My adventures in Linux began in 1998 when I downloaded and installed my first distribution. After working with it for a while, I discovered issues I definitely would have liked to see improved upon. For example, I didn't like the arrangement of the bootscripts or the way programs were configured by default. I tried a number of alternative distributions to address these issues, yet each had its pros and cons. Finally, I realized that if I wanted full satisfaction from my Linux system, I would have to build my own from scratch.

What does this mean? I resolved not to use pre-compiled packages of any kind, nor CD-ROMs or boot disks that would install basic utilities. I would use my current Linux system to develop my own customized system. This “perfect” Linux system would then have the strengths of various systems without their associated weaknesses. In the beginning, the idea was rather daunting, but I remained committed to the idea that a system could be built that would conform to my needs and desires rather than to a standard that just did not fit what I was looking for.

After sorting through issues such as circular dependencies and compile-time errors, I created a custom-built Linux system that was fully operational and suitable to individual needs. This process also allowed me to create compact and streamlined Linux systems which are faster and take up less space than traditional operating systems. I called this system a Linux From Scratch system, or an LFS system for short.

As I shared my goals and experiences with other members of the Linux community, it became apparent that there was sustained interest in the ideas set forth in my Linux adventures. Such custom-built LFS systems serve not only to meet user specifications and requirements, but also serve as an ideal learning opportunity for programmers and system administrators to enhance their Linux skills. Out of this broadened interest, the Linux From Scratch Project was born.

This Linux From Scratch book provides readers with the background and instruction to design and build custom Linux systems. This book highlights the Linux from Scratch project and the benefits of using this system. Users can dictate all aspects of their system, including directory layout, script setup, and security. The resulting system will be compiled completely from the source code, and the user will be able to specify where, why, and how programs are installed. This book allows readers to fully customize Linux systems to their own needs and allows users more control over their system.

I hope you will have a great time working on your own LFS system, and enjoy the numerous benefits of having a system that is truly your own.

There are many reasons why somebody would want to read this book. The principal reason is to install a Linux system from the source code. A question many people raise is, “why go through all the hassle of manually building a Linux system from scratch when you can just download and install an existing one?” That is a good question and is the impetus for this section of the book.

One important reason for LFS's existence is to help people learn how a Linux system works from the inside out. Building an LFS system helps demonstrate what makes Linux tick, and how things work together and depend on each other. One of the best things that this learning experience provides is the ability to customize Linux to your own tastes and needs.

A key benefit of LFS is that it allows users to have more control over the system without relying on someone else's Linux implementation. With LFS, you are in the driver's seat and dictate every aspect of the system, such as the directory layout and bootscript setup. You also dictate where, why, and how programs are installed.

Another benefit of LFS is the ability to create a very compact Linux system. When installing a regular distribution, one is often forced to include several programs which are probably never used. These programs waste disk space, or worse, CPU cycles. It is not difficult to build an LFS system of less than 100 megabytes (MB), which is substantially smaller than the majority of existing installations. Does this still sound like a lot of space? A few of us have been working on creating a very small embedded LFS system. We successfully built a system that was specialized to run the Apache web server with approximately 8MB of disk space used. Further stripping could bring this down to 5 MB or less. Try that with a regular distribution! This is only one of the many benefits of designing your own Linux implementation.

We could compare Linux distributions to a hamburger purchased at a fast-food restaurant—you have no idea what might be in what you are eating. LFS, on the other hand, does not give you a hamburger. Rather, LFS provides the recipe to make the exact hamburger desired. This allows users to review the recipe, omit unwanted ingredients, and add your own ingredients to enhance the flavor of the burger. When you are satisfied with the recipe, move on to preparing it. It can be made to exact specifications—broil it, bake it, deep-fry it, or barbecue it.

Another analogy that we can use is that of comparing LFS with a finished house. LFS provides the skeletal plan of a house, but it is up to you to build it. LFS maintains the freedom to adjust plans throughout the process, customizing it to the user's needs and preferences.

An additional advantage of a custom built Linux system is security. By compiling the entire system from source code, you are empowered to audit everything and apply all the security patches desired. It is no longer necessary to wait for somebody else to compile binary packages that fix a security hole. Unless you examine the patch and implement it yourself, you have no guarantee that the new binary package was built correctly and adequately fixes the problem.

The goal of Linux From Scratch is to build a complete and usable foundation-level system. Readers who do not wish to build their own Linux system from scratch may not benefit from the information in this book. If you only want to know what happens while the computer boots, we recommend the “From Power Up To Bash Prompt” HOWTO located at http://axiom.anu.edu.au/~okeefe/p2b/ or on The Linux Documentation Project's (TLDP) website at http://www.tldp.org/HOWTO/From-PowerUp-To-Bash-Prompt-HOWTO.html. The HOWTO builds a system which is similar to that of this book, but it focuses strictly on creating a system capable of booting to a BASH prompt. Consider your objective. If you wish to build a Linux system while learning along the way, then this book is your best choice.

