blog.gauner.org

Lightning strikes

tex — Wed, 25 Aug 2010 17:16:17 +0000

Lightning sucks. A thunderblot struck our house and toasted my dsl splitter and my router. Did you ever want to know how a splitter that has been hit by a thunderblot looks? Here are the pictures.

mini-buildd and Linux-Vserver

tex — Wed, 07 Jul 2010 10:39:56 +0000

After discovering mini-buildd, a tiny Debian buildd, I’ve tried to set it up inside some vservers. mini-buildd uses LVM-Snapshots to avoid duplicate work when creating build chroots. I will setup a base debian chroot once and create a snapshot each time a build chroot is needed. This, however, is where the fun begins. The problem is that Linux-Vserver prevents its guests from performing most of the syscalls and ioctls needed by lvm2.

I didn’t manage to get the setup fully working so far but I wanted to share my experience in case anyone tries the same!

The basic setup of mini-buildd is quiet easy. I’ve decided for a setup with three versers, one for the repository, one buildd for amd64 and ond buildd for i386.

vs-buildd-rep - 192.168.10.1
vs-buildd-amd64 - 192.168.10.2
vs-buildd-i386 - 192.168.10.3

First we need to create these vservers:

newvserver --ip 192.168.10.1/24 --domain localdomain --hostname vs-buildd-rep --vsroot /srv/vserver/ --mirror http://ftp.de.debian.org/debian --interface eth0 --dist lenny --arch amd64
newvserver --ip 192.168.10.2/24 --domain localdomain --hostname vs-buildd-amd64 --vsroot /srv/vserver/ --mirror http://ftp.de.debian.org/debian --interface eth0 --dist lenny --arch amd64
newvserver --ip 192.168.10.3/24 --domain localdomain --hostname vs-buildd-i386 --vsroot /srv/vserver/ --mirror http://ftp.de.debian.org/debian --interface eth0 --dist lenny --arch i386

After installing the vservers we need make some adjustments for LVM and set some capabilities:

cp -a /dev/loop* /srv/vserver/vs-buildd-amd64/dev/
cp -a /dev/mapper/control /srv/vserver/vs-buildd-amd64/dev/mapper/
echo "SECURE_MOUNT" &gt;&gt; /etc/vserver/vs-buildd-amd64/ccapabilities
echo "SECURE_REMOUNT" &gt;&gt; /etc/vserver/vs-buildd-amd64/ccapabilities
echo "ADMIN_CLOOP" &gt;&gt; /etc/vserver/vs-buildd-amd64/ccapabilities
echo "ADMIN_MAPPER" &gt;&gt; /etc/vserver/vs-buildd-amd64/ccapabilities
echo "MKNOD" &gt;&gt; /etc/vserver/vs-buildd-amd64/bcapabilities
echo "SYS_RESOURCE" &gt;&gt; /etc/vserver/vs-buildd-amd64/bcapabilities
echo "SYS_ADMIN" &gt;&gt; /etc/vserver/vs-buildd-amd64/bcapabilities
cp -a /dev/loop* /srv/vserver/vs-buildd-i386/dev/
cp -a /dev/mapper/control /srv/vserver/vs-buildd-i386/dev/mapper/
echo "SECURE_MOUNT" &gt;&gt; /etc/vserver/vs-buildd-i386/ccapabilities
echo "SECURE_REMOUNT" &gt;&gt;  /etc/vserver/vs-buildd-i386/ccapabilities
echo "ADMIN_CLOOP" &gt;&gt; /etc/vserver/vs-buildd-i386/ccapabilities
echo "ADMIN_MAPPER" &gt;&gt; /etc/vserver/vs-buildd-i386/ccapabilities
echo "MKNOD" &gt;&gt; /etc/vserver/vs-buildd-i386/bcapabilities
echo "SYS_RESOURCE" &gt;&gt; /etc/vserver/vs-buildd-i386/bcapabilities
echo "SYS_ADMIN" &gt;&gt; /etc/vserver/vs-buildd-i386/bcapabilities

Please note that these capabilities give the vs-buildd guests pretty much control over the host, so be careful how far you trust your buildds!

