16.04, Network stops working [closed]

Ubuntu 16.04. Network (both cable or wi-fi) stops working after a certain amount of time.

This is my /var/log/syslog after the last appearing of the problem

davide@brenna:~$ cat /var/log/syslog
Apr 29 09:30:23 brenna colord[1150]: (colord:1150): Cd-WARNING **: failed to get session [pid 4355]: Device o indirizzo non esistente
Apr 29 09:30:40 brenna anacron[896]: Job `cron.daily' terminated
Apr 29 09:30:40 brenna anacron[896]: Normal exit (1 job run)
Apr 29 09:32:28 brenna com.ubuntu.OneConf[1671]: WARNING:oneconf.hosts:Error in loading other_hosts file: [Errno 2] No such file or directory: '/home/davide/.cache/oneconf/3bdacd8fb8c349449cd523c9f50dfcb9/other_hosts'
Apr 29 09:36:46 brenna AptDaemon: INFO: Quitting due to inactivity
Apr 29 09:36:46 brenna AptDaemon: INFO: Quitting was requested
Apr 29 09:36:46 brenna org.debian.apt[943]: 09:36:46 AptDaemon [INFO]: Quitting due to inactivity
Apr 29 09:36:46 brenna org.debian.apt[943]: 09:36:46 AptDaemon [INFO]: Quitting was requested
Apr 29 09:40:15 brenna upowerd[1831]: (upowerd:1831): UPower-Linux-WARNING **: energy 44,400000 bigger than full 31,912500
Apr 29 09:40:23 brenna avahi-daemon[940]: Withdrawing address record for 192.168.0.216 on eth0.
Apr 29 09:40:23 brenna avahi-daemon[940]: Leaving mDNS multicast group on interface eth0.IPv4 with address 192.168.0.216.
Apr 29 09:40:23 brenna gnome-session[1803]: [2045:2151:0429/094023:ERROR:cloud_print_proxy_backend.cc(538)] Notifications for connector 9EEEB091-559D-9344-6BAC-C8DDB4835FE9 disabled.
Apr 29 09:40:23 brenna gnome-session[1803]: [2045:2151:0429/094023:ERROR:cloud_print_proxy_backend.cc(538)] Notifications for connector 9EEEB091-559D-9344-6BAC-C8DDB4835FE9 disabled.
Apr 29 09:40:23 brenna avahi-daemon[940]: Interface eth0.IPv4 no longer relevant for mDNS.
Apr 29 09:40:23 brenna systemd[1]: Starting Cleanup of Temporary Directories...
Apr 29 09:40:23 brenna systemd-tmpfiles[7098]: [/usr/lib/tmpfiles.d/var.conf:14] Duplicate line for path "/var/log", ignoring.
Apr 29 09:40:23 brenna systemd[1]: Started Cleanup of Temporary Directories.
Apr 29 09:40:23 brenna whoopsie[920]: [09:40:23] Cannot reach: https://daisy.ubuntu.com
Apr 29 09:40:23 brenna whoopsie[920]: [09:40:23] offline
Apr 29 09:40:24 brenna whoopsie[920]: [09:40:24] Cannot reach: https://daisy.ubuntu.com
Apr 29 09:41:23 brenna whoopsie[920]: [09:41:23] Cannot reach: https://daisy.ubuntu.com

Removing the plug and reinserting it (or switching off the wi-fi card and re-enabling it) solves the problem until the next reboot (i.e. the network works indefinitely after that until the reboot).

This is mostly annoying, especially because there is no visual output when this happens. It just stops working, and when you try to submit an online request (maybe write a post to a forum, or try to reach a new page) it just does not work anymore.

Any hints?

