Using a non-standard location for avahi services

Question

I want to use avahi on a system with a read-only rootfs where /etc is not writable.

I can start avahi-daemon with the -f option to specify a non-standard location for the avahi-daemon.conf file (default location is /etc/avahi/avahi-daemon.conf). However I can't find any way to specify a non-standard location for the service definitions (default location is /etc/avahi/services). Is there any option for this ?

Answer 1

It seems that Avahi does not provide any configuration option for searching for service definitions in a non-standard location (other than rebuilding with a custom --prefix, but that obviously has other implications). In case someone else needs this, these are the options I've found:

• Symlink /etc/avahi/services to a different directory. For this to work, the avahi daemon must be started with the --no-chroot option; otherwise it will not be able to reach out of the chroot jail.
• Bind mount a different directory on /etc/avahi/services. This does not require that --no-chroot is used.

Both options work fine.

Answer 2

(Using a answer window as it has more formatting options)

Note that Avahi service definitions allow wildcards. This might be adequate to allow the same definition on multiple hosts, thus allowing read-only /etc:

<?xml version="1.0" standalone='no'?><!--*-nxml-*-->
<!DOCTYPE service-group SYSTEM "avahi-service.dtd">
<service-group>
  <name replace-wildcards="yes">%h</name>
  <service>
    <type>_ssh._tcp</type>
    <port>22</port>
  </service>
</service-group>