Comment 8 for bug 1700079

Here's the info collected an machine that experienced the problem on June 23rd:

# grep -F 2017-06-23 /var/log/dpkg.log
2017-06-23 07:47:29 startup archives unpack
2017-06-23 07:47:29 upgrade openvpn:amd64 2.3.10-1ubuntu2 2.3.10-1ubuntu2.1
2017-06-23 07:47:29 status triggers-pending libc-bin:amd64 2.23-0ubuntu9
2017-06-23 07:47:29 status half-configured openvpn:amd64 2.3.10-1ubuntu2
2017-06-23 07:47:29 status unpacked openvpn:amd64 2.3.10-1ubuntu2
2017-06-23 07:47:29 status half-installed openvpn:amd64 2.3.10-1ubuntu2
2017-06-23 07:47:29 status triggers-pending systemd:amd64 229-4ubuntu17
2017-06-23 07:47:29 status triggers-pending ureadahead:amd64 0.100.0-19
2017-06-23 07:47:29 status half-installed openvpn:amd64 2.3.10-1ubuntu2
2017-06-23 07:47:29 status unpacked openvpn:amd64 2.3.10-1ubuntu2.1
2017-06-23 07:47:29 status unpacked openvpn:amd64 2.3.10-1ubuntu2.1
2017-06-23 07:47:29 trigproc libc-bin:amd64 2.23-0ubuntu9 <none>
2017-06-23 07:47:29 status half-configured libc-bin:amd64 2.23-0ubuntu9
2017-06-23 07:47:29 status installed libc-bin:amd64 2.23-0ubuntu9
2017-06-23 07:47:29 trigproc systemd:amd64 229-4ubuntu17 <none>
2017-06-23 07:47:29 status half-configured systemd:amd64 229-4ubuntu17
2017-06-23 07:47:30 status installed systemd:amd64 229-4ubuntu17
2017-06-23 07:47:30 trigproc ureadahead:amd64 0.100.0-19 <none>
2017-06-23 07:47:30 status half-configured ureadahead:amd64 0.100.0-19
2017-06-23 07:47:30 status installed ureadahead:amd64 0.100.0-19
2017-06-23 07:47:30 startup packages configure
2017-06-23 07:47:30 configure openvpn:amd64 2.3.10-1ubuntu2.1 <none>
2017-06-23 07:47:30 status triggers-pending libc-bin:amd64 2.23-0ubuntu9
2017-06-23 07:47:30 status unpacked openvpn:amd64 2.3.10-1ubuntu2.1
2017-06-23 07:47:30 status unpacked openvpn:amd64 2.3.10-1ubuntu2.1
2017-06-23 07:47:30 status unpacked openvpn:amd64 2.3.10-1ubuntu2.1
2017-06-23 07:47:30 status unpacked openvpn:amd64 2.3.10-1ubuntu2.1
2017-06-23 07:47:30 status unpacked openvpn:amd64 2.3.10-1ubuntu2.1
2017-06-23 07:47:30 status unpacked openvpn:amd64 2.3.10-1ubuntu2.1
2017-06-23 07:47:30 status unpacked openvpn:amd64 2.3.10-1ubuntu2.1
2017-06-23 07:47:30 status half-configured openvpn:amd64 2.3.10-1ubuntu2.1
2017-06-23 07:47:30 status installed openvpn:amd64 2.3.10-1ubuntu2.1
2017-06-23 07:47:30 trigproc libc-bin:amd64 2.23-0ubuntu9 <none>
2017-06-23 07:47:30 status half-configured libc-bin:amd64 2.23-0ubuntu9
2017-06-23 07:47:30 status installed libc-bin:amd64 2.23-0ubuntu9
2017-06-23 07:47:30 startup packages configure

/var/log/syslog:

