Configure static IP address on Ubuntu 16.04 LTS Server

Ubuntu 16.04 has been out for just over a month now, and I’m in the process of upgrading some boxen. In some cases I’ve been completely reinstalling them for that clean fresh feel, and find myself once again having to configure static IP addresses.

Doing this can be problematic (made worse by the fact that even the official Ubuntu LTS documentation doesn’t give correct advice), particularly when it comes to DNS resolution, and in my case, a very-old-school habit of blindly wanting to edit the /etc/resolv.conf file which you really should not be doing any more these days.

Step 1. Edit the /network/interfaces file

sudo nano /etc/network/interfaces

sudo nano /etc/network/interfacesThe interfaces file is where you need to change from the default “dhcp” setting to add some information about the “static” IP address that you want to configure.

In this case, look for the line in the file that says “# The primary network interface” and directly beneath this you’ll see something like (the default DHCP configuration):

auto ens160
iface ens160 inet dhcp

If you’ve been using previous versions of Ubuntu you might have noticed that the interface name above “ens160” looks a bit odd. It used to be called “eth0” or “eth1”, but as from Ubuntu 15.10 the interface name is now allocated based on a few other factors – read more about that here if you’re interested.

Simply comment, remove or edit the line that says ends with “dhcp” and add the following information (here’s an example only):

iface <interface> inet static
	address 192.168.0.100
	netmask 255.255.255.0
	gateway 192.168.0.1

Next you’ll want to add the nameservers by adding the line “dns-nameservers” followed by a list of IP addresses.  A lot of people use Google’s public DNS, or if you have details from your service provide use them instead.

dns-nameservers 8.8.8.8 8.8.4.4

PRO-TIP: Double-check the file again, and ensure all details are correct, before proceeding.  If you are configuring a remote system you could easily cut yourself off if you get it wrong.

Save the file, and you’re done.

Step 2. Restart the networking service (or reboot)

Once you are confident the change has been made, and if you don’t want to reboot you can just restart the networking service.

sudo /etc/init.d/networking restart

After doing this, and provided you don’t get any errors, your primary network interface should now be configured with the static IP address details you have provided.

Failing that, a reboot will also do the trick quite nicely, and with the current version of 16.04 I suspect there’s a bug that is causing “ifconfig -a” not to update unless you perform a reset.

sudo reboot

Good luck, and may your boxen be correctly addressed.

A Big Result On Graph Isomorphism

It’s not often that I see excitement from multiple friends in the world of academia. Everyone who appreciates these problems for what they are, and what solving them might bring to the world will be watching on with interest this week – including me!

Gödel's Lost Letter and P=NP

laci

Lszl Babai is one of the world experts on complexity theory, especially related to groups and graphs. He also recently won the 2015 ACM Knuth Prize, for which we congratulate him.

Today we wish to discuss a new result that he has announced that will place graph isomorphism almost in polynomial time.

More exactly Lszl shows that Graph Isomorphism is in Quasipolynomial Time: that is time of the form

$latex displaystyle 2^{O(log(n))^{c}}, &fg=000000$

for some constant $latex {c}&fg=000000$. Polynomial time is the case when $latex {c=1}&fg=000000$, but any $latex {c}&fg=000000$ is a huge improvement over the previous best result.

Luca Trevisan already has made a post on this result, and Scott Aaronson likewise. Luca further promises to be in Chicago next Tuesday when Lszl gives his talk on the result—here is the abstract of the talk:

We outline an algorithm that solves the Graph Isomorphism (GI) problem and the…

View original post 555 more words

Visual note taking or data mapping – where’s the App?

brain-note-takingFor a while now I’ve been searching for a tool that doesn’t exist.  Well, at least I can’t seem to find it… yet. Perhaps you’ll join the dots here and let me know if you’ve found/built/seen it.

Let me begin with an outline of the problem that this tool would solve:

“You love giving recommendations to friends for Apps and other cool stuff online, but you always get that “oh, what was it again” moment.  Wouldn’t it be great if you could easily stash URL Bookmarks and simple notes in visual form for easy recall?”

Yes, I hear you scream, just use <insert something you’ve seen/used here>, so let me explain what I have used and why it doesn’t do what I want specifically for the above mentioned purpose.

  • Evernote – love it & use it, but it doesn’t allow you to create a tree, and it doesn’t have a visual interface.
  • Action Outline – bought it at least a decade ago, and is about as close to what I want without the visual interface; quick to use, great tree outliner.
  • Microsoft OneNote – like the other Office products I find it heavy and cumbersome, does too much and still no visual interface.
  • Trello – this is an incredible online “kanban” inspired collaborative tool, but it would be hard to incorporate a visual interface into.
  • Notepad & Text Editors – yes, I’m a hardcore Unix geek from way back, but ASCII art only stretches so far.

My vision for what I imagine to be the perfect software tool to solve this problem would be like this:

  • To understand what a visual map looks like, have a play with the Visual Thesaurus or Visuwords, then come back here.
  • Open your new notebook/datamap document, the first thing you see is a blank ‘node’ – a circle or oval shape that you can click on and type text into, just like iMindMap.
  • You can paste a URL into the node and maybe you’ll get some metadata from the page, like Title and Description, or maybe even a Thumbnail appear.
  • When you want to expand out from there, just double-click (or maybe there is a small + symbol) that creates a new node that is linked to the previous one (its parent).
  • As you add nodes to begin with it might not make sense, there’s no structure and that’s just okay.
  • But as you add more nodes, some will “match” existing ones, so you drag one onto another and are prompted to give that similarity a name, which creates a new parent and joins them underneath.
  • Grafting of entire sections of nodes is as easy as drag and drop.

My research notes on this, which I have re-visited several times over the last couple of years, reveal this collection of visual mapping and related websites, SDKs and APIs, so if you’re going to build this amazing tool maybe this is a head start for you 🙂

Now, as luck would have it, as I was writing this post I stumbled across a tool called “The Brain” which I am now trialling.  It is absolutely the closest thing to what I imagine so far, but it’s a bit on the expensive side.