Something is listening on port 53

Question

I want to set up bind9, but something is listening on port 53. It's local address is ubuntu.ubuntu-do:domain. How to disable it, so it wouldn't listen anymore? I think it is dnsmasq, but still I don't know hot to disable it.

Solution

Port 53 is reserved for the Domain Name System (DNS).

In your case it is the DNS cacher dnsmasq of the package dnsmasq-base. This pre-installed package is a dependency of network-manager, the network manager of your desktop environment (e.g. Unity, GNOME, …).

For this reason, don't uninstall the package dnsmasq-base and/or disable the service. Install bind9 and all is fine

sudo apt-get install bind9

Now you should see something like this, bind9 (named) is also running on port 53:

% sudo netstat -tulpn | grep ":53 "
tcp        0      0 192.168.2.131:53        0.0.0.0:*               LISTEN      8921/named      
tcp        0      0 127.0.0.1:53            0.0.0.0:*               LISTEN      8921/named      
tcp        0      0 127.0.1.1:53            0.0.0.0:*               LISTEN      1223/dnsmasq    
tcp6       0      0 :::53                   :::*                    LISTEN      8921/named      
udp        0      0 192.168.2.131:53        0.0.0.0:*                           8921/named      
udp        0      0 127.0.0.1:53            0.0.0.0:*                           8921/named      
udp        0      0 127.0.1.1:53            0.0.0.0:*                           1223/dnsmasq    
udp6       0      0 :::53                   :::*                                8921/named  

---

Use the command

sudo netstat -tulpn

to show the ports and listening processes for udp and tcp. For DNS it's usually UDP.

Use

ps -p PID -o comm=

to show the command name for the given process id (PID).

Comments

[fufs]

everything would be cool, except that when I type: "sudo service dnsmasq disable" it says that that service is not recognized, when i type "sudo apt-get remove dnsmasq" it says no program installed, but when I type "sudo netstat -tulpn" it says the port 53 is used by dnsmasq. Why?

[A.B.]

Sorry, updated my answer.

[not2savvy]

Unfortunately, this answer does not explain how to disable dnsmasq. I'd like to disable it because I want to run dnsmasq from a docker container instead.