Today I was able to update before the problem occured, so the syslog us a

davide@brenna:~$ cat /var/log/syslog
Apr 30 09:19:18 brenna colord[1137]: (colord:1137): Cd-WARNING **: failed to get session [pid 4254]: Device o indirizzo non esistente
Apr 30 09:19:31 brenna anacron[962]: Job `cron.daily' terminated
Apr 30 09:19:31 brenna anacron[962]: Normal exit (1 job run)
Apr 30 09:26:23 brenna AptDaemon: INFO: Quitting due to inactivity
Apr 30 09:26:23 brenna AptDaemon: INFO: Quitting was requested
Apr 30 09:26:23 brenna org.debian.apt[891]: 09:26:23 AptDaemon [INFO]: Quitting due to inactivity
Apr 30 09:26:23 brenna org.debian.apt[891]: 09:26:23 AptDaemon [INFO]: Quitting was requested
Apr 30 09:29:18 brenna avahi-daemon[979]: Withdrawing address record for 192.168.0.216 on eth0.
Apr 30 09:29:18 brenna avahi-daemon[979]: Leaving mDNS multicast group on interface eth0.IPv4 with address 192.168.0.216.
Apr 30 09:29:18 brenna avahi-daemon[979]: Interface eth0.IPv4 no longer relevant for mDNS.
Apr 30 09:29:18 brenna systemd[1]: Starting Cleanup of Temporary Directories...
Apr 30 09:29:18 brenna systemd-tmpfiles[4409]: [/usr/lib/tmpfiles.d/var.conf:14] Duplicate line for path "/var/log", ignoring.
Apr 30 09:29:18 brenna gnome-session[2299]: [2547:2656:0430/092918:ERROR:cloud_print_proxy_backend.cc(538)] Notifications for connector 9EEEB091-559D-9344-6BAC-C8DDB4835FE9 disabled.
Apr 30 09:29:18 brenna gnome-session[2299]: [2547:2656:0430/092918:ERROR:cloud_print_proxy_backend.cc(538)] Notifications for connector 9EEEB091-559D-9344-6BAC-C8DDB4835FE9 disabled.
Apr 30 09:29:18 brenna systemd[1]: Started Cleanup of Temporary Directories.
Apr 30 09:29:18 brenna whoopsie[982]: [09:29:18] Cannot reach: https://daisy.ubuntu.com
Apr 30 09:29:18 brenna whoopsie[982]: [09:29:18] offline
Apr 30 09:29:19 brenna whoopsie[982]: [09:29:19] Cannot reach: https://daisy.ubuntu.com
Apr 30 09:32:46 brenna whoopsie[982]: [09:32:46] Cannot reach: https://daisy.ubuntu.com
Apr 30 09:33:02 brenna whoopsie[982]: [09:33:02] Cannot reach: https://daisy.ubuntu.com
Apr 30 09:33:18 brenna whoopsie[982]: [09:33:18] Cannot reach: https://daisy.ubuntu.com
Apr 30 09:38:24 brenna whoopsie[982]: [09:38:24] Cannot reach: https://daisy.ubuntu.com
Apr 30 09:39:00 brenna dbus[891]: [system] Activating service name='org.debian.apt' (using servicehelper)
Apr 30 09:39:01 brenna AptDaemon: INFO: Initializing daemon
Apr 30 09:39:01 brenna org.debian.apt[891]: 09:39:01 AptDaemon [INFO]: Initializing daemon
Apr 30 09:39:01 brenna dbus[891]: [system] Successfully activated service 'org.debian.apt'
Apr 30 09:39:01 brenna AptDaemon.PackageKit: INFO: Initializing PackageKit compat layer
Apr 30 09:39:01 brenna org.debian.apt[891]: /usr/lib/python3/dist-packages/aptdaemon/worker/pkworker.py:35: PyGIWarning: PackageKitGlib was imported without specifying a version first. Use gi.require_version('PackageKitGlib', '1.0') before import to ensure that the right version gets loaded.
Apr 30 09:39:01 brenna org.debian.apt[891]:   from gi.repository import PackageKitGlib as pk
Apr 30 09:39:01 brenna org.debian.apt[891]: 09:39:01 AptDaemon.PackageKit [INFO]: Initializing PackageKit compat layer
Apr 30 09:39:01 brenna AptDaemon: INFO: CommitPackages() was called: dbus.Array([dbus.String('')], signature=dbus.Signature('s')), dbus.Array([dbus.String('')], signature=dbus.Signature('s')), dbus.Array([dbus.String('')], signature=dbus.Signature('s')), dbus.Array([dbus.String('')], signature=dbus.Signature('s')), dbus.Array([dbus.String('ubuntu-core-launcher')], signature=dbus.Signature('s')), dbus.Array([dbus.String('')], signature=dbus.Signature('s'))
Apr 30 09:39:01 brenna org.debian.apt[891]: 09:39:01 AptDaemon [INFO]: CommitPackages() was called: dbus.Array([dbus.String('')], signature=dbus.Signature('s')), dbus.Array([dbus.String('')], signature=dbus.Signature('s')), dbus.Array([dbus.String('')], signature=dbus.Signature('s')), dbus.Array([dbus.String('')], signature=dbus.Signature('s')), dbus.Array([dbus.String('ubuntu-core-launcher')], signature=dbus.Signature('s')), dbus.Array([dbus.String('')], signature=dbus.Signature('s'))
Apr 30 09:39:01 brenna AptDaemon.Trans: INFO: Queuing transaction /org/debian/apt/transaction/c920bbc5aef04a96b9cfe22ca0070cab
