Diary Products - Hannes Schmidt blogs

Install Squid 3.2.x on Ubuntu 12.04 (Precise) LTS

Fri, 25 Jan 2013 00:51:21 +0000

This is how I upgraded the Squid package from 3.1.19 to 3.2.6 on my Ubuntu 12.04 installations. The 3.2.x branch contains support for multiple cores, so that's a pretty important update to have. 12.04 is an LTS release, so I'm really not sure why 3.2.6 hasn't been backported to it. Anyhow, here's how I did it:

Set up the dquilt shell alias as described in the Debian New Maintainer's Guide:

alias dquilt="quilt --quiltrc=${HOME}/.quiltrc-dpkg"

Create ~/.quiltrc-dpkg containing

Inotify for Python

Thu, 24 Jan 2013 20:27:08 +0000

The other day, I was trying to use Linux' inotify(7) functionality in a Python script. The obvious contender seems to be pynotify, being the top Google result, as well as being mentioned in the O'Reilly title Python for Unix and Linux System Administration. Unfortunately, I found myself dumbfounded by its API. The native inotify(7) functionality is simple and elegant, what does a scripting wrapper have to add on top of it? If it were an abstraction that unifies the various platform-specific filesystem notification approaches, I would be able to digest a thick, opinionated API, but a mere wrapper for one particular platform should be just that: a wrapper, as thin as possible.

Lightweight and fast HTTP proxies

Sun, 20 Jan 2013 00:24:10 +0000

I recently evaluated several open-source HTTP proxy servers. I was looking for something lightweight and fast, without a persistent cache or with no cache at all.

Debugging System Preference Panes with ARC under Mountain Lion

Tue, 18 Dec 2012 19:47:38 +0000

First of all, follow the accepted answer in this StackOverflow question. That takes care of the basics. Second, if your application is using ARC (as it should if it targets Lion and higher) you may have to explicitly disable garbage collection for the System Preferences application. System Preferences is using ARC by default but there seems to be some crutch in place that causes it to switch to GC when launched by Xcode. This crutch will cause

Garbage Collection enabled !

in the debug log and the

To use the â€œ...â€ preferences pane, System Preferences must quit and reopen.

error sheet to be displayed when your preference pane is selected. Clicking OK will restart System Preferences and you will lose your debug session.

I found that setting OBJC_DISABLE_GC to YES will override the crutch and cause System Preferences to start with ARC enabled, letting you debug your preference pane as intended. In Xcode, edit the scheme (Menu Product - Edit scheme), select the Run action and click the arguments tab. To the Environment Variables list, add an entry for OBJC_DISABLE_GC and YES.

This is on Xcode 4.5.2 (4G2008a) on OS X 10.8.2.

Installing Mosh on Ubuntu Hardy

Fri, 27 Jul 2012 06:24:46 +0000

I recently had to get into the Mosh pit with my good old friend Hardy Heron aka Ubuntu 8.04 TLS.

wget --no-check-certificate https://github.com/keithw/mosh/zipball/mosh-1.2.2
mv mosh-1.2.2 mosh-1.2.2.zip
unzip mosh-1.2.2.zip
cd keithw-mosh-df955aa
sudo sed -i -r 's/#\s*(.*hardy-backports.*)/\1/' /etc/apt/sources.list
sudo apt-get update
sudo apt-get install build-essential autoconf automake libprotobuf-dev \
                     protobuf-compiler libncurses5-dev zlib1g-dev libio-pty-perl
./autogen.sh
protobuf_CFLAGS=" " protobuf_LIBS="-lprotobuf" ./configure --prefix="/usr"
sed -i s/LITE_RUNTIME/SPEED/ src/protobufs/*.proto
make
sudo make install

NSTreeController's add, addChild, insert and insertChild methods

Fri, 09 Jul 2010 19:59:00 +0000

I had a hard time interpreting Apple's documentation of NSTreeController's mutator methods and their corresponding canXyz methods. My experiments did reveal symmetry in and consistency among the semantics of these methods, it's just that their naming is a bit odd (I say that coming from a strong Java background). The docs didn't help much either. I only investigated NSTreeController in entity mode, but I would guess that these methods behave identically in object mode as far as the pre-conditions and the position of the new node are concerned.

add: Creates a new entity and makes it the last sibling of the selected entity. IOW, the new entity becomes the last child of the selected entity's parent. Without a selection, the entity becomes the last top-level (orphan) entity. Think appendSibling.
canAdd: Have never observed it to be false.
insert: Creates a new entity and makes it a sibling of the selected entity, immediately preceding it. Without a selection, the entity becomes the first top-level entity. Think prependSibling.
canInsert: Have never observed it to be false.
addChild: Does nothing if the selected entity is a leaf. Otherwise, creates a new entity and adds it as the last child of the selection. Think appendChild.
canAddChild: False if selection is a leaf.
insertChild: Does nothing if the selected entity is a leaf. Otherwise, creates a new entity and adds it as the first child of the selection.Think prependChild.
canInsertChild: False if selection is a leaf.

