I backed up my 320GB hard drive to a file with dd:
Code:
dd if=/dev/sda of=dev_sda.17-Mar-2012 bs=1048576
The main idea was to be able to be able to completely replace my hard drive from this backup if necessary, but I'd also like to be able to restore individual files. I realize I could use this dd technique to backup each partition separately (there are six partitions on there), and then use the loopback device to mount those individual files, but I'd like to just have a single backup of the entire disk that can be used to both replace the disk and to restore individual files.
So, I'm imagining making this file available as some new device file, say, /dev/sdax, and then seeing /dev/sdax1, /dev/sdax5, /dev/sdax6, etc, and then being able to mount each of those. Or, how else can I get at the individual files in that 320GB backup file?
What's your Operating System? Syntax for creating loop devices changes over Operating Systems (Linux uses losetup while Solaris uses lofiadm).
Anyway, assuming you are using Linux, you may execute the following command to mount the filesystem image:
Code:
# first check which loop device is free; it shows the first free loop device
losetup -f
# connect the loop device (say loop0) to the image
losetup /dev/loop0 /path/to/dev_sda.17-Mar-2012
mount /dev/loop0 /mnt
# when you are done, unmount the filesystem and detach the loop device
umount /mnt
losetup -d /dev/loop0
Or, you can do this with one command:
Code:
mount -t ext3 -o loop /path/to/dev_sda.17-Mar-2012 /mnt
mount -t ext3 -o loop /path/to/dev_sda.17-Mar-2012 /mnt
I've tried that (actually, -t ext4), but:
Code:
mount: wrong fs type, bad option, bad superblock on /dev/loop0,
missing codepage or helper program, or other error
I also tried without -t. I think the reason is that I used dd to copy the entire disk, not individual partitions. That is, I used "if=/dev/sda" as opposed to "if=/dev/sda1". /dev/sda itself doesn't have a filesytem, right?
I could copy at the partition level, but I want to copy at the disk level because I want to get the boot sector so I can use this backup to replace the entire hard drive, but I also want to use this backup to restore individual files.
Now, I guess I just can't get the offset right. Trying to mount partition number 5:
Code:
# losetup -o 16GB /dev/loop1 /path/to/dev_sda.17-Mar-2012
# mount /dev/loop1 /mnt
NTFS signature is missing.
Failed to mount '/dev/loop1': Invalid argument
The device '/dev/loop1' doesn't seem to have a valid NTFS.
Maybe the wrong device is used? Or the whole disk instead of a
partition (e.g. /dev/sda, not /dev/sda1)? Or the other way around?
You don't need to use losetup to use loop devices anymore, just -o loop.
A wild guess of 16GB isn't going to have the precision necessary to hit the beginning of a partition. You should be giving it a length, too. fdisk -ul to make it display in 512-byte blocks, and then use those to figure out the exact offset.
Here's an example using an old disk image I happened to have around:
Code:
$ /sbin/fdisk -ul gorgon-aug-7.img
You must set cylinders.
You can do this from the extra functions menu.
Disk gorgon-aug-7.img: 0 MB, 0 bytes
16 heads, 63 sectors/track, 0 cylinders, total 0 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Device Boot Start End Blocks Id System
gorgon-aug-7.img1 * 63 98783 49360+ 83 Linux
gorgon-aug-7.img2 98784 1099727 500472 82 Linux swap / Solaris
Partition 2 has different physical/logical endings:
phys=(1023, 15, 63) logical=(1090, 15, 63)
gorgon-aug-7.img3 14772240 39102335 12165048 5 Extended
Partition 3 has different physical/logical beginnings (non-Linux?):
phys=(1023, 15, 63) logical=(14655, 0, 1)
Partition 3 has different physical/logical endings:
phys=(1023, 15, 63) logical=(38791, 15, 63)
gorgon-aug-7.img4 1099728 14772239 6836256 83 Linux
Partition 4 has different physical/logical beginnings (non-Linux?):
phys=(1023, 15, 63) logical=(1091, 0, 1)
Partition 4 has different physical/logical endings:
phys=(1023, 15, 63) logical=(14654, 15, 63)
gorgon-aug-7.img5 14772303 16237871 732784+ 83 Linux
gorgon-aug-7.img6 16237935 39102335 11432200+ 83 Linux
Partition table entries are not in disk order
# Partition 1 starts at 63. In bytes that's 63*512 = 32256 bytes.
# Partition 1 ends at 98783, so is 98783-63 long, i.e. 50544640 bytes.
$ sudo mount -o loop,offset=32256,sizelimit=50544640 gorgon-aug-7.img mnt
$ ls mnt
System.map-2.6.34-gentoo-r1 grub vmlinuz-2.6.34-gentoo-r1
boot lost+found
config-2.6.34-gentoo-r1 memtest86
$
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