Avahi

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Avahi is a free Zero Configuration Networking (Zeroconf) implementation, including a system for multicast DNS/DNS-SD service discovery. It allows programs to publish and discover services and hosts running on a local network with no specific configuration. For example you can plug into a network and instantly find printers to print to, files to look at and people to talk to. It is licensed under the GNU Lesser General Public License (LGPL). (Source: Wikipedia:Avahi (software))

Installation

Install avahi and nss-mdns, available in the official repositories.

# pacman -S avahi nss-mdns

Enable Avahi Daemon under sysvinit system

After installing Avahi you will need to restart the dbus daemon before you can start avahi-daemon.

Note: avahi-daemon depends on dbus daemon, so it should be added after dbus in the DAEMONS array in rc.conf file
Note: Sometimes adding avahi-daemon to /etc/rc.conf can cause it to load too early and fail. One possible solution is to add it as "/etc/rc.d/avahi-daemon start" in /etc/rc.local.

Enable Avahi Daemon under Native systemd system

You can enable Avahi Daemon at startup with the following command:

# systemctl enable avahi-daemon.service

Using Avahi

Obtaining IPv4LL IP address

By default, if you are getting IP using DHCP, you are using dhcpcd package. It can attempt to obtain an IPv4LL address if it failed to get one via DHCP. By default this option is disabled. To enable it, comment noipv4ll string:

/etc/dhcpcd.conf
...
#noipv4ll
...

Alternatively, run avahi-autoipd, included in avahi package:

# avahi-autoipd -D

Hostname resolution

Avahi also allows you to access computers using their hostnames. Note: you must install nss-mdns for this to work.

Suppose you have machines with names maple, fig and oak, all running avahi. Avahi can be set up so that you do not have to manage a /etc/hosts file for each computer. Instead you can simply use maple.local to access whatever services maple has. However by default, .local querying is disabled in Arch Linux. To enable it edit the file /etc/nsswitch.conf and change the line:

hosts: files dns

to

hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4

A small section of users in Ubuntu noticed a slowdown in DNS querying; it was attributed to this change. Whether it applies to Arch Linux too, is not known. (Reference: Ubuntu Bug 94940) -- I found this to be true for Arch; However, I just used the line:

hosts: files mdns4_minimal dns mdns4

and I get the correct behavior without slower DNS.

Note: I had to remove mdns completely to prevent slowdowns. However, mdns_minimal alone appeared to be sufficient.

Avahi also has quite a few nifty utilities which can help you discover which services are being used on a network. The avahi-discover (Avahi Zeroconf Browser) shows the various services on your network. You can also browse SSH and VNC Servers using bssh and bvnc respectively.

There's a good list of software with Avahi support at their website: http://avahi.org/wiki/Avah4users

Note: For run avahi-discover you need to install Avahi, pygtk and python-dbus.

File sharing

NFS

If you have an NFS share set up, you can use Avahi to be able to automount them in Zeroconf-enabled browsers (such as Konqueror on KDE and Finder on Mac OS X). Create a .service file in /etc/avahi/services with the following:

/etc/avahi/services/nfs_Zephyrus_Music.service
 <?xml version="1.0" standalone='no'?>
 <!DOCTYPE service-group SYSTEM "avahi-service.dtd">
 <service-group>
   <name replace-wildcards="yes">NFS Music Share on %h</name>
   <service>
     <type>_nfs._tcp</type>
     <port>2049</port>
     <txt-record>path=/data/shared/Music</txt-record>
   </service>
 </service-group>

The port is correct if you have insecure as an option in your /etc/exports; otherwise, it needs to be changed (note that insecure is needed for OS X clients). The path is the path to your export, or a subdirectory of it. For some reason the automount functionality has been removed from Leopard, however a script is available. This was based upon this post.

Samba

Note: samba package from extra repository build without an avahi suuport.
/etc/avahi/services/smb.service
 <?xml version="1.0" standalone='no'?>
 <!DOCTYPE service-group SYSTEM "avahi-service.dtd">
 <service-group>
    <name replace-wildcards="yes">Samba Shares on %h</name>
    <service>
        <type>_smb._tcp</type>
        <port>139</port>
    </service>
 </service-group>
Note: If you are trying to connect with OS X Lion the port needs to be 445, not 139.

GShare

You can grab gshareAUR from the Arch User Repository and have shared files between the LAN, with no configuration, no hours in samba hacking, no nothing - it just works.

Vsftpd

Sourced from ubuntuforums.org. If you would rather use a regular ftp service, install vsftpd and avahi. Change the settings of vsftpd according to what is shown on the ubuntuforums page or according to your own personal preferences (See 'man vsftpd.conf).

