Before you can actually start doing something with a package, you need to unpack it first. Often you will find the package files being tar'ed and gzip'ed (you can determind this by looking at the extension of the file. tar'ed and gzip'ed archives have a .tar.gz or .tgz extension for example)). I'm not going to write down every time how to ungzip and how to untar an archive. I will tell you how to do that once, in this paragraph. There is also the possibility that you have the ability of downloading a .tar.bz2 file. Such a file is tar'ed and compressed with the bzip2 program. Bzip2 achieves a better compression than the commonly used gzip does. In order to use bz2 archives you need to have the bzip2 program installed. Most if not every distribution comes with this program so chances are high it is already installed on your system. If not, install it using your distribution's installation tool.
To start with, change to the $LFS/usr/src directory by running:
cd $LFS/usr/src
When you have a file that is tar'ed and gzip'ed, you unpack it by running either one of the following two commands, depending on the filename format:
tar xvzf filename.tar.gz
tar xvzf filename.tgz
When you have a file that is tar'ed and bzip'ed, you unpack it by running:
bzcat filename.tar.bz2 | tar xv
Some tar programs (most of them nowadays but not all of them) are slightly modified to be able to use bzip2 files directly using either the I or the y tar parameter which works the same as the z tar parameter to handle gzip archives.
When you have a file that is tar'ed, you unpack it by running:
tar xvf filename.tar
When the archive is unpacked a new directory will be created under the current directory (and this document assumes that you unpack the archives under the $LFS/usr/src directory). You have to enter that new directory before you continue with the installation instructions. So everytime the book is going to install a program, it's up to you to unpack the source archive.
After you have installed a package you can do two things with it. You can either delete the directory that contains the sources or you can keep it. If you decide to keep it, that's fine by me. But if you need the same package again in a later chapter you need to delete the directory first before using it again. If you don't do this, you might end up in trouble because old settings will be used (settings that apply to your normal Linux system but which don't always apply to your LFS system). Doing a simple make clean or make distclean does not always guarantee a totally clean source tree. The configure script can also have files lying around in various subdirectories which aren't always removed by a make clean process.
There is on exception to that rule: don't remove the linux kernel source tree. A lot of programs need the kernel headers, so that's the only directory you don't want to remove, unless you are not going to compile any software anymore.