Live Image

Contained here are the secrets to spinning out an RTXI live CD.

Building from scratch.

To build from scratch, you will need two things:

• An internet connection.
• *.deb files from an already-compiled, aufs-patched real-time kernel.

If you don't have deb files from an aufs-patched kernel, compile one using install_rt_aufs_kernel.sh. The script differs from the generic one in that it compiles a module for AUFS, which is needed for the live casper filesystem to work. You can follow along the generic custom install instructions on rtxi.org/install, except you want to compile a kernel for a generic processor architecture instead of the one specific to your machine.

1. Clone this repo.

git clone https://github.com/rtxi/live-image

In the base of the directory, you will find the following:

• build-from-scratch.sh, the script the builds a live CD.
• chroot-script.sh, a script used by build-from-scratch.sh.
• build-rt-aufs-kernel.sh, which builds deb files for real-time kernels with the aufs module.
• deb_files, the directory where the build-from-scratch.sh script expect deb files for real-time kernels to be stored.

2. Build an Aufs-enabled RT kernel.

Skip this step if you already compiled them. Just stick the kernels - header and image - in the deb_files directory. If not, continue.

First, open the build-rt-aufs-kernel.sh script. Near the top will be a section for setting up environment variables. The main ones to pay attention to are:

1. LINUX_VERSION, the kernel version.
2. ARCH, the architecture of the kernel you're building.
3. XENOMAI_VERSION, the Xenomai version.
4. AUFS_VERSION, Aufs version (same as LINUX_VERSION sans minor revision number).
5. LINUX_CONFIG_URL, url to kernel deb image in Ubuntu's kernel repository (used to extract the starting kernel config for a particular kernel version.)

Edit these parameters to match what you want to build. Then, run:

sudo ./build-rt-kernel-aufs.sh

The script will download all source code, images, etc. needed in the /opt directory and then compile the kernel. It will not actually install the kernel. The kernel configurations to tweak are the same as they are for default (non-Aufs) kernels, with the exception:

--> Filesystems --> Miscellaneous filesystems --> Aufs (enable as module)

Once the kernel is built, it will be copied to the deb_files folder.

Note: If you ever try this with an PREEMPT_RT kernel, it will fail. Aufs and the RT patch are not compatible.

3. Run build-from-scratch.sh

Run the build-from-scratch.sh script in the base of the 'live-image' repo. You don't need to run the script as root. Bits that need root permissions will prompt you for your password.

This will take a while to run, especially if your system or network connection is slow. The script will multithread when doing heavier tasks. You will need to be present for a few steps, such as:

1. Telling the system to not use kexec-tools for handling reboots.
2. Prompting you for your password if Ubuntu's sudo timer went out while some step was running.

Other than that, the script will handle everything. Your system will be somewhat unresponsive during compression and image generation steps.

4. Test out the live CD.

When the script finishes executing, you'll see a new directory in your repo called image_chroots. Inside, there will be another directory called build_[DATE]_[TIME], with DATE and TIME corresponding to when you executed the script.

Within the build directory, there are two *iso files, one for the generic Ubuntu CD and another for the new live image. The live image is named rtxi_[RTXI_VERSION][UBUNTU_FLAVOR][UBUNTU_VERSION]_[ARCH].iso. Test out the live image. Clone it to a USB or burn it on a CD to demo RTXI and also install it.

To clone to a USB within Linux, use dd:

$ sudo dd if=the-new-live-cd.iso of=/dev/your_device bs=1M && sync

If done from another OS, try using UNetbootin.