September 2007 Archives

##cowsay is live!

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Have you ever wanted to have talking cows? Well, now you have your chance. On the Freenode IRC network, there is now a ##cowsay, and yours truly runs it! If you ever need support with cowsay, feel free to stop on by. Or if you just want to show us your favorite cowsay art, we want to see that too.

Music and DRM

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Along the same lines as my previous post here, Red Hat has posted a call for mashups of their video "Birdsong: A Requiem for DRM". I'm not a really creative person in those types of things, however, if you are, feel free to use the source files and create something better.

My criticism of the existing video is that it's far too abstract for an audience that does not already know what DRM is, why it's bad, that it's a futile effort, and it needs to stop.

An artist that gets it

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Trent Reznor of Nine Inch Nails seems to get why people steal music (the ridiculously high price, of which the artist sees very little), and he's encouraging it. I think that it's high time that an artist take a stand against a record company (which Trent has a history of doing), and finally just outright told his fans to steal his music.

Way to go, Trent!

The American legal system has now hit a new low. Ernie Chambers, a state senator in Nebraska, has filed a lawsuit against God (complaint, pdf). Yes, a lawsuit against God, seeking a permanent injunction against "terroristic threats".

Chambers makes it quite clear that he understands that God is omnipresent (thus giving the Nebraska court proper jurisdiction), and omniscient (thus obviating the need for personal notice to be served). In a creative moment that surely took lots of energy to produce, he accuses God of causing "fearsome floods, egregious earthquakes, horrendous hurricanes, terrifying tornados [sic], pestilential plagues, ferocious famines, devastating drouths [sic]....". He goes on to note that "Defendant has directed said chroniclers to assemble and dissiminate [sic] in written form, said admissions, throughout the Earth in order to inspire fear, dread, anxiety, terror and uncertainty, in order to coerce obedience to Defendants will"

He then goes on to request the court to "grant Plaintiff summary judgement" or, "in the alternative. to set a date for a hearing as expeditiously as possible if the Court deems such a hearing not to be a futile act".

My head is spinning.

Oprofile (the profiling utility) does not work properly in a VMWare guest, due to the lack of the hardware performance counters that it relies on. The workaround for this is to set 'options oprofile timer=1' in /etc/modprobe.conf

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Tip of the day: ifup-local

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Have you ever wanted local initialization actions to be taken when you bring up an interface on RHEL? Put your commands in /sbin/ifup-local. It gets called like '/sbin/ifup-local eth0' if you're bringing up eth0. A practical example for when you might want to do this is populating the ARP cache of the host with some predefined stuff.

Interestingly, there's also an option for a /sbin/ifup-pre-local. which gets called before ifup-$DEVICETYPE. Not sure what one would use this for in practice, any ideas?

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Tip of the day: drop_caches

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OK, so as you know, I'm a systems architect at a service provider. I'm going to start posting tips that I get from various other people, and stuff that I generally don't want to forget and might be useful to other people here. The first in this hopefully regular series is about the drop_caches tunable. It's available in kernel 2.6.16 and above, and exists in /proc/sys/vm.

If you echo various values to it, various kernel cache data structures are dropped. This is a non-destructive operation, so if you still see stuff hanging out after it, it's likely that it was dirty cache. Anyhow, on to the values:

1 - drop the pagecache
2 - drop the dentry and inode caches
3 - drop both the dentry and inode caches, as well as the pagecache.

Here's an example of the impact on the pagecache by doing this:

[root@rugrat ~]# free
total used free shared buffers cached
Mem: 2060656 1448748 611908 0 239620 649220
-/+ buffers/cache: 559908 1500748
Swap: 4194296 41056 4153240
[root@rugrat ~]# echo 3 > /proc/sys/vm/drop_caches
[root@rugrat ~]# free
total used free shared buffers cached
Mem: 2060656 615108 1445548 0 244 89128
-/+ buffers/cache: 525736 1534920
Swap: 4194296 41056 4153240

Note how the pagecache went from ~650MB to around ~89MB after dropping it. In practicality, you would likely never want to do this. However, if you are performing testing on the machine in question, you likely want to test the efficiency of the hardware ,and not the kernel's caching mechanisms.

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