Petit up du sujet.
Il semblerait que mon problème soit de retour. J'ai réinstallé ubuntu 16.04 car trop de problème avec la 18.04, mais la perte de connexion revient régulièrement, et cette fois je pense avoir trouvé une piste : le renew DHCP. Elle expire toutes les 2 heures et cette fois la coupure semble bien coïncider.
J'ai allumé mon PC vers 13h15 et je me suis rendu compte que je n'avais plus de connexion vers 15h30 donc à quelques minutes près ça ressemble au renew qui ne s'est pas fait correctement.
Mais je ne vois aucune erreur dans les logs... alors que je vois bien ma déconnexion/reconnexion manuelle...
Voici le syslog (on voit bien qu'avant mon intervention, il n'y a aucun renew DHCP de fait) :
Oct 5 13:22:18 renaud-pc anacron[1231]: Job `cron.daily' terminated
Oct 5 13:22:18 renaud-pc anacron[1231]: Normal exit (1 job run)
Oct 5 13:26:35 renaud-pc ntpd[1620]: 91.189.91.157 local addr 192.168.1.11 -> <null>
Oct 5 13:29:54 renaud-pc ntpd[1620]: 62.210.167.248 local addr 192.168.1.11 -> <null>
Oct 5 13:30:57 renaud-pc ntpd[1620]: 95.81.173.155 local addr 192.168.1.11 -> <null>
Oct 5 13:31:01 renaud-pc ntpd[1620]: 137.74.28.231 local addr 192.168.1.11 -> <null>
Oct 5 13:32:07 renaud-pc ntpd[1620]: 212.83.179.156 local addr 192.168.1.11 -> <null>
Oct 5 13:32:07 renaud-pc systemd[1]: Starting Cleanup of Temporary Directories...
Oct 5 13:32:07 renaud-pc systemd-tmpfiles[5545]: [/usr/lib/tmpfiles.d/var.conf:14] Duplicate line for path "/var/log", ignoring.
Oct 5 13:32:07 renaud-pc systemd[1]: Started Cleanup of Temporary Directories.
Oct 5 13:41:43 renaud-pc ntpd[1620]: 91.189.89.198 local addr 192.168.1.11 -> <null>
Oct 5 13:44:25 renaud-pc ntpd[1620]: 212.85.158.10 local addr 192.168.1.11 -> <null>
Oct 5 14:13:05 renaud-pc ntpd[1620]: 37.187.2.84 local addr 192.168.1.11 -> <null>
Oct 5 14:17:01 renaud-pc CRON[5911]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly)
Oct 5 14:34:55 renaud-pc ntpd[1620]: 149.202.2.105 local addr 192.168.1.11 -> <null>
Oct 5 14:35:05 renaud-pc ntpd[1620]: 91.224.149.41 local addr 192.168.1.11 -> <null>
Oct 5 14:54:11 renaud-pc ntpd[1620]: 151.80.211.8 local addr 192.168.1.11 -> <null>
Oct 5 15:17:01 renaud-pc CRON[6147]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly)
Oct 5 15:17:20 renaud-pc avahi-daemon[1138]: Withdrawing address record for 192.168.1.11 on enp2s0.
Oct 5 15:17:20 renaud-pc avahi-daemon[1138]: Leaving mDNS multicast group on interface enp2s0.IPv4 with address 192.168.1.11.
Oct 5 15:17:20 renaud-pc avahi-daemon[1138]: Interface enp2s0.IPv4 no longer relevant for mDNS.
