No network access after Ubuntu 14.04->16.04->18.04 upgrade
Recently I was tending to my fleet of personal servers and I ran into a problem which essentially took my system offline and with it a number of websites I host.
After the upgrade my system did not automatically start eth0 with its assigned static IP address, only the loopback device was configured. Thankfully DigitalOcean provides easy console access. So i started some debugging:
m@box:~$ ifconfig
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 1000 (Local Loopback)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
m@box:~$ cat ifconfig-a.log
eth0: flags=4098<BROADCAST,MULTICAST> mtu 1500
ether 04:01:01:8a:1b:01 txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 1000 (Local Loopback)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
Turns out the root cause was no ifup or ifdown, which were both scripts required by /etc/init.d/networking to bring up networking
m@box:~$ ifup eth0
-bash: ifup: command not found
m@box:~$ ifdown eth0
-bash: ifdown: command not found
Excerpt from /etc/init.d/networking
m@box:~$ grep -in "ifup\|ifdown" /etc/init.d/networking
3:# Provides: networking ifupdown
17:[ -x /sbin/ifup ] || exit 0
18:[ -x /sbin/ifdown ] || exit 0
101:ifup_hotplug () {
115: ifup $ifaces "$@" || true
141: if ifup -a $exclusions $verbose && ifup_hotplug $exclusions $verbose
157: if ifdown -a --exclude=lo $verbose; then
172: ifdown -a --exclude=lo $verbose || true
173: if ifup --exclude=lo $state $verbose ; then
188: ifdown -a --exclude=lo $verbose || true
191: if ifup -a --exclude=lo $exclusions $verbose && ifup_hotplug $exclusions $verbose
Temp fix to get back onto the internet to actually install networkd/netplan:
m@box:~$ sudo ifconfig eth0 up
# xx.xx.xx.xx/24 is your static IP
m@box:~$ sudo ip addr add xx.xx.xx.xx/24 dev eth0
# xx.xx.xx.1 is your gateway
m@box:~$ sudo ip route add default via xx.xx.xx.1 dev eth0
long-term fix, install netplan, configure it to manage networkd:
m@box:~$ sudo apt-get install netplan.io
We configure netplan(/etc/netplan/01-netcfg.yaml):
network:
version: 2
renderer: networkd
ethernets:
eth0:
dhcp4: no
dhcp6: no
addresses: [xx.xx.xx.xx/24]
gateway4: xx.xx.xx.1
nameservers:
addresses: [8.8.8.8, 8.8.4.4]
next we apply the new changes and make sure it gives no errors:
m@box:~$ sudo netplan --debug apply
** (generate:1883): DEBUG: 19:19:36.239: Processing input file //etc/netplan/01-netcfg.yaml..
** (generate:1883): DEBUG: 19:19:36.240: starting new processing pass
** (generate:1883): DEBUG: 19:19:36.240: eth0: setting default backend to 1
** (generate:1883): DEBUG: 19:19:36.244: Generating output files..
** (generate:1883): DEBUG: 19:19:36.244: NetworkManager: definition eth0 is not for us (backend 1)
DEBUG:netplan generated networkd configuration exists, restarting networkd
DEBUG:no netplan generated NM configuration exists
DEBUG:device eth0 operstate is up, not replugging
DEBUG:netplan triggering .link rules for eth0
DEBUG:device lo operstate is unknown, not replugging
DEBUG:netplan triggering .link rules for lo
now the last step is to reboot and make sure the new configuration persists.
And viola, after a reboot everything stayed in place:
m@box:~$ ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet xx.xx.xx.xx netmask 255.255.255.0 broadcast xx.xx.xx.255
inet6 xx::xx:xx:xx:xx prefixlen 64 scopeid 0x20<link>
ether 04:01:xx:xx:xx:xx txqueuelen 1000 (Ethernet)
RX packets 654 bytes 69420 (69.4 KB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 517 bytes 108478 (108.4 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 1000 (Local Loopback)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0