Difference between revisions of "Avahi"

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[[Category:Networking]]
 
[[Category:Networking]]
 
[[fr:Avahi]]
 
[[fr:Avahi]]
 +
[[ja:Avahi]]
 
From [[Wikipedia:Avahi (software)]]:
 
From [[Wikipedia:Avahi (software)]]:
:''"[http://avahi.org/ Avahi] is a free [[Wikipedia:Zero-configuration networking|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)."''
+
:[http://avahi.org/ Avahi] is a free [[Wikipedia:Zero-configuration networking|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).
  
 
== Installation ==
 
== Installation ==
[[pacman|Install]] {{Pkg|avahi}} and {{Pkg|nss-mdns}}, available in the [[official repositories]].
+
[[Install]] the {{Pkg|avahi}} package.
  
 
You can manage the Avahi daemon with {{ic|avahi-daemon.service}} [[systemd#Using units|using systemd]].
 
You can manage the Avahi daemon with {{ic|avahi-daemon.service}} [[systemd#Using units|using systemd]].
  
 
== Using Avahi ==
 
== Using Avahi ==
 +
 +
=== Hostname resolution ===
 +
Avahi provides local hostname resolution using a "''hostname''.local" naming scheme. To enable it, install the {{Pkg|nss-mdns}} package and start {{ic|avahi-daemon.service}}.
 +
 +
Then, edit the file {{ic|/etc/nsswitch.conf}} and change the line:
 +
hosts: files dns myhostname
 +
to:
 +
hosts: files mdns_minimal [NOTFOUND=return] dns myhostname
 +
 +
{{Note|If you experience slowdowns in resolving {{ic|.local}} hosts try to use {{ic|mdns4_minimal}} instead of {{ic|mdns_minimal}}.}}
 +
 +
==== Configuring mDNS for custom TLD ====
 +
 +
The {{ic|mdns_minimal}} module handles queries for the {{ic|.local}} TLD only. Note the {{ic|<nowiki>[NOTFOUND=return]</nowiki>}}, which specifies that if {{ic|mdns_minimal}} cannot find {{ic|*.local}}, it will not continue to search for it in {{ic|dns}}, {{ic|myhostname}}, etc.
 +
 +
In case you want Avahi to support other TLDs, you should:
 +
* replace {{ic|1=mdns_minimal [NOTFOUND=return]}} with the full {{ic|mdns}} module. There also are IPv4-only and IPv6-only modules {{ic|mdns[46](_minimal)}}
 +
* customize {{ic|/etc/avahi/avahi-daemon.conf}} with the {{ic|domain-name}} of your choice
 +
* whitelist Avahi custom TLDs in {{ic|/etc/mdns.allow}}
 +
 +
==== Tools ====
 +
 +
Avahi includes several utilities which help you discover the services running on a network. For example, run
 +
$ avahi-browse -alr
 +
to discover services in your network.
 +
 +
The Avahi Zeroconf Browser ({{ic|avahi-discover}} – note that it needs avahi's optional dependencies {{Pkg|pygtk}} and {{Pkg|python2-dbus}}) shows the various services on your network. You can also browse SSH and VNC Servers using {{ic|bssh}} and {{ic|bvnc}} respectively.
 +
 +
There's a good list of software with Avahi support at their website: http://avahi.org/wiki/Avah4users
 +
 +
=== Firewall ===
 +
 +
Be sure to open UDP port {{ic|5353}} if you're using a [[firewall]].
 +
 +
===Link-Local (Bonjour/Zeroconf) chat===
 +
 +
Avahi can be used for bonjour protocol support under linux. Check [[Wikipedia:Comparison of instant messaging clients]] or [[List of applications#Instant messaging]] for a list of clients supporting the bonjour protocol.
 +
 
=== Obtaining IPv4LL IP address ===
 
=== Obtaining IPv4LL IP address ===
 +
 +
{{Merge|dhcpcd|should be merged into the main page}}
 +
 
By default, if you are getting IP using DHCP, you are using the {{Pkg|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:
 
By default, if you are getting IP using DHCP, you are using the {{Pkg|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:
  