Oct 5 15:17:21 renaud-pc ntpd[1620]: Deleting interface #3 enp2s0, 192.168.1.11#123, interface stats: received=575, sent=576, dropped=0, active_time=7200 secs
Oct 5 15:17:21 renaud-pc ntpd[1620]: 178.249.167.0 local addr 192.168.1.11 -> <null>
Oct 5 15:17:21 renaud-pc ntpd[1620]: 92.243.6.5 local addr 192.168.1.11 -> <null>
Oct 5 15:17:21 renaud-pc ntpd[1620]: 212.83.187.62 local addr 192.168.1.11 -> <null>
Oct 5 15:17:21 renaud-pc ntpd[1620]: 37.187.101.146 local addr 192.168.1.11 -> <null>
Oct 5 15:17:21 renaud-pc ntpd[1620]: 151.80.19.218 local addr 192.168.1.11 -> <null>
Oct 5 15:17:21 renaud-pc ntpd[1620]: 195.154.41.195 local addr 192.168.1.11 -> <null>
Oct 5 15:17:40 renaud-pc whoopsie[1588]: [15:17:40] Cannot reach: https://daisy.ubuntu.com
Oct 5 15:17:40 renaud-pc whoopsie[1588]: [15:17:40] offline
Oct 5 15:51:32 renaud-pc NetworkManager[1230]: <info> [1538747492.1103] device (enp2s0): state change: activated -> deactivating (reason 'user-requested') [100 110 39]
Oct 5 15:51:32 renaud-pc NetworkManager[1230]: <info> [1538747492.1105] manager: NetworkManager state is now DISCONNECTING
Oct 5 15:51:32 renaud-pc NetworkManager[1230]: <info> [1538747492.1733] audit: op="device-disconnect" interface="enp2s0" ifindex=2 pid=2394 uid=1000 result="success"
Oct 5 15:51:32 renaud-pc NetworkManager[1230]: <info> [1538747492.1741] device (enp2s0): state change: deactivating -> disconnected (reason 'user-requested') [110 30 39]
Oct 5 15:51:32 renaud-pc avahi-daemon[1138]: Withdrawing address record for fe80::cfdf:26bd:a020:3428 on enp2s0.
Oct 5 15:51:32 renaud-pc avahi-daemon[1138]: Leaving mDNS multicast group on interface enp2s0.IPv6 with address fe80::cfdf:26bd:a020:3428.
Oct 5 15:51:32 renaud-pc avahi-daemon[1138]: Interface enp2s0.IPv6 no longer relevant for mDNS.
Oct 5 15:51:32 renaud-pc NetworkManager[1230]: <info> [1538747492.2066] dhcp4 (enp2s0): canceled DHCP transaction, DHCP client pid 1411
Oct 5 15:51:32 renaud-pc NetworkManager[1230]: <info> [1538747492.2066] dhcp4 (enp2s0): state changed bound -> done
Oct 5 15:51:32 renaud-pc NetworkManager[1230]: <info> [1538747492.2071] dns-mgr: Writing DNS information to /sbin/resolvconf
Oct 5 15:51:32 renaud-pc dnsmasq[1421]: configuration des serveurs amonts à partir de DBus
Oct 5 15:51:32 renaud-pc NetworkManager[1230]: <info> [1538747492.2335] manager: NetworkManager state is now DISCONNECTED
Oct 5 15:51:32 renaud-pc dbus[1140]: [system] Activating via systemd: service name='org.freedesktop.nm_dispatcher' unit='dbus-org.freedesktop.nm-dispatcher.service'
Oct 5 15:51:32 renaud-pc systemd[1]: Starting Network Manager Script Dispatcher Service...
Oct 5 15:51:32 renaud-pc dbus[1140]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher'
Oct 5 15:51:32 renaud-pc systemd[1]: Started Network Manager Script Dispatcher Service.
Oct 5 15:51:32 renaud-pc nm-dispatcher: req:1 'down' [enp2s0]: new request (2 scripts)
Oct 5 15:51:32 renaud-pc nm-dispatcher: req:1 'down' [enp2s0]: start running ordered scripts...
Oct 5 15:51:33 renaud-pc ntpd[1620]: Deleting interface #6 enp2s0, fe80::cfdf:26bd:a020:3428%2#123, interface stats: received=0, sent=0, dropped=0, active_time=9250 secs
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.4791] device (enp2s0): Activation: starting connection 'Connexion filaire 1' (8bb8eaa7-4c02-39a2-9500-54e1970d3c66)
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.4792] audit: op="connection-activate" uuid="8bb8eaa7-4c02-39a2-9500-54e1970d3c66" name="Connexion filaire 1" pid=2394 uid=1000 result="success"
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.4794] device (enp2s0): state change: disconnected -> prepare (reason 'none') [30 40 0]
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.4795] manager: NetworkManager state is now CONNECTING
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.4801] device (enp2s0): state change: prepare -> config (reason 'none') [40 50 0]
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.4804] device (enp2s0): state change: config -> ip-config (reason 'none') [50 70 0]
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.4808] dhcp4 (enp2s0): activation: beginning transaction (timeout in 45 seconds)
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.4826] dhcp4 (enp2s0): dhclient started with pid 6677
Oct 5 15:51:37 renaud-pc dhclient[6677]: DHCPREQUEST of 192.168.1.11 on enp2s0 to 255.255.255.255 port 67 (xid=0x766088f9)
Oct 5 15:51:37 renaud-pc dhclient[6677]: DHCPACK of 192.168.1.11 from 192.168.1.10
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.5027] address 192.168.1.11
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.5028] plen 24 (255.255.255.0)
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.5028] gateway 192.168.1.1
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.5028] server identifier 192.168.1.10
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.5028] lease time 7200
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.5028] nameserver '192.168.1.10'
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.5029] nameserver '192.168.1.2'
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.5029] domain name 'lapalisse.lan'
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.5029] dhcp4 (enp2s0): state changed unknown -> bound
Oct 5 15:51:37 renaud-pc avahi-daemon[1138]: Joining mDNS multicast group on interface enp2s0.IPv4 with address 192.168.1.11.
