How to install and use ReaR (Migration & Recovery tool) on CentOS 7 / RHEL 7

Install-Rear-CentOS7

ReaR or Relax & Recover is a migration & disaster recovery tool. REAR creates  a bootable image for the running Linux machine & when required same bootable image can be used to recover the system. Same image can be used to restore the OS to different hardware as well & hence REAR can also be used as a migration tool. REAR even detects the change of network cards, disk layouts or storage devices i.e. IDE to SCSI or CCISS.

REAR preserves the last condition of the OS including its partition, boot loader configuration, all the system data etc. It is successor to mkcdrc, it has been designed to simple & maintenance free. Its simple setup & forget nature make it the perfect solution for disaster recovery & migrations, in fact it is the leading open source disaster recovery solution.

In this tutorial, we will discuss how to setup REAR & use it to create a recovery of OS, store it on a NFS share & then we will restore the OS from created recovery image.

So before we proceed with REAR installation, we will create a NFS share on a remote machine for storing our recovery images.

Creating NFS share

We are using another CentOS 7 machine with IP address 192.168.0.106 for using as a NFS server. To install NFS on the machine, execute the following command,

[[email protected] ~]$  sudo yum install nfs-utils

After NFS package has been installed, we will create a directory for storing the image

[[email protected] ~]$ sudo mkdir /backup

Now we will configure the created directory for NFS share, open the NFS configuration file

Edit the file ‘/etc/exports’ and make the following entry,

[[email protected] ~]$ sudo vi /etc/exports

/backup       *(fsid=0,rw,sync,no_root_squash,no_subtree_check,crossmnt)

Once done, save the file, exit & restart the NFS service to implement the changes made,

[[email protected] ~]$ sudo systemctl restart nfs

Next we will install & configure the REAR server.

REAR installation & configuration on CentOS 7 / RHEL 7

We now need to install the packages for REAR & required packages for creating ISO image of the backup server. To install all these packages, run the following command

[[email protected] ~]$ sudo yum install rear syslinux genisoimage

Install-rear-package-CentOS7

Next we will configure the REAR server to storing the created backup ISO images on our remote NFS server. Open the REAR configuration file i.e. ‘/etc/rear/local.conf‘,

Add the below details for NFS server in the following format,

[[email protected] ~]$ sudo vi /etc/rear/local.conf
OUTPUT=ISO
BACKUP=NETFS
BACKUP_URL=nfs://192.168.0.106/backup

ReaR-Backup-Path-CentOS7

Save file & exit. We are now ready to create our first backup image of the system.

Creating Backup ISO

To create the disaster recovery of the system & generate the backup file, execute the following command,

[[email protected] ~]$ sudo rear -d -v mkbackup

REAR will now examine & gather the necessary files required  like disk layout, boot loader information etc & then will create an ISO image for OS under the directory ‘/var/lib/rear/output‘. After which all the files along with backup ISO image will be transferred to the NFS share.

ReaR-Command-mkbackup-CentOS7

Note:- This process can take some time depending on the size of the operating system.

Recovering the system

Now we need the recovery ISO (rear-localhost.iso) that was created & is available on our NFS server,

rear-localhost-iso-centos7

We will burn the ISO on CD or DVD & will boot up the system using the same. Once the system boots up with the image, we will be presented with a REAR menu,

Relax-and-Recover-Bootloader

Select the first option i.e. ‘Recover localhost‘ (‘localhost’ is the hostname of the system) & press enter. After this, we will now have our login menu, login using root without password,

Note:- We could also choose second option “Automatic Recover localhost“, but we need to make sure that there should not be any errors during recovery. Some common errors occurring during automatic recovery are due to network changes, disk layout changes etc. So if you are restoring the OS to same system, you can try out ‘Automatic Recovery‘ to automate the recovery process otherwise opt for Manual recovery.

ReaR-Rescue-Mode

Next step is to configure networking on our system as all other system related files are on our NFS share. To add an IP address, execute the following command

# ip addr add 192.168.0.50/24 dev enp0s3
# ip link set enp0s3 up

We can now access our NFS server, so we can now start the system recovery. Start recovery by executing,

# rear -d -v recover

Rear-Revover-Command-Options

Now follow the on screen instructions,

Continue-Recovery-Option-ReaR

It will now ask for HDD layout (if it differ from original), after selecting the layout start recovery by pressing ‘5‘, system recovery will now start ,

Rear-Recovery-Progress-CentOS7

Depending on system data, recovery will take some time. Once the recovery has been completed, reboot the system.

Reboot-after-Rear-Recovery

Now remove the recovery DVD from the system & let the system start. Once fully booted, you can access the system with the same credentials as before & system will have all the data & services as there were previously on your system.

This completes our tutorial on REAR, Relax & Recover . If you have any queries or questions, please so leave them in the comment box below.

5 Responses

  1. Zack says:

    Hi, I am trying to recover a kvm guest but when type ” rear -d -v recover” , it does not go forward and fails generating the following error
    mount.nfs: portmap query failed: RPC: Remote system error – Network is unreachable
    ——
    ERROR : Mount command ‘mount -v -t nfs -o nfsvers=3,nolock <nfs-server-ip:/ /tmp/rear.ZBovVKifdgtx1zE/outoutfs’ failed.
    Please advise

    • Subhasish Saha says:

      Hi Jack,

      I believe your rear export location is not properly exported. First try to mount it manually. If worked, then go for rear. From the error it seems you have port connectivity issue.

    • Vinay Gupta says:

      1. Check you have network connectivity with nfs server. : –>ping nfs_server from recovery point.
      2. Try to mount the exported filesystem -> mount -t nfs nfs_server_ip:/exported_dir /local_mount

  2. Adibb says:

    Hi,

    I already get the rear-localhost-iso, but may I know for the other like “backup.tar.gz” that your show above do i need to create this or it already been create with ” sudo rear -d -v mkbackup”

  3. Adibb says:

    Hi,
    1)I successful make “rear-localhost.iso”, do I need to make “backup.tar.gz”?
    2)Can I make pendrive as bootable instead burn to CD/DVD? because I already try use pendrive as bootable, it cannot load to “REAR” interface

    Please advise.

    Thanks

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