Please not that these are empirical findings. I am pretty confident that they are accurate for the mutators, I am pretty sure that they are incomplete for the canXyz methods. In other words, even if canAdd seems to be true all the time, I wouldn't assume that add always succeeds and still bind to canAdd.

Debian/Ubuntu packages for Hudson CI

Wed, 05 May 2010 17:19:32 +0000

The awesome Hudson Continuous Integration project seems to be undergoing some organizational changes at the moment. Its leader, Kohsuke Kawaguchi has left Sun/Oracle and started up his own company revolving around professional services for Hudson, it seems. Let's hope this is not going to be one of those messy "open-source project going commercial" scenarios. Anyways, one of the more immediate problems caused by the changes is that the Debian package repository did not get any updates since late March. In a Hudson mailing list Kohsuke casually announced that he'd be pushing packages to this Hudson CI Debian and Ubuntu package repository but this fact isn't reflected on the official Hudson website yet which is why I am mentioning it here, putting all of my SEO weight behind the link ;-).

Bind9 with DLZ and MySQL backend on Ubuntu Jaunty (9.04), Lucid (10.04) and Precise (12.04)

Thu, 24 Dec 2009 22:48:59 +0000

Update 06/27/2010: This workaround is still necessary for Lucid (10.04 LTS) and Precise (12.04 LTS). These instructions still work for those releases with minor adjustments (see the updates at the end of the article).

This forum post got me started but I got stuck in various places and thought I'd summarize what worked for me. I'm not going to explain much but if you're going to work with Bind and DLZ you probably know what you're dealing with. I also won't go into configuring DLZ because that depends on your particular DB schema and there is sufficient documentation on the DLZ website.

We need MySQL of course:

Domain Name (Dis)service

Fri, 18 Sep 2009 16:41:07 +0000

There are plenty of openly accessible DNS servers available that do name resolution for you. Most Internet providers run them for their customers. There are also DNS providers that encourage you to replace your ISP's name server with theirs. OpenDNS is one example. They even do it without charging you! But remember, hardly anything on the Internet is free. Someone will have to pay the bill. AFAIK, OpenDNS' business model is based on advertising revenue, so the advertiser pays the bill. This is how it works: If you accidentally type a URL with a nonexistent domain name, OpenDNS will resolve it to one of their web servers instead of returning an NXDOMAIN error. The web server will then serve a page with web search results related to the mistyped domain name and some advertisements.

Installing dbd-mysql for 64-bit binary installation of MySQL

Sun, 21 Jun 2009 01:02:44 +0000

The dbd-mysql gem assumes (?) an i386 architecture when building the native component of the driver. You'll need to set ARCHFLAGS appropriately and point the build at the installation of MySQL.

sudo env ARCHFLAGS="-arch x86_64" \
     gem install mysql -- \
     --with-mysql-config=/usr/local/mysql/bin/mysql_config

That should fix it.

Multiple Google Notifier instances for multiple accounts on Mac OS X

Fri, 19 Jun 2009 19:29:22 +0000

I use Google Notifier to have my Gmail account checked for new mail periodically and automatically. I have a secondary Gmail account that I don't use that often but that I would like to have notifier check as well. Unfortunately, Google Notifier currently supports a single Gmail account only. Here's a simple hack that works well for a few gmail accounts. In a nutshell, you need to clone the application package and modify the bundle id in the clone's Contents/Info.plist file.

Copy the Google Notifier application from Applications to a temporary location.

Overriding DHCP- or VPN-assigned DNS servers in Mac OS X Leopard

Sun, 03 May 2009 20:13:55 +0000

I'll have to break sad news to you: /etc/resolv.conf has been made redundant in Mac OS X. The dig and nslookup utilities still read it but most applications use a different mechanism for picking DNS servers when resolving host names. They generally go through Darwin's resolver library which instead of reading /etc/resolv.conf looks up DNS servers via the SystemConfiguration framework backed by configd. Survival of the fittest, I guess, or, Darwin's intelligent design.

