Tuesday, August 31, 2010

Ntfsclone, Backup/Restore ntfs partitions

So i did a fresh install of xp and installed a couple apps and wanted to make an appropriate backup image using linux. Being the Backtrack user that i am, the popular choice of backup/imaging known to me at the time were the programs dd or partimage. For my purposes, dd would'nt be a valid choice as it will back up used space as well as unused space, so i was left with partimage.

Partimage is a great program, but support for ntfs file systems were experimental. However, i proceeded to try it out and all went fine, the backup was succesful. However, i didn't want to risk trying a restore and lose everything on that partition (as docs said the support for ntfs was experimental). I then turned to google to find a reasonable alterative.

A few minutes after, i learned of ntfsclone (and its already installed on backtrack 4 as well). Ntfsclone will do as the name says, clone ntfs drives. You can clone to an image file, disk or stdout (useful for piping to programs like split, gzip, bzip etc) . It had the major feature i was looking for that was also present in partimage; the ability to backup only the used blocks of data on the partition and not the entire partition itself. Actually, it backs up the used space on the partition and fills the rest of the image with zero's which makes for easy compression.

Usage is quite simple

To make clone of partition 1 on device sda
# ntfsclone --save-image -o /mnt/usb/disk.img /dev/sda1

To restore image
# ntfsclone --restore-image -O /dev/sda1 /mnt/usb/disk.img //note we are using the capital O in the options to overite the destination /dev/sda1 if existing

Because of the file size limit (4G) on fat32 formatted disks, if you are cloning any drive bigger than four gigs and wanted to copy the saved image to a fat 32 disk, you will therefore run into issues. To overcome this, the following commands can be utilized.

# ntfsclone --save-image -o - /dev/sda1 | split -d -b 1000m - XPSP2.img_ // the '-' will cause ntfsclone to output to standard out. The split utility will split the data every 1000 megabytes (1 gig) from its standard in '-' and output to files with the prefix XPSP2.img_ and because of the '-d' option, numbers will be appended to the individual files. Example: XPSP2.img_01, XPSP2.img_02, XPSP2.img_03.

Just something important to note, taking from the article here:

If you want to copy, move or restore a system or boot
partition to another computer, or to a different disk or partition (e.g.
hda1→hda2, hda1→hdb1 or to different disk sector offset) then you will need to
take extra care.

Usually, Windows will not be able to boot, unless you
copy, move or restore NTFS to the same partition which starts at the same sector
on the same type of disk having the same BIOS legacy cylinder setting as the
original partition and disk had.

The ntfsclone utility guarantees to
make an exact copy of NTFS but it will never deal with booting issues. This is
by design: ntfsclone is a filesystem, not system utility. Its aim is only to
clone NTFS, not to clone Windows. Therefore ntfsclone can be used as a very fast
and absolutely reliable building block for Windows cloning, but itself it's not

Resources/Good Reading:

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