Apr 30 09:39:01 brenna org.debian.apt[891]: 09:39:01 AptDaemon.Trans [INFO]: Queuing transaction /org/debian/apt/transaction/c920bbc5aef04a96b9cfe22ca0070cab
Apr 30 09:39:01 brenna AptDaemon.Worker: INFO: Simulating trans: /org/debian/apt/transaction/c920bbc5aef04a96b9cfe22ca0070cab
Apr 30 09:39:01 brenna org.debian.apt[891]: 09:39:01 AptDaemon.Worker [INFO]: Simulating trans: /org/debian/apt/transaction/c920bbc5aef04a96b9cfe22ca0070cab
Apr 30 09:39:01 brenna AptDaemon.Worker: INFO: Committing packages: dbus.Array([], signature=dbus.Signature('s')), dbus.Array([], signature=dbus.Signature('s')), dbus.Array([], signature=dbus.Signature('s')), dbus.Array([], signature=dbus.Signature('s')), dbus.Array([dbus.String('ubuntu-core-launcher')], signature=dbus.Signature('s')), dbus.Array([], signature=dbus.Signature('s'))
Apr 30 09:39:01 brenna org.debian.apt[891]: 09:39:01 AptDaemon.Worker [INFO]: Committing packages: dbus.Array([], signature=dbus.Signature('s')), dbus.Array([], signature=dbus.Signature('s')), dbus.Array([], signature=dbus.Signature('s')), dbus.Array([], signature=dbus.Signature('s')), dbus.Array([dbus.String('ubuntu-core-launcher')], signature=dbus.Signature('s')), dbus.Array([], signature=dbus.Signature('s'))
Apr 30 09:39:02 brenna AptDaemon.Worker: INFO: Processing transaction /org/debian/apt/transaction/c920bbc5aef04a96b9cfe22ca0070cab
Apr 30 09:39:02 brenna org.debian.apt[891]: 09:39:02 AptDaemon.Worker [INFO]: Processing transaction /org/debian/apt/transaction/c920bbc5aef04a96b9cfe22ca0070cab
Apr 30 09:39:02 brenna gnome-session[2299]: debconf: DbDriver "passwords" warning: could not open /var/cache/debconf/passwords.dat: Permission denied
Apr 30 09:39:04 brenna kernel: [ 1491.033247] audit_printk_skb: 52 callbacks suppressed
Apr 30 09:39:04 brenna kernel: [ 1491.033251] audit: type=1400 audit(1462001944.072:28): apparmor="STATUS" operation="profile_replace" profile="unconfined" name="/usr/bin/ubuntu-core-launcher" pid=4526 comm="apparmor_parser"
Apr 30 09:39:03 brenna gnome-session[2299]: message repeated 2 times: [ debconf: DbDriver "passwords" warning: could not open /var/cache/debconf/passwords.dat: Permission denied]
Apr 30 09:39:05 brenna AptDaemon.Worker: INFO: Finished transaction /org/debian/apt/transaction/c920bbc5aef04a96b9cfe22ca0070cab
Apr 30 09:39:05 brenna org.debian.apt[891]: /usr/lib/python3/dist-packages/aptdaemon/progress.py:491: Warning: Source ID 41 was not found when attempting to remove it
Apr 30 09:39:05 brenna org.debian.apt[891]:   GLib.source_remove(id)
Apr 30 09:39:05 brenna org.debian.apt[891]: /usr/lib/python3/dist-packages/aptdaemon/progress.py:491: Warning: Source ID 42 was not found when attempting to remove it
Apr 30 09:39:05 brenna org.debian.apt[891]:   GLib.source_remove(id)
Apr 30 09:39:05 brenna org.debian.apt[891]: 09:39:05 AptDaemon.Worker [INFO]: Finished transaction /org/debian/apt/transaction/c920bbc5aef04a96b9cfe22ca0070cab
Apr 30 09:39:06 brenna gnome-session[2299]: (unity-control-center:4593): unity-control-center-WARNING **: Could not load /usr/share/themes/Adwaita/index.theme: File o directory non esistente
Apr 30 09:39:21 brenna gnome-session[2299]: /usr/bin/update-manager:28: PyGIWarning: Gtk was imported without specifying a version first. Use gi.require_version('Gtk', '3.0') before import to ensure that the right version gets loaded.
Apr 30 09:39:21 brenna gnome-session[2299]:   from gi.repository import Gtk
Apr 30 09:39:21 brenna gnome-session[2299]: /usr/lib/python3/dist-packages/UpdateManager/UnitySupport.py:29: PyGIWarning: Dbusmenu was imported without specifying a version first. Use gi.require_version('Dbusmenu', '0.4') before import to ensure that the right version gets loaded.
Apr 30 09:39:21 brenna gnome-session[2299]:   from gi.repository import Dbusmenu, Unity
Apr 30 09:39:21 brenna gnome-session[2299]: /usr/lib/python3/dist-packages/UpdateManager/UnitySupport.py:29: PyGIWarning: Unity was imported without specifying a version first. Use gi.require_version('Unity', '7.0') before import to ensure that the right version gets loaded.
Apr 30 09:39:21 brenna gnome-session[2299]:   from gi.repository import Dbusmenu, Unity
Apr 30 09:39:23 brenna com.ubuntu.OneConf[2070]: WARNING:oneconf.hosts:Error in loading other_hosts file: [Errno 2] No such file or directory: '/home/davide/.cache/oneconf/3bdacd8fb8c349449cd523c9f50dfcb9/other_hosts'

