Ubuntu – Local DNS server

adhocdhcpdnsnetwork-manager

I am currently trying to set up an ad-hoc network for passing notes while I'm in class. The idea is to run a chat server on my laptop (I'm using prosody, that's up and running), so we can share information.

I have also set up a BIND DNS server on my laptop so my friends can just log in using my hostname instead of manually setting up their accounts to point to my IP address.

I am having two seperate issues in this regard.
1) I can't really figure out how to make their computers use my laptop as their DNS server. Should I install a DHCP server too?
2) My computer refuses to use my own DNS server. I think it's because of the dnsmasq that networkmanager runs. I can work around it by editing /etc/hosts, but I do want to use my server locally.

I am running 16.04.

For future generations: in regards to number 2, i just went to NetworkManagers config file and removes the line including dnsmasq. Otherwise dnsmasq refuses to use a dns server on localhost.

In addition, i set up my ad-hoc network to do manual ip address for me, because automatic didn't work for me at all. So i used NetworkManager to give me a static IP and then all my clients use the DHCP from dnsmasq just fine.

Best Answer

  • You can do this with dnsmasq.

    Dnsmasq accepts DNS queries and either answers them from a small, local, cache or forwards them to a real, recursive, DNS server. It loads the contents of /etc/hosts so that local hostnames which do not appear in the global DNS can be resolved and also answers DNS queries for DHCP configured hosts.

    Installing dnsmasq is just a case of using apt-get.

    sudo apt-get install dnsmasq
    

    Setup dnsmasq as DNS DHCP

    Looking at the file /etc/dnsmasq.conf first. The lines are listed are those that I changed from their defaults. Just uncomment and amend them as necessary. (Remove the ‘#’ from the beginning of the line).

    sudo nano /etc/dnsmasq.conf
    domain-needed
    bogus-priv
    no-resolv
    no-poll
    server=/example.com/192.168.0.5
    server=8.8.8.8
    server=208.67.220.220
    local=/example.com/
    address=/doubleclick.net/127.0.0.1
    no-hosts
    addn-hosts=/etc/dnsmasq_static_hosts.conf
    expand-hosts
    domain=example.com
    dhcp-range=192.168.0.20,192.168.0.50,72h  
    dhcp-host=mylaptop,192.168.0.199,36h
    dhcp-option=option:router,192.168.0.1
    dhcp-option=option:ntp-server,192.168.0.5
    dhcp-option=19,0 # ip-forwarding off
    dhcp-option=44,192.168.0.5 # set netbios-over-TCP/IP aka WINS
    dhcp-option=45,192.168.0.5 # netbios datagram distribution server
    dhcp-option=46,8           # netbios node type
    

    What these lines will do for you.

    • domain-needed This tells dnsmasq to never pass short names to the upstream DNS servers. If the name is not in the local /etc/hosts file then “not found” will be returned.

    • bogus-priv All reverse IP (192.168.x.x) lookups that are not found in /etc/hosts will be returned as “no such domain” and not forwarded to the upstream servers.

    • no-resolv Do not read resolv.conf to find the servers where to lookup dns.

    • no-poll Do not poll resolv.conf for changes

    • server=8.8.8.8 Set one or more DNS servers to use when addresses are not local. These are open DNS servers.

    • local=/example.com/ Our local domain, queries in these domains are answered from /etc/hosts or the static-hosts files.

    • address=/doubleclick.net/127.0.0.1 Use this force an address for the specified domains. e.g to block adverts force doubleclck.net to localhost

    • no-hosts This options stops dnsmasq using the local /etc/hosts file as a source for lookups .

    • addn-hosts=/etc/dnsmasq_static_hosts.conf Force dnsmasq to use this file for lookups. It is in the same format as /etc/hosts.

    • expand_hosts So we can see our local hosts via our home domain without having to repeatedly specify the domain in our /etc/hosts file.

    • domain This is your local domain name. It will tell the DHCP server which host to give out IP addresses for.

    • dhcp-range This is the range of IPs that DHCP will serve: 192.168.0.20 to 192.168.0.50, with a lease time of 72 hours. The lease time is how long that IP will be linked to a host.

    • dhcp-host=mylaptop,192.168.0.199,36h Any machine saying they are hostname = ‘mylaptop’ gets this IP address

    • dhcp-option=option:router,192.168.0.1 When a host is requesting an IP address via DHCP also tell it the gateway to use.

    • dhcp-option=option:ntp-server,192.168.0.5 When a host is requesting an IP address via DHCP also tell it the NTP to use.

    In the file /etc/dnsmasq_static_hosts.conf you can add a list of local machines with static IP addresses in the same format as the hosts file. It is also an easy way of creating aliases or CNAME records.

    192.168.0.8  mail mail.example.com
    192.168.0.9  smtp smtp.example.com
    192.168.0.120 mythtvbox mythtvbox.example.com
    

    Starting and stopping the service

    sudo service dnsmasq start
    sudo service dnsmasq stop
    sudo service dnsmasq restart
    

    And one more thing to do. Terminate all other DHCP servers on local network. Your DHCP/DNS server must be only one.