Create a ftp.service file in /etc/avahi/services and paste in that file

<?xml version="1.0" standalone='no'?>
   <!DOCTYPE service-group SYSTEM "avahi-service.dtd">
   <service-group>
   <name>FTP file sharing</name>
   <service>
   <type>_ftp._tcp</type>
   <port>21</port>
   </service>
   </service-group>

When you are done, (re)start avahi-daemon and vsftpd in your /etc/rc.d directory.

/etc/rc.d/avahi-daemon restart
/etc/rc.d/vsftpd restart

After that you should be able to browse through the ftp server from another computer in your network. The steps shown in this section are created so that the ftp server is 'advertised' by avahi to the local Zeroconf network.

Unless you are using GNOME or KDE, you might not be able to log in to the ftp server directly through your file manager, and so you will have to use a ftp client pointed to the IP address of the server or the hostname of the machine (as shown in this section).

Giver

Giver is a mono program that allows simple file-sharing between two desktops when both are running Giver. All you need to do is click and drag the file to the name or picture of the person you wish to send the file to.

A package is on the AUR.

Note that this depends on gnome-sharp, which has heavy GNOME dependencies.

Link-Local XMPP Chat

Link-Local XMPP clients need TCP port 5298 allowed for incoming connections. Check Simple stateful firewall: opening ports to incoming connections for more details if you use iptables.

Gajim

Gajim is a Jabber/XMPP instant messenger client written in PyGTK. In the accounts setup just enable "Local" account.

Pidgin

Pidgin is an instant messaging client that supports quite a few commonly used IM protocols. In addition to these, it supports Bonjour.

Just select 'Bonjour' as the protocol type when you add an account, and enter a username. The first and last name you enter in the 'Advanced' tab will be what the other person (whom you are chatting with) sees, and 'local alias' under 'User Options' in the 'Basic' tab will be what you see of your own name (you could try putting in something like I, me or myself).

Once this is done, other Pidgin (iChat) users who are on the local network will see you and be able to chat with you. To implement file-sharing, you just send and receive files like you would do with a regular IM session.

Kopete

Kopete is the KDE equivalent of Pidgin. It supports the Bonjour/Link-local XMPP protocol. One need to create an account in Kopete, by simply entering the desired name.

Telepathy

Telpathy is a communication framework which supports different protocols using plugins. The Telepathy Salut plugin provides support for Bonjour/Link-Local XMPP protocol. Empathy is a GNOME front-end to Telepathy. Officially, KDE does not support Telepathy, but work is going on which will eventually replace Kopete. KDE Telepathy is available in extra.

Airprint from Mobile Devices

Avahi along with CUPS also provides the capability to print to just about any printer from airprint compatible mobile devices. In order to enable print capability from your device, simply create an avahi service file for your printer in /etc/avahi/services and restart avahi. An example of a generic services file for an HP-Laserjet printer would be similar to the following with the name, rp, ty, adminurl and note fields changed. Save the file as /etc/avahi/services/youFileName.service:

 <?xml version="1.0" standalone='no'?>
 <!DOCTYPE service-group SYSTEM "avahi-service.dtd">
 <service-group>
   <name>yourPrnterName</name>
   <service>
     <type>_ipp._tcp</type>
     <subtype>_universal._sub._ipp._tcp</subtype>
     <port>631</port>
     <txt-record>txtver=1</txt-record>
     <txt-record>qtotal=1</txt-record>
     <txt-record>rp=printers/yourPrnterName</txt-record>
     <txt-record>ty=yourPrnterName</txt-record>
     <txt-record>adminurl=http://198.168.7.15:631/printers/yourPrnterName</txt-record>
     <txt-record>note=Office Laserjet 4100n</txt-record>
     <txt-record>priority=0</txt-record>
     <txt-record>product=virtual Printer</txt-record>
     <txt-record>printer-state=3</txt-record>
     <txt-record>printer-type=0x801046</txt-record>
     <txt-record>Transparent=T</txt-record>
     <txt-record>Binary=T</txt-record>
     <txt-record>Fax=F</txt-record>
     <txt-record>Color=T</txt-record>
     <txt-record>Duplex=T</txt-record>
     <txt-record>Staple=F</txt-record>
     <txt-record>Copies=T</txt-record>
     <txt-record>Collate=F</txt-record>
     <txt-record>Punch=F</txt-record>
     <txt-record>Bind=F</txt-record>
     <txt-record>Sort=F</txt-record>
     <txt-record>Scan=F</txt-record>
     <txt-record>pdl=application/octet-stream,application/pdf,application/postscript,image/jpeg,image/png,image/urf</txt-record>
     <txt-record>URF=W8,SRGB24,CP1,RS600</txt-record>
   </service>
 </service-group>

Troubleshooting

Error while mounting SD card

If dmseg returns something like

mmc0: error -100 whilst initialising SD card

right after you attempted to mount an SD card, then you might have permission issue with avahi. To solve this, simply add your user to the avahi group. There is no need to relog, reinserting the card should do it.

See also