Line 21: Line 63:
 
  # avahi-autoipd -D
 
  # avahi-autoipd -D
  
=== Hostname resolution ===
+
== Adding services ==
Avahi also allows you to access computers using their hostnames. '''Note:''' you must install {{Pkg|nss-mdns}} for this to work, and have {{ic|avahi-daemon.service}} enabled and running.
+
  
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 {{ic|/etc/hosts}} file for each computer. Instead you can simply use {{ic|maple.local}} to access whatever services ''maple'' has. However by default, {{ic|.local}} querying is disabled in Arch Linux. To enable it edit the file {{ic|/etc/nsswitch.conf}} and change the line:
+
Avahi advertises the services whose {{ic|*.service}} files are found in {{ic|/etc/avahi/services}}. If you want to advertise a service for which there is no {{ic|*.service}} file, it is very easy to create your own.
hosts: files myhostname dns
+
to:
+
hosts: files myhostname mdns_minimal [NOTFOUND=return] dns
+
  
The {{ic|mdns_minimal}} module handles queries for the {{ic|.local}} TLD only. In case you have configured Avahi to use a different TLD, you'll also need to add the full {{ic|mdns}} module at the end. There also are IPv4-only and IPv6-only modules {{ic|mdns[46](_minimal)}}.
+
As an example, let's say you wanted to advertise a quote of the day (QOTD) service operating per [http://tools.ietf.org/html/rfc865 RFC865] on TCP port 17 which you are running on your machine
  
Avahi includes several utilities which help you discover the services running on a network. For example, run
+
The first thing to do is to determine the {{ic|<type>}}. {{ic|man avahi.service}} indicates that the
avahi-browse -alr
+
type should be "the DNS-SD service type for this service. e.g. '_http._tcp'". Since the [http://www.dns-sd.org/ServiceTypes.html DNS-SD register was merged into the IANA register in 2010], we look for the service name on the [http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml IANA register] or in {{ic|/etc/services}} file. The service name shown there is {{ic|qotd}}. Since we're running QOTD on tcp, we now know the service is {{ic|_qotd._tcp}} and the port (per IANA and RFC865) is 17.
to discover services in your network.
+
  
The Avahi Zeroconf Browser ({{ic|avahi-discover}}) shows the various services on your network. You can also browse SSH and VNC Servers using {{ic|bssh}} and {{ic|bvnc}} respectively.
+
Our service file is thus:
  
There's a good list of software with Avahi support at their website: http://avahi.org/wiki/Avah4users
+
{{hc|qotd.service|<nowiki>
{{Note|{{ic|avahi-discover}} needs pygtk and python-dbus to be installed.}}
+
<?xml version="1.0" standalone='no'?><!--*-nxml-*-->
 +
<!DOCTYPE service-group SYSTEM "avahi-service.dtd">
 +
 
 +
<service-group>
 +
 
 +
  <name replace-wildcards="yes">%h</name>
 +
 
 +
  <service>
 +
    <type>_qotd._tcp</type>
 +
    <port>17</port>
 +
  </service>
 +
 
 +
</service-group>
 +
</nowiki>}}
 +
 
 +
For more complicated scenarios, such as advertising services running on a different server, DNS sub-types and so on, consult {{ic|man avahi.service}}.
 +
 
 +
=== SSH ===
 +
 
 +
Avahi comes with an example service file to advertise a SSH server. To enable it:
 +
# cp /usr/share/doc/avahi/ssh.service /etc/avahi/services/
  
 
===File sharing===
 
===File sharing===
  
 
====NFS====
 
====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 OS X). Create a {{ic|.service}} file in {{ic|/etc/avahi/services}} with the following contents:
+
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 macOS).
 +
 
 +
Create a {{ic|.service}} file in {{ic|/etc/avahi/services}} with the following contents:
 
{{hc|/etc/avahi/services/nfs_Zephyrus_Music.service|<nowiki>
 
{{hc|/etc/avahi/services/nfs_Zephyrus_Music.service|<nowiki>
 
<?xml version="1.0" standalone='no'?>
 
<?xml version="1.0" standalone='no'?>
Line 56: Line 115:
 
