Archive for October, 2007

Deceiving checksums

Ever tried to copy a file or burn a CD, only to find out that the copy seems just fine, but not according to the checksum? Sometimes it’s worth digging a bit deeper: (or so it seems to me as a geek)

ubuntu@ubuntu:/mnt/hda2/ISO$ cat md5sum.txt
d2334dbba7313e9abc8c7c072d2af09c ubuntu-7.10-desktop-i386.iso
ubuntu@ubuntu:/mnt/hda2/ISO$ dd if=/dev/hdd | md5sum
1425008+0 records in
1425008+0 records out
729604096 bytes (730 MB) copied, 165.264 seconds, 4.4 MB/s
04af936c32bf2a26062a70360dd447cb -

Game, set, and … no match. (For the record, “md5sum /dev/hdd” wouldn’t illustrate my point here.) Let’s see what we have:

ubuntu@ubuntu:/mnt/hda2/ISO$ ls -l *.iso
-rw-r--r-- 1 ubuntu ubuntu 729608192 2007-10-28 13:05 ubuntu-7.10-desktop-i386.iso

Ah, 4096 bytes missing; now, with some dd / md5sum use it turns out that the preceding part was a perfect copy, as expected. Well, I’m using that live CD to blog about it while installing; it finished already, so I’m assuming it worked out… 🙂

(Next time I intend to stick to K3b, as I’m guessing it copes with these problems (integrated verification process) or never creates them in the first place. It wasn’t available on the live-CD, though.)

An older story is when I tried a poor man’s backup of a 40 GB drive:

$ nc -l -p 5678 > hda # host waits for data
# nc 5678 < /dev/hda # start backup on a Linux live-CD

This worked fine, or so it seemed. I checksummed different parts of the original and the copy (binary-search style), and narrowed down an inconsistent piece. Finally I must have noticed that this chunk got different checksums at two different times. While transmission errors are theoretically possible, I wouldn’t normally expect them with both computers in the same room and on the same switch.

Running the live-CD, I was naively assuming all partitions to be copied were mounted read-only, so there could be no change on the disk either. Maybe the hardware was crashing on me…?

Nope. Evidently:

# swapoff -a

would have helped before copying the whole disk. Sigh! 😉

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Microsoft apparently does not think all the versions of Windows Vista provide enough choice for the market. So, to ensure a better selection, they now seem to be looking at Linux systems as well: SuSE from Novell; Xandros; Linspire; and finally Turbolinux. Given these announcements of patent agreements (“protections”), I’m sure said distributors won’t “notice” any complaints… for now.

What will happen with resisting companies like Red Hat, though? And what will Microsoft do when fully recognising the success of non-commercial projects such as Ubuntu? (Nah, never mind, certainly there are no evil strategies here. I’ll sleep well tonight.)

Anyhow – if you thought that the EU ruling would stop these agreements, you may want to share the doubts of Groklaw on the Commission’s settlement with Microsoft (which brings into mind what my association predicted one month ago).

Oh, and OSI has approved two licenses (MS-PL, MS-RL) from Microsoft. After all, what is software worth if it doesn’t have a brand new license? (Bonus points for certain features, such as incompatibility with the GPL.)

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The Register reports that a California judge has allowed a class action response against target.com for discrimination against blind users. The website was claimed to be unusable with screen readers, which could be in violation of federal and state laws.

While changes have been made to the site recently, the matter can now be pursued from a national perspective – on behalf of all legally blind US individuals who tried to access the site – and similarly for California with local regulations.

Hopefully this will bring us closer to WAI compliance, which would help along the full potential of the World Wide Web. Either way, I for one will celebrate if this turns out to kill unusable web services, such as Flash sites…

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Dear Microsoft,

I’d like to present my own invitation to you, on an informal note: my association, the FFII, has just announced the winner of a 2,488 Euro award for lobbying against OOXML.

Given that several nominees did not wish for money, and considering the energy you (as the original author) have spent to discredit the proposal internationally, we thought it only fair to offer the price for your collection!

(Maybe this would pay for at least 5% of your partners’ bills in Sweden. No – my mistake – you “retracted” the promise; now, we did consider more suitable means of gratification – chairs for instance – to various parties, but unfortunately we could only do so much at a time.)

Details on the award ceremony will be available shortly; meanwhile, should you choose to accept the offer, you’re welcome to contact me or the board for some preliminary info.

Granted, it may seem like a small effort of ours in the light of your fines of 500 million Euro, or – say – your investments in the sue-happy SCO (a company which, incidentally, is about to collapse).

But: it’s the thought that counts, right?

A good friend

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