I'm trying to
mount and access a floppy image file in the .ima format (raw dump to floppy, similar to .img) on ArchLinux.
This file is part of a set of 30. It is not bootable, but rather a continuation of a set. The purpose is not manipulation for the sake of installation or cloning. I'm interested in the documentation contained with other data on the disk.
Image file information
Here is some info about this image file:
# file U19.IMA U19.IMA: PC formatted floppy with no filesystem # fdisk -lu U19.IMA Disk U19.IMA: 1.4 MiB, 1474560 bytes, 2880 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 (parted) print Error: /home/meh/Downloads/U19.IMA: unrecognised disk label Model: (file) Disk /home/meh/Downloads/U19.IMA: 1475kB Sector size (logical/physical): 512B/512B Partition Table: unknown Disk Flags:
Here's the generic error message:
mount -o ro,loop U19.IMA /mnt/cd/ mount: wrong fs type, bad option, bad superblock on /dev/loop0, missing codepage or helper program, or other error
I've tried many combinations trying to specify a type with -t i.e. ntfs, msdos, iso9660, vfat, and always getting that same error. I thought it's maybe some kind of ntfs file format but ntfs-3G doesn't do much better so no it's not:
# ntfs-3g -o loop U19.IMA /mnt NTFS signature is missing. Failed to mount '/home/meh/Downloads/U19.IMA': Invalid argument The device '/home/meh/Downloads/U19.IMA' 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? # ntfsclone -r -o file.img U19.IMA ntfsclone v2013.1.13 (libntfs-3g) ERROR: Input file is not an image! (invalid magic)
Someone suggested maybe a Minix fs. While it is not clear if I can really mount such a filesystem with my current configuration I tried:
mount -t minix -o loop U19.IMA /mnt/cd which gave the generic error but there was this at the bottom of the log: VFS: Can't find a Minix filesystem V1 | V2 | V3 on device loop0.
It seems this is not conclusive, as when you specify a specific type of filesystem you will have a specific type of error in the log. Also tried
# fuseiso U19.IMA /mnt/cd init: wrong standard identifier in volume descriptor 0, skipping.. init: wrong standard identifier in volume descriptor 1, skipping.. init: wrong standard identifier in volume descriptor 2, skipping.. init: wrong standard identifier in volume descriptor 3, skipping.. init: wrong standard identifier in volume descriptor 4, skipping.. init: wrong standard identifier in volume descriptor 5, skipping.. init: wrong standard identifier in volume descriptor 6, skipping.. init: wrong standard identifier in volume descriptor 7, skipping.. init: wrong standard identifier in volume descriptor 8, skipping.. init: wrong standard identifier in volume descriptor 9, skipping.. init: wrong standard identifier in volume descriptor 10, skipping.. init: wrong standard identifier in volume descriptor 11, skipping.. init: wrong standard identifier in volume descriptor 12, skipping.. init: wrong standard identifier in volume descriptor 13, skipping.. init: wrong standard identifier in volume descriptor 14, skipping.. init: wrong standard identifier in volume descriptor 15, skipping.. init: wrong standard identifier in volume descriptor 16, skipping.. init: wrong standard identifier in volume descriptor 17, exiting..
Where I can see such things with
[ 5316.082629] FAT-fs (loop0): invalid media value (0xf6) [ 5316.082644] FAT-fs (loop0): Can't find a valid FAT filesystem
lsmod | grep loop gives
loop 18511 0
There is no alternate superblock of any kind:
# mkfs -n U19.IMA mke2fs 1.42.8 (20-Jun-2013) U19.IMA is not a block special device. Proceed anyway? (y,n) y Filesystem label= OS type: Linux Block size=1024 (log=0) Fragment size=1024 (log=0) Stride=0 blocks, Stripe width=0 blocks 184 inodes, 1440 blocks 72 blocks (5.00%) reserved for the super user First data block=1 Maximum filesystem blocks=1572864 1 block group 8192 blocks per group, 8192 fragments per group 184 inodes per group
Contrary to many cases I read about, there seems to be no need to specify any offset here as there are no partition built in the image. In such cases, sometimes the
dd command is used to transfer the content to a similar image using an offset value which allows mounting. This seems the same as specifying an offset to the
mount command directly. But this should be easy, like in this other case where a simple
losetup is used and then the loop device is mounted. I can link the .ima file with losetup but when I try to mount the loop device I end up with my initial error message.
