To develop an installer or debug it could be very challenging for the sake of limited resource. Besides, long turn around time is another big big challenge as well. It could be a nightmare.
The limited resource here means:
The long turn around time here means:
The limited resource here means:
- You have no idea where the log will be.
- You may not fetch the log you want.
- You don't manage to access the log even you know where it is.
The long turn around time here means:
- You can't reproduce the breakpoint within 5 minutes because you have to restart the machine and wait for image-level copying.
I will take an example below to elaborate the essence of an installer challenge. LAVA is a tool for debian, and I will talk about Ubuntu.
Ubuntu Desktop installer
To develop Ubuntu Desktop installer on a real machine in OEM mode. I often turn on debug mode by injecting debug parameters in the kernel parameter line and go to /var/log/installer/debug. To hardcode the frequently used parameters in the bootloader (say grub.cfg of grub) may be a good idea, because it takes much attention to input the parameters. The following parameters are the ones I used very much:
- debug -- automatic-oem-config debug
I tweak casper/filesystem.squashfs sometime as well to dump more special messages at the stage 1 of recovery. Besides, to install useful tools by choort/dpkg may be a good idea as well. A better text editor and the ability to ssh connect remotely may help me to interact with the installer and monitor the log in run time.
To leverage tweaking squashfs is useful, however it also pays off. A typical Ubuntu desktop squashfs could be 1 ~ 2G. If you are not using solid state disks, it takes a log of time to extract the squashfs, modify it, and then re-pack it back to a squashfs. Frequent flow looks like:
- sudo unsquashfs -d ./fs filesystem.squashfs (extract files)
- sudo mksquashfs ./fs/ filesystem.squashfs.mod (pack modified files)
- sudo cp filesystem.squashfs.01 ./<somewhere of your installing media>/casper/filesystem.squashfs (deploy)
An auxiliary could be an ftp server to download debug tools.
