After installing Ubuntu 8.04 (hardy) desktop, there are some things you might want to change. This article focus on system configuration (mostly editing in /etc) and requires superuser access (using sudo). Some of this changes requires reboot to take effect.

Fix terminal font rendering bug

There is a bug which gives bad font rendering in the terminal window. Fix it by doing this in a terminal:

cd /etc/fonts/cond.d
sudo unlink 10-hinting-medium.conf
sudo ln -s ../conf.avail/10-hinting-full.conf

Fix bug in DHCP client

Fix a bug in the DHCP client described here.

GNU Screen has support for scrollback, but by default you have to use awkward keys to use it. I would like to be able to use Shift-PageUp, Shift-PageDown and the mousewheel to scroll, just like you can do in xterm.

It was not easy to configure Screen for this, and it involves cooperation with the terminal emulator. But I finally managed to achieve a solution which works pretty well. Add this to your ~/.Xresources file (create it f you don’t have it already) (you need to log out for this to take effect):

GNU Screen allows you to open several sub-windows within one terminal window. By default, you switch between them using Ctrl-A followed by n or p. I think this is a bit clumsy, I would like to switch with Ctrl-Tab and Ctrl-Shift-Tab just like you switch tabs in Firefox and many other applications. The sub-windows in Screen is conceptually just like tabs in Firefox, so it’s logical to use the same keys to switch between them.

When you deploy a web application in a JavaEE application server, it usually consist of a .war archive.

Sometimes, the web application needs some configuration parameters. The most common way to do this is to have <context-param> in web.xml. That is simple and works fine except that the web.xml file needs to be inside the .war archive. This makes it inconvenient to change a configuration parameter since you have to repack the .war archive. You also have to set the same value several times if several web applications share the same configuration.

When you install Ubuntu 8.04 (hardy) desktop, you get a lot of packages installed by default. Most users will never use many of these packages, so you end up with a lot of unnecessary packages. Most of these packages are harmless and only waste disk space when not used.

However, some packages can actually affect the system in a negative way, such as draining resources (other then disk space), and you should consider removing them if you not actively use them.

(This post has been edited since it was first published.)

I wondered why you usually mount / (the root file system) read-write in Linux and decided to do some experiments to find out if it is possible to have it mounted read-only.

So why do you want to do that? Perhaps you have the root file system on a read-only media, such as CD-ROM. Or on a writable media which can only handle a limited number of writes, such as a CD-RW or flash disk. It would also increase security since it will be more difficult (though not impossible) for some malware to infect your system.

(This article has been edited since it’s first publication.)

In Linux, and other UNIX-like systems, you have to be root (have superuser privileges) in order to listen to TCP or UDP ports below 1024 (the well-known ports).

This port 1024 limit is a security measure. But it is based on an obsolete security model and today it only gives a false sense of security and contributes to security holes.

The port 1024 limit forces you to run all network daemons with
superuser privileges, which might open security holes. Without the port 1024 limit, most network daemons (except sshd), could be run without superuser privileges. Some daemons try to remedy this potential security hole by dropping the superuser privileges after binding to the port, but you still need to start the daemon as root. And this does not work if the daemon is written in Java, which is quite popular for web servers.

Unintentional catching of runtime exceptions

Unfortunately, checked exceptions in Java are defined as all Exceptions which are not RuntimeExceptions. This makes it a bit tricky to catch all checked exceptions (but not any runtime exceptions). It would have been better if checked exceptions were defined by a specific class, CheckedException, but that’s too late to change now.

Too often Java programmers catch all exceptions when they really only should catch checked exceptions. However, there is a quite easy workaround to catch all checked exceptions, and nothing else:

When the built-in HDD controller in my computer broke down, I decided to try running my computer diskless with LAN booting. I use Ubuntu Linux 6.10 and I have another computer with a large HDD acting as server.

I followed the instructions in this HOWTO. I changed MODULES to “netboot” in initramfs.conf and I had to add a driver for my network adapter to the modules file in the initramfs configuration. It took me a while to realize why it didn’t work without the network adapter driver. I also mounted /tmp as tmpfs.

I’m currently developing my first AJAX based web application. The goal is to have a pure AJAX application, i.e. never reload the entire page, use only background XMLHTTPRequest to contact the server.

My observations so far is that it is possible to do most of the application logic I need. But the performance of Javascript execution in the browser is a big obstacle. The application is centered around a list of data items in a scrollable area. The list is loaded as preformatted XHTML with an AJAX request and then some Javascript is used to decorate it with event handlers. I would like to display up to 1000 items at once, but I quickly realized that this wasn’t possible. The Javascript loop triggered the timeout in the browser after about five seconds. This timeout does not count waiting for the server to deliver the response, it only counts the client Javascript code to process the response. This timeout is reasonable, it’s clearly not acceptable for the user to wait over five seconds for the browser to process the server response (in addition to wait for the server and network to deliver the response). After limiting to 100 item, it works.