</service-group></nowiki>}}
 
</service-group></nowiki>}}
  
The port is correct if you have ''insecure'' as an option in your {{ic|/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 [http://www.macosxhints.com/article.php?story=20071116042238744 a script is available]. This was based upon [http://ubuntuforums.org/showthread.php?p=4387032#post4387032 this post].
+
The port is correct if you have ''insecure'' as an option in your {{ic|/etc/exports}}; otherwise, it needs to be changed (note that ''insecure'' is needed for macOS 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 [http://www.macosxhints.com/article.php?story=20071116042238744 a script is available]. This was based upon [http://ubuntuforums.org/showthread.php?p=4387032#post4387032 this post].
  
 
====Samba====
 
====Samba====
Should work out-of-the-box.
+
With the Avahi daemon running on both the server and client, the file manager on the client should automatically find the server.
 
+
====GShare====
+
You can grab {{aur|gshare}} 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====
 
====Vsftpd====
Sourced from [http://ubuntuforums.org/showthread.php?t=218630 ubuntuforums.org].
+
You can also auto-discover regular FTP servers, such as vsftpd. Install the {{Pkg|vsftpd}} package and change the settings of vsftpd according to your own personal preferences (see [http://ubuntuforums.org/showthread.php?t=218630 this thread on ubuntuforums.org] or {{ic|man vsftpd.conf}}).
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
+
Create a {{ic|.service}} file in {{ic|/etc/avahi/services}} with the following contents:
<?xml version="1.0" standalone='no'?>
+
{{hc|/etc/avahi/services/ftp.service|<nowiki>
    <!DOCTYPE service-group SYSTEM "avahi-service.dtd">
+
<?xml version="1.0" standalone='no'?>
    <service-group>
+
<!DOCTYPE service-group SYSTEM "avahi-service.dtd">
    <name>FTP file sharing</name>
+
<service-group>
    <service>
+
  <name>FTP file sharing</name>
 +
  <service>
 
     <type>_ftp._tcp</type>
 
     <type>_ftp._tcp</type>
 
     <port>21</port>
 
     <port>21</port>
    </service>
+
  </service>
    </service-group>
+
</service-group>
When you are done, [[systemd#Using units|restart]] the {{ic|avahi-daemon.service}} and {{ic|vsftpd.service}} services.
+
</nowiki>}}
  
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.
+
The FTP server should now be advertised by Avahi. You should now be able to find the FTP server from a file manager on another computer in your network. You might need to enable [[#Hostname resolution]] on the client.
  
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 [[Avahi#Hostname_resolution|this section]]).
+
===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 {{ic|/etc/avahi/services/}}. An example of a generic services file for an HP-Laserjet printer would be similar to the following with the {{ic|name}}, {{ic|rp}}, {{ic|ty}}, {{ic|adminurl}} and {{ic|note}} fields changed.
  
====Giver====
+
{{hc|/etc/avahi/services/airprint.service|<nowiki>
[http://code.google.com/p/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.
+
<?xml version="1.0" standalone='no'?><!--*-nxml-*-->
 +
<!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=(GPL Ghostscript)</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>
 +
</nowiki>}}
  
A package is on the {{AUR|giver}}.
+
Alternatively, https://raw.github.com/tjfontaine/airprint-generate/master/airprint-generate.py can be used to generate Avahi service files. It depends on {{Pkg|python2}} and {{Pkg|python2-pycups}}. The script can be run using:
  
Note that this depends on gnome-sharp, which has heavy GNOME dependencies.
+
# python2 airprint-generate.py -d /etc/avahi/services
  
===Link-Local (Bonjour/Zeroconf) chat===
+
{{Note|If your printer under http://localhost:631/printers is "Not Shared", this python script won't output any file to /etc/avahi/services; in that case, you'll need to "Modify Printer" under one of the CUPS drop-down menus to turn sharing on.  If that doesn't work, check out the ArchWiki on [[CUPS printer sharing]].}}
  
Avahi can be used for bonjour protocol support under linux. Check [[Wikipedia:Comparison of instant messaging clients]] or [[List of Applications#Instant messaging]] for a list of clients supporting the bonjour protocol.
+
== Modifying the service-types database ==
 +
As noted above, avahi comes with tools to browse advertised services. Both {{ic|avahi-browse}} and {{ic|avahi-discover}} use a database file to furnish descriptions of the relevant service. That database contains the names of many, but not all, services.
  