As per request

davide@brenna:~$ lspci -nn | grep Network
07:00.0 Network controller [0280]: Intel Corporation Centrino Wireless-N 2230 [8086:0887] (rev c4)
davide@brenna:~$ lspci -nn | grep Eth
09:00.0 Ethernet controller [0200]: Qualcomm Atheros AR8161 Gigabit Ethernet [1969:1091] (rev 10)

I found this via the systemd journal

mag 05 12:18:32 brenna avahi-daemon[939]: Withdrawing address record for 192.168.0.216 on eth0.
mag 05 12:18:32 brenna gnome-session[1789]: [2013:2119:0505/121832:ERROR:cloud_print_proxy_backend.cc(538)] Notifications for connector 9EEEB091-559D-9344-6BAC-C8DDB4835
mag 05 12:18:32 brenna gnome-session[1789]: [2013:2119:0505/121832:ERROR:cloud_print_proxy_backend.cc(538)] Notifications for connector 9EEEB091-559D-9344-6BAC-C8DDB4835
mag 05 12:18:32 brenna avahi-daemon[939]: Leaving mDNS multicast group on interface eth0.IPv4 with address 192.168.0.216.
mag 05 12:18:32 brenna systemd[1]: Starting Cleanup of Temporary Directories...
mag 05 12:18:32 brenna whoopsie[931]: [12:18:32] Cannot reach: https://daisy.ubuntu.com
mag 05 12:18:32 brenna whoopsie[931]: [12:18:32] offline
mag 05 12:18:32 brenna avahi-daemon[939]: Interface eth0.IPv4 no longer relevant for mDNS.
mag 05 12:18:32 brenna systemd-tmpfiles[4930]: [/usr/lib/tmpfiles.d/var.conf:14] Duplicate line for path "/var/log", ignoring.
mag 05 12:18:33 brenna systemd[1]: Started Cleanup of Temporary Directories.
mag 05 12:18:33 brenna whoopsie[931]: [12:18:33] Cannot reach: https://daisy.ubuntu.com

and this question about avahi-daemon. Investingating in this direction---

The problem got solved with the normal updates, so it is not clear where the problem exactly was.

Check the content of /etc/network/interfaces. Though I could be mistaken, it sounds to me as though you are managing your networks from the GUI. I have previously had problems with conflicts between my /etc/network/interfaces file and the Ubuntu GUI setup.

If /etc/network/interfaces has networks set up in it, try removing them and using just the GUI setup. If this does not work, and that file just has the following lines in it, try the steps below.

auto lo
iface lo inet loopback

If your /etc/network/interfaces file has just the those lines, my first try would be to delete everything in your Ubuntu GUI networking and put into /etc/network/interfaces:

auto eth0
iface eth0 inet dhcp

Or to configure a static IP (for cases in which you don't have a dhcp router):

auto eth0
iface eth0 inet static
  address 192.168.1.14
  gateway 192.168.1.1
  netmask 255.255.255.0
  network 192.168.1.0
  broadcast 192.168.1.255

And replace eth0 with eth1 or wlan0 etc for a secondary ethernet or a wireless card.

Then run sudo /etc/init.d/networking restart to test it, then reboot to see if it worked.

P.S.: I make no guarantees of this working. It's hard to tell from the limited quantity of information that you're able to post where the problem lies. This is just the first thing I would try.