infrastructure/scripts/kvm/README.md

KVM Switch: Mac ↔ Nobara

Software KVM to switch Dell U3821DW monitor and Logitech MX peripherals between Mac and Nobara.

Hardware

• Monitor: Dell U3821DW (USB-C to Mac, HDMI 2 to Nobara)
• Keyboard: Logitech MX Keys S
• Mouse: Logitech MX Master 3S
• Bolt #1: Connected directly to Nobara
• Bolt #2: Connected to Dell monitor USB hub (routes to Mac via USB-C)

Channel Setup

Channel	Code	Connection	Computer
2	0x01	Bolt #1	Nobara
3	0x02	Bolt #2 (via monitor)	Mac

Mac Setup

Prerequisites

# Install m1ddc (DDC control for Apple Silicon)
brew install m1ddc

# Install hidapitester
curl -sL https://github.com/todbot/hidapitester/releases/latest/download/hidapitester-macos-arm64.zip -o /tmp/hidapitester.zip
unzip -o /tmp/hidapitester.zip -d ~/bin/
chmod +x ~/bin/hidapitester

Install Script

mkdir -p ~/scripts
cp to_nobara.sh ~/scripts/
chmod +x ~/scripts/to_nobara.sh

Keyboard Shortcut (Logi Options+)

1. Logi Options+ → MX Keys S → Smart Actions
2. Create action triggered by F12
3. Action: Open File → ~/scripts/to_nobara.sh

Nobara Setup

Prerequisites

# Install ddcutil
sudo dnf install -y ddcutil

# Add user to i2c group (REBOOT REQUIRED)
sudo usermod -aG i2c $USER

# Install hidapitester
mkdir -p ~/bin
curl -sL https://github.com/todbot/hidapitester/releases/latest/download/hidapitester-linux-amd64.zip -o /tmp/hidapitester.zip
unzip -o /tmp/hidapitester.zip -d ~/bin/
chmod +x ~/bin/hidapitester
rm /tmp/hidapitester.zip

# Udev rule for non-root HID access
echo 'SUBSYSTEM=="usb", ATTRS{idVendor}=="046d", ATTRS{idProduct}=="c548", MODE="0666"' | \
  sudo tee /etc/udev/rules.d/99-logitech-bolt.rules
sudo udevadm control --reload-rules && sudo udevadm trigger

Install Script

mkdir -p ~/scripts
cp to_mac.sh ~/scripts/
chmod +x ~/scripts/to_mac.sh

Keyboard Shortcut (GNOME)

1. Settings → Keyboard → Custom Shortcuts
2. Add shortcut:
   • Name: KVM to Mac
   • Command: /home/USER/scripts/to_mac.sh
   • Shortcut: F12

Pairing Peripherals

Each device must be paired to BOTH Bolt receivers:

MX Master 3S / MX Keys S

1. Press Easy-Switch button to select channel (2 for Nobara, 3 for Mac)
2. Hold 3 seconds until LED blinks fast
3. Use Logi Options+ (Mac) or Solaar (Linux) to complete pairing

Install Solaar (Linux)

sudo dnf install solaar
solaar &
# Click "Pair new device" while peripheral is blinking

Troubleshooting

Monitor doesn't switch

• Check DDC/CI is enabled: Monitor Menu → Others → DDC/CI → On
• Mac: Ensure USB-C cable supports data (not video-only)
• Linux: Ensure user is in i2c group and rebooted

Peripherals don't switch

• Verify devices are paired to both Bolt receivers
• Check device indices with: solaar show (Linux)
• Device indices (0x01, 0x02) depend on pairing order

Find correct device indices

# On Linux with solaar
solaar show

# Or query via HID++
hidapitester --vidpid 046d/c548 --list-detail

DDC Input Codes (Dell U3821DW)

Input	Code
HDMI 1	17
HDMI 2	18
USB-C	27
DP 1	15
DP 2	16