===Airprint from Mobile Devices===
+
Sadly, it doesn't contain the QOTD service we just created. Thus {{ic|avahi-browse -a}} would show the following ugly entry
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'?><!--*-nxml-*-->
+
  <!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>
+
  
Alternatively, https://raw.github.com/tjfontaine/airprint-generate/master/airprint-generate.py can be used to generate Avahi service files. It depends on python2 and pycups. The script can be run using: {{bc|# python2 airprint-generate.py -d /etc/avahi/services}}
+
+ wlp2s0 IPv4 MyServer                                        _qotd._tcp local
  
=== Firewall ===
+
=== Getting the sources ===  
 +
 
 +
First, download the files {{ic|build-db.in}} and {{ic|service-types}} files from the {{ic|service-type-database}} subdirectory in the [https://github.com/lathiat/avahi the avahi github mirror] to a build directory.
 +
 
 +
wget https://raw.githubusercontent.com/lathiat/avahi/master/service-type-database/build-db.in
 +
wget https://raw.githubusercontent.com/lathiat/avahi/master/service-type-database/service-types
 +
 
 +
=== Modify the sources ===
 +
 
 +
Second, create the following script:
 +
 
 +
#!/bin/bash
 +
sed -e 's,@PYTHON\@,/usr/bin/python2.7,g' \
 +
    -e 's,@DBM\@,gdbm,g' < build-db.in > build-db
 +
chmod +x build-db
 +
 
 +
This mimics what the Makefile would do if one were building all of avahi. It creates a file named build-db.
 +
 
 +
$./whatever_you_named_the_script.sh
 +
$ ls
 +
build-db build-db.in service-types whatever_you_named_the_script.sh
 +
 
 +
Third, make the changes needed to add your new QOTD service to the {{ic|service-types}} file. This file has one entry per line, with the entries in the format {{ic|type:Human Readable Description}}. Note that the human readable description can contain spaces.
 +
 
 +
In our example, we add the following entry to the end of the file:
 +
 
 +
_qotd._tcp:Quote of the Day (QOTD) Server
 +
 
 +
==== Build and install the new database ====
 +
 
 +
Now run the {{ic|build-db}} python script (be sure to use python2 not python3). This will build the {{ic|service-types.db}} file. Check to make sure it's been built and use {{ic|gdbmtools}} to make sure the new database is loadable and contains the new entry:
 +
 
 +
$/usr/bin/python2.7 build-db
 +
$ls
 +
build-db build-db.in service-types service-types.db whatever_you_named_the_script.sh
 +
$gdbmtool service-types.db
 +
 +
Welcome to the gdbm tool.  Type ? for help.
 +
 +
gdbmtool>fetch _qotd._tcp
 +
Quote of the Day (QOTD) Server
 +
gdbmtool>quit
 +
 
 +
Now copy the old database to a backup location, move the new database to the live directory and use {{ic|avahi-browse}} database dump command to make sure avahi sees the new entry:
 +
 
 +
$cp /usr/lib/avahi/service-types.db /backup-directory
 +
$sudo cp /build-directory/service-types.db /usr/lib/avahi/service-types.db
 +
$avahi-browse -b | grep QOTD
 +
Quote of the Day (QOTD) Server
  
Be sure to open UDP port 5353 if you're using iptables:
+
The entry in {{ic|avahi-browse}} should now be:
  # iptables -A INPUT -p udp -m udp --dport 5353 -j ACCEPT
+
  
If you're following the more-than-useful [[Simple Stateful Firewall]] format for your firewall:
+
+ wlp2s0 IPv4 MyServer                                        Quote of the Day (QOTD) Server local
  # iptables -A UDP -p udp -m udp --dport 5353 -j ACCEPT
+
  
