Avahi

Resources

avahi is Article description::a zeroconf service discovery and publishing program. A common use for it is to be able to connect to machines via yourhostname.local within your LAN.

Installation

Kernel

KERNEL Required options

Networking support  --->
   Networking options  --->
     [*]   IP: multicasting

USE flags

Some packages are aware of the zeroconf USE flag pulling in avahi.

USE flags for net-dns/avahi System which facilitates service discovery on a local network

`autoipd`	Build and install the IPv4LL (RFC3927) network address configuration daemon
`bookmarks`	Install the avahi-bookmarks application (requires dev-python/twisted)
`dbus`	Enable dbus support for anything that needs it (gpsd, gnomemeeting, etc)
`doc`	Add extra documentation (API, Javadoc, etc). It is recommended to enable per package instead of globally
`gdbm`	Add support for sys-libs/gdbm (GNU database libraries)
`gtk`	Use gtk3 for the avahi utilities (overrides USE=gtk2) and build the avahi-ui-gtk3 library
`gtk2`	Use gtk2 for the avahi utilities (overridden by USE=gtk) and build the avahi-ui library
`howl-compat`	Enable compat libraries for howl
`introspection`	Add support for GObject based introspection
`ipv6`	Add support for IP version 6
`mdnsresponder-compat`	Enable compat libraries for mDNSResponder
`mono`	Build Mono bindings to support dotnet type stuff
`nls`	Add Native Language Support (using gettextGNU locale utilities)
`python`	Add optional support/bindings for the Python language
`qt5`	Add support for the Qt 5 application and UI framework
`selinux`	!!internal use only!! Security Enhanced Linux support, this must be set by the selinux profile or breakage will occur
`systemd`	Enable use of systemd-specific libraries and features like socket activation or session tracking
`test`	Enable dependencies and/or preparations necessary to run tests (usually controlled by FEATURES=test but can be toggled independently)

Data provided by the Gentoo Package Database · Last update: 2021-01-31 00:06 More information about USE flags

Server

root #emerge --ask net-dns/avahi

Client

root #emerge --ask sys-auth/nss-mdns

Configuration

Server Services

systemd

Enable the server to start whenever systemd thinks it is appropriate:

root #systemctl enable avahi-daemon.service

If you want to use it right away, also start the service:

root #systemctl start avahi-daemon.service

OpenRC

Be sure to add the service to the default runlevel for the server daemon to start on system boot. Do so with the rc-update command:

root #rc-update add avahi-daemon default

Start the service (without restarting) with the rc-service command:

root #rc-service avahi-daemon start

Client Files

Add the appropriate mdns into the hosts line in /etc/nsswitch.conf, An example line looks like:

FILE /etc/nsswitch.conf

hosts:       files mdns_minimal [NOTFOUND=return] dns mdns

Once this is installed it should be possible to ping the hostname of the machine appending .local. For example:

user $ping yourhostname.local

Troubleshooting

Check avahi-daemon is running and listen for 5353 UDP:

root #ss -ltunp | grep 5353

Output:

udp   UNCONN 0      0                          0.0.0.0:5353        0.0.0.0:*     users:(("avahi-daemon",pid=4072,fd=13))
udp   UNCONN 0      0                                *:5353              *:*     users:(("avahi-daemon",pid=4072,fd=14))

Commands like host and dig do not use /etc/nsswitch.conf, so they can't be used for Avahi diagnostic. Use getent hosts yourhostname.local instead.

For example:

user $getent hosts gentoo-desktop.local

Output when mdns_minimal in /etc/nsswitch.conf:

fe80::bbbd:5967:6af8:9d27 gentoo-desktop.local

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