avahi-daemon.service produces errors in the journal when used with
systemd-networkd and systemd-resolved. The avahi-daemon cannot open the
/etc/resolv.conf file because it starts before systemd-resolved. Journal
entries are provided below.


Background:

According to `man systemd-resolved,` it is advisable to remove
/etc/resolv.conf and link /etc/resolv.conf to /run/systemd/resolve/resolv.conf.
The reason being that systemd-resolved will read nameservers from
systemd.network files and populate /run/systemd/resolve/resolv.conf.
When avahi-daemon starts before systemd-resolved, the target of the
/etc/resolv.conf link is not present on /run. Therefore,
avahi-daemon.service is dependent on systemd-resolve.


Solution:
Change avahi-daemon's dependency on /etc/resolv.conf and read
/run/systemd/resolve/resolv.conf instead and add a
"After=systemd-resolved.service" to avahi-daemon.service. This also
creates other problems. What about network mounts in /etc/fstab using nfs or
samba? I've also had to put mount options for a cifs mount like
"x-systemd.requires=systemd-networkd-wait-online.service" in /etc/fstab.
When avahi-daemon does not load, name resolution fails, all kinds of
network related services fail. Now everything has to have
"After=systemd-networkd-wait-online" added to their systemd.unit files.
This means the system pauses significantly; i.e. services block.

What else needs to read /etc/resolv.conf? At this time there is no
libnss-resolve (libnss-resolve.so, shipped with systemd) to add a "resolve"
in /etc/nsswitch.conf for systemd-resolved. Everything that depends on
/etc/resolv.conf will also need After=systemd-networkd-wait-online.service
lines added to their systemd.unit files too.

Another bug could be filed with systemd since systemd-resolved is there.

Workaround:
# Execute as root
mkdir -p /etc/systemd/system/avahi-daemon.service.d
printf "[Unit]\nAfter = systemd-resolved.service\n" > \
  /etc/systemd/system/avahi-daemon.service.d/ad.conf
systemctl daemon-reload


Journal:

Oct 01 18:41:32 incense avahi-daemon[625]: Successfully dropped root
privileges.
Oct 01 18:41:32 incense avahi-daemon[625]: avahi-daemon 0.6.31 starting
up.
Oct 01 18:41:49 incense avahi-daemon[625]: Successfully called chroot().
Oct 01 18:41:49 incense avahi-daemon[625]: Successfully dropped
remaining capabilities.
Oct 01 18:41:49 incense avahi-daemon[734]: chroot.c: open() failed: No
such file or directory
Oct 01 18:41:49 incense avahi-daemon[625]: Failed to open
/etc/resolv.conf: Invalid argument
Oct 01 18:41:49 incense avahi-daemon[625]: No service file found in
/etc/avahi/services.
Oct 01 18:41:49 incense avahi-daemon[625]: Network interface enumeration
completed.
Oct 01 18:41:49 incense avahi-daemon[625]: Registering HINFO record with
values 'I686'/'LINUX'.
Oct 01 18:41:49 incense avahi-daemon[625]: Server startup complete. Host
name is incense.local. Local service cookie is 128518944.
Oct 01 18:41:49 incense avahi-daemon[625]: Joining mDNS multicast group
on interface enp3s0.IPv4 with address 192.168.7.61.
Oct 01 18:41:49 incense avahi-daemon[625]: New relevant interface
enp3s0.IPv4 for mDNS.
Oct 01 18:41:49 incense avahi-daemon[625]: Registering new address
record for 192.168.7.61 on enp3s0.IPv4.
...

Been looking through my journal for errors, and noticed this.

I assume I'm seeing the same bug.


A few additional pieces of info for you (that may or may not be helpful):

     Jul  2 22:04:41 Love2d avahi-daemon[621]: Successfully dropped
remaining capabilities.

     Jul  2 22:04:41 Love2d avahi-daemon[630]: chroot.c: open() failed:
No such file or directory
     Jul  2 22:04:41 Love2d avahi-daemon[621]: Failed to open
/etc/resolv.conf: Invalid argument

     Jul  2 22:04:41 Love2d avahi-daemon[621]: No service file found in
/etc/avahi/services.
---------------------------------------------------------------------------------
/etc/resolv.conf is linked like this:
     resolv.conf -> /var/run/NetworkManager/resolv.conf

cat resolv.conf gives:
     # Generated by NetworkManager
     nameserver 8.8.8.8
     nameserver 8.8.4.4

 From man pages:
       nameserver Name server IP address
               Internet address of a name server that the resolver
should query, either an IPv4 address  (in  dot  notation),  or an  IPv6
               address in colon (and possibly dot) notation as per RFC
2373.  Up to MAXNS (currently 3, see <resolv.h>) name servers may be
               listed, one per keyword.  If there are multiple servers,
the resolver library queries them in the order listed. If no name‐
               server  entries  are  present,  the default is to use the
name server on the local machine.  (The algorithm used is to try a
               name server, and if the query times out, try the next,
until out of name servers, then repeat trying all  the name  servers
               until a maximum number of retries are made.)

---------------------------------------------------------------------------------
avahi.org is temporarily unavailavable, a couple of quick links are
available below

  * doxygen documentation <http://www.avahi.org/doxygen/>
  * avahi 0.6.32
    <https://github.com/lathiat/avahi/releases/download/v0.6.32/avahi-0.6.32.tar.gz>
  * github: lathiat <http://github.com/lathiat/avahi>
  * mailing list <http://lists.freedesktop.org/mailman/listinfo/avahi>

i morkaround this way


cat /lib/systemd/system/avahi-daemon.service

[Unit]
Description=Avahi mDNS/DNS-SD Stack
After=network-online.target

[Service]
Type=dbus
BusName=org.freedesktop.Avahi
ExecStart=/usr/sbin/avahi-daemon -s
ExecReload=/usr/sbin/avahi-daemon -r
NotifyAccess=main

[Install]
WantedBy=multi-user.target
Also=avahi-daemon.socket
Alias=dbus-org.freedesktop.Avahi.service

Reproduced here with debian-9.1.0-amd64+Gnome
Appending this line:
After=network-online.target
to the [Unit] section of /lib/systemd/system/avahi-daemon.service
then at next boot avahi-daemon message disappears.

Reproduced in several computers with Debian 9.2 :

$ sudo journalctl -b -p err
-- Logs begin at Tue 2017-11-21 22:12:42 CET, end at Thu 2017-11-23
14:22:56 CET. --
nov 23 14:21:31 system avahi-daemon[490]: chroot.c: open() failed: No
such file or directory

If that workaround is a solution, please fix this for next updates.

Hello,
Am Manley Marcus Kobenan, a banker, a France origin but resided here in
Cote d'Ivoire for work, I stopped at your profile and will love to know
more about you,I have a business that will profit both of us in your
country that I want us to discuss about. I will be glad to hear from you
soon for more details, take care dear.

Manley Marcus Kobenan

This issue has supposedly been fixed in

https://github.com/systemd/systemd/commit/3e06055500755053050620a45236ef606507e1bd

which is part of systemd v234 and later.