 
==See also==
 
==See also==
 
* [http://avahi.org/ Avahi] - Official project website
 
* [http://avahi.org/ Avahi] - Official project website
* [http://en.wikipedia.org/wiki/Avahi_%28software%29 Wikipedia entry]
+
* [[wikipedia:Avahi (software)|Wikipedia entry]]
 
* [http://www.apple.com/support/downloads/bonjourforwindows.html Bonjour for Windows] - Enable Zeroconf on Windows
 
* [http://www.apple.com/support/downloads/bonjourforwindows.html Bonjour for Windows] - Enable Zeroconf on Windows
 
* http://www.zeroconf.org/
 
* http://www.zeroconf.org/

Latest revision as of 12:48, 30 October 2016

From Wikipedia:Avahi (software):

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).

Installation

Install the avahi package.

You can manage the Avahi daemon with avahi-daemon.service using systemd.

Using Avahi

Hostname resolution

Avahi provides local hostname resolution using a "hostname.local" naming scheme. To enable it, install the nss-mdns package and start avahi-daemon.service.

Then, edit the file /etc/nsswitch.conf and change the line:

hosts: files dns myhostname

to:

hosts: files mdns_minimal [NOTFOUND=return] dns myhostname
Note: If you experience slowdowns in resolving .local hosts try to use mdns4_minimal instead of mdns_minimal.

Configuring mDNS for custom TLD

The mdns_minimal module handles queries for the .local TLD only. Note the [NOTFOUND=return], which specifies that if mdns_minimal cannot find *.local, it will not continue to search for it in dns, myhostname, etc.

In case you want Avahi to support other TLDs, you should:

  • replace mdns_minimal [NOTFOUND=return] with the full mdns module. There also are IPv4-only and IPv6-only modules mdns[46](_minimal)
  • customize /etc/avahi/avahi-daemon.conf with the domain-name of your choice
  • whitelist Avahi custom TLDs in /etc/mdns.allow

Tools

Avahi includes several utilities which help you discover the services running on a network. For example, run

$ avahi-browse -alr

to discover services in your network.

The Avahi Zeroconf Browser (avahi-discover – note that it needs avahi's optional dependencies pygtk and python2-dbus) 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

Firewall

Be sure to open UDP port 5353 if you're using a firewall.

Link-Local (Bonjour/Zeroconf) chat

Avahi can be used for bonjour protocol support under linux. Check Wikipedia:Comparison of instant messaging clients or List of applications#Instant messaging for a list of clients supporting the bonjour protocol.

Obtaining IPv4LL IP address

Merge-arrows-2.pngThis article or section is a candidate for merging with dhcpcd.Merge-arrows-2.png

Notes: should be merged into the main page (Discuss in Talk:Avahi#)

By default, if you are getting IP using DHCP, you are using the 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:

# avahi-autoipd -D

Adding services

Avahi advertises the services whose *.service files are found in /etc/avahi/services. If you want to advertise a service for which there is no *.service file, it is very easy to create your own.

As an example, let's say you wanted to advertise a quote of the day (QOTD) service operating per RFC865 on TCP port 17 which you are running on your machine

The first thing to do is to determine the <type>. man avahi.service indicates that the type should be "the DNS-SD service type for this service. e.g. '_http._tcp'". Since the DNS-SD register was merged into the IANA register in 2010, we look for the service name on the IANA register or in /etc/services file. The service name shown there is qotd. Since we're running QOTD on tcp, we now know the service is _qotd._tcp and the port (per IANA and RFC865) is 17.

Our service file is thus:

qotd.service
<?xml version="1.0" standalone='no'?><!--*-nxml-*-->
<!DOCTYPE service-group SYSTEM "avahi-service.dtd">

<service-group>

  <name replace-wildcards="yes">%h</name>

  <service>
    <type>_qotd._tcp</type>
    <port>17</port>
  </service>

</service-group>

For more complicated scenarios, such as advertising services running on a different server, DNS sub-types and so on, consult man avahi.service.

