Chris You just need to update the /etc/resolv.conf file on each of your clients to point them at both DNS's.
e.g nameserver 192.168.1.2 nameserver 192.168.1.3 The client will now ask both DNS servers. It will get a response even if one of them is off-line. Your solution to move the SD card to another RPI is fine, unless the issue is a corrupted SD Card. Wasn't this the original issue that you are trying to avoid? Personally, I'd rather have two systems fully operational all the time. To discover that the back up solution is not working at the critical moment is the same as not having a backup at all. The added benefit is maintenance. You can take one off-line to update/upgrade whilst the other continues to provide service. Kevin -----Original Message----- From: Dnsmasq-discuss [mailto:dnsmasq-discuss-boun...@lists.thekelleys.org.uk] On Behalf Of Chris Green Sent: 02 September 2021 13:45 To: dnsmasq-discuss@lists.thekelleys.org.uk Subject: [Dnsmasq-discuss] Further thoughts/questions on failover I'm still ruminating on this problem! :-) A number of people are using docker containers to manage this, one live dnsmasq in a container is the default DNS/DHCP for the system and another dnsmasq container is maintained to keep its files in sync with the running one. So far so good. What I don't follow is what happens if/when failure occurs as I don't see how the replacement dnsmasq instance can appear at the same address on the LAN. So, unless all systems are rebooted they will lose DNS won't they? E.g. My default dnsmasq instance runs on a system at 192.168.1.2, if I had a 'clone' docker container on my desktop machine it would be at address 192.168.1.3. So, if 192.168.1.2 dies and I start the dnsmasq container on my desktop machine it's at 192.168.1.3 but all machines on the network are configured (until reboot or DHCP reload time) to use 192.168.1.2. Am I missing something very obvious here (probably!). Just maintaining a Rasberry Pi image and updating the dnsmasq files on it would actually work better (for me anyway) as I could copy it out to an actual SD card regularly and all I'd need to do to recover after a failure would be to plug the SD card into a non-dead Pi and turn it on. -- Chris Green _______________________________________________ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk https://lists.thekelleys.org.uk/cgi-bin/mailman/listinfo/dnsmasq-discuss _______________________________________________ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk https://lists.thekelleys.org.uk/cgi-bin/mailman/listinfo/dnsmasq-discuss
