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Anand Rathnas
Anand Rathnas

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Turning a 2013 Dell E6540 into a Dedicated TV Media Controller

#tv #ubuntu #liveusb

TL;DR: I spent 12+ hours fighting Ubuntu 24.04's layered squashfs, hidden welcome wizards, and Chrome sandbox crashes to create a turnkey live USB for my old Dell E6540 laptop. Here's everything I learned so you don't have to.

The Setup

I have a Dell Latitude E6540 (circa 2013) collecting dust. I also have a TV that needs a dedicated browser for streaming. The plan: create a custom Ubuntu live USB that boots directly into Chrome, no setup wizards, no login screens, just plug and play.

Hardware:

The Journey (aka What Went Wrong)

1. Ubuntu 24.04's Layered Squashfs

The Problem: Ubuntu 24.04 doesn't use a single filesystem.squashfs anymore. It uses a layered system:

casper/
├── minimal.squashfs           # Base layer
├── minimal.standard.squashfs  # Standard additions
└── minimal.standard.live.squashfs  # Live environment customizations
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What I Tried: Merging all layers into one filesystem.squashfs.

What Happened: Boot failure - "File system layers are missing"

The Fix: Keep ALL layers intact. Only modify the specific layer containing what you need to change. Casper expects the layered structure.

Reference: Ubuntu Casper Manual

2. Finding gnome-initial-setup

The Problem: The GNOME initial setup wizard kept appearing on boot. I needed to remove it.

What I Tried: Searching and removing from the top layer only.

What Happened: Still appeared. The binary wasn't in the top layer.

The Fix: Search ALL layers using unsquashfs -l (list mode - fast!) instead of extracting:

for layer in minimal minimal.standard minimal.standard.live; do
  FOUND=$(unsquashfs -l "$CASPER_DIR/${layer}.squashfs" 2>/dev/null | \
    grep -E "gnome-initial-setup" || true)
  if [ -n "$FOUND" ]; then
    echo "Found in ${layer}.squashfs!"
  fi
done
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Lesson: gnome-initial-setup lives in minimal.squashfs (the base layer).

3. The "Welcome to Ubuntu" Imposter

The Problem: After removing gnome-initial-setup, a "Welcome to Ubuntu" wizard STILL appeared.

What I Tried: Removing more gnome-initial-setup files, masking systemd services, creating done files.

What Happened: Still appeared. Different icon, different behavior.

The Fix: It's NOT gnome-initial-setup. It's ubuntu-desktop-bootstrap - a completely different snap package!

# Search for the REAL culprit
unsquashfs -l layer.squashfs | grep -E "ubuntu-desktop-bootstrap|desktop-bootstrap"
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Lesson: Don't assume. Check the actual desktop shortcut or process name.

4. Auto-Login Configuration

The Problem: System landed on login screen instead of auto-logging in.

The Fix: Configure GDM properly in the squashfs:

mkdir -p "$SQUASH_DIR/etc/gdm3"
cat > "$SQUASH_DIR/etc/gdm3/custom.conf" << 'EOF'
[daemon]
InitialSetupEnable=false
AutomaticLoginEnable=true
AutomaticLogin=ubuntu
EOF
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5. Chrome Crashes on Live USB

The Problem: Chrome installed fine but crashed immediately on launch. Error reporter appeared.

What I Tried: Adding --disable-gpu (wrong assumption about nomodeset).

The Real Problem: Chrome's sandbox doesn't play nice with overlayfs (used by live USB environments).

The Fix:

google-chrome-stable \
  --no-first-run \
  --no-default-browser-check \
  --disable-session-crashed-bubble \
  --no-sandbox \
  "https://your-url-here"
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Note: --no-sandbox reduces security but is necessary for live USB environments.

6. pactl: command not found

The Problem: Script failed with pactl: command not found on Ubuntu 24.04 live environment.

