Avahi Container Start Script

Using the Avahi Container Start Script

Overview

The avahicontainer_start script is a utility included in RF Swift containers to enable service discovery through Avahi. This script is particularly useful when working with PlutoSDR and other devices that rely on zeroconf/mDNS discovery.

Script Details

The avahicontainer_start script in /usr/sbin initializes the D-Bus daemon and Avahi service within a container:

What This Script Does

1. Create D-Bus Directory: Creates the /var/run/dbus directory if it doesn’t exist
2. Start D-Bus Daemon: Launches the D-Bus system daemon in the background
3. Wait Period: Pauses for 2 seconds to ensure D-Bus is fully initialized
4. Start Avahi Daemon: Launches the Avahi daemon in daemon mode (-D)

When to Use This Script

Use the avahicontainer_start script when:

• Working with PlutoSDR or similar devices that use network service discovery
• Running tools that require mDNS (multicast DNS) or service discovery
• Encountering “Avahi daemon not running” or similar errors

Using the Script

Manual Execution

To manually start Avahi in a running container:

# Inside your RF Swift container
avahicontainer_start

Verifying It’s Working

After running the script, you can verify that Avahi is properly running:

# Check if Avahi is running
ps aux | grep avahi

# Test service discovery
avahi-browse -a

PlutoSDR Example

When working with PlutoSDR, you can use this script to enable automatic discovery:

# Start Avahi service
avahicontainer_start

# Wait a moment for services to register
sleep 2

# Find PlutoSDR on the network
iio_info -s

# Should show something like:
# Available IIO contexts:
# Context 0: ip:pluto.local

Troubleshooting

Common Issues

If the script doesn’t solve your service discovery issues:

1. Network Configuration: Ensure your container is using the host network (the default for RF Swift)

   # Check network mode of your container
   rfswift container list

2. Firewall Settings: Multicast DNS uses UDP port 5353 - ensure it’s not blocked

   # Check if multicast traffic is allowed
   sudo iptables -L | grep 5353

3. Multiple Avahi Instances: Sometimes conflicts occur if the host is also running Avahi

   # On your host system, temporarily stop Avahi if needed
   sudo systemctl stop avahi-daemon

Advanced Usage

Auto-Starting Avahi

To automatically start Avahi when running a container:

rfswift run -i sdr_full -n pluto_container -e "avahicontainer_start && /bin/bash"

Custom Service Files

You can add custom Avahi service files to advertise specific services:

# Create a custom service file
cat > /etc/avahi/services/myservice.service << EOF
<?xml version="1.0" standalone='no'?>
<!DOCTYPE service-group SYSTEM "avahi-service.dtd">
<service-group>
  <name>MyCustomService</name>
  <service>
    <type>_myservice._tcp</type>
    <port>12345</port>
  </service>
</service-group>
EOF

# Restart Avahi to apply
avahi-daemon -r