Merge pull request mvallim#28 from mvallim/readme-environments-definition

Update readme to more clearly specify build/live/target systems

Author: mvallim

README.md

@@ -14,9 +14,15 @@ This procedure shows how to create a **bootable** and **installable** Ubuntu Liv
 
 [![build-focal](https://github.com/mvallim/live-custom-ubuntu-from-scratch/actions/workflows/build-focal.yml/badge.svg)](https://github.com/mvallim/live-custom-ubuntu-from-scratch/actions/workflows/build-focal.yml)
 
+## Terms
+
+* `build system` - the computer environment running the build scripts that generate the ISO.
+* `live system` - the computer environment that runs from the live OS, generated by a `build system`.  This may also be referred to as the `chroot environment`.
+* `target system` - the computer environment that runs after installation has completed from a `live system`.
+
 ## Prerequisites (GNU/Linux Debian/Ubuntu)
 
-Install applications we need to build the environment.
+Install packages we need in the `build system` required by our scripts.
 
 ```shell
 sudo apt-get install \
@@ -35,6 +41,8 @@ mkdir $HOME/live-ubuntu-from-scratch
 
 ## Bootstrap and Configure Ubuntu
 
+`debootstrap` is a program for generating OS images.  We install it into our `build system` to begin generating our ISO.
+
 * Checkout bootstrap
 
   ```shell
@@ -64,6 +72,8 @@ mkdir $HOME/live-ubuntu-from-scratch
 
 > Reference: https://en.wikipedia.org/wiki/Chroot
 
+From this point we will be configuring the `live system`.
+
 1. **Access chroot environment**
 
    ```shell
@@ -399,6 +409,8 @@ sudo umount $HOME/live-ubuntu-from-scratch/chroot/run
 
 ## Create the CD image directory and populate it
 
+We are now back in our `build environment` after setting up our `live system` and will continue creating files necessary to generate the ISO.
+
 1. Access build directory
 
    ```shell
@@ -492,7 +504,8 @@ sudo umount $HOME/live-ubuntu-from-scratch/chroot/run
 
 ## Create manifest
 
-In the next steps the creation of the manifest is important because it tells us which version of each package installed in the Live version and which packages will be removed or maintained in the version that will be installed (persisted in the hard drive).
+Next we create a file `filesystem.manifest` to specify each package and it's version that is installed on the `live system`.  We create another file `filesystem.manifest-desktop` which specifies which files will be installed on the `target system`.  Once the Ubiquity installer completes, it will
+remove packages specified in `filesystem.manifest` that are *not* listed in `filesystem.manifest-desktop`.
 
 1. Access build directory
 
@@ -520,7 +533,7 @@ In the next steps the creation of the manifest is important because it tells us
 
 ## Compress the chroot
 
-After everything has been installed and preconfigured in the **chrooted** environment, we need to generate an image of everything that was done by following the next steps.
+After everything has been installed and preconfigured in the **chrooted** environment, we need to generate an image of everything that was done by following the next steps in the `build environment`.
 
 1. Access build directory
 
@@ -728,6 +741,11 @@ It is simple and easy, using "dd"
 ```shell
 sudo dd if=ubuntu-from-scratch.iso of=<device> status=progress oflag=sync
 ```
+
+## Summary
+
+This completes the process of creating a live Ubuntu installer from scratch.  The generated ISO may be tested in a virtual machine such as `VirtualBox` or written to media and booted from a standard PC.
+
 ## Contributing
 
 Please read [CONTRIBUTING.md](CONTRIBUTING.md) for details on our code of conduct, and the process for submitting pull requests to us.