Routine Log Rotation Suspended my IPv6 Today.

Today is May 1.

On most Linux systems, there are “log rotations” which can take place daily, weekly, or monthly. Log rotations frequently but not always require that a service be restarted. This is because while log files have been renamed, the service which is writing log data to them, retains a handle to the same file as before, unless that service is restarted. Once the service is restarted, it obtains a new handle from the O/S, for a fresh log file.

Most of my log rotations have no side-effects. But when I set up my ‘OpenVPN’ -protocol VPN server, I decided to set up a monthly log rotation associated with it, which also has as post-log-rotate job, to restart this VPN.

Oddly enough, this does not impede the VPN service from restarting. But as a side-effect, this knocks my (Debian) ‘Miredo’ client off-line every time, which gives me IPv6 connectivity when it is running, by way of a Teredo server.

It seems that the authors of ‘Miredo’ have already observed, that restarting something that upsets the IP stack in this way, can knock their client off-line, and so the makers of this package omitted any logging, or log rotation, for ‘Miredo’. But whenever by VPN server is restarted, this affects the Teredo client I just named.

Today is May 1. So therefore in a routine way, my IPv6 address was knocked off-line by the monthly log rotation this morning. And this effect lasted, until I manually restarted the Teredo client in question.

So as I am writing this, I have an IPv6 address again.

Dirk