Once you have many Debian servers, maintenance would be a problem. I just counted that I have more then 30 etch servers running in several vserver machines. Sometimes, I would like to install Debian package in all of these servers. However, it takes too much time to ssh /vserver enter into every hosts, and answer the installation questions one by one.

Thanks for the debconf(1), it’s quite easy to do non-interactive installation, since debconf already provide a noninteractive frontend. All you need to do is set the configuration before you install the package. It can be done by debconf-set-selections.

First, you have to install the package in one hosts. It would be better if you install/test the package on the same distribution version and package version. Here is an example for install localepurge. localepurge is a software for superfluous locale data, that will save you some disk space. As a Chinese, I usually don’t need Spanish, Franch and any other hundreds of different locale data.

Once you install the localepurge, you can use debconf-get-selections to dump the configuration you did.  The debconf-get-selections is part of the debconf-utils. The command would look like

# debconf-get-selections |grep ^localepurge
localepurge	localepurge/quickndirtycalc	boolean	true
localepurge	localepurge/remove_no	note
localepurge	localepurge/mandelete	boolean	true
localepurge	localepurge/showfreedspace	boolean	true
localepurge	localepurge/verbose	boolean	false
localepurge	localepurge/nopurge	multiselect	en, en_US.UTF-8, zh, zh_TW, zh_TW.UTF-8
localepurge	localepurge/dontbothernew	boolean	false
localepurge	localepurge/none_selected	boolean	false

So, these are the questions the debconf will ask you. (Since the questions has different priorities, you might not be asked for all the questions) The localepurge/nopurge line is the locales data we want to keep, so we also want to let the other servers have the same settings. You can use debconf-set-selections to set the values in the other servers.

# echo "localepurge localepurge/nopurge multiselect en, en_US.UTF-8, zh, zh_TW, zh_TW.UTF-8"|debconf-set-selections

Then you can now install the package, it will use the default value you just gave. If you need to install many servser, and do not want to see the question dialogs. You can use noninteractive fronetend to bypas the questions.

# DEBIAN_FRONTEND=noninteractive dpkg-reconfigure localepurge

This is a Tips for Debian system.

Thanks clkao (高大師) for the great svn-mirror tool. I am using svn-mirror 0.68-3 on Debian Etch for mirror svn repository from the damn far and slow European svn server, so I can enjoy the super faster checkout and show the log messages on local server.

However, since the the svn server is slow and connection is not stable (otherwise I don’t need svn-mirror anyway). The connection might be dropped or the process could be killed by accident in the long mirroring process. The problem is once the program is killed (Ex: by Control+C), then it will run into a dead lock situation. You will keep seeing this messages, and never get the mirror work again.

Waiting for sync lock on /mirror/remote: openwrt:25221.

In order to fix the problem, I wrote a simple script svn-mirror-unlock.pl. It’s for clean the dead lock.

$ svn-mirror-unlock.pl
svn-mirror-unlock.pl: unlock SVMREPOS path
$ perl svn-mirror-unlock.pl unlock /home/svn mirror/remote

This is a tip for Debian.

It’s been almost one year for not maintaining the wiki.debian.org.tw web site. Since I joined the current company, I spent all my time for dealing with routine jobs every signal day. I don’t even want to use my laptop at home, after I finish the jobs every day.

Lately, the wiki.debian.org.tw becomes more unstable. People usually see `Service is not available’ pages in the last couple weeks. One of the reason is the disk is full, the other reason is there are too much spam articles.

Finally, I spent a few hours this weekend for the site. First thing I do, it’s to upgrade the server and the mediawiki software. Frankly speaking, it’s not hard at all, since the wiki is installed in a vserver based on the Debian. All I need to do is running `aptitude dist-upgrade’, to upgrade the distribution from sarge to etch. And then I sync the mediawiki source tree, from 1.7.1 to 1.11.1. It’s also very easy, since mediawiki provide a upgrade script for check and modify the database schema.

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If you ever read my blog entry for setting up the Debian.org.tw, you probably already know that I love to use reverse proxy in the front of my web servers. This approach can solve the signal IP address for multiple Vservers problem, also it can provide web cache which reducing the server loading.

Since the proxy server (Squid) pass the http session to the real web servers, one of the problem is that my web servers always saw signal source IP address, which is the proxy’s IP address. Even through the proxy server still put the client’s IP in the `X-Forwarded-For’ http header, it’s still painful to retrieve the correct IP address from the head in every web application.

Thanks for Thomas Eibner, who wrote the reverse proxy add forward module for apache. The module simply check the IP address to see if it comes from the proxy server, if it is it will put the IP address in `X-Forwarded-Host’ or `X-Host’ to `Host’ header. So you don’t need to worry about the wrong IP address, and track the http requests more easily.

Debian package is ported by Piotr Roszatycki, but it’s still the old 0.5 version. Since the 0.6 is out, I filed a bugreport for remind him. For my etch servers, I back-ported the package with the last version. You can download it from my personal repository.

BTW, Piotr Roszatycki use yada for libapache2-mod-rpaf, who is also the maintainer of yada. After reading the yada’s script file `debian/packages’, I really feel like I went to my `good’ old days with RPM/specs.