I think you have the terminology a little mixed up.
If you mount a something without supplying -o loop "mount" will assume
the filesystem resides in a DEVICE.
If you mount a something WHILE supplying -o loop you tell "mount" that
it should mount it using a loop device. Note device here, it's trickery
really as what it does is that "mount" will FIRST create a new device
node "/dev/loop0" for example and then it will mount from that device
Thanks Stefan, Now it makes real sense.
I guess I am back to my original question:
What does 'SB validate failed' indicate and what it really means to my
fdisk reports the structure of the Jaz disk as:
$ sudo fdisk -ul jaz7.img
Disk jaz7.img (SGI disk label): 255 heads, 63 sectors, 0 cylinders
Units = sectors of 1 * 512 bytes
----- partitions -----
Pt# Device Info Start End Sectors Id System
8: jaz7.img1 3072 2091007 2087936 a SGI xfs
9: jaz7.img2 0 3071 3072 0 SGI volhdr
11: jaz7.img3 0 2091007 2091008 6 SGI volume
----- Bootinfo -----
----- Directory Entries -----
0: sgilabel sector 3 size 512
I went ahead and tried to mount Partition 8 from image using the offset
and loop options of the mount command:
$ sudo mount -t xfs -o loop,offset=$((512*3072)) jaz7-partition.img /mnt
mount: wrong fs type, bad option, bad superblock on /dev/loop1,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
And system log says:
XFS: bad magic number
XFS: SB validate failed
So I am guessing I have one of these 3 cases:
1- Bad partition table, good file system
2- Good partition table, corrupt file system
3- Or both gone south!!!
I checked the man pages of 'vh' on Irix. It seems that the volhdr
partition is 'usually' 2 megabytes but the disk in question has 3072*512
Can this be a sign of corruption ?
So where would you start looking at if you wanted to fix this problem ?
Partition table or the file system ?