I have recently installed a iSCSI environment on a Ubuntu Server. In this system i have used images created with the following command:
dd if=/dev/zero of=/storage/lun1.img bs=1024k count=20000
as seen on: http://www.howtoforge.com/using-iscsi-on-ubuntu-9.04-initiator-and-target
They have then been partitioned and formated via the iSCSI initiator.
The problem i have now is that i would like to mount these images, if the iSCSI server goes down to get the data.
How do I mount these image files?
fdisk lun4.img:
Disk lun4.img: 0 MB, 0 byte
33 heads, 61 sectors/track, 0 cylinders
Units = sectors of 2013 · 512 = 1030656 byte
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Device Boot Start End Blocks Id System
lun4.img1 1 1017 1023580 83 Linux
mount -o loop,offset=512 -t ext4 lun4.img /mnt
mount: wrong fs type, bad option, bad superblock on /dev/loop0,
missing codepage or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
Best Answer
Assuming they're formatted with a filesystem your kernel supports you can mount them by using a loopback mount. A loopback mount allows you to mount a file as though it's a block device.
If you've partitioned the virtual "disks" that the image files represent you'll have to do some hackery with the
mountcommand to loopback mount the filesystems in the partitions. You can see what I'm talking about in this article. Basically, you're telling themountcommand to seek a specified offset into the file. That offset corresponds to the starting location of the partition inside the file.