Setup Domain Name for Raspberry Pis, wired to Local Network
In my previous article, I have shared my experience about sharing internet connection received by my Desktop PC, to the RPis. While this setup is okay to me, there is a small matter that bugged me. Whenever I need to reach other RPi from another RPi or from my connected desktop PC (e.g. doing SSH), It requires me to remember & type in the target machine’s IP Address. I want to improve this experience further by just typing the hostname of the target machine such as ssh pi@rylai instead of ssh pi@10.128.20.12
I understand that in order to achieve this, I would need to setup & run Domain Name System (DNS) servers in my RPis LAN. But, it’s another “I know ( what I should do), but I don’t know (the technical detail of how to do it)” problem to me. After I spent a couple of days searching references which fit to my case, I then bumped with this article. Someone has done it, but I’d like to prove it and see if it fits & works on my RPis LAN.
In this article, I am going to share my experience of how I setup the primary & secondary servers on my Desktop PC and my old Raspbery Pi 2 Model B, I connected to the RPis Private Local Network.
Updated the IP Addresses
I did not change any physical parts that are involved in the private network. However, in order to get this done by following the article, I changed each RPis and my desktop PC’s IP Addresses as in the following list:
Since I updated the network’s address to xxx.xxx.0.0 (netmask 255.255.0.0), these updates will allow me to connect more nodes up to 255 x 255 = 65k devices. Thus, I won’t need to feel worry with re-updating my network’s IP Addresses in the future, when I’ll add more devices into the private network.
I applied the new IP Addresses to RPis through reverting the IP Address configuration I made in dhcpcd.conf file, moved them into /etc/network/interfaces file and also changed the host’s IP Address in the /etc/hosts file.
I also did similar change on my Dekstop PC’s /etc/network/interfaces and /etc/hosts files.
I then restarted all RPis and my PC after making these changes on each of these machines, to ensure the changes took effect.
Setup Primary DNS Server on My Ubuntu PC
The software which runs DNS server in Linux OS is bind9. I installed bind9 and an additional software(dnsutils ) software on my Ubuntu Dekstop PC, through running this command:
sudo apt-get update && sudo apt-get install bind9 bind9utils bind9-doc dnsutils
Then, I modified bind9’s default config to ensure that it will run on IPV4 mode.
Next, I modified /etc/bind/named.conf.options , /etc/bind/named.conf.local files to put my Private network’s address and the new IP Addresses of each connected hosts, into bind9 ‘s configurations.
Then, I created /etc/bind/zones/db.<my private network's domain name> as the zone’s config file and /etc/bind/zones/db.<my private network's unmasked ip address's parts> as the reversed zone’s config file. I changed these files, as shown in the following screenshots.
After I modified & created these files, I then run named-checkconf & named-checkzone commands to ensure that the changes are valid.
I also wanted to ensure my desktop PC still could access the connected RPis by specified hostname, instead of IP address later. To achieve this, I replaced /etc/resolv.conf file with a symbolic link to /run/resolvconf/resolv.conf .
Then I modified /etc/resolvconf/resolv.conf.d/head file, by entering nameserver entries with IP Addresses of Google’s DNS servers and my Desktop PC.
Lastly, I rebooted my Ubuntu Dekstop PC to see if all changes that I made would take effect and the Primary DNS server ran properly.
Setup Secondary DNS Server on the Raspberry Pi 2 Model B
Setup a secondary DNS is an optional path. I decided to do it anyway, just to make sure when my PC is turned off and my clusterd RPis are still running, the RPis still could reach each other by specifying their host names. I decided to run the secondary DNS server on my Raspberry Pi 2 Model B, so that I could maximise the number of RPis 3 in the private network to be focusing on actual works that will happen in future.
Setup bind9 on my RPi 2 is quiet similar to setting it up on my Desktop PC earlier. 1st, I did SSH to the Rpi 2, ran update repository command followed by apt-get command for installing bind9, bin9utils, bind9-doc & dnsutils .
Then, I did same changes on my PC’s bind9 default config file, to enforce bind9 will run on IPV4 mode later.
Next, I edited both/etc/bind/named.conf.options & /etc/bind/named.conf.local files as shown in these following screenshots:
Notice the different settings in the named.conf.local file compared to the Primary DNS’s file: the type of each zones are set as slave and within each of zones, there is masters entry which points to the Primary DNS’s IP address.
I did not create zone files for secondary DNS server. Thus, I just rebooted my Raspberry Pi 2 to see the changes that I made earlier.
Testings
Once I rebooted my desktop PC and my Raspberry Pi2, I then began conducting a number of Tests, to confirm that the Primary & Secondary DNS are working properly. For 1st Test, I did ping, dig& ssh from my Dekstop PC to one of Raspberry Pi3.
As we could see, the Primary DNS server (My PC) was able to reach the RPis by their hostnames. Next, I ran dig against one of the RPis by host name, from my PC.
We noticed more interesting info appeared from dig , such as the IP Addresses of Primary & Secondary DNS servers, beside the RPi’s full domain name and its IP Address.
2nd Test was doing same thing as in 1st Test, but this was done from within an RPi3.
Lastly, for the final test, I turned off bind9 service on my Desktop PC, to simulate if the Primary DNS server is downed, the Secondary DNS server will serve as the Naming server.
Then I performed ping & ssh commands from within an RPi 3 to other RPi3 or 2.
As shown in the screenshots, the secondary DNS server was successful took over the Primary DNS server’s role when it is turned off.
Next plans
At this point, my clustered RPis can “talk” each other by specifying their host names, instead by their IP Addresses. Also, we could ensure that this feature won’t be gone when I turned off my PC (the Primary DNS server), as long as my RPi 2 B (the Secondary DNS server) is still connected & functional.
In the future, I am going to utilise these clustered ARM Small Computers for serving as my personal R&D infrastructure, supporting my backend application’s development, such as: running Jenkins build in master/slaves mode, running clustered Redis database instances, simulating HA & Load Balancing test scenarios against my Application’s Backend API, security tests, running Docker swarm master/worker containers and many more.
Reference(s)
- How to Setup a DNS Server for a Home Lab on Ubuntu 14.04 — https://techpolymath.com/2015/02/16/how-to-setup-a-dns-server-for-a-home-lab-on-ubuntu-14-04/
