# About ${CLFS}

Throughout this book, the environment variable `CLFS` will be used several times. It is paramount that this variable is always defined. It should be set to the mount point chosen for the CLFS partition. Check that the `CLFS` variable is set up properly with:

    echo ${CLFS}

Make sure the output shows the path to the CLFS partition's mount point, which is `/mnt/clfs` if the provided example was followed. If the output is incorrect, the variable can be set with:

    export CLFS=/mnt/clfs

Having this variable set is beneficial in that commands such as `install -dv ${CLFS}/tools` can be typed literally. The shell will automatically replace ${CLFS} with /mnt/clfs (or whatever the variable was set to) when it processes the command line.

If you haven't created the `${CLFS}` directory, do so at this time by issuing the following commands:

    install -dv ${CLFS}

Do not forget to check that `${CLFS}` is set whenever you leave and reenter the current working environment (as when doing a su to `root` or another user).