Is my iso repairable ?

[infoseeker]

Just downloaded the Knoppix iso and booting it gave errors, so I checked the iso :


md5sum -c KNOPPIX_V4.0.2CD-2005-09-23-EN.iso.md5
KNOPPIX_V4.0.2CD-2005-09-23-EN.iso: FAILED
md5sum: WARNING: 1 of 1 computed checksum did NOT match

'ls' produces:

total 711832
728190976 2005-09-24 00:58 KNOPPIX_V4.0.2CD-2005-09-23-EN.iso
69 2005-09-24 03:37 KNOPPIX_V4.0.2CD-2005-09-23-EN.iso.md5


Please say YES :evil:
Downloads take a looooong time here in South Africa !

[UnderScore]

There are two common file transfer protocols for Linux ISO images that guarantee the file you download is not corrupt: Bittorrent or Rsync.
Make a backup of you current corrupt ISO & then Download the bittorrent client for your choice or use rsync.
Direct either program to overwrite the exisiting current ISO. It will not delete it but will figure out which bits are corrupt & will donwload the appropriate bits. See http://www.knoppix.net/forum/viewtopic.php?t=20700

[Harry Kuhman]

In all likelyhood no. I say this because I've found that a very common problem with Knoppix downloads from mirrors is that the Linux mirror is treating the ISO file as if it is a text file and not a binary, and when it transfers the file to a MS DOS based system the Linux new line characters are translated to CR/LF pairs. If you check the exact sizes of the files and you find that your download is larger than the ISO should be then this is almost certainly what has happened to you (it used to happen to me about 50% of the time before BitTorrent became available).

This is why we say that it is absolutely critical that you run the md5 test is you use a mirror. Otherwise your chances of getting a good disc are about 50% or less.

I don't think that this is a problem that you can simply reverse by converting all CR/LF pairs back to new line, since there may be some legitimate bytes in the binary that do match CR/LF. But that's the likely problem if you want to try to fix it. If you can get the md5 sum correct by making a fix then your ISO will be right.

This is one of the primary reasons we advise users to use BitTorrent rather than the mirrors. In addition to just being faster, BitTorrent does it's own internal corruption checks on the file and it does not suffer from the new line to CR/LF translation problem.

If your file is the correct size then just maybe BitTorrent can correct it. Since BitTorrent treats the file as a serise of blocks and checks each of those, it can fix an iso (even if downloaded from a mirror) if only a few blocks are bad. It will analize the file and obtain just the blocks it needs to make the fix. But if the new line to CR/LF bug hit you then the entire ISO will likely need replaced and it would be better to start fresh. I suggest using BitTorrent this time, although some people need to get hit by this bug several times before they are willing to learn to use a tool that is new to them.

See the Downloading faq for more details.

[Dave_Bechtel]

--You may be better off ordering a CD instead of DL'ing, if you can find someplace that ships to SA.


Just downloaded the Knoppix iso and booting it gave errors, so I checked the iso :


md5sum -c KNOPPIX_V4.0.2CD-2005-09-23-EN.iso.md5
KNOPPIX_V4.0.2CD-2005-09-23-EN.iso: FAILED
md5sum: WARNING: 1 of 1 computed checksum did NOT match

'ls' produces:

total 711832
728190976 2005-09-24 00:58 KNOPPIX_V4.0.2CD-2005-09-23-EN.iso
69 2005-09-24 03:37 KNOPPIX_V4.0.2CD-2005-09-23-EN.iso.md5


Please say YES :evil:
Downloads take a looooong time here in South Africa !

[angor]

> I don't think that this is a problem that you can simply reverse by converting all CR/LF pairs back to new line,
> since there may be some legitimate bytes in the binary that do match CR/LF.

But would these occurrences not have been translated to CRCRLF?
s,CRLF,LF, (hey - this is meant symbolically :-) would then restore the original state.

[Harry Kuhman]

> I don't think that this is a problem that you can simply reverse by converting all CR/LF pairs back to new line,
> since there may be some legitimate bytes in the binary that do match CR/LF.

But would these occurrences not have been translated to CRCRLF?
s,CRLF,LF, (hey - this is meant symbolically :-) would then restore the original state.
Maybe. I though aout this and that's why I changed my wording from a statement that it absolutely can't be fixed to this wording. But I don't want to be over encouraging and something was and still is nagging at the back on my mind that says there is a got-ya waiting to happen if one tries this. But I was low on sleep when I wrote it and still am, just can't put my finger one where it could go wrong. And, of course, we don't really know how his file became corrupt, although my past experience points to this as a likely source. So I gave the poster the best info I could; if he's up to the simple code to make the change then good luck to him, and he has the md5 of what the result should be to check himself. Hopefully he will post back and let us know what happens.

[Harry Kuhman]

'ls' produces:

total 711832
728190976 2005-09-24 00:58 KNOPPIX_V4.0.2CD-2005-09-23-EN.iso
69 2005-09-24 03:37 KNOPPIX_V4.0.2CD-2005-09-23-EN.iso.md5

Well, here's something else of interest: I found my copy of the CD iso and looked it over. My file shows as the same size as yours. So it seems that the NL->CR/LF bug did not hit you, as that bug increases the file size. So it looks like some other corruption hit your mirror download. Depending on it's nature, it's likely that BitTorrent can indeed correct this file with minimal downloading (just replacing he bad part).

[infoseeker]

and when it transfers the file to a MS DOS based system
The iso was d/l using gFTP from within Ubuntu. Will have a go with BitTorrent.

My wife has a habit of shutting down Linux when I am away.....maybe she pressed the reset button :evil: or a mains dip :cry:

[infoseeker]

The iso has been successfuly repaired :D. I copied it into the Bittorrent destination folder and when I next saw the progress it was at 78%, so all that had to be done was d/l the remainder. Worth remembering.
Now I need to sort out the next list of issues...like the Xserver (I have an intel 82865G Integrated Graphics which doesn't seem to be supported), but isn't that what Linux is there for.....tweaking :D

[Harry Kuhman]

...I copied it into the Bittorrent destination folder and when I next saw the progress it was at 78%, so all that had to be done was d/l the remainder. Worth remembering....
Gald it worked, but even better is to remember to use BT in the first place. Sounds like you had a lot of corruption that needed fixed.