safecopy --stage1 doesn't report any issue with the data and the output up to stage 3 remains the same and yields the same error:
# safecopy U19.IMA test.img --stage1 Low level device calls enabled mode: 2 Reported hw blocksize: 4096 Reported low level blocksize: 4096 File size: 1474560 Blocksize: 4096 Fault skip blocksize: 147456 Resolution: 147456 Min read attempts: 1 Head moves on read error: 0 Badblocks output: stage1.badblocks Marker string: BaDbLoCk Starting block: 0 Source: U19.IMA Destination: test.img . ;-} 100% Done! Recovered bad blocks: 0 Unrecoverable bad blocks (bytes): 0 (0) Blocks (bytes) copied: 360 (1474560)
Here's the top of the file and the content seems to be intact:
dd if=U19.IMA | hexdump -C | head -n 10 00000000 f6 f6 f6 f6 f6 f6 f6 f6 f6 f6 f6 f6 f6 f6 f6 f6 |................| * 00004600 34 2e 30 2e 32 20 33 38 36 75 6e 69 78 20 46 6e |4.0.2 386unix Fn| 00004610 64 20 53 65 74 20 35 20 6f 66 20 31 30 0a 00 00 |d Set 5 of 10...| 00004620 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
Since a raw image consists of a sector-by-sector binary copy of the source medium, the actual format of the file contents will depend on the file system of the disk from which the image was created (such as a version of FAT).[...] Since IMG files hold no additional data beyond the disk contents, these files can only be handled by programs that can detect their file systems.
Following suggestions, I proceeded to analyze some of the other image files in the set(30):
fdisk -lu U14.IMA Disk U14.IMA: 1.4 MiB, 1474560 bytes, 2880 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 Disklabel type: dos Disk identifier: 0x00000000 This doesn't look like a partition table. Probably you selected the wrong device. Device Boot Start End Blocks Id System U14.IMA1 3840 11519 3840 0 Empty U14.IMA2 2425393152 4850786447 1212696648 0 Empty U14.IMA3 ? 2425393296 4850786591 1212696648 90 Unknown U14.IMA4 ? 2425393296 4850786591 1212696648 90 Unknown
Sorry but it does look like a partition table but it is unusual. It includes the id 90 property:
90h MBR, EBR CHS, LBA x86, 68000, 8080/Z80 Hidden, Filesystem FreeDOS Free FDISK Hidden FAT16 (corresponds with 04h i.e. MS Fat16 DOS 3.0+ < 65536 sectors)
So trying to mount the image I get:
# mount -t auto U14.IMA /mnt/cd mount: unknown filesystem type 'sysv' <-----
As someone hinted, you need to have something specific like 'System V and Coherent filesystem support' compiled in the kernel in order to use something like
mount -t sysv. The sysv string is not so suprising, since this is part of AT&T UNIX System V/386 Release 4 Version 2.1 install media - a port which was supported by Sun until 2006 - and these images ended up in the wild in 2007. Actually a text file bundled with the images indicates that they are required for installation because of the nature of the boot sector and the format in use. There is an indication that the material was originally in Teledisk (TD0) format. I want to stress here that this is not original material. In any case I can't actually calculate the offsets like explained in the question - either I don't end up with integers when dividing by 512, and even if I try it seems I can't find the proper offset -
dd: cannot skip to specified offset, 0 writes etc. So at this point the answer is about forensics, and no longer about an image file.
