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EmergencyBox Auto-Start Configuration

This guide explains how to configure EmergencyBox to start automatically when your DD-WRT router boots.

Prerequisites

  • DD-WRT router with USB port
  • USB drive with two partitions:
    • /dev/sda1 (ext4) - EmergencyBox application files
    • /dev/sda2 (ext4) - Entware packages
  • Entware already installed on sda2
  • EmergencyBox files deployed to /tmp/mnt/sda1/www

The Problem with DD-WRT

DD-WRT has a read-only root filesystem after boot, which prevents creating symlinks in /opt. Traditional approaches like rm -rf /opt && ln -s /tmp/mnt/sda2 /opt fail because:

  1. Root filesystem becomes read-only shortly after boot
  2. /opt exists as a directory in the firmware
  3. You cannot remove or replace it

The Solution: mount --bind

The mount --bind command allows you to overlay a directory on top of another, even on read-only filesystems:

mount --bind /tmp/mnt/sda2 /opt

This makes /opt point to the USB partition content without needing to modify the root filesystem.

Installation Steps

Method 1: Web Interface (Recommended)

  1. Open DD-WRT Web Interface

    http://192.168.1.1

  2. Navigate to Commands Section

    Administration → Commands

  3. Paste Startup Script

    Copy the contents of startup_script.sh into the "Startup" text box.

  4. Save Configuration

    Click "Save Startup" button at the bottom of the Commands section.

  5. Reboot Router

    # Via web interface:
Administration → Management → Reboot Router

# Or via telnet/SSH:
reboot

  6. Wait and Test

    Wait 60-90 seconds for the router to fully boot, then test:

    http://192.168.1.1:8080

Method 2: Python Script (Automated)

Note: The web API method may not work reliably on all DD-WRT versions. If it fails, use Method 1.

python3 scripts/setup_autostart_web.py

Startup Script Explanation

sleep 5
# Wait for system to fully boot before running commands

while [ ! -b /dev/sda2 ]; do sleep 1; done
# Wait for USB device to be detected (block device exists)

mkdir -p /tmp/mnt/sda1 /tmp/mnt/sda2
# Create mount points

mount /dev/sda2 /tmp/mnt/sda2 2>/dev/null
mount /dev/sda1 /tmp/mnt/sda1 2>/dev/null
# Mount USB partitions (suppress errors if automount already did it)

mount --bind /tmp/mnt/sda2 /opt
# KEY FIX: Overlay Entware directory over /opt

mkdir -p /opt/share
ln -sfn /tmp/mnt/sda1/www /opt/share/www
# Create symlink for web files

/opt/etc/init.d/rc.unslung start
# Start Entware services

sleep 3
# Wait for services to initialize

/opt/sbin/lighttpd -f /opt/etc/lighttpd/lighttpd.conf &
# Start web server in background

Troubleshooting

EmergencyBox not accessible after reboot

  1. Check if router has booted

    ping 192.168.1.1

  2. Verify USB is mounted

    python3 scripts/router_telnet.py "mount | grep sda"

    Should show both sda1 and sda2 mounted.

  3. Check if mount --bind worked

    python3 scripts/router_telnet.py "ls -la /opt/sbin/lighttpd"

    Should show the lighttpd binary exists.

  4. Check if lighttpd is running

    python3 scripts/router_telnet.py "ps | grep lighttpd"

  5. View startup script in NVRAM

    python3 scripts/router_telnet.py "nvram get rc_startup"

    Note: This only works if you configured via web interface. The web interface stores commands differently than NVRAM.

Manual Start (if auto-start fails)

python3 scripts/router_telnet.py "mount --bind /tmp/mnt/sda2 /opt && mkdir -p /opt/share && ln -sfn /tmp/mnt/sda1/www /opt/share/www && /opt/sbin/lighttpd -f /opt/etc/lighttpd/lighttpd.conf"

Key Technical Points

Why mount --bind?

  • Works on read-only filesystems: Doesn't require modifying root
  • Survives across operations: Can be done after boot
  • Transparent to applications: Programs see /opt as if it's the real location

Why not use NVRAM rc_startup?

Testing showed that nvram set rc_startup=... doesn't reliably execute on DD-WRT. The web interface uses a different mechanism that works more consistently.

USB Automount

  • Enabled by default: nvram get usb_automnt returns 1
  • Required for ext4: DD-WRT kernel lacks built-in ext4 module
  • Automount loads ext4: Uses special mechanisms to enable ext4 support
  • Script is idempotent: Mounting already-mounted partitions is safe (errors suppressed)

Testing After Reboot

After router reboots, run these checks:

# 1. Ping router
ping -c 3 192.168.1.1

# 2. Check mount points
python3 scripts/router_telnet.py "mount | grep sda"

# 3. Check /opt overlay
python3 scripts/router_telnet.py "ls /opt/sbin/lighttpd"

# 4. Check lighttpd process
python3 scripts/router_telnet.py "ps | grep lighttpd"

# 5. Test web interface
curl http://192.168.1.1:8080

Files Modified

  • DD-WRT: Startup commands (via web interface)
  • This repository:
    • startup_script.sh - The startup script content
    • AUTOSTART_SETUP.md - This documentation

References