There are too many good reasons to build your own LFS system to list them all here. This section is only the tip of the iceberg. As you continue in your LFS experience, you will find the power that information and knowledge truly bring.

Building an LFS system is not a simple task. It requires a certain level of existing knowledge of Unix system administration in order to resolve problems, and correctly execute the commands listed. In particular, as an absolute minimum, the reader should already have the ability to use the command line (shell) to copy or move files and directories, list directory and file contents, and change the current directory. It is also expected that the reader has a reasonable knowledge of using and installing Linux software.

Because the LFS book assumes at least this basic level of skill, the various LFS support forums are unlikely to be able to provide you with much assistance; you will find that your questions regarding such basic knowledge will likely go unanswered, or you will simply be referred to the LFS essential pre-reading list.

Before building an LFS system, we recommend reading the following HOWTOs:

The host must be running at least a 2.6.2 kernel compiled with GCC-3.0 or higher. There are two main reasons for this requirement. First, the Native POSIX Threading Library (NPTL) test suite will segfault if the host's kernel has not been compiled with GCC-3.0 or a later version. Second, the 2.6.2 or later version of the kernel is required for the use of Udev. Udev creates devices dynamically by reading from the sysfs file system. However, support for this filesystem has only recently been implemented in most of the kernel drivers. We must be sure that all critical system devices get created properly.

In order to determine whether the host kernel meets the requirements outlined above, run the following command:

cat /proc/version

This will produce output similar to:

Linux version 2.6.2 (user@host) (gcc version 3.4.0) #1
    Tue Apr 20 21:22:18 GMT 2004

If the results of the above command do not state that the host kernel is either 2.6.2 (or later), or that it was not compiled using a GCC-3.0 (or later) compiler, one will need to be installed. There are two methods you can take to solve this. First, see if your Linux vendor provides a 2.6.2 (or later) kernel package. If so, you may wish to install it. If your vendor doesn't offer a 2.6.2 (or later) kernel package, or you would prefer not to install it, then you can compile a 2.6 kernel yourself. Instructions for compiling the kernel and configuring the boot loader (assuming the host uses GRUB) are located in Chapter 8. This second option can also be seen as a gauge of your current Linux skills. If this second requirement is too steep, then the LFS book will not likely be much use to you at this time.

To make things easier to follow, there are a few typographical conventions used throughout this book. This section contains some examples of the typographical format found throughout Linux From Scratch.

./configure --prefix=/usr

This form of text is designed to be typed exactly as seen unless otherwise noted in the surrounding text. It is also used in the explanation sections to identify which of the commands is being referenced.

install-info: unknown option '--dir-file=/mnt/lfs/usr/info/dir'

This form of text (fixed-width text) shows screen output, probably as the result of commands issued. This format is also used to show filenames, such as /etc/ld.so.conf.

Emphasis

This form of text is used for several purposes in the book. Its main purpose is to emphasize important points or items.

http://www.linuxfromscratch.org/

This format is used for hyperlinks both within the LFS community and to external pages. It includes HOWTOs, download locations, and websites.

cat > $LFS/etc/group << "EOF"
root:x:0:
bin:x:1:
......
EOF

This format is used when creating configuration files. The first command tells the system to create the file $LFS/etc/group from whatever is typed on the following lines until the sequence end of file (EOF) is encountered. Therefore, this entire section is generally typed as seen.

[REPLACED TEXT]

This format is used to encapsulate text that is not to be typed as seen or copied-and-pasted.

passwd(5)

This format is used to refer to a specific manual page (hereinafter referred to simply as a “man” page). The number inside parentheses indicates a specific section inside of man. For example, passwd has two man pages. Per LFS installation instructions, those two man pages will be located at /usr/share/man/man1/passwd.1 and /usr/share/man/man5/passwd.5. Both man pages have different information in them. When the book uses passwd(5) it is specifically referring to /usr/share/man/man5/passwd.5. man passwd will print the first man page it finds that matches “passwd”, which will be /usr/share/man/man1/passwd.1. For this example, you will need to run man 5 passwd in order to read the specific page being referred to. It should be noted that most man pages do not have duplicate page names in different sections. Therefore, man [program name] is generally sufficient.

This book is divided into the following parts.

The software used to create an LFS system is constantly being updated and enhanced. Security warnings and bug fixes may become available after the LFS book has been released. To check whether the package versions or instructions in this release of LFS need any modifications to accommodate security vulnerabilities or other bug fixes, please visit http://www.linuxfromscratch.org/lfs/errata/6.1.1/ before proceeding with your build. You should note any changes shown and apply them to the relevant section of the book as you progress with building the LFS system.