In a previous post, we discussed how to manually set up a Linux system that restores itself on every reboot, just like Faronics Deep Freeze.
Today, let's take it one step further: we'll customize an Ubuntu ISO so that:
-
It boots directly into a self-healing system,
-
It automatically sets up writable storage on a flash drive,
-
It wipes that flash drive every time you reboot.
No user intervention needed. Fully turnkey.
Prerequisites
Before we begin, you'll need:
-
✅ A Linux system to prepare everything (Ubuntu preferred)
-
✅ The Ubuntu 22.04 LTS ISO
-
✅ A blank DVD or a bootable USB stick for burning
-
✅ A second USB flash drive (at least 8GB) for temporary write space
-
✅ Basic familiarity with the Linux terminal
Step 1: Set Up a Working Folder
First, install a few helper tools:
sudo apt update
sudo apt install squashfs-tools xorriso isolinux syslinux-utils
Now, set up a working folder:
mkdir ~/ubuntu-custom
cd ~/ubuntu-custom
Step 2: Extract the Ubuntu ISO
Download your Ubuntu ISO and extract it:
wget https://releases.ubuntu.com/22.04/ubuntu-22.04.4-desktop-amd64.iso
# Mount and copy contents
mkdir mnt
sudo mount -o loop ubuntu-22.04.4-desktop-amd64.iso mnt
rsync -a mnt/ extract-cd/
sudo umount mnt
You now have a modifiable copy of the ISO contents in extract-cd/.
Step 3: Add Our Auto-Wipe and Overlay Scripts
Inside extract-cd/, we'll embed a tiny custom startup script.
Create the directory if it doesn't exist:
mkdir -p extract-cd/casper/scripts
Now create the script:
nano extract-cd/casper/scripts/wipe-usb-overlay
Paste this:
#!/bin/bash
#
# Set up an OverlayFS using a flash drive, wiping it every boot
DEVICE=$(blkid | grep "TYPE=\"ext4\"" | grep -v "cdrom" | awk '{print $1}' | tr -d ':') # crude but works
MOUNTPOINT=/media/usb
mkdir -p $MOUNTPOINT
mount $DEVICE $MOUNTPOINT
# Reformat USB flash drive
mkfs.ext4 -F $DEVICE
# Re-mount it fresh
mount $DEVICE $MOUNTPOINT
# Create upper and work directories for overlay
mkdir -p $MOUNTPOINT/upper
mkdir -p $MOUNTPOINT/work
# Mount overlay
mkdir -p /cow
mount -t overlay overlay -o lowerdir=/,upperdir=$MOUNTPOINT/upper,workdir=$MOUNTPOINT/work /cow
# Switch root to overlay
mount --bind /cow /
Save and close.
Make it executable:
chmod +x extract-cd/casper/scripts/wipe-usb-overlay
Step 4: Hook It Into Boot
Now, modify the boot sequence so Ubuntu will run this script automatically.
Edit extract-cd/casper/initrd by decompressing and editing:
cd extract-cd/casper
mkdir initrd
cd initrd
gzip -dc ../initrd | cpio -id
Now edit init (the master boot script):
nano init
Find a good spot after the root filesystem is mounted (you can search for mountroot) and insert:
# Custom wipe USB overlay setup
/scripts/wipe-usb-overlay
Then rebuild initrd:
find . | cpio --create --format='newc' | gzip > ../initrd
cd ..
rm -rf initrd
Step 5: Rebuild the ISO
Back in your main ubuntu-custom/ directory:
cd ~/ubuntu-custom
sudo mkisofs -D -r -V "UBUNTU_FREEZE" -cache-inodes -J -l \
-b isolinux/isolinux.bin -c isolinux/boot.cat -no-emul-boot \
-boot-load-size 4 -boot-info-table -o ubuntu-deepfreeze.iso extract-cd
This creates ubuntu-deepfreeze.iso — your brand-new Deep Freeze-style Ubuntu image!
Step 6: Burn and Boot
-
Burn
ubuntu-deepfreeze.isoto a DVD, or -
Flash it to a USB stick using
Rufus,dd, orbalenaEtcher.
When you boot:
✅ Ubuntu will load fresh
✅ It will wipe and set up the USB flash drive automatically
✅ All system changes will disappear on reboot
✅ No user input is needed
Final Notes
| Area | Notes |
|---|---|
| Flash Drive Wear | Consider using durable, higher-end flash drives |
| Security | Add a UUID check if you want to verify the correct flash drive |
| Performance | Booting from USB stick (read-only) is much faster than DVD |
Conclusion
Now you have a true turnkey Deep Freeze system for Ubuntu —
no more worries about malware, user errors, broken settings, or clogged hard drives.
This setup is perfect for schools, labs, libraries, pop-up installations, and experiments.
All built with 100% free and open-source tools.
Linux is magic.
