Sometimes, there is a need to check some patch in the installation system. Of course, we have an article that describe how to Create a Modified Installation System but this one takes a lot of time to prepare, you need a remote server and several things can break.You can also use Driver Update, but that expects you are able to build RPM with the changes you want to test.
Here you can see the simplest way...
Starting-Up
Start installation from media by adding startshell=1 to the Linuxrc commandline. This will make installation open a shell window before starting YaST/Installer.
You can also boot directly to the installation without adding startshell=1 to the command line but it that case you can't change files that are loaded when the installer starts. Your choice :)
Preparing Installation System
By default, the installation system is read-only but we can cheat it ;)! Let's assume we want to change some YaST script in /usr/share/YaST/clients/ directory in this example.
# The only writable directory is /tmp (and /var...)
cd /tmp
# Copy all clients to /tmp
mkdir clients
cp -ar /usr/share/YaST/clients/* /tmp/clients/
# Bind the writable directory to the original location
mount --bind /tmp/clients /usr/share/YaST/clients
Now you can edit, extend, remove, compile ... etc. the writable clients directory. Hint: If you want to start network (and your network supports DHCP) to copy the patched sources using network, just simply enter dhcpcd eth0 (or similarly according to your current setup).
And ... that's all folks!
Continuing with the Installation
If you have used startshell=1, just simply enter exit command or press Ctrl+d.







