Workshop Exercise 3.1 - Booting an Edge Device

Table of Contents

• Objective
• Step 1 - Writing the ISO to a USB Device
• Step 2 - Booting Your Edge Device
• Step 3 - Creating Our Customized ISO
• Solutions

Objective

In this exercise, we’re going to use our customized ISO to provision our edge devices.

If you have a monitor/keyboard available at your station, feel free to use them. If not, contact with the instructor for more information.

Note

This exercise is for students with physical devices. If you do not have one and are instead virtualizing an edge device, proceed to the next exercise.

Step 1 - Writing the ISO to a USB Device

There are multiple ways and utilities that can be used to copy an ISO onto a flash drive. On linux, the easiest way is to use the dd command to copy the ISO onto your USB device. However, other applications including Fedora Media Writer can also be used. For Windows, Rufus is one such utility.

On your linux system, use the dd command to copy the ISO to the USB device:

dd if=~/generate-iso/rhde-ztp.iso of=/dev/sdz

Note

This operation does require root, and ensure that you’re referencing at the correct device in the of parameter. More information can be found in the RHEL Documentation.

Step 2 - Booting Your Edge Device

The basic idea is to boot from the newly created flash drive on your edge device. The basic steps are: Insert USB Device > Boot Device > Enter Boot Menu > Select USB Device To Boot From.

For OnLogic devices, the boot menu option key is F10. For Intel Devices, the boot menu option key is DEL.

Step 3 - Creating Our Customized ISO

First, ensure the following files are present in the ~/generate-iso/ directory which were created in earlier exercies:

.
├── grub.cfg
├── isolinux.cfg
├── ks.cfg
└── rhel-8.7-x86_64-boot.iso

Next, create a file called recook.sh with the following contents:

#!/bin/bash

# Ensure this script is run as root
if [ "$EUID" != "0" ]; then
    echo "Please run as root" >&2
    exit 1
fi

# Set a few bash options
cd "$(dirname "$(realpath "$0")")"
set -ex

# Create a temp dir
tmp=$(mktemp -d)
mkdir "$tmp/iso"

# Mount the boot iso into our temp dir
mount rhel-8.7-x86_64-boot.iso "$tmp/iso"

# Create a directory for our new ISO
mkdir "$tmp/new"

# Copy the contents of the boot ISO to our new directory
cp -a "$tmp/iso/" "$tmp/new/"

# Unmount the boot ISO
umount "$tmp/iso"

# Copy our customized files into the new ISO directory
cp ks.cfg "$tmp/new/iso/"
cp isolinux.cfg "$tmp/new/iso/isolinux/"
cp grub.cfg "$tmp/new/iso/EFI/BOOT/"

# Push directory of new ISO for later commands
pushd "$tmp/new/iso"

# Create our new ISO
mkisofs -o ../rhde-ztp.iso -b isolinux/isolinux.bin -J -R -l \
    -c isolinux/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table -eltorito-alt-boot \
    -e images/efiboot.img -no-emul-boot -graft-points -joliet-long -V "RHEL-8-7-0-BaseOS-x86_64" . 
isohybrid --uefi ../rhde-ztp.iso
implantisomd5 ../rhde-ztp.iso

# Return to previous directory
popd

# Cleanup and give user ownership of ISO
mv "$tmp/new/rhde-ztp.iso" ./
rm -rf "$tmp"
chown $(stat -c '%U:%G' .) ./rhde-ztp.iso

Once the file has been created, make the script executable and then run it the script via sudo: chmod ug+x recook.sh && sudo ./recook.sh

After the script completes, you should have a new ISO called rhde-ztp.iso within this directory.

Note

If the mkisofs, isohybrid, and implantisomd5 commands aren’t available, you may need to install the genisoimage, syslinux, and isomd5sum packages.

Solutions

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