Jun 23 07:47:30 baz ovpn-foo[31061]: event_wait : Interrupted system call (code=4)
Jun 23 07:47:30 baz ovpn-foo[31061]: /sbin/ip addr del dev tun0 192.168.176.254/25
Jun 23 07:47:30 baz ovpn-foo[31061]: SIGTERM[hard,] received, process exiting
Jun 23 07:47:30 baz ovpn-foo[6943]: OpenVPN 2.3.10 x86_64-pc-linux-gnu [SSL (OpenSSL)] [LZO] [EPOLL] [PKCS11] [MH] [IPv6] built on Jun 22 2017
Jun 23 07:47:30 baz ovpn-foo[6943]: library versions: OpenSSL 1.0.2g 1 Mar 2016, LZO 2.08
Jun 23 07:47:30 baz ovpn-foo[6944]: Control Channel Authentication: using '/etc/openvpn/foo/tls-auth.key' as a OpenVPN static key file
Jun 23 07:47:30 baz ovpn-foo[6944]: UDPv4 link local: [undef]
Jun 23 07:47:30 baz ovpn-foo[6944]: UDPv4 link remote: [AF_INET]192.2.0.1:1194
Jun 23 07:47:30 baz systemd[1]: Reloading.
Jun 23 07:47:30 baz systemd[1]: Started ACPI event daemon.
Jun 23 07:47:31 baz ovpn-foo[6944]: [vmbc75b4bd0d6a] Peer Connection Initiated with [AF_INET]192.2.0.1:1194
Jun 23 07:47:33 baz ovpn-foo[6944]: TUN/TAP device tun0 opened
Jun 23 07:47:33 baz ovpn-foo[6944]: do_ifconfig, tt->ipv6=1, tt->did_ifconfig_ipv6_setup=0
Jun 23 07:47:33 baz ovpn-foo[6944]: /sbin/ip link set dev tun0 up mtu 1500
Jun 23 07:47:33 baz ovpn-foo[6944]: /sbin/ip addr add dev tun0 192.168.176.254/25 broadcast 192.168.176.255
Jun 23 07:47:33 baz ovpn-foo[6944]: ERROR: Linux route add command failed: external program exited with error status: 2
Jun 23 07:47:33 baz ovpn-foo[6944]: Initialization Sequence Completed
Jun 23 07:47:36 baz ovpn-foo[6944]: event_wait : Interrupted system call (code=4)
Jun 23 07:47:36 baz ovpn-foo[6944]: /sbin/ip addr del dev tun0 192.168.176.254/25
Jun 23 07:47:36 baz ovpn-foo[6944]: SIGTERM[hard,] received, process exiting

At that point, the connectivity was lost requiring manual intervention to start the VPN client again:

Jun 23 11:52:11 baz systemd[1]: Starting OpenVPN connection to foo...
Jun 23 11:52:11 baz systemd[1]: Started OpenVPN service.
Jun 23 11:52:11 baz ovpn-foo[9847]: OpenVPN 2.3.10 x86_64-pc-linux-gnu [SSL (OpenSSL)] [LZO] [EPOLL] [PKCS11] [MH] [IPv6] built on Jun 22 2017
Jun 23 11:52:11 baz ovpn-foo[9847]: library versions: OpenSSL 1.0.2g 1 Mar 2016, LZO 2.08
Jun 23 11:52:11 baz ovpn-foo[9849]: Control Channel Authentication: using '/etc/openvpn/foo/tls-auth.key' as a OpenVPN static key file
Jun 23 11:52:11 baz systemd[1]: Started OpenVPN connection to foo.
Jun 23 11:52:11 baz ovpn-foo[9849]: UDPv4 link local: [undef]
Jun 23 11:52:11 baz ovpn-foo[9849]: UDPv4 link remote: [AF_INET]192.2.0.1:1194
Jun 23 11:52:11 baz ovpn-foo[9849]: [vmbc75b4bd0d6a] Peer Connection Initiated with [AF_INET]192.2.0.1:1194
Jun 23 11:52:13 baz ovpn-foo[9849]: TUN/TAP device tun0 opened
Jun 23 11:52:13 baz ovpn-foo[9849]: do_ifconfig, tt->ipv6=1, tt->did_ifconfig_ipv6_setup=0
Jun 23 11:52:13 baz ovpn-foo[9849]: /sbin/ip link set dev tun0 up mtu 1500
Jun 23 11:52:13 baz ovpn-foo[9849]: /sbin/ip addr add dev tun0 192.168.176.254/25 broadcast 192.168.176.255
Jun 23 11:52:13 baz ovpn-foo[9849]: ERROR: Linux route add command failed: external program exited with error status: 2
Jun 23 11:52:13 baz ovpn-foo[9849]: Initialization Sequence Completed