Ok, ok, I'll stop trying to be funny ... Anyways, this would be all swell if there wasn't the occasional need for manually specifying DNS servers. For me this need typically arises when I connect to a VPN managed by an operator from hell. After hours and hours of hard work (my fingertips still hurt from all the googling) I present to you a solution:

With the VPN connected, launch scutil with root privileges:

hannes-mbp:~ Sysop$ sudo scutil
Password:

List all network services with DNS configuration:

> list State:/Network/Service/[^/]+/DNS
  subKey [0] = State:/Network/Service/A3551F2D-62CE-1234-B79A-6EE50CA7AE30/DNS
  subKey [1] = State:/Network/Service/F194302A-846C-4321-9325-6813DAE148F2/DNS

Pick one and show its contents.

> show State:/Network/Service/A3551F2D-62CE-1234-B79A-6EE50CA7AE30/DNS
<dictionary> {
  SupplementalMatchDomains : <array> {
    0 : 
  }
  ServerAddresses : <array> {
    0 : 192.168.1.74
    1 : 217.0.43.81
  }
  SupplementalMatchOrders : <array> {
    0 : 100000
  }
}

Ahh, this is the one! So let's get rid of those pesky servers. Obtain a working copy of the DNS configuration entry. It's called ... drum roll ... well, obviously: "d" (rolls eyes).

> d.init
> get State:/Network/Service/A3551F2D-62CE-1234-B79A-6EE50CA7AE30/DNS
> d.show
<dictionary> {
  SupplementalMatchDomains : <array> {
    0 : 
  }
  ServerAddresses : <array> {
    0 : 192.168.1.74
    1 : 217.0.43.81
  }
  SupplementalMatchOrders : <array> {
    0 : 100000
  }
}

Reset the ServerAddresses entry to an empty array:

> d.add ServerAddresses *
> d.show
<dictionary> {
  ServerAddresses : <array> {
  }
  SupplementalMatchDomains : <array> {
    0 : 
  }
  SupplementalMatchOrders : <array> {
    0 : 100000
  }
}

Write the working copy back:

> set State:/Network/Service/A3551F2D-62CE-1234-B79A-6EE50CA7AE30/DNS

Note, that the line

d.add ServerAddresses *

clears the ServerAddresses array, thereby removing all DNS-servers tied to that particular connection ("service" in Apple-talk). Without service-specific DNS servers, Mac OS will fall back to DNS servers from other network services. Not sure how exactly that works. If you want to specify particular DNS servers, use

d.add ServerAddresses * 10.0.1.2 112.21.44.66

By the way, the "*" signifies array values, so it's not some kind of wild card.

Pimp Da Kitty

Sat, 13 Dec 2008 07:46:59 +0000

I have been converted. After having preferred Windows on the desktop for the past 15 years, after six generations of

Yet Another Way To Screw Up The Control Panel,^™

I felt the urge to try something else. Something that

Just Works.^™

Those fifteen years were an interesting ride but for some reason the pride and satisfaction of finding just the right combination of registry settings that would let me mount a Samba share had worn off. I want to spend my time on something creative. Defragmenting the registry, scanning regularly for malware, and trying to find anti-virus software that doesn't take five minutes to load is fun and all, but how about an operating system that doesn't need any of that? You guessed right, I have become a Mac user. Enough of the trivialities, in this article I would like to list a handful of very useful Mac OS X applications and utilities I couldn't live without anymore.

Increase Wireshark Font Size on Mac OS X

Mon, 08 Dec 2008 01:58:21 +0000

Wireshark has a preference setting for the font of the capture display but it won't let you change the main font used for other UI elements such as like menu, toolbar and dialog windows. The default for the main font is illegibly small on my Mac OS X Leopard system -- I used Macports to install Wireshark and its dependencies. To fix it you need to add the gtk-font-name setting to your .gtkrc-2.0 preference file:

echo 'gtk-font-name = "Sans 14"' >> ~/.gtkrc-2.0

This will affect all applications using the GTK 2.0 toolkit but I guess that's ok.

Drupal vs. Wordpress

Mon, 01 Dec 2008 01:46:55 +0000

A close relative of mine asked me to help him with choosing, installing and maintaining a blog for him. I am a big fan of Drupal (the software behind this blog, in case you were wondering) but just couldn't bring myself to recommend it. Don't get me wrong, Drupal is IMHO superior in almost all technical aspects but its user interface is just not as easy to use as WordPress. The person in question being a fairly inexperienced user of web technologies, usability was a major concern. The result can be admired at Hartwig Schmidt's blog.