Linux From Scratch - Version cross-r12.0-499

Chapter 2. Preparing the Host System

2.4. Setting The $LFS Variable

Throughout this book, the environment variable LFS will be used several times. You should ensure that this variable is always defined throughout the LFS build process. It should be set to the name of the directory where you will be building your LFS system - we will use /mnt/lfs as an example, but the choose any directory name you want. Choose a directory location and set the variable with the following command: 

export LFS=/mnt/lfs

Having this variable set is beneficial in that commands such as mkdir -v $LFS/tools can be typed literally. The shell will automatically replace “$LFS” with “/mnt/lfs” (or whatever value the variable was set to) when it processes the command line.

Create the directory: 

mkdir -pv $LFS

If you don't have much space in the partition holding the directory, you can mount another partition on it.

[Caution]

Caution

Do not forget to check that LFS is set whenever you leave and reenter the current working environment (such as when doing a su to root or another user). Check that the LFS variable is set up properly with: 

echo $LFS

Make sure the output shows the path to your LFS system's build location, which is /mnt/lfs if the provided example was followed. If the output is incorrect, use the command given earlier on this page to set $LFS to the correct directory name.

[Note]

Note

One way to ensure that the LFS variable is always set is to edit the .bash_profile file in both your personal home directory and in /root/.bash_profile and enter the export command above. In addition, the shell specified in the /etc/passwd file for all users that need the LFS variable must be bash to ensure that the /root/.bash_profile file is incorporated as a part of the login process.

Another consideration is the method that is used to log into the host system. If logging in through a graphical display manager, the user's .bash_profile is not normally used when a virtual terminal is started. In this case, add the export command to the .bashrc file for the user and root. In addition, some distributions use an "if" test, and do not run the remaining .bashrc instructions for a non-interactive bash invocation. Be sure to place the export command ahead of the test for non-interactive use.