[lug] Debugging a startup problem

[Jed S. Baer]

Followup:

Shutdown machine, turned power completely off to it.

Unplugged network cable, cleaned plug and jack with De-Oxit. Plugged back
in.

Reboot, using --debug on the kernel line. Same problem with network. It
doesn't come up. There is a green LED lit on the port on the PC.
Unplug/replug cable, no change.

Unloading/reloading driver has no effect.

What does work, is issuing 'service network-manager restart'. Confirmed
this by again rebooting, and immediately upon logging in, issuing that
command. Here's what seems relevant:

08:30:28 avahi-daemon[645]: Withdrawing workstation service for eth3.
08:30:28 kernel: [ 1758.705861] init: job_change_state: Destroyed inactive instance network-interface (eth3)
08:30:33 kernel: [ 1764.065792] r8169 0000:01:00.0 eth3: renamed from eth0
08:30:33 kernel: [ 1764.082280] systemd-udevd[3132]: renamed network interface eth0 to eth3
08:30:33 kernel: [ 1764.085411] init: event_pending_handle_jobs: New instance network-interface (eth3)
08:30:33 kernel: [ 1764.091485] init: network-interface (eth3) pre-start process (3137)
08:30:33 kernel: [ 1764.099310] init: network-interface (eth3) pre-start process (3137) exited normally
08:30:33 kernel: [ 1764.099371] init: network-interface (eth3) state changed from pre-start to spawned
08:30:33 kernel: [ 1764.099490] init: network-interface (eth3) state changed from spawned to post-start
08:30:33 kernel: [ 1764.099553] init: network-interface (eth3) state changed from post-start to running
08:38:10 NetworkManager[3290]: <info> (eth3): carrier is OFF
08:38:10 NetworkManager[3290]: <info> (eth3): new Ethernet device (driver: 'r8169' ifindex: 3)
08:38:10 NetworkManager[3290]: <info> (eth3): exported as /org/freedesktop/NetworkManager/Devices/0
08:38:10 NetworkManager[3290]: <info> (eth3): device state change: unmanaged -> unavailable (reason 'managed') [10 20 2]
08:38:10 NetworkManager[3290]: <info> (eth3): bringing up device.
08:38:10 NetworkManager[3290]: <info> (eth3): preparing device.
08:38:10 NetworkManager[3290]: <info> (eth3): deactivating device (reason 'managed') [2]
08:38:10 kernel: [ 2220.594902] r8169 0000:01:00.0 eth3: link down
08:38:10 kernel: [ 2220.594923] IPv6: ADDRCONF(NETDEV_UP): eth3: link is not ready
08:38:10 kernel: [ 2220.594942] r8169 0000:01:00.0 eth3: link down
08:38:12 NetworkManager[3290]: <info> (eth3): carrier now ON (device state 20)
08:38:12 NetworkManager[3290]: <info> (eth3): device state change: unavailable -> disconnected (reason 'carrier-changed') [20 30 40]
08:38:12 NetworkManager[3290]: <info> Activation (eth3) starting connection 'Ethernet connection 1'
08:38:12 NetworkManager[3290]: <info> (eth3): device state change: disconnected -> prepare (reason 'none') [30 40 0]
08:38:12 NetworkManager[3290]: <info> Activation (eth3) Stage 1 of 5 (Device Prepare) scheduled...
08:38:12 NetworkManager[3290]: <info> Activation (eth3) Stage 1 of 5 (Device Prepare) started...
08:38:12 NetworkManager[3290]: <info> Activation (eth3) Stage 2 of 5 (Device Configure) scheduled...
08:38:12 NetworkManager[3290]: <info> Activation (eth3) Stage 1 of 5 (Device Prepare) complete.
08:38:12 NetworkManager[3290]: <info> Activation (eth3) Stage 2 of 5 (Device Configure) starting...
08:38:12 NetworkManager[3290]: <info> (eth3): device state change: prepare -> config (reason 'none') [40 50 0]
08:38:12 NetworkManager[3290]: <info> Activation (eth3) Stage 2 of 5 (Device Configure) successful.
08:38:12 NetworkManager[3290]: <info> Activation (eth3) Stage 3 of 5 (IP Configure Start) scheduled.
08:38:12 NetworkManager[3290]: <info> Activation (eth3) Stage 2 of 5 (Device Configure) complete.
08:38:12 NetworkManager[3290]: <info> Activation (eth3) Stage 3 of 5 (IP Configure Start) started...
08:38:12 NetworkManager[3290]: <info> (eth3): device state change: config -> ip-config (reason 'none') [50 70 0]
08:38:12 kernel: [ 2222.392503] r8169 0000:01:00.0 eth3: link up
08:38:12 kernel: [ 2222.392522] IPv6: ADDRCONF(NETDEV_CHANGE): eth3: link becomes ready

But I note that messages such as 'link is not ready' and carrier state don't appear during the boot process -- only when restarting network manager.

During this process, a 2nd PC was connected to the router, and had no network dropouts.