Archive for the ‘linux’ Category

Filenames and UNIX

David Wheeler posted a nice analysis of the problems with filenames in UNIX / Linux / … Well worth a read for those who need technical expertise in this area.

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I’ve been following this for a while now. With platforms like Linux around, why not aim for open hardware? OSNews has the latest (here and here).

Update 23 April: added link to second OSNews article.

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I’ve always found the man page for top to be painful to get through1, so I was quite happy when I found some old tips on how to get the most out of this nice utility. Not everything is in there, but it should be enough.

Another thing I’ve been looking for since ages ago is iotop (available in Debian and Ubuntu), letting you monitor disk activity on a per-process basis. This feature requires kernel version 2.6.20 or later.

1 In a way it feels like reading the man page for mplayer from end to end, albeit 7,000 lines shorter.

Update 7 April: thought I might as well mention jnettop too (its package name in Debian and Ubuntu), and you should of course know about dstat.

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I just discovered an interesting take on common Linux distributions. (Having some familiarity with them helps, but I take no responsibility either way… 8) )

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Ubuntu wallpaper

Here’s the classical Ubuntu logo in 3D (interestingly provided by the alias ilovewindows 8) – click on the link for more of his artwork).

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Conspiracy meetings

(About the move of my blog: it was in part due to buggy Blogspot code, but now I also have a more flexible solution. Overkill at this point, maybe, but that’s me. 🙂 )

I’ll go to FOSDEM this weekend (where the former President of the FFII will be speaking), and hopefully see Richard Stallman come here next Tuesday.

Next week is the BRM for OOXML, and I wouldn’t want to be in Alex Brown‘s shoes. Maybe the meeting itself won’t be so dramatic – no press allowed there, for one thing – but it’ll be interesting to see just how much bullying ISO national bodies are going to take from Microsoft, I mean ECMA. Basically, the strategy has changed from “OOXML is a perfect standard, and there isn’t even as much as a spelling error” to “look, since we’re good guys, we’ll include your idea too – now there are at least two ways to do everything”. To use a car analogy (sorry):

You: This car is not working, the engine is broken.
ECMA: How do you know? Let’s give it some time.
You: It is broken, alright.
ECMA: OK, look. We added a new one.
You: Doesn’t work.
ECMA: Yes it does. Start both engines.
You: I told you, the old one is broken. Why didn’t you just fix it?
ECMA: Come on, one of them is new, isn’t it great!

All that is missing is a press release from SCO that endorses OOXML. (Oh, is it flying pig season again? The fine company that made up random lawsuits about Linux, then went through bankruptcy proceedings, is now getting $100 million in support. Maybe I have been focused on the wrong career?)

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NX session

I finally got around to testing NX (remote desktop, see “background” below) for Linux.

After doing a “stress-test” from an “impressive” distance of 5 kilometres, I’d say it’s quite responsive, and otherwise appears to work as advertised. I especially like the resume functionality (suspend one or more login sessions), and resize-on-demand (i.e. toggling full-screen mode, or changing the resolution with the desktop adjusting).

As for the rest (sound etc.), it appears to behave properly, but then again, I’ve only just started using this. Graphically intense (e.g. 3D) applications don’t work smoothly – no surprise there – on the other hand, neither does glxgears (20 FPS). Maybe by default, no frames are skipped.


Getting the (freeware) NX system up and running roughly means to:

  • Install nxclient, nxnode and nxserver on the host.
  • Generate DSA public key, and private key (without a passphrase) for the “nx” user.
  • Install nxclient on other machines; use the private key to authenticate as “nx”, then use your login for the host.

Apparently it’s a little more complicated than this, but for instance you can use an existing SSH server configuration which allows only public key authentication (hint, hint). That would only get you past the first security layer, though (the “nx” user), or I didn’t see how to specify the user’s private key in the client. A workaround I use is to use NX’s own password database for authenticating users. (I could live with that, but is there a way to avoid this duplication? I guess it could also be a problem with other authentication methods.)

NoMachine’s documentation covers many things, so I’m not sure what else to address for now. However, I could mention that – lacking suitable free software packages – I’ve tried instead to compile some stuff (see the repository) into an NX client on Debian stable/etch (on a G4 machine). After working around a configuration bug, I seem to be able to login and so on, but get stuck on a “Launching session” dialog. If I get this to work, I should be presenting some documentation soon after.


NX is a technology for remote access (similar to that of rdesktop) to Linux or Solaris systems. It’s based on SSH and X, but offers significant improvements in terms of security (as compared to (e.g.) some VNC solutions) as well as latency and bandwidth requirements (ssh -X, anyone?).

Sadly, the official package from NoMachine is freeware, but there doesn’t seem to be a free software equivalent yet. While – strictly speaking – there is such code available for building a server or a client, only some server code (FreeNX) seems to be reasonably up to speed so far (but I hope this will change soon).

GNOME oddities?

I’ve hit on some bugs when running GNOME on the host, but it could be unrelated to NX. More specifically, I’ve experienced that gnome-terminal can get confused and open a terminal on the host; trying to logout in XFCE can close the remote GNOME session… 🙂 Given that, I try not to login with GNOME-ish stuff when it’s already running on the host. (Instead, I use something like fluxbox, but that now fails to logout at all in an NX session, weird…)

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(Sorry about the headline, couldn’t resist.1)

Glyn Moody Gets It. In Linux Journal, he writes about OOXML and Microsoft’s successes with OSI and EU antitrust: Is Microsoft Hijacking Open Source?

1 (Also familiar from snail-mailing the “sorry that I forgot to use a stamp” excuse.)

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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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