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.5043] device (enp2s0): state change: ip-config -> ip-check (reason 'none') [70 80 0]
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.5050] device (enp2s0): state change: ip-check -> secondaries (reason 'none') [80 90 0]
Oct 5 15:51:37 renaud-pc avahi-daemon[1138]: New relevant interface enp2s0.IPv4 for mDNS.
Oct 5 15:51:37 renaud-pc avahi-daemon[1138]: Registering new address record for 192.168.1.11 on enp2s0.IPv4.
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.5053] device (enp2s0): state change: secondaries -> activated (reason 'none') [90 100 0]
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.5055] manager: NetworkManager state is now CONNECTED_LOCAL
Oct 5 15:51:37 renaud-pc whoopsie[1588]: [15:51:37] Cannot reach: https://daisy.ubuntu.com
Oct 5 15:51:37 renaud-pc dhclient[6677]: bound to 192.168.1.11 -- renewal in 2741 seconds.
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.5837] manager: NetworkManager state is now CONNECTED_GLOBAL
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.5838] policy: set 'Connexion filaire 1' (enp2s0) as default for IPv4 routing and DNS
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.5840] dns-mgr: Writing DNS information to /sbin/resolvconf
Oct 5 15:51:37 renaud-pc dnsmasq[1421]: configuration des serveurs amonts à partir de DBus
Oct 5 15:51:37 renaud-pc dnsmasq[1421]: utilise le serveur de nom 192.168.1.10#53 (via enp2s0)
Oct 5 15:51:37 renaud-pc dnsmasq[1421]: utilise le serveur de nom 192.168.1.2#53 (via enp2s0)
Oct 5 15:51:37 renaud-pc NetworkManager[1230]: <info> [1538747497.6529] device (enp2s0): Activation: successful, device activated.
Oct 5 15:51:37 renaud-pc nm-dispatcher: req:2 'up' [enp2s0]: new request (2 scripts)
Oct 5 15:51:37 renaud-pc nm-dispatcher: req:2 'up' [enp2s0]: start running ordered scripts...
Oct 5 15:51:37 renaud-pc whoopsie[1588]: [15:51:37] The default IPv4 route is: /org/freedesktop/NetworkManager/ActiveConnection/1
Oct 5 15:51:37 renaud-pc whoopsie[1588]: [15:51:37] Not a paid data plan: /org/freedesktop/NetworkManager/ActiveConnection/1
Oct 5 15:51:37 renaud-pc whoopsie[1588]: [15:51:37] Found usable connection: /org/freedesktop/NetworkManager/ActiveConnection/1
Oct 5 15:51:37 renaud-pc whoopsie[1588]: [15:51:37] online
Oct 5 15:51:38 renaud-pc avahi-daemon[1138]: Joining mDNS multicast group on interface enp2s0.IPv6 with address fe80::cfdf:26bd:a020:3428.
Oct 5 15:51:38 renaud-pc avahi-daemon[1138]: New relevant interface enp2s0.IPv6 for mDNS.
Oct 5 15:51:38 renaud-pc avahi-daemon[1138]: Registering new address record for fe80::cfdf:26bd:a020:3428 on enp2s0.*.
Oct 5 15:51:40 renaud-pc ntpd[1620]: Listen normally on 7 enp2s0 192.168.1.11:123
Oct 5 15:51:40 renaud-pc ntpd[1620]: Listen normally on 8 enp2s0 [fe80::cfdf:26bd:a020:3428%2]:123
Oct 5 15:51:40 renaud-pc ntpd[1620]: new interface(s) found: waking up resolver
J'ai aussi regardé les logs sur le serveur, et pas de trace de renew avant mon intervention...