Arch Linux

makikatze

Member

Registered: 2017-08-28

Posts: 6

Mounting huge UDF iso fails

Hi at everybody,

today I encountered my first "can not solve this on my own" problem while using Arch Linux on my server. I tried to mount a huge (63G) iso image that is definitely a UDF image (checked that manually via xxd output). I even tried to download the first 8M to my Macbook Pro and mount the iso image there. That worked (without all the data, obviously, but the header was recognized and could be used to mount at least the first 8M of the image).

But on my server, the command fails with the following message on the console:

armbrust@hetzner ~/conversion % mkdir iso && sudo mount ./mount.iso iso
mount: /home/armbrust/conversion/iso: wrong fs type, bad option, bad superblock on /dev/loop0, missing codepage or helper program, or other error.

The command produces some output in the dmesg log which looks like this (this is the whole output produced during the mount command):

[ 1814.702524] UDF-fs: warning (device loop0): udf_load_vrs: No anchor found
[ 1814.702526] UDF-fs: Scanning with blocksize 512 failed
[ 1814.702745] UDF-fs: warning (device loop0): udf_load_vrs: No anchor found
[ 1814.702745] UDF-fs: Scanning with blocksize 1024 failed
[ 1814.702850] UDF-fs: incorrect dstring lengths (114/32)
[ 1814.702921] UDF-fs: Scanning with blocksize 2048 failed
[ 1814.702946] UDF-fs: warning (device loop0): udf_load_vrs: No VRS found
[ 1814.702947] UDF-fs: Scanning with blocksize 4096 failed

Other tools like 7-Zip are not able to extract or read the iso file, the isoinfo command from the cdrtools package tells me:

Setting input-charset to 'UTF-8' from locale.
CD-ROM is NOT in ISO 9660 format

Can I do anything about that as my Macbook can read the image, but my Arch Linux server can't?

Best,
Michael

R00KIE

Forum Fellow

From: Between a computer and a chair

Registered: 2008-09-14

Posts: 4,734

Re: Mounting huge UDF iso fails

Where was that iso created and with which tool (or tools)? Your dmesg output seems to point either to a non compliant format on that udf filesystem or that linux does not support that variant or version and complains.

Make sure you double check that the image is actually udf as it may look like udf because of some stray header but the actual content is not udf. I have never tried 7-zip together with udf filesystems/images but if it should handle that and it doesn't then I'd say that might lend some weight to the hypothesis of a bad image (or not udf).

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R00KIE
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makikatze

Member

Registered: 2017-08-28

Posts: 6

Re: Mounting huge UDF iso fails

Unfortunately I don't know which tool was used to create the ISO image, I only know that it originates from a Windows PC.

If it was a bad image, why can macOS open the image and Linux can't? 7-Zip on macOS can't open the file either, by the way. So it seems to be in a non-compliant format that can be handled by some tools or systems, but not Linux?

Could it help to upload the first 8M somewhere, so you can at least check the header to see if something is wrong with the file or could be easily changed to make it compliant?

R00KIE

Forum Fellow

From: Between a computer and a chair

Registered: 2008-09-14

Posts: 4,734

Re: Mounting huge UDF iso fails

Uploading the first 8M would not help me as I don't have much experience with udf, I was just applying common debugging procedure to the problem.

You could try check on macos which options/parameters the iso gets mounted with and then try to replicate that on linux. You should also check the udf mount options as adjusting them may help. Another thing you could try is trying to get some more info about that udf filesystem from a tool that can actually open/mount it.

Since linux can't do anything with it you could try windows tools if you have access to a machine with windows or try running the tools with wine, of the top of my head I can remember only one tool that might help: isobuster. That said, you seem to have access to a machine that can deal with that iso, if you are trying to get this to work on linux out of curiosity then plow on, otherwise just copy everything from the iso on the mac and move on because from what you say this seems to be an uphill battle.

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R00KIE
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progandy

Member

Registered: 2012-05-17

Posts: 5,196

Re: Mounting huge UDF iso fails

Maybe your UDF image has a nonstandard blocksize? It seems that this won't be detected correctly, you can try to mount it with "bs=..."
Edit: Nevermind. Somehow I missed the different blocksizes tested in the mount dmesg output.

Last edited by progandy (2017-08-29 10:19:06)

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| alias CUTF='LANG=en_XX.UTF-8@POSIX ' |

makikatze

Member

Registered: 2017-08-28

Posts: 6

Re: Mounting huge UDF iso fails

Uploading the first 8M would not help me as I don't have much experience with udf, I was just applying common debugging procedure to the problem.

You could try check on macos which options/parameters the iso gets mounted with and then try to replicate that on linux. You should also check the udf mount options as adjusting them may help. Another thing you could try is trying to get some more info about that udf filesystem from a tool that can actually open/mount it.

Since linux can't do anything with it you could try windows tools if you have access to a machine with windows or try running the tools with wine, of the top of my head I can remember only one tool that might help: isobuster. That said, you seem to have access to a machine that can deal with that iso, if you are trying to get this to work on linux out of curiosity then plow on, otherwise just copy everything from the iso on the mac and move on because from what you say this seems to be an uphill battle.

Well, I would need to download the file for more than 30 hours, that's why I wanted to get it to work there

I will try to check how macOS handles the file and maybe get the right mount options to make it work on Linux. And if that does not work, I try the isobuster application to get more infos about the iso.

Thank you very much for your help!

EDIT: Seems like the error is a too long string for the UDF volume.

UDF-fs: incorrect dstring lengths (114/32)

seems to indicate that the name cannot be longer than 32 chars but it reads 114 (which could be the case for this iso, IsoBuster gives me a really long name). I think I'll file this as a kernel bug and we'll see what they say about it.

Last edited by makikatze (2017-08-29 15:44:55)