Getting Started

Preliminaries

Before we can actually create the VM, some things you need to take care of. First, we need to have a system where we can actually build the software. Next, we need to analyze the host system so we can optimize our VM. Choosing the optimal values for RAM and CPU cores can significantly decrease the build time.

Build Environment

I have created a fairly nice environment for us to use while building LFS. It is a custom LiveCD I created using much of the knowledge I gained form the first time I created LFS. The CD has all of the prerequisite software installed. So you will able to start right away.

You can download the file below. Remember, put it on the machine's hard drive!

Download: lfs-cd.iso

Calculate the amount of RAM

Building software is a RAM intensive process. This is one area where throwing RAM at the problem will make a huge difference. This is an important and complex issue, so read the following carefully and make sure that you understand the issues completely.

When using Windows, this value must be set to 25% of the total available RAM. This is why you need at least 2GB of main memory on your physical machine.

Linux and Macs, on the other hand, are not as resource intensive, so you can raise this up to 50% of your total main memory. This assumes you are not going to be using the physical machine for anything else while you are running the LFS virtual machine.

The problem is that this value should not change between the different physical machines you are going to use this VM on. So if you plan on doing any work on a different machine you must set this value to the appropriate minimum value. For example, if you are going to build LFS on an Ubuntu Linux machine with 4GB of RAM, and work on it at school on a Windows machine 3GB of RAM, set the virtual machine's RAM to 768MB.

For simplicities sake, we are going to build a 32-bit operating system. The main effect of this decision is that the OS cannot access any RAM greater than 3GB. In other words, 3GB is the maximum amount of RAM you can use.

After you have decided on how much RAM to use, write it down.

Determining The Number of Cores

You can compile much of LFS in parallel. This means you can take advantage of the multi-core nature of modern computers. Virtualbox only allows you to use multiple cores if your host computer has Vt-x or AMD-V enabled.

On most AMD multi-core machines, AMD-V is available. Unfortunately, Intel segments its processor pricing partially based on have Vt-x or not. This means it is difficult to predict if a particular processor has Vt-x or not. To further complicate the issue, many commodity motherboards disable these visualization extensions in the BIOS.

You best bet is to try turning on the extensions in the VM's settings. VirtualBox should complain if it cannot access the extensions.

The easiest way to find out if the extensions are available is to google for your processor's model and Vt-x or AMD-V. You should be able to determine if they are available on the processor. If it is available, but VirtualBox cannot access the extension, then it is probably disabled in your motherboard's BIOS. Try finding a setting that will enable it.

Creating the VM

LFS is going to need to be installed into a new virtual machine. Start by clicking the New button in VirtualBox.

1. Set the VM's name to "lfs" and set the OS type to "Linux 2.6/3.x"
2. Set the amount of RAM to the value you wrote down a minute ago. Be sure to use proper 2ⁿ number, i.e. 1GB = 1024.
3. We now need to create our virtual machine's hard drive.
   1. Make the image a VDI file (default).
   2. Make the image a dynamically expanding (default), this option works best on USB.
   3. The image name should be "lfs" (the default). The disk should be 4GB in size.

Our VM is created, but we are not done yet. We are going to need a special "build" hard drive and we need it to boot off of a ISO image.

1. Select lfs from the VM list and click the Settings.
2. Click System to bring up the system management page.
3. Click the Processor tab to and make sure Enable PAE/NX is checked.
4. If you have the Vt-x or AMD-V extension enabled, you need to do the following. Set the number of processors, on the Processor tab, to 50% of your system's physical cores. On the Motherboard tab, check the Enable I/O ACPI box. Finally, on the Acceleration tab, make sure both boxes are checked.
5. Click Storage in the left panel to bring up the storage page.
6. Under Controller: IDE click on the empty CDROM entry.
7. On the right hand side, click on CD icon to bring up a list of known ISO files. Your list is probably empty. Click the Choose a virtual CD/DVD disk file.
8. You will need to select the lfs-cd.iso file you downloaded. Note, do not put this file on your USB drive as this will cause a huge loss in performance.
9. Click the Controller: SATA entry. Click the Add Hard Disk button (second button in the highlighted entry).
10. In the resulting dialog box, click the Create new disk button.
    1. Make the image a VDI file (default).
    2. Make the image a dynamically expanding (default), this option works best on USB.
    3. The image name should be "LFS Build". The disk should be 4GB in size.
    4. Click the Create button.

Booting From The CD

We are finally ready to get started! Because your VM's hard drive is blank, your machine will boot from the CDROM, a.k.a the LFS ISO image file. You will see a bunch of messages scroll by as the OS boots. These messages are for debugging purposes in case you have trouble booting the ISO file.

Eventually you will reach the desktop. This is an LXDE desktop. The desktop has a Start Menu in the lower left corner of the screen. I have already installed the VirtualBox Guest Additions. Hence, the screen resolution should match the VM's window size.

Advice — Read This!!!!

Below is some advice that I had to learn the hard way. I really recommend that you read it carefully. It will save you time and quite a bit of effort.

Tips On Using VirtualBox

One of the best features of a virtual machine is its ability to take snapshots. A snapshot is a record of written to disk of the virtual machine's state at the time the snapshot was taken. This means basically that a image is taken of the VM's RAM and hard drive. The benefit is that at any time you can revert back to a previous snap shot.

You will mess up somewhere while creating your LFS system. Taking frequent snapshots will allow you to revert back to a "good" state. You can think of snapshots as "game saves." They allow you to jump backwards in time to whenever you took the snapshot.

Maximizing Virtual Machine Performance

VM's by their nature run slower than an installed OS. But there are ways to squeeze pretty good performance out of them. The first is to cut-down on running applications in the host system. The host system's multitasking may treat the VM as just any other application. When you are doing a sixty minute compile, you do not want the host to give the VM the same priority as Firefox. So, do not run any applications in the host while the VM is running. This is not an absolute rule though. If you have a fast machine, a lot of time, or copious amounts of RAM you can multi-task in the host OS. I would still recommend that you do not do it on the longer and more intensive compiles. The easiest way to avoid multitasking in the host OS is to run VirtualBox in full-screen mode, this way you avoid the temptation.

The Book

Linux from Scratch (LFS) is installed by following all the steps in a book. For your convenience I have placed the book onto the desktop of the LiveCD. Use that book, not the one listed on their website. The one on their website gets updated frequently. The off-line copy is a stable version, you are less likely to run into new bugs.

It is very important that you read and understand the white part of the book. This is what will make up the majority of your next test, so pay attention. The book is not overly long, you could read it cover to cover in about five hours. Don't just blindly copy/paste the steps this will cause you to fail certain steps. Realize that creating a LFS system is difficult, time consuming, and error prone. You may need to make multiple tries at each part before you get a working system.

Do to how the book has you do the steps, you need to be able to get better performance out of your terminal window. Use the LXterminal (it is in the shortcut bar) rather than xterm, it has more features (like a working copy-paste system). LXterminal works essentially just like the terminal emulator we have used in class. Here is a list of short-cuts that will be of great benefit.