Posts Tagged ‘dns’

Clearing DNS caches

December 11th, 2013

Just moved your site to a new provider/host and want to try and clear various DNS caches? Well, using http://www.opendns.com/support/cache/ will clear OpenDNS and https://developers.google.com/speed/public-dns/cache will clear Google’s: so that should get quite a few people sorted (if you are running Chrome copying chrome://net-internals/#dns into the address bar will clear your local cache).

Any body know any other DNS cache clearing snippets?

[Techy] localdomain settings in Linux Mint using DNSMasq

May 12th, 2013

If you are developing websites on Linux Mint, then you might want to set a DNS Wildcard so that anything on localdomain (*.localdomain) resolves to your machine (i.e. test.localdomain , anything.localdomain). So how can you do this?

First of all, you need to install dnsmasq “a lightweight, easy to configure DNS forwarder and DHCP server”, this can be simply done using:
sudo apt-get install dnsmasq

Now you just need to configure it. Create a file in /etc/dnsmasq.d/ using something like nano, pico, vi, emacs :

sudo nano -w /etc/dnsmasq.d/localdomain.conf

with the following settings:

address=/localdomain/127.0.0.1
listen-address=127.0.0.1

This will tell DNSMasq to setup a wildcard for everything on “localdomain” to point to 127.0.0.1 and to listen for DNS requests on 127.0.0.1. Now just restart DNSmasq:
sudo service dnsmasq restart
and you are nearly done.

You now just need to change your DNS servers in network manager. On the Linux Mint task bar, right click on the network icon and select “Edit connections” and edit the connection you are using. Select “IPv4 Settings”. If you have “Automatic (DHCP)” selected, change it to “Automatic (DHCP Addresses only)”. Then add the DNS server 127.0.0.1 and others of your choosing (such as the Google 8.8.8.8 and 8.8.4.4 ones). All should now be working!

Net: Shortest Valid Domain Names

January 22nd, 2009

For the system I’m building, I’m putting in a check for valid domain names (technically URI/URLs) and one of the checks is for the length of the domain name. So what is the shortest domain name around?

Well, I suspect in the uk it’s the British library at bl.uk [5 characters] and in the .com range I suspect it’s Paypal’s x.com [6 characters], but an article on Valleywag has just altered me to the fact that Google has one of the shortest Chinese domain names g.cn [4 characters] and Ulster Television has u.tv, but even those are beaten by both the Western Samoa top level domain name has a website making ws [2 characters] and the Vatican’s va [2 characters] – making them the shortest domain name I’m aware of.

Why have some of them got full stops at the end of the links ( such as http://ws. and http://va. ): it’s to stop your browser trying to “fix the links” and change them to http://ws.com and http://va.com which are different sites.

The answer to the question of “how short can a domain name be” is currently 2 characters (unless a top level domain is started with less than 2). A full web based URI/URL has a minimum length of 9 (4 for the protocol ‘http’, 3 for the protocol separation ‘://’ and then 2 for the domain/host name). Of course, you could also use the FTP protocol which brings it down to 8 or be pedantic and insist the shortest web orientated URL is http://va.:80/ at 14 characters.

See also top level domains with websites.

Avoid US Domain Registrars – A Response

March 5th, 2008

My darling other half has just made another interesting blog post – this time about avoiding US domain registrars due to eNom (the second largest domain name registrar according to Webhosting.info) disabling domain names belonging to a British National (based in Spain) selling holidays/vacations in Cuba to European citizens (Nytimes article).

Sounds good in theory – but in practice, it’s a bit more difficult.

Why? Well, I mainly use a registrar called DirectI/ResellerClub (as I have a lot of domain names – over 60) who are based in India – but (ignoring the fact they now have a US office) I could, in theory, still have my domain names disabled by the US courts: because DirectI get their domain names (like all other .com/.net/.cc or .tv domain name providers) from a company called Verisign GRS who are the “root provider” (also known as the “authoritative directory provider”) of all those domains. And they are based in the USA and hence the US courts could just ask Verisign to suspend the domain names at their level.

“Ah ha!”, I hear you cry – what about my nice safe .co.uk or .eu domain name that I brought for a UK company such as Heart Internet? Well, again, there’s a catch. All .uk domain names are via Nominet (a UK based company) and all .eu domain names are from Eurid (a Belgium based company) – so on the “registrar” level they are safe (apart from the inter-country co-operation agreements). But ALL domain names (.com/.net/.uk and .eu) are ultimately allocated by an organisation called the Internet Assigned Numbers Authority (IANA) which is part of Internet Corporation For Assigned Names And Numbers (ICANN) which, whilst being a “private-public partnership” is a US organisation currently under the control of the US Department of Commerce (at least it’s a change – ICANN and IANA used to be run by the US Department of Defense).

So there you go – all your domain names are belong to the US Government!

Techy: cPanel DNS Cleardown script

August 10th, 2006

Do you have many “old” cPanel servers? Perhaps you have the cpanel servers configured in a DNS cluster for redudancy? If so, you may encounter the same problem as I did where you have “stale” (or old) DNS zones cluttering up the server. Here’s a script to get rid of any unused zone files (use at your own risk yadda yadda yadda – you will have to rebuild /etc/named.conf afterwards):
» Read more: Techy: cPanel DNS Cleardown script

gamy-dance
%d bloggers like this: