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Article ref. no : FS-FBS-20070817-I01
Last revised : 28 October 2014
Version: 3.2

Restore
Operating system restore from backup copy
(bare metal recovery)



A typical procedure for the recovery of the operating system onto a new hard drive

  1. Connect a new hard drive to a working computer (preferably directly to the backup server)
    1. create a new partition
    2. mark the partition as active
    3. format the partition
    4. restore all the files from the backup on the partition

  2. Connect the drive to the target computer
    1. start the computer from the installation CD and choose the repair option
    2. create a boot sector
    3. remove the installation CD
    4. restart the computer.
Explanations

1b - the partition may be marked as active in the Disk Management Console or by fdisk/diskpart command
1c - the disk can be formatted with the same file system as originally used or with another file system
2b - the boot sector should be created with the use of the Recovery Console and the command from Table 2 or with an automatic repair option built in Windows installer

All the steps of this procedure are essential when recovering the system. If any of these steps are skipped, the operating system may not start. This procedure is only an example of the proceedings. More advanced users may use other tools and other order of steps needed to start the system.



Introduction

Operating system installation, depending on system version and computer’s speed takes a half hour on the average. But that is not all. Installing applications, configuring them, configuring the system to work with the company’s local area network and restore the user’s profile and data will also take time. All of that combined may take as long as several hours. All things considered, the computer will be unusable for an entire day.

In the "Operating system backup" article we have described how to create a backup task to create a single backup or periodical backups of operating system files. If you have such a backup you can restore a functioning operating system.

Completing a disaster recovery procedure will mean the user will not need to reinstall and reconfigure the whole system, which will alleviate adverse consequences of the failure.

Drive type and partition format

Programs backing up an operating system as a disk image/partition image in addition to files also save allocation tables (FAT/MFT) and boot sectors. Therefore if the user performs operating system restore they will not be able to change the partition’s format and the drive type will have to be the same too.

Operating system backups created using Ferro Backup System are much more flexible. The drive and the format of the partition can be different from the original ones. The disk can come from another vendor, be of a different size and type. An operating system installed on an SCSI drive can be restored and booted on an S-ATA or P-ATA drive.

The size of the system partition must be sufficient to accommodate all backed up files, which is the only requirement. The file system may be different from the original one. If the user wishes to downgrade the file system to an older one, they must bear in mind that some differences exist between them. If NTFS was the original file system and the user intends to use FAT 32, the 4GB maximum file size limit existing in FAT 32 may be seen as an obstacle.

The allocation table will be automatically restored when files are copied to the new drive and the boot sectors can be recreated using one or two commands that we will discuss in further sections of this article.


See below for the three steps to restore and restart an operating system from a backup copy created using Ferro Backup System.


System partition preparation

If the disk drive on which you are planning to restore an operating system in the target PC you need to boot the PC from a Windows installation CD or a boot disk. After entering the command shell you need to run the partition management command. Depending on the system shell you are using it will be fdisk (Windows 95, Windows 98, Windows Me) or diskpart (Windows NT, Windows 2000, Windows XP, Windows 2003, Windows Vista, Windows 2008).

Command shellOperating systemCommand
MS-DOS (boot disk, installation disk)Windows 95, Windows 98, Windows Mefdisk
Recovery console (installation disk)Windows NT, Windows 2000, Windows XP, Windows 2003, Windows Vista, Windows 2008, Windows Server 2012, Windows 8diskpart

Table 1. Commands to create a system partition


If you can connect the disk drive to a PC with a functional Windows system, you can use any partitioning software.

In any case, you need to create at least one partition big enough to accommodate all files of the restored operating system. It is also vital to remember to set the newly created partition as active.

After the system partition is created, it needs to be formatted. Any file system can be used, regardless of the original file system. The FORMAT command is available both in MS-DOS and in the recovery console. It needs to be accompanied by a drive letter and the desired file system can also be selected here (e.g. format C: /FS:FAT32).

After the system partition is created and formatted, files can be unpacked from the backup copy.

Restoring files from the backup copy

Click on the Restore tab in FBS Server, select the backup copy to be restored and restore all files to the location of your choice by clicking on Unpack.

If you are restoring the operating system onto a new hard disk which is not yet installed in the target computer, you can connect it to the backup server or to another PC on the local network. When unpacking files from the backup copy, just select the newly created partition.

If the disk drive is already installed in the target PC and you don’t want to take it out, you will need to extract the files to a temporary folder and then copy them to CD/DVD media, a USB storage device or an external hard disk and transfer them to the target computer.

Creating the boot section

After the computer is turned on, BIOS will read the first sector of the boot drive, the so-called Master Boot Record (MBR). A small program stored in the MBR will then launch another small program saved in the first sector of the active partition (boot sector), which in turn will boot the operating system.

Those missing initial disk and partition sectors need to be written to the formatted disk to which you have copied the operating system files. If you attempt to boot the PC without doing so, the following message will come up:



Fig. 1 No operating system on disk selected as boot drive in BIOS

Fig. 1 No operating system on disk selected as boot drive in BIOS


In Windows 9x/Me you need to boot the PC from a boot disk or an installation CD and run the sys.com command (e.g. SYS C:). This will rewrite the Windows 95, Windows 98 or Windows Me boot section to the drive using block parameters from BIOS.

In Windows NT, Windows 2000, Windows XP and Windows 2003 you need to boot the computer from the installation CD and then proceed to the recovery console. In the command shell you need to run the fixboot command (e.g. fixboot C:). This will write a new boot sector to the system partition.

In Windows Vista and Windows 2008 the procedure is similar. You boot the PC from the installation CD and go to the recovery console. In the command shell you run the bootrec command using the fixboot switch (e.g. bootrec /fixboot). The command is the equivalent of the fixboot command from the previous Windows versions and will write a new boot sector to the system partition. If the operating system is restored to a different drive (SCSI/ATA) or a drive with geometry different from that of the original drive, you will also need to use the bootrec command with the rebuildbcd switch (e.g. bootrec /rebuildbcd). This will rebuild the BCD store, which contains hardware information required to boot the operating system.

Command shellOperating systemCommand
MS-DOS (boot disk, installation disk)Windows 95, Windows 98, Windows Mesys
Recovery console (installation disk)Windows NT, Windows 2000, Windows XP, Windows 2003fixboot
Recovery console (installation disk)Windows Vista, Windows 2008, Windows 7, Windows Server 2012, Windows 8bootrec /fixboot
bootrec /rebuildbcd (if disk type is changed)

Table 2. Commands used to create the boot section


Summary

As you can see, restoring an operating system from a backup copy is not complicated or time consuming. Restoring Windows will take depending on version from several to a dozen or so minutes, most of which will be spent on drive formatting and file copying. If any of the above steps are unclear, read the article "Operating system restore – Windows Vista (in preparation)”, where you can find more details on operating system restore.


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