System Recovery Procedures: Linux Server

Was busy lately studying, learning and applying project management stuffs now will be using my systems hat for system recovery procedures for UNIX/Linux I will start with Linux Platform.

Purpose of this how-to is only to recover the OS data on same server at minimal amount of time and to bring the system to previous working condition with acceptable level of RTO.  In scope only is recovery from same hardware server model. 

Pre-Conditions:

1.  Restore the required OS data and directories (/, /usr, /var, /home..etc)  to different server in the same network if there was no backup of data in local hard drive.
2.  Do tar backup of OS data to make the easy transfer to source server and from destination server

Preparation Checklist:
1. Make sure you have MAC address/IP details and Hard Disk details of source server.  (get the details from centralized server)
2. Download same level of RHEL boot CD/DVD.
3. Use iLO/RSA management remote virtual media if you don’t use PXE boot to avoid physical presence in DC during recovery process.

Recovery Procedure:
5. Power on the server and configure boot order so that it will boot from CD or PXE NIC adapter.
6. Boot the OS into rescue mode (type: linux rescue in the boot prompt)
7. Configure the NIC adapter with IP address, subnet mask and default gateway.

#ifconfig eth0 <192 .168.2.2=""> netmask <255 .255.255.0=""> up
#route add default gw <192 .168.1.10="">  
#ping

8. Access the correct Hard disk and do the partition layout using fdisk and create LVM configuration using lvm and place the filesystem/swap space on partition/logical volume.

Example:
#fdisk /dev/sda  ##(create three partitions sda1,sda2,sd3 ), n – to create new partion , t – to change type ( 82 for Linux swap and 8e for LVM) , a – to enable boot flag
#mkfs.ext3 /dev/sda1  ; e2label /dev/sda1 /boot 
#mkswap /dev/sda2 
#lvm pvcreate /dev/sda3 
#lvm vgcreate –s 32M vg_root_01 /dev/sda3
#lvm lvcreate -l --name lv_root vg_root_01
#mkfs.ext3 /dev/rootvg/lv_root
#mkdir /recover
#mount /dev/rootvg/lv_root /recover


9. Restore the tar file from remote server

#cd /recover
#ssh user@remote-server dd if=file.tar.gz  | tar –zxvf  -

10. Install the GRUB boot loader in the hard disk

#/recover/sbin/grub
grub>geometry (hd0,0)
grub>root (hd0,0)
grub>setup (hd0)
grub>quit

11. Verify /recover/etc/filesystems and /recover/etc/modprobe.conf

12. Reboot the system and Boot from Hard Disk