31.94.22.136: Migrated comment #6197

2025-12-30T09:07:09Z

Migrated comment #6197

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This script stopped working with Trixie, so I spent the day rewriting the shutdown portion so that it's usable going forward. Enjoy!

### X-C1 Safe Power-Off (xoff)

# What this does (by design)
# • xoff → clean Linux shutdown
# • All filesystems unmounted
# • Then hardware power is cut via X-C1 GPIO pulse
# • Board stays off (manual power-on required)
# • Reboot remains safe (no power cut)

# Prerequisites
# • Raspberry Pi with X-C1 board attached
# • Raspberry Pi OS (Bullseye / Bookworm / Trixie)
# • GPIO27 wired to X-C1 soft power-cut input (default)
# • Root filesystem on ext4 (standard)

## Step 1 — Install required packages

sudo apt update
sudo apt install -y gpiod

# Verify GPIO access:

gpioinfo -c gpiochip0 | grep GPIO27

# You should see: "line 27: "GPIO27" input"

## Step 2 — Create the hardware power-cut script
# This script only triggers the X-C1 power cut. It does not shut down Linux.

sudo tee /usr/local/sbin/xc1-powercut.sh > /dev/null <<'EOF'
#!/usr/bin/env bash
set -euo pipefail

# Pulse GPIO27 HIGH briefly to trigger X-C1 hard power cut
/usr/bin/gpioset -c gpiochip0 -p 100ms 27=1
EOF

sudo chmod 0755 /usr/local/sbin/xc1-powercut.sh

## Step 3 — Create the systemd shutdown unit
# This ensures the GPIO pulse fires after all filesystems are unmounted, but only on poweroff, not reboot.

sudo tee /etc/systemd/system/xc1-cutpower.service > /dev/null <<'EOF'
[Unit]
Description=X-C1: cut power at end of poweroff (after unmount)
DefaultDependencies=no
After=umount.target
Before=systemd-poweroff.service

[Service]
Type=oneshot
ExecStart=/bin/sh -c 'sync; sleep 0.2; /usr/local/sbin/xc1-powercut.sh'
TimeoutStartSec=5

[Install]
WantedBy=poweroff.target
EOF

# Activate it:

sudo systemctl daemon-reload
sudo systemctl enable xc1-cutpower.service

# Confirm attachment:

systemctl show -p After -p Before xc1-cutpower.service
systemctl list-dependencies --plain poweroff.target | grep xc1
systemctl list-dependencies --plain reboot.target | grep xc1 || echo "not attached to reboot"

# Expected: Attached to poweroff.target, Not attached to reboot.target

## Step 4 — Install the xoff command
# We deliberately avoid shell aliases so this works consistently across SSH, scripts, and non-interactive shells

sudo tee /usr/local/bin/xoff > /dev/null <<'EOF'
#!/usr/bin/env bash
exec sudo systemctl poweroff
EOF

sudo chmod 0755 /usr/local/bin/xoff

# If you previously used an alias, remove it:

unalias xoff 2>/dev/null || true
sed -i '/^alias xoff=/d' ~/.bashrc

# Verify:

type -a xoff

# Expected: xoff is /usr/local/bin/xoff

## Step 5 — Test sequence

# Test poweroff (expected to cut power)

xoff

# Expected behavior: System shuts down cleanly, Power is cut, Board stays off, Manual power-on required

# Test reboot (must NOT cut power)

sudo reboot

# Expected behavior: Normal reboot, Power remains applied, No manual intervention required

### Summary

# You now have:
# • A clean, modern, maintainable X-C1 power-off implementation
# • No deprecated GPIO sysfs
# • No vendor scripts
# • No reboot hazards
# • No disk corruption risk

CommentStreams:5711125217364fdf6de9d9a7bf1553fd - Revision history

31.94.22.136: Migrated comment #6197