19 January 2009
How to setup PPTP VPN in Linux
Create a file /etc/ppp/peers/name: pty "pptp host --nolaunchpppd" name username remotename PPTP require-mppe-128 file /etc/ppp/options.pptp ipparam name Add this line to the file /etc/ppp/chap-secrets: username PPTP password * Create a file /etc/ppp/ip-up.d/tunnel #!/bin/sh if [ "${PPP_IPPARAM}" = "name" ]; then route add -net RemoteNetworkWithNetmask dev ${PPP_IFACE} fi RemoteNetworkWithNetmask is the network on the remote side you want to access via the VPN tunnel, e.g. 172.16.0.0/12.
Connect by running sudo pon name
16 January 2009
Things you might want to change in Ubuntu 8.04 (hardy) desktop, part 1
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.
11 January 2009
How to use mousewheel in GNU Screen
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 ~/.
10 January 2009
How to use Ctrl-Tab in GNU Screen
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.
16 December 2008
Configure web applications in JBoss
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 .
8 December 2008
Packages you might want to remove from Ubuntu 8.04 (hardy) desktop
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.
26 July 2008
Linux with / mounted read-only
(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.
31 October 2007
Why can only root listen to ports below 1024?
(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
21 May 2007
Common mistakes with exceptions in Java
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.
28 March 2007
Linux on diskless workstation
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.