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I'm working on a network with ~10 kubuntu desktops (and numerous servers and IP phones) and am trying to get dnsmasq to specify another dns server as a failover. I tried using

server=192.168.0.90

but that just added the single dhcp/dns server to /etc/resolv.conf on my test machine (dynamic IP and freshly rebooted with no lease).

3 Answers 3

41

Answered my own question, thanks to rfc2132

dhcp-option=6,192.168.0.90,192.168.0.98

However, RFC2132 specifies option 5 as a list of name servers and option 6 as a list of domain name servers, and I'm not sure what the difference is. Either way, option 6 put them correctly as

nameserver 192.168.0.90
nameserver 192.168.0.98

in /etc/resolv.conf

7
  • 1
    Unfortunately /etc/resolv.conf refreshes after restart Nov 20, 2014 at 9:27
  • 5
    @FeridMovsumov use server=8.8.8.8 in /etc/dnsmasq.conf
    – Tek
    Mar 31, 2016 at 4:43
  • 3
    @Tek Google needs to know everything?
    – ceving
    Aug 7, 2016 at 11:35
  • 1
    @ceving If not google then your ISP
    – Tek
    Aug 7, 2016 at 12:42
  • 3
    This is the respective textual option which I prefer over opaque numbers like 6: dhcp-option=option:dns-server,... Jul 30, 2020 at 4:51
10

Posting as a separate answer rather than a comment on yours because that way I can use links.

Option 5 is for IEN 116 nameservers — a ridiculously obsolete protocol that Jon Postel wanted dead over twenty years ago. Solaris still supports it, but won't in the next version.

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1

Another way is to set your dnsmasq server to be the DNS server for DHCP, and use /etc/resolv.conf on the dnsmasq server to specify your list of DNS servers. That way you can easily change DNS (and set aliases) without having to wait for DHCP renewal - just either restart or kill -HUP dnsmasq to reload the config.

1
  • Andrew, 'kill' command expects process identifier not process name. You should use either kill -HUP pidof dnsmasq or killall -HUP dnsmasq .
    – user213709
    Mar 23, 2014 at 7:44

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