[Dnsmasq-discuss] second dnsmasq machine for "hot standby" - proposals, wanted

Modem Man modem-man at gmx.net
Sat Jul 9 13:47:53 BST 2011

dnsmasq-discuss-request at lists.thekelleys.org.uk schrieb:
> From: Michael Rack, from Freilassing, Germany
> If you can be sure, that your NSLU2 does not react for ssh then try this:
> Make sure, your Hot-Standby can login via ssh to the Master-Device 
> without needing a password (ssh-keygen).
This ssh thing is already on my "need to learn" task list.
For different reasons, but I understand your idea now.
And - yes this will usually fail if NSLU2 is down.
> So lets begin:
> 1) change your dnsmasq-configuration to use a dhcp-leasefile
>          dhcp-leasefile=/var/state/dnsmasql.leases
> 2) create a bash-script on your hot-standby
>> #!/bin/bash
>> scp master-server:/var/state/dnsmasql.leases /var/state/dnsmasql.leases
>> if [ $? -ne 0 ]
>> then
>>     /sbin/ip addr add [ip.of.master.server]/24 brd + dev eth0
>>     /etc/init.d/dnsmasq start
>> else
>>     /etc/init.d/dnsmasq stop
>>     /sbin/ip addr del [ip.of.master.server]/24 dev eth0
>> fi
> 3) add this script to run periodicly on your hot-standby
okay, I see. Catching two things with one hit - availability and shared
leases file.
If secure copy via ssh fails, I add also the static addr of my master
server to eth0 interface and start dnsmasq here.
After scp is working again, I stop the backup dnsmasq and remove the addr.
Sounds usable for my. I'll try it out and give a feedback after some weeks.

May be, I'll try to combine this with the proposal of Bill Riemers ...
reporting both DNS servers the same time:
In this case I would try if I can run the backup machine with dnsmasq
(only DNS). In case of failure,
I reconfigure it to also serve DHCP and restart dnsmasq.
Let's see if this will work.

Thank you both Michael and Bill for the help.

DoS sometimes comes from between firewall and NSLU2.
Nobody needs a better firewall here.
Somebody needs more beating ;-)

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