SSH

Avahi comes with an example service file to advertise a SSH server. To enable it:

# cp /usr/share/doc/avahi/ssh.service /etc/avahi/services/

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 macOS).

Create a .service file in /etc/avahi/services with the following contents:

/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 macOS 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

With the Avahi daemon running on both the server and client, the file manager on the client should automatically find the server.

Vsftpd

You can also auto-discover regular FTP servers, such as vsftpd. Install the vsftpd package and change the settings of vsftpd according to your own personal preferences (see this thread on ubuntuforums.org or man vsftpd.conf).

Create a .service file in /etc/avahi/services with the following contents:

/etc/avahi/services/ftp.service
<?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>

The FTP server should now be advertised by Avahi. You should now be able to find the FTP server from a file manager on another computer in your network. You might need to enable #Hostname resolution on the client.

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/. 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.

/etc/avahi/services/airprint.service
<?xml version="1.0" standalone='no'?><!--*-nxml-*-->
<!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=(GPL Ghostscript)</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>

Alternatively, https://raw.github.com/tjfontaine/airprint-generate/master/airprint-generate.py can be used to generate Avahi service files. It depends on python2 and python2-pycups. The script can be run using:

# python2 airprint-generate.py -d /etc/avahi/services
Note: If your printer under http://localhost:631/printers is "Not Shared", this python script won't output any file to /etc/avahi/services; in that case, you'll need to "Modify Printer" under one of the CUPS drop-down menus to turn sharing on. If that doesn't work, check out the ArchWiki on CUPS printer sharing.

Modifying the service-types database

As noted above, avahi comes with tools to browse advertised services. Both avahi-browse and avahi-discover use a database file to furnish descriptions of the relevant service. That database contains the names of many, but not all, services.

Sadly, it doesn't contain the QOTD service we just created. Thus avahi-browse -a would show the following ugly entry

+ wlp2s0 IPv4 MyServer                                        _qotd._tcp local

Getting the sources

First, download the files build-db.in and service-types files from the service-type-database subdirectory in the the avahi github mirror to a build directory.

wget https://raw.githubusercontent.com/lathiat/avahi/master/service-type-database/build-db.in
wget https://raw.githubusercontent.com/lathiat/avahi/master/service-type-database/service-types

Modify the sources

Second, create the following script:

#!/bin/bash
sed -e 's,@PYTHON\@,/usr/bin/python2.7,g' \
    -e 's,@DBM\@,gdbm,g' < build-db.in > build-db
chmod +x build-db

This mimics what the Makefile would do if one were building all of avahi. It creates a file named build-db.

$./whatever_you_named_the_script.sh
$ ls
build-db build-db.in service-types whatever_you_named_the_script.sh

Third, make the changes needed to add your new QOTD service to the service-types file. This file has one entry per line, with the entries in the format type:Human Readable Description. Note that the human readable description can contain spaces.

In our example, we add the following entry to the end of the file:

_qotd._tcp:Quote of the Day (QOTD) Server

Build and install the new database

Now run the build-db python script (be sure to use python2 not python3). This will build the service-types.db file. Check to make sure it's been built and use gdbmtools to make sure the new database is loadable and contains the new entry:

$/usr/bin/python2.7 build-db
$ls
build-db build-db.in service-types service-types.db whatever_you_named_the_script.sh
$gdbmtool service-types.db

Welcome to the gdbm tool.  Type ? for help.

gdbmtool>fetch _qotd._tcp
Quote of the Day (QOTD) Server
gdbmtool>quit

Now copy the old database to a backup location, move the new database to the live directory and use avahi-browse database dump command to make sure avahi sees the new entry:

$cp /usr/lib/avahi/service-types.db /backup-directory
$sudo cp /build-directory/service-types.db /usr/lib/avahi/service-types.db
$avahi-browse -b | grep QOTD
Quote of the Day (QOTD) Server

The entry in avahi-browse should now be:

+ wlp2s0 IPv4 MyServer                                        Quote of the Day (QOTD) Server local

See also