Quick historical image source OS emulation with qemu
AT&T UNIX System V Release 4 Version 2.1
LABEL Version X of X AT&T UNIX SVR4.0 2.1 -------------------------------------------------- U01.IMA Maintanace Disk1 2.1 2 of 2 U02.IMA Remote Terminal 2.1 1 of 1 Package U03.IMA BSD Comp. Pkg. 2.1 1 of 2 U04.IMA BSD Comp. Pkg. 2.1 2 of 2 U05.IMA Networking Supp. 2.1 1 of 1 Util. Pkg. U06.IMA Xenix Comp. Pkg 2.1 1 of 1 U07.IMA FACE Pkg. 2.1 1 of 1 U08.IMA FMLI Pkg. 2.1 1 of 1 U09.IMA Editing Utils. 2.1 1 of 1 U10.IMA OA&M Basic & Ext. 2.1 1 of 3 U11.IMA OA&M Basic & Ext. 2.1 2 of 3 U12.IMA OA&M Basic & Ext. 2.1 3 of 3 U13.IMA Foundation Set 2.1 1 of 10 Base System Pkg. 2 User System U14.IMA Base 2.1a 1 of 10 U15.IMA Base 2.1 2 of 10 U16.IMA Base 2.1a 2 of 10 U17.IMA Base 2.1 3 of 10 U18.IMA Base 2.1 4 of 10 U19.IMA Base 2.1 5 of 10 U20.IMA Base 2.1 6 of 10 U21.IMA Base 2.1 7 of 10 U22.IMA Base 2.1 8 of 10 U23.IMA Base 2.1 10 of 10 U24.IMA Maintanance 1 2.1 1 of 2 U25.IMA Base 2.1 9 of 10 U26.IMA Printer Pkg 2.1 3 of 3 U27.IMA Printer Pkg 2.1 2 of 3 U28.IMA Printer Pkg 2.1 1 of 3 U29.IMA 16 to unlimited 2.1 1 of 1 User License U30.IMA 2 to 16 User 2.1 1 of 1 License
As was suggested, I installed from a prior image in the set. It involves using
qemu like explained here basically starting with image 14 (first
losetup /dev/loop0 U14.IMA then a simple
qemu-system-x86_64 -m 256 -hda test.img -fda /dev/loop0 -boot a), as U19 is not bootable. What is nice here is that you don't have to mount/umount images in the OS itself, you just use
ctrl-alt-2 or 1 with qemu to access or leave the monitor and you use
list blocks to see what is mounted and
change floppy0 imagename in that interface to change the image file i.e. during install for instance.
I had to supply U19.IMA (disk 5) during installation (for a textual log of the install, see this - a highlight is the reference to MS-DOS!), and I ended up with this i.e. a properly installed AT&T UNIX Sys V 386 OS, so this pretty much confirms U19.IMA is a working disk image:
By default /dev/fd is mounted on /dev/fd and there is also floppy access through a block (/dev/dsk/f0) and raw (/dev/dsk/f0) device. Changing directory to the floppy just shows files numbered from 1 to 23 (this is just the structure of the character device I guess). You can also
cat the raw and block devices and see the floppy data is there but that's as close as it gets.
I've noticed that in that OS, you don't install stuff from floppies by launching some script from a directory on them like you do with decompressed binary files for instance - here you use
pkgadd -d diskette1 (surely that last word is some alias, but I found a reference to the -d switch in the SCO stuff for pkgadd(1M) and generally it appears often in commercial Unix (Oracle, HP share pkgadd(1M) ). Issuing the command launches a routine where you supply floppies and you have no control, except saying "no" after the routine finds out what's in the drive. In the case of disks which begin an installation sequence (U03, U05 etc.), this will install then ask for the next floppy etc until the package install is complete. If you put a floppy that isn't the beginning of a set, it finds basically nothing but tells you maybe you have to use the
installpkg command instead.
Will I be installing a physical floppy drive to my rig to access the data in that image file?