Now start the vservers, fix some broken defaults, upgrade to squeeze and install the requried packages.

When editing the sources.list you should replace all occurences of lenny by squeeze like so:

:%s/lenny/squeeze/g

The reason for not installing squeeze directly with newvserver is that, at the time of this writing, newvserver can not handle squeeze.

For the repository vserver:

vserver vs-buildd-rep start
vserver vs-buildd-rep enter
update-rc.d cron defaults; /etc/init.d/cron start; vi /etc/apt/sources.list; aptitude update &amp;&amp; aptitude install aptitude apt &amp;&amp; aptitude updgrade; aptitude dist-upgrade; aptitude install mini-buildd-rep vim htop screen ssh exim4
a2endmod userdir
dpkg-reconfigure tzdata
dpkg-reconfigure locales
dpkg-reconfigure exim4-config

The Vservers need some way of sending mail, so the best would be to setup a mailserver somewhere, e.g. in the host, and then confiure it as a smarthost inside the vservers.

The next one is the amd64 buildd:

vserver vs-buildd-amd64 start
vserver vs-buildd-amd64 enter
dpkg-reconfigure locales; update-rc.d cron defaults; /etc/init.d/cron start; vi /etc/apt/sources.list; aptitude update &amp;&amp; aptitude install aptitude apt &amp;&amp; aptitude updgrade; aptitude dist-upgrade; aptitude install mini-buildd-bld vim htop screen ssh exim4
a2endmod userdir
dpkg-reconfigure tzdata
dpkg-reconfigure exim4-config

And the same for i386:

vserver vs-buildd-i386 start
vserver vs-buildd-i386 enter
dpkg-reconfigure locales; update-rc.d cron defaults; /etc/init.d/cron start; vi /etc/apt/sources.list; aptitude update &amp;&amp; aptitude install aptitude apt &amp;&amp; aptitude updgrade; aptitude dist-upgrade; aptitude install mini-buildd-bld vim htop screen ssh exim4
a2endmod userdir
dpkg-reconfigure tzdata
dpkg-reconfigure exim4-config

The setup of the mini-buildd is a bit tricky since the repository and the buildds depend on each other. So after performing the above steps you’ll probably need to reconfigure each.

in vs-buildd-rep: dpkg-reconfigure mini-buildd-rep
in vs-buildd-amd64 and vs-buildd-i386: dpkg-reconfigure mini-buildd-bld

To be continued!

Thats it for now. Howevery, so far I didn’t manage to get the buildds working. There are still some issues with the LVs. I’ll update this post as soon as I figure out how to fix this.

Perl Best Practices

tex — Tue, 29 Jun 2010 13:56:59 +0000

Recently I’ve read a really interesting book. A book every perl developer should read. At least have a look at Appendix B which lists all guidelines in a brief summary.

Speedport W722V – Features? We ain’t need no Features!

tex — Wed, 23 Jun 2010 10:51:37 +0000

Dear Deutsche Telekom,
I’ve just got to love your great CPE products. The Speedport W722V ist a great product, a impressive piece of german engineering! It provides lots and lots of usefull features. For example you can us it as a doorstop, paperweight or to prettify your home.

But the point is: It is absolutely useless as a Internet-Router for me! It doesn’t allow incoming ICMP (Ping), it got no internal S0 (ISDN) Bus and it doesn’t allow VPN-Passthrough (GRE, Protocol 21). I even suspect it to have a severely broken QoS, but I can’t proof that right now. And this is only after a few days of playing around with this device. Not to think of what I’d find if I gave it some more time.

Die Konfiguration unserer Speedports ist auf Einfachheit getrimmt. Der Reichtum an einstellbaren Funktionen und Konfigurationsoptionen ist nicht das Ziel der Entwicklung, eher schon eine Reduktion auf das Wesentliche.

