Customize Linux from the Bottom—Building Your Own Linux Base System

One of the advantages of using Linux is that there are many documents and tools to help you customize your system and solve problems. The code is no secret. Everything inside and outside is open. Besides, there are many other useful sources in print and on the Web. There is no other system which can compare to Linux in this respect, not even Free BSD, let alone any proprietary operating systems.

Typically, for a problem, we might work out a few different solutions. We always want to pick the best one, of course, but it is not easy to know which is the best until we have tried each of them. To solve a problem, in many cases, we can find answers by consulting Linux HOWTOS and docs, or asking Linux guys in our organization. As an alternative, you can post a message on a Linux newsgroup and hope someone on there can give you a quick reply. If you want to pay, there are many Linux-related companies providing technical services as well. (If the problem is stubborn, as the last straw, kick your buggy box a few times, as I did sometimes. You must be careful—don't break it and then reboot. That should work; otherwise repeat the problem-solving sequence from the beginning again.)

gdb is an excellent debugging support for applications on the base system. If we don't want or are unable to run a full gdb on the target system, that is, the base system, we can run small remote gdb facilities as either a gdb stub or a gdb server on the target. Besides, things like the syslogd dæmon can also help debugging on the target system.

There are many good problem-solving strategies. Whatever approaches we use, the goal is to find the proper solution. It is usually safe to follow a successful example. For example, we learn something by checking things inside a Red Hat rescue system. We can do this simply with the following few commands:

cat rescue.img | gzip -d > rescue_root.img
mkdir rescue_root
mount -o loop rescue_root.img rescue_root

Here rescue.img is the compressed rescue floppy image found in the Red Hat distribution's images directory. Then we can check its contents by:

ls rescue_root

bin dev etc lib lost+found mnt proc sbin tmp usr

This article is only an introduction to customization of the Linux base system. For a particular situation, it could be rather complex, especially when modifications at the code level are required, such as to support specialized hardware. But, we have shown that it is a manageable task. Our purpose is to make things simple in order to encourage people to take the challenge. By creating our own customized base system with a moderate effort, we get a power engine which can drive us into the bright future.

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