Now that we have KMS, it happens things go bad enough that when X goes
down, one can no longer access any console to see what
happened. Mainly, one can distinguish between two cases.
- The good one: the machine is still accessible over the
network. Unfortunately, that requires having a spare machine to ssh
into the first machine, but that means one can run
dmesg, look
into X logs, possibly run X inside gdb and see where it breaks
(because glibc s backtrace isn t exactly an excellent tool to
get the idea of what s going on and that s the tool used in X to
print a backtrace in the log through a signal handler).
- The bad one: the machine is no longer accessible over the
network. Likely, the kernel is in such a bad shape that one is
never going to know what happened. Usually, writing logs to disc
didn t happen, so logs won t magically show up at next reboot.
I m going to discuss the second case. There s a nice tool in the
kernel which makes it possible to send kernel logs over the
network. It s called
netconsole. As far as limitations are
concerned, one shall note that it s UDP only, and over Ethernet (in
other words: no wireless). The good news is that it can usually make
the last crucial lines available.
Let s call the crashy machine a
patient and the logging machine a
doctor.
One should keep in mind that if something goes wrong while configuring
the
netconsole module, it can be unloaded at anytime through:
sudo modprobe -r netconsole
Easy case: on a local network
Here s an example: Patient s IP is
192.168.0.1, doctor's IP is
192.168.0.2.
Doctor setup
What one needs on the receiving side: only
netcat. A tiny warning,
there are several implementations. Here s the appropriate syntax:
# netcat-traditional:
nc -l -u -p 6666 tee ~/netconsole.log
# netcat-openbsd:
nc -l -u 6666 tee ~/netconsole.log
The
nc command is handled through the alternatives system, one can
use
update-alternative --config nc to pick the appropriate one if
several
netcat-* packages are installed. To list the current one, an
easy way is
readlink -f $(which nc).
Using
tee means that incoming messages are going to be printed, both
to the standard output and to the specified file.
Running as non-privileged user is sufficient.
Patient setup
Now, to have the patient send stuff to the doctor, a simple
modprobe
is needed:
sudo modprobe netconsole netconsole=@/,6666@192.168.0.2/
What happens here? One requests the
netconsole module to be loaded,
and one specifies the parameters. Details can be read in the Linux
kernel documentation (
Documentation/networking/netconsole.txt), but
concentrating on the points of interest here:
- 192.168.0.2: The doctor s IP.
- 6666: The UDP port to which packets are sent. 6666 is the default
and can be omitted.
That s all! On the doctor side, one should see something along those
lines:
[2920549.188090] console [netcon0] enabled
[2920549.188102] netconsole: network logging started
Slightly harder case: over internet
Because one might not have a second machine handy, it s also possible
to go through a router and send stuff across the internet.
Here s an example: Patient s IP is
192.168.0.1, connecting to
internet through a router, which IP is
192.168.0.254. The doctor,
available over the internet, is
192.0.32.10.
Doctor setup
Exactly the same as in the previous case. The main issue one can run
into is firewalls at this point. That s why one may want to switch
from the default 6666 port to another one which wouldn t be
filtered. One can think of 53 (DNS), but that means running
nc as
root since it s a privileged port (below 1024).
Patient setup
Routing is also possible, but that requires an extra parameter: the
MAC address of the router. To obtain it, one can use the
arp
command:
/usr/sbin/arp 192.168.0.254
Supposing it returned the
01:02:03:04:05:06 address, loading the
module becomes:
sudo modprobe netconsole netconsole=@/,6666@192.0.32.10/01:02:03:04:05:06
Now, if you re running into firewall-related issues, you can change
the source for the UDP packets. The default is 6665, but assuming you
want to send from an unfiltered 1234 port, that becomes:
sudo modprobe netconsole netconsole=1234@/,6666@192.0.32.10/01:02:03:04:05:06
I ve written previously about my reading habits, online and offline, and the patterns I extrapolate to content consumption in general. I ve been talking with other people about this as well, and am beginning to develop a model to apply to my daily life.
There are plenty of unsatisfactory metaphors circulating in this area: we eat the information diet , drink from the fire hose , endure the information explosion , and so on. None of them describe the richness of my experience: the profound variations in style, texture, speed, depth and movement are lost in this kind of dry imagery.
Instead, I think of it like respiration.
We inhale information, and we also exhale it transformed. We do this, consciously or unconsciously, every moment of our lives. Sometimes we do it quickly, other times slowly, and it can be relaxing or stimulating. We only retain a small amount of what we take in, but it becomes a part of us. We can immerse ourselves deeply, meditatively, in a series of breaths, or fail to notice as we breathe shallowly or pause altogether. One breath may be virtually silent, the next filled with a song or a question or a piercing whistle.