Why: Ubuntu 24.04 uses PipeWire, and pactl (PulseAudio control) may not be available in the minimal live environment.

The Fix: Check before using:

if command -v pactl &>/dev/null; then
  HDMI_SINK=$(pactl list short sinks | grep -i hdmi | head -1 | awk '{print $2}')
  [ -n "$HDMI_SINK" ] && pactl set-default-sink "$HDMI_SINK"
else
  echo "Warning: pactl not available"
fi
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7. Slow USB Write on macOS

The Problem: Writing 6GB ISO took 1085 seconds (~18 minutes).

The Fix: Use raw device /dev/rdisk instead of /dev/disk:

# Slow (~18 min for 6GB)
sudo dd if=ubuntu.iso of=/dev/disk4 bs=4m

# Fast (~2 min for 6GB) - use rdisk
RAW_DEVICE=$(echo "/dev/disk4" | sed 's|/dev/disk|/dev/rdisk|')
sudo dd if=ubuntu.iso of=$RAW_DEVICE bs=4m status=progress
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Why: /dev/rdisk bypasses macOS's buffer cache, giving ~10x faster writes.

8. EFI Partition Extraction

The Problem: Custom ISO wouldn't boot on UEFI systems.

The Fix: Extract and preserve the original EFI partition:

# Get EFI partition info from original ISO
EFI_INFO=$(xorriso -indev "$ISO_IN" -report_el_torito as_mkisofs 2>&1 | \
  grep -A1 "append_partition 2")
INTERVAL=$(echo "$EFI_INFO" | grep -oP '\d+d-\d+d' | head -1)

# Extract it
START_SECTOR=$(echo "$INTERVAL" | cut -d'-' -f1 | tr -d 'd')
END_SECTOR=$(echo "$INTERVAL" | cut -d'-' -f2 | tr -d 'd')
COUNT=$((END_SECTOR - START_SECTOR + 1))
dd if="$ISO_IN" of="$EFI_IMG" bs=512 skip="$START_SECTOR" count="$COUNT"
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The Final Solution

I built a Docker-based tool that:

  1. Downloads Ubuntu 24.04 desktop ISO
  2. Extracts and modifies the layered squashfs
  3. Removes ALL welcome wizards (gnome-initial-setup, gnome-tour, ubuntu-desktop-bootstrap)
  4. Configures auto-login
  5. Pre-installs wallpapers, Chrome policies, dark mode
  6. Rebuilds a bootable hybrid ISO (BIOS + UEFI)
  7. Writes to USB with one command 
./make.sh  # Does everything: clean, build, write to USB
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Use It Yourself

If you have a Dell E6540 (or similar older laptop) and want a dedicated TV/media controller:

GitHub: github.com/tv6540/cubic2

Requirements:

Usage:

git clone https://github.com/tv6540/cubic2
cd cubic2
./make.sh
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The script will:

  1. Prompt for sudo (kept alive during build)
  2. Show USB device picker
  3. Confirm before erasing
  4. Download Ubuntu ISO (cached for future builds)
  5. Build custom ISO in Docker
  6. Write to USB

Boot the USB, and the setup script runs automatically to configure display, install Chrome, and you're ready to stream.

Key Takeaways

  1. Ubuntu 24.04 uses layered squashfs - don't merge them, modify in place
  2. unsquashfs -l is your friend - list files without extracting (fast!)
  3. ubuntu-desktop-bootstrap != gnome-initial-setup - check process names
  4. Chrome needs --no-sandbox on live USB - overlayfs breaks the sandbox
  5. Use /dev/rdisk on macOS - 10x faster USB writes
  6. Get all prompts upfront - nobody wants to wait 20 min then type "yes"

Hardware Recommendation

The Logitech K400 Plus is perfect for this setup:

  • Wireless with tiny USB receiver
  • Built-in trackpad
  • Media keys
  • Long battery life
  • Compact for couch use

Built with mass frustration, mass trial-and-error, and mass caffeine.

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