How to make an image backup of my HDD?

alibeheshti · 05-30-2007, 07:59 PM

I need to make an image backup of my HDD,I have a redhat version 9 but I dont know how I can create this image.I need to have such an image backup to be able to restore it in case of any HDD crash.

Thanks

jay73 · 05-30-2007, 08:03 PM

You could consider partimage: it will back up your system to a bunch of compressed files - it should easily fit on a single DVD as partimage, unlike many other solutions, saves only the used space on partitions.

alibeheshti · 05-30-2007, 08:17 PM

Quote:

Originally Posted by jay73

You could consider partimage: it will back up your system to a bunch of compressed files - it should easily fit on a single DVD as parimage, unlike many other solutions, saves only the used space on partitions.

how I can use patimage ? what are the other solutions than partimage ?

jay73 · 05-30-2007, 09:13 PM

Well, you could also use dd - that is a command which will copy/clone your partitions to the last individual bit. This approach tends to take quite a bit of time for larger partitions, not to mention that you waste a lot of space on your back-up medium because it copies over all the empty space as well.

Then there is the mindi/mondo couple; very reliable and it can be used as an alternative to partimage.

As for partimage, I'll let it speak for itself:

http://www.partimage.org/Main_Page

lujan · 05-30-2007, 10:23 PM

I use G4U for all my hard disk cloning and recovering needs.

jschiwal · 05-31-2007, 07:47 PM

I just tried an experiment where I created a loopback filesystem on test.img. First I added files to the mounted filesystem. Then I used gzip to compress is. Then I deleted most of the files and used gzip again. Because the patterns for the deleted files still exist on the image, the file size was the same.

Next I used dd to create a large zeroed out file using up most of the space in the filesystem. Then I deleted the file and tried compressing again. This time the filesize was a lot less. I knew it would help but I wanted to post real results:

Code:

jschiwal@hpamd64:~>ls -lh test* -d
drwxr-xr-x 18 jschiwal users 4.0K 2007-05-31 18:25 test
-rw-r-----  1 jschiwal users 2.4G 2007-05-31 10:35 test1.img.gz
-rw-r-----  1 jschiwal users 2.4G 2007-05-31 17:29 test2.img.gz
-rw-r-----  1 jschiwal users 303M 2007-05-31 18:30 test3.img.gz
-rw-r-----  1 jschiwal users 4.0G 2007-05-31 09:51 test.img

The filesystem is on test.img. Test1.img.gz is using gzip before the deletions. Test2.img.gz is the gzipped filesystem after deletions. Test3.img.gz is the gzipped filesystem after creating the large file of zero's with the command: "dd if=/dev/zero of=zero bs=1024 count=$((1024*512*31)) && rm zero". I based the count on the result of "df test/".
Before zeroing: 2.4G
After zeroing: 303M.

If I had been using a real partition, I would probably have entered the "sync" command to make sure that the cache was emptied. For such a large file, it may not be necessary.

So zeroing out most of the free space this way can dramatically reduce the size of the final backup image file.

If you use dd, you can pipe the output through gzip or bzip2 to reduce the size of the image. Restoring, you can simply use "zcat backup.img | dd of=/dev/hda1" to restore the hda1 device from a gzipped image.

This sites wiki has a page on using dd that includes backing up partitions.

Technically, you could simply redirect the output of zcat to the device. Remember that in Linux "everything is a file". "zcat backup-hda1-May15-2007.img.gz >/dev/hda1"
or
"gunzip -c backup-hda1-May15-2007.img.gz >/dev/hda1"

----

IMHO image backups are useful mainly for new installs, rather than for periodic backups. When recovering from a fatal drive problem, you can use dd using any rescue disk. If you use a large tool such as partimage, you need to make sure you have a live distro or rescue disk that contains the partimage program.
Also, you it would be easy to script the recovery of several partitions using the dd command. So after booting up with an emergency restore rescue disk, you could just start the script to restore the system to the point where you could start using a more sane backup/restore system.

Junior Hacker · 06-01-2007, 01:25 AM

jschiwal

I've got allot of useless partitions, over 60 of them, I was just going to delete them but can't find the time. Nor can I find the time to play with this, but Lord knows I will. This surely seems plausible. I have but just one question, which part of that dd command points to un-allocated sectors in a file system?. Actually, you used a bs of 1024 which is equal to two sectors, and files are written to clusters/blocks, not sectors, so it is not necessary to try and zero out individual sectors when eliminating un-allocated space in an image file, one would chase un-allocated clusters/blocks. In a fragmented file system, what part of that dd command finds un-allocated clusters/blocks/sectors.
It looks to me, that what you achieved, was to make an image of the format information, eliminating anything that could be a file in the data portion of sectors.

AwesomeMachine · 06-01-2007, 10:08 AM

See this post:

http://www.linuxquestions.org/questi...d.php?t=362506

linuxlastslonge · 06-01-2007, 11:31 AM

if you *have* to make an image of your system, i'd recommend systemimager. otherwise, i'd recommend tgz'ing up /etc and your /home dir, and call it a day.

saikee · 06-01-2007, 01:13 PM

There are tons of possibilities around but a Linux user will never know how much he/she missed out if he/she doesn't use the dd command, which is possibly the simplest, fastest and more reliable around.

Awesomemachine's thread is one of the master pieces on the subject of dd.

I hate to see gold is taken for iron in an offer.