[Telekom Team @ T-Online Foren]

The quote says that they aim for simplicity and not for features, and they’re good at it. Very good. This device is so simplistic that it is basically useless for all but the most basic users.

I’ll look for a better CPE and try to return this device as soon as possible. Maybe they find somebody who can make better use of it than me.

Update: It looks like the Speedport is killing long running connections after a while (a few hours at most). I’ve heard about that one … that’s very disappointing when working over SSH.

Presidents on Twitter

tex — Thu, 13 May 2010 17:25:44 +0000

President Hugo Chavez announced the incident via his account on the social networking site Twitter.

ROFL, literaly.

DENIC FAIL

tex — Wed, 12 May 2010 15:38:36 +0000

This is was it looks like when most of the german nameservers are down. This image shows the traffic of popular .de site. The drop isn’t remotely as sharp as I thought it would be.

Perl: Wide character in print

tex — Thu, 29 Apr 2010 14:16:30 +0000

Wanna get rid of these annoying “Wide character in print” warning perl gives you sometimes when dealing with unicode/UTF-8?

Use

binmode(STDOUT, ":utf8");

on STDOUT or the appropriate filehandle, and perl will treat it as UTF-8 capable.

You could also use the “-CSDA” option to tell perl that.

Before:

#!/usr/bin/perl -w
use charnames ':full';
print "\N{GREEK CAPITAL LETTER DELTA}\n";

Gives:

./wide_char.pl
Wide character in print at ./wide_char.pl line 9.
Δ

After:

#!/usr/bin/perl -w
use charnames ':full';
binmode(STDOUT, ":utf8");
print "\N{GREEK CAPITAL LETTER DELTA}\n";

Threads in Perl are broken

tex — Thu, 01 Apr 2010 20:15:49 +0000

Ok, for most experienced perl programmers this is not new, but let me repeat it:

Threads in Perl are broken. Really, really, severe broken. Do not use threads with Perl.

Thread async is probably ok for smaller computations but for anything else use fork().

Not only are IPC-Signals really dangerous with threads and DBI can’t work with threads but also the memory usage is magnitudes higher with threads than with fork(). At the moment I’m hacking a perl app that uses a lot ressouces but I was impressed how fast I could kill my system with fair amout of concurrent threads. From Java I was used to threads being very lightweight, but with Perl this is the other way round. My app has its core part modularized and I’ve wrote it once using threads and once using fork(). The threads-version uses about 300MB RSS while the fork()ing version uses no more the 30MB RSS for the same workload. Quiet a difference.

Aprilscherze?

tex — Wed, 17 Mar 2010 19:30:19 +0000

Ja ist denn schon 1. April?

Es geschehen noch Zeichen und Wunder:

virt-manager: Error starting domain

tex — Tue, 16 Mar 2010 17:09:22 +0000

Using KVM/virt-manager in Debian sid is interesing. You’ll get nice and fresh errors from time to time. KVM is constantly improving but you have to deal with unexpected changes from time to time which tend to break existing VMs.

With the latest version I’ve got this error:

Error starting domain: internal error unable to reserve PCI address 0:0:3

The long text:

Traceback (most recent call last):
File “/usr/share/virt-manager/virtManager/engine.py”, line 589, in run_domain
vm.startup()
File “/usr/share/virt-manager/virtManager/domain.py”, line 1208, in startup
self._backend.create()
File “/usr/lib/python2.5/site-packages/libvirt.py”, line 317, in create
if ret == -1: raise libvirtError (‘virDomainCreate() failed’, dom=self)
libvirtError: internal error unable to reserve PCI address 0:0:3

The solution was to edit the /etc/libvirt/qemu/.xml and change the conflicting PCI id. The line looked like this before:

and like that after the change:

Don’t forget to reload libvirt after this change.