Sebastian Kirsch: Blog

Thursday, 21 December 2006

The trouble with X11 authentication

Filed under: — Sebastian Kirsch @ 09:12

I used to have problems with the X11 server of Mac OS X 10.4 (X11.app): After a while, applications could no longer authenticate to the X server – programs that were running still worked, but I could not start any new X11 applications. If I restarted the X server, it worked for a while, then authentication would fail again.

The best explanation I found for this behaviour was this: The X server uses MIT magic cookies for authentication, and the cookies become invalid after the IP address changes. This is on a laptop, so I move between different networks all the time, and everytime I did, the X authentication would fail.

In previous versions of X11.app, there was a handy checkbox in the preferences to turn off authentication; unfortunately, this is gone in 10.4. The only way of turning off authentication is via the commandline:

$ defaults write com.apple.x11 no_auth 1
$ defaults write com.apple.x11 nolisten_tcp 1

The first command turns off authentication, the second one disables connections to the X server via TCP (programs can only use /tmp/.X11-unix/X0 unix domain socket to speak with the X server, which is faster and which they do anyway.) This limits the possibilities for mischief somewhat.

The downside of this is that you cannot use X via the network anymore – although you could get around this limitation by allowing TCP connections and firewalling the port off instead. And it is marginally unsafe, since any local program can connect to the X server, even if they were started by other users. But since this is practically a single user machine anyway, I do not care about the last part.

Tuesday, 12 December 2006

OLPC

Filed under: — Sebastian Kirsch @ 09:47

Yesterday, I got my hands on an OLPC:

This was one of the prototypes that are about to go into production. Unfortunately, it didn’t have a battery pack, so I could not see it in action, but just getting my hands on one was pretty awesome. It is very small and light, and does feel more like a toy, or like an appliance than like a real laptop. All of the electronics are housed in the display, and the bottom of the case has just the battery, the keyboard and the touchpad. The display can be twisted around to function as a kind of tablet computer – I would guess that this is intended mostly for reading. The two “ears” on either side of the screen are the wifi antennae.

They built in some nifty technical details. For example, there are a number ways to save energy. The network controller can do mesh routing with the CPU turned off, and the display can hold an image with the CPU turned off. There are no moving parts (main storage is flash), and the keyboard is dust- and water-resistant. The display has a monochrome mode and a color mode; the monochrome mode is about 200dpi (enough for comfortable reading), while the color mode as a lower resolution. I don’t know exactly what processor it has, but it’s equivalent to a 400-500MHz x86 CPU (ie. enough for most tasks.) You can find more info about the specs on the OLPC hardware wiki page.

And the most important part (as a friend pointed out): I can see some kid caring about this device. It’s cool. It looks good. It doesn’t feel fragile. I could definitely see someone giving this device to a six-year-old for school. (And he wouldn’t have to worry about being beaten up for it, like he would for having an iBook.) I could see myself buying one just because it’s cool. It’s probably the only laptop you can take to the beach and be reasonably certain that it will still work afterwards.

Monday, 04 December 2006

Mountain lions, oh my!

Filed under: — Sebastian Kirsch @ 10:08

After seeing this warning sign at Rancho San Antonio, I’d be wary of wandering around there in the dark:



Anyway, this is kind of a post without a purpose. I got my new camera on Friday, it’s a Pentax K100D, so I finally have an SLR again. (My previous camera was a Minolta X-700, which served me well for a number of years, but became too cumbersome in the end – it was film, no automatic drive (I had an external drive), no auto-focus, no built-in flash, … basically, everything you expect from a modern camera was missing. Apart from that it was great: very light, very small body for an SLR, bright viewfinder, and very reliable. Taught me lots of stuff about photography.)

So … I wanted to take the camera out and shoot some photos this weekend, but this was prevented by my other evening activities. (Note to self: Don’t expect to be able to take pictures in daylight if you went to sleep at 5am the previous night.) But since I wanted to know how the camera would fare in low-light situations, I took it out anyway to take some pictures at dusk. (My digital compact was notoriously shitty in this kind of lighting, and I’m very much a fan of available-light photography.)

A few pictures these outings are in my MTV gallery.

Work hard, play hard

Filed under: — Sebastian Kirsch @ 09:01

I can proudly attest that I am indeed doing my best to live up to the second part of this maxim.

On friday, I went to the company’s holiday party – taking place in a warehouse in the port of San Francisco. There were several different areas, some with live music, some with DJs, as well as plenty of food and booze. I am still amazed at the scale of this party – though if you want to accomodate several thousand employees in Mountain View, as well as their dates/spouses, nothing less would have done. The only downside: The party closed down at 12am, after only four hours. I’d have expected something like this to go on until the wee hours of the morning. After all, isn’t the purpose of a holiday party to get utterly wasted, get to know sides of your coworkers that you would never have expected, and have deep philosophical discussions with your team leader/manager/VP/CEO? (NB: A friend of mine in Saarbrücken was exceptionally good at this. At every university event, he had the uncanny ability to get at least one of the professors or other higher-ups completely drunk, hold long and deep discussions with them and become their best buddy.)

But fortunately, some people had the foresight to organize an afterparty, which took place at a club in downtown SF, and kept us going until about 3am. And since I didn’t have to drive, I could even imbibe alcohol with impunity. Thanks to Lorenzo, our driver!

On saturday, it predictably took me quite a while to get out of bed, but the next evening’s activities were already afoot: I went to SF with a friend to watch Shortbus at the Lumière Theatre. Definitely a movie worth watching. It was released unrated in the US, and if it had not, this could possibly have been the ratings board’s shortest job ever: Yes, there is lots of sex in this movie, but I don’t feel that it is gratuitous. The whole movie is about sex, and the rôle of sex in modern relationships. It has some very sweet scenes, and amazingly funny at times. (Quote from the movie: “Was that the first time someone sang the Star Spangled Banner into your ass?” – “No.") (Check out Jay Brannan’s music as well.)

This was followed up by a trip to the usual place. Well, not quite the usual place: This time, it was The Bar instead of The Café. What makes people choose so completely ungoogleable names for places? We ran into some friends from the previous weekends, and were quickly introduced to other people around. I was wearing a Google t-shirt (when everyone around you wears them all the time, you kinda forget …) and it turned out that there were at least five people from Google in the bar! Talk about a small world…

After stopping by one of our new-found friends’ place for further drinks, we finally made it home by about 5am. Oh, and since I was the designated driver, I didn’t have any alcohol that evening – but I increasingly find that it doesn’t matter. As long as there’s good music and nice people, I don’t need alcohol to have fun.


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