Mailinglist Archive: opensuse (2912 mails)

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[SLE] ISO directory chunks--mkisofs--backup and restore
  • From: Ted Hilts <thilts@xxxxxxxxxxxxxxxx>
  • Date: Wed, 02 Feb 2005 11:00:51 -0700
  • Message-id: <42011553.6030601@xxxxxxxxxxxxxxxx>
Using my SuSE 9.1 Pro CD #1 to bring up "rescue mode" in order to create an image backup of /dev/hdb2 where Linux is located I could do the following steps:

# mount /dev/some_other_drive /mnt (as a place to store the ISO image)
# dd if=/dev/hdb2 of =/mnt/image_dir/image_file conv=noerror,sync
# mkisofs -R -l -L -A "some_label" -o /mnt/image_dir/image_file /another_drive/make_cdrom/iso_image

These 3 steps will create a true image of the entire 80Gig drive when only 8Gig of space is used. But I do not have the storage capacity to duplicate an 80 Gig drive (I have Linux on just one primary partition for the entire drive) and I don't want to create a set of DVDs or CDs with nothing on them. Apparently "dd" thinks in blocks and not directories and since fragmentation might occur I cannot assume all primary directory structures below "/", such as "/lib" and "/var" are contiguous and even if there were a way of making them contiguous I don't know how to specify the number of blocks for the "dd" command (start and end points for each directory chunk).
So it seems that a true image backup is not feasible in my case because of size and the large number of CDs required????

Therefore, I was thinking of doing the following instead (again using the rescue mode):
1. Using "cp" command I would copy the directory chunks /boot, /var, /etc, /dev, /lib and other directories one at a time over to a location on another drive (call it "drive" for now with the directory "store_here" holding each of the above directories chunks but only one at at time).
2. Each time for each directory chunk (example is "/var") I would do:
# mkisofs -R -l -L -A "some_label" -o /drive/store_here/var /another_drive/make_cdrom/iso_image

NOTE: Apparently in rescue mode there is no mkisofs command available -- only when in level 5.

Anyway, I don't this this will work -- but I don't know why???

Normally (in my experience) "var" in the directory string "/drive/store_here/var" would be a file name (not a directory structure) and would be created using "dd". So instead of step 2, if I were to first create each of these directory structures into a compressed tar ball and then run mkisofs where now -- for example -- "var" is a compressed tarball of the directory "/var" I would end up with an ISO file system for each directory that I could blast onto one or a few CDs or a single DVD. I should be able to decompress and untar the tar ball from the CD ROM and put the contents anywhere I want???

But this means I do not have a true image of /dev/hdb2 or even partial images of /dev/hdb2 because I took each directory like "/lib" and "/var" and "/boot" and so on and tar balled and compressed each of them into a single file no longer considered true image pieces of /dev/hdb2. This might be okay?

I think I answered my own question above. Anyway, let's say I've got these compressed tar balls blasted onto CD ROMS as ISO images. Could I use these CD ROMs as backup for the above mentioned directories on /dev/hdb2 so, for example, if part of "/var" on /dev/hdb2 was erased could I restore the damaged directory chunk using the CD ROM as described for that directory??? (I would be surprised to get NO for an answer because I think this is the standard UNIX process for back ups)

Further --and this is the primary concern -- let's say the drive /dev/hdb2 goes corrupt and is no longer readable. Could I use these CD ROMs (directory chunks) to reestablish the linux system on a replacement drive and would I have to create partitions for each directory chunk? I could probably use the method in QUESTION 3. But I am wondering if there are other and better ways or maybe I've missed something very important..


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