We maintain a balance in our breathing, and I aspire to do the same with information: reading and writing, listening and speaking, seeing and being seen. I don t mean this simplistically, that I should do both in equal proportion (imagine trying to write as many words as you read!), but doing both consistently. It is often only when I share an idea that I come to understand it deeply, no matter how much I have read about it. By writing it down, or telling someone about it, I naturally fill in the gaps in my understanding and create mental structures which help me recall and apply what I ve learned.
My input and output should be balanced appropriately for my circumstances. Rapid-fire email is like hyperventilation: I can do it for a while, reading and replying in quick succession, and even feel energized by it, but if I go on for too long, I get dizzy. Running might call for a certain breathing ratio, and Yoga quite a different one. Both can be healthy practices, but they are different, and each requires focus and consistency.
Another key lesson from breathing is to let go. A friend recently told me about his daily online news routine, which included closing any unread tabs at the end of the session. I will sometimes hang onto an article or a video for days or weeks before I find the opportunity to take it in. I eventually get around to most of them, but meanwhile they are taking up space and causing a continuous low level of anxiety or guilt. This information isn t going anywhere, and if it s truly significant for me, it will most likely turn up again. If it doesn t, that s OK too.
Similarly, it s not wise to breathe stale, indoor air for too long. I will try to step outside regularly, and engage with people and media from outside my usual sphere. When the weather is tolerable, I ll open up the house and let plenty of fresh air circulate. This will help me avoid getting stuck in the echo chamber of my own ideas, or in groupthink.
Perhaps most significantly, I will try to remember that information exchange, like breathing, is not an end in itself. It is a means to action. This will remind me to get out of my head regularly, and do something significant with what I ve learned.
Ready? Breathe.
I m sure Vodafone want a great experience for their users, but I think they re failing to separate out platform improvements share and share alike, and 
For the past month, I got disconnected from basically all of my usual activities. Not only from Debian work (well, yes, I followed up on a couple of important bugs and releases, but I was in a very low power consumption mode of sorts), DebConf organization/following (some people have contacted me regarding the DebConf 12 venue decision, for which we should start working and have a presentation soon) Even the always-so-important Real Life got pushed aside. I barely participated in this year's 
In this post I'll describe the changes made to the kernel and some of the
Squeeze packages for the Freaky Wall.
The plan is to submit whishlist bugs to the BTS on the hope of having all what
is needed for this project available on Debian after the Squeeze release, as
my feeling is that a freeze is not the right time to push this changes... ;)
I'm giving access here to all the changes made to the source packages, but if
anyone wants the binary packages (amd64 only) send me an email and I'll give
you the URL of an apt repository that contains all the modified packages (it's
the one at work, that contains other modified packages) or, if there is
interest, I can put them on people.debian.org.
Kernel
To be able to build the firewall we need a kFreeBSD kernel with some options
not compiled on the version distributed with Debian.
To compile the kernel I've followed the procedure described on the following
debian-bsd mailing list post:
Somebody linked me to 
In the last years I noticed a growing trend of people pushing for "new" rules about what is appropriate or not for single developers or for the project as a whole. In too many cases even just considering these ideas to be an obvious fact... I prefer to not give specific examples because these would divert the attention from the main topic and would be affected by my own biases.
At this point I believe it is useful to remember that all ethical issues which are not explicitly covered by the Social Contract are just the developers' own opinions. It may even be a good idea, but other developers are not and should not be compelled to agree with it no matter how good or important you believe it is.
You are entitled to having your own ethics and even ranting about it on Planet Debian, but I am entitled to not caring at all without this making me a worse Debian Developer. Let's try to be grown ups and not be excessively annoyed by other people's choices.
This is why I want to convey this simple message to the people who keep preaching about what is proper for me or for Debian: please fuck you. If I want to receive lectures about what is right or wrong then I surely know where I can find a priest.
For some reason, now I see fit to mention that I have an 
On 24th of October we've been to the concert of 
You re probably manipulating Debian packages everyday, but do you know what those files are? This article will show you their bowels Surely they are more than file archives otherwise we would just use TAR archives (you know those files ending with .tar.gz). Let s have a look!
1. It s two TAR file archives in an AR file archive!
A .deb file is actually an archive using the AR format, you can manipulate it with the 
At 
When doing porter uploads, one must not forget to pass
-m"My Name <my@email.addr>" to dpkg-buildpackage,
e.g. with --debbuildopts for cowbuilder. Thanks Aur lien
and sorry to everyone who got the upload mails.
(How are the rules for sponsored uploads? I get conflicting info
on these, and indeed, the one I sponsored never showed up on my QA
DDPO page )
About a month ago, at the end of August, I finished a 10-day Vipassana meditation course. This was probably one of the more extreme activities I have ever participated in, and it's well worth a blog post.
I found out about the course in a ridiculously trivial way, by following a link in a Reddit comment (I wonder if I could track down that comment...). The 
