View source for OS Builder/Edit a config file

This recipe will show you how to apply a change to a config file on the resulting XO image.

Note that a very small config file change may break the OS, sometimes spectacularly, sometimes in subtle ways. Make sure you test your changes in depth, no matter how simple they may appear.

=Simple edit using sed=

For this configuration change, we will use a regular expression, with the tool sed.

* Add the "custom_scripts" module to the modules list
* At the end of your config file, add this section:
 [custom_scripts]
 custom_script_0=%(oob_config_dir)s/config_edit.sh
* In the same directory as your config file, create a file called "config_edit.sh", containing:
 #!/bin/bash -x 
 set -e
 echo 'VOIDS YOUR WARRANTY!'
 sed -i 's/CONFIG_VALUE="yes"/CONFIG_VALUE="no"/' $INSTALL_ROOT/etc/sometool/sometool.conf

=Example uses=

Note that using these example changes can affect your build significantly.
 
* Edit /usr/share/olpc-utils/xorg.conf.d/xo1.75.conf to change DontZap from true to false, or to enable RenderAccel

=Hints=

* Test your sed replacements manually, on an installed image, until you have them right.
* Remember to test the resulting build for subtle problems.