adding biosdevname=0 to KERNEL_CMDLINE
Handling network interface 'eth0'
eth0 is a physical device
Handled network interface 'eth0'
Cannot include default keyboard mapping (no 'defkeymap.*' found in /lib/kbd/keymaps)
Copying logfile /var/log/rear/rear-ol9-client.log into initramfs as '/tmp/rear-ol9-client-partial-2023-05-31T12:19:48+00:00.log'
Copying files and directories
Copying binaries and libraries
Copying all kernel modules in /lib/modules/5.15.0-3.60.5.1.el9uek.x86_64 (MODULES contains 'all_modules')
Copying all files in /lib*/firmware/
Skip copying broken symlink '/etc/mtab' target '/proc/10353/mounts' on /proc/ /sys/ /dev/ or /run/
Ignoring irrelevant broken symlink /usr/lib/modules/5.15.0-3.60.5.1.el9uek.x86_64/build
Ignoring irrelevant broken symlink /usr/lib/modules/5.15.0-3.60.5.1.el9uek.x86_64/source
Testing that the recovery system in /var/tmp/rear.10orO0oAXWuOgQf/rootfs contains a usable system
Creating recovery/rescue system initramfs/initrd initrd.cgz with gzip default compression
Created initrd.cgz with gzip default compression (88819621 bytes) in 8 seconds
Making ISO image
Wrote ISO image: /var/lib/rear/output/rear-ol9-client.iso (100M)
Copying resulting files to nfs location
Saving /var/log/rear/rear-ol9-client.log as rear-ol9-client.log to nfs location
Copying result files '/var/lib/rear/output/rear-ol9-client.iso /var/tmp/rear.10orO0oAXWuOgQf/tmp/VERSION /var/tmp/rear.10orO0oAXWuOgQf/tmp/README /var/tmp/rear.10orO0oAXWuOgQf/tmp/rear-ol9-client.log' to /var/tmp/rear.10orO0oAXWuOgQf/outputfs/
ol9-client at nfs location
Making backup (using backup method NETFS)
Creating tar archive '/var/tmp/rear.10orO0oAXWuOgQf/outputfs/ol9-client/backup.tar.gz'
Archived 376 MiB [avg 10132 KiB/sec] OK
Archived 376 MiB in 39 seconds [avg 9872 KiB/sec]
Exiting rear mkbackup (PID 2696) and its descendant processes ...
Running exit tasks
You should also rm -Rf --one-file-system /var/tmp/rear.10orO0oAXWuOgQf

With the backup complete, simulate a failure in the ol9-client VM.
```
sudo rm -rf /lib
```
This change may cause the VM to fail after reboot and provides a reference point to check after recovery.
Exit the ol9-client VM.
```
exit
```

Verify the backup files exist on the NFS server.

ssh opc@$(sudo virsh -q domifaddr ol9-nfs | awk '{ print $4 }' | cut -d "/" -f 1) "sudo ls -al /storage/ol9-client"

Example Output:

[oracle@ol-kvm ~]$ ssh opc@$(sudo virsh -q domifaddr ol9-nfs | awk '{ print $4 }' | cut -d "/" -f 1) "sudo ls -al /storage/ol9-client"            
total 494168
drwxr-x---. 2 root root       155 Jun  1 12:38 .
drwxr-xr-x. 3 root root        24 Jun  1 12:37 ..
-rw-------. 1 root root   2032510 Jun  1 12:38 backup.log
-rw-------. 1 root root 399333695 Jun  1 12:38 backup.tar.gz
-rw-------. 1 root root       202 Jun  1 12:37 README
-rw-------. 1 root root 104531968 Jun  1 12:37 rear-ol9-client.iso
-rw-------. 1 root root    112013 Jun  1 12:37 rear-ol9-client.log
-rw-------. 1 root root         0 Jun  1 12:38 selinux.autorelabel
-rw-------. 1 root root       274 Jun  1 12:37 VERSION

Recover using ReaR

A successful backup is only good when its recovery works. Without testing the recovery process, users are just guessing, leading to a recipe for disaster.

Copy the ReaR recovery ISO to the host system.
```
ssh opc@$(sudo virsh -q domifaddr ol9-nfs | awk '{ print $4 }' | cut -d "/" -f 1) "sudo cat /storage/ol9-client/rear-ol9-client.iso" > ~/rear-ol9-client.iso
```
ReaR defaults to using the hostname in the naming of files in the backup process, thus creating the ISO file with the name rear-ol9-client.iso,

Copy the ISO to the default KVM storage location.

sudo cp rear-ol9-client.iso /var/lib/libvirt/images/

Stop the client VM.
```
sudo virsh destroy ol9-client
```
This action performs a forced shutdown of the VM. Verify the VM is “shut off” by running sudo virsh list --all.

Backup the client VM configuration.

sudo virsh dumpxml ol9-client > ol9-client.xml
cp ol9-client.xml ol9-client.xml.bak

Edit the client VM XML configuration and update it to allow booting from the recovery ISO file.

Open the VM defination using vi ~/ol9-client.xml or your editor of choice. Find the OS section, add the cdrom device, and enable the boot menu.

<os>
  <type arch='x86_64' machine='pc-q35-rhel8.6.0'>hvm</type>
  <boot dev='cdrom'/>
  <boot dev='hd'/>
  <bootmenu enable='yes'/>
</os>

Edit the devices section and change the cdrom source to the name of the recovery ISO file.

...
    <disk type='file' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <source file='/var/lib/libvirt/images/rear-ol9-client.iso'/>
      <target dev='sda' bus='sata'/>
      <readonly/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>
...

Save and close the file.

Update the client VM definition.
```
sudo virsh define ~/ol9-client.xml
```
Start the client VM and connect to its console.
```
sudo virsh start ol9-client; sudo virsh console ol9-client
```
The boot menu should start the recovery process and present the Relax-and-Recover menu.

Select Recover ol9-client and follow any provided instructions. Log in to the recovery system as root without a password.
Start the recovery.
```
rear recover
```
The free lab environment requests confirmation of the disk configuration. Answer yes to the prompt and let the recovery continue.
Exit from the recovery session.
```
exit
```
Then type Ctrl+], where the ] is the closing bracket, to release control of the KVM console.

Verify the Recovery

Stop the client VM.
```
sudo virsh destroy ol9-client
```
Restore the original client VM definition.
```
sudo virsh define ~/ol9-client.xml.bak
```
This command updates the VM definition, not the contents of the associated VM disk.
Start the VM
```
sudo virsh start ol9-client
```
Connect to the ol9-client VM and list the contents of the /lib directory.
```
ssh opc@$(sudo virsh -q domifaddr ol9-client | awk '{ print $4 }' | cut -d "/" -f 1) ls -lH /lib
```
The -H option follows symlinks, which /lib is to /usr/lib on Oracle Linux.

Note: If the command fails to run, try again, as the VM may not be entirely up and running yet.

Summary

That completes this lab and demonstrates how Linux administrators can use ReaR, making it an essential tool for their Linux-based backup solutions.

For More Information

More Learning Resources

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Title and Copyright Information

Use ReaR to Perform an Oracle Linux Backup

F82527-01

June 2023