hobby raspberry_pi

It is world famous now. It is a dirt cheap ARM-based computer running Linux. Just bought one for myself. I installed Raspbian Wheezy which can be downloaded from here: http://www.raspberrypi.org/downloads. It is the recommended download for newbies so I went straight to it. I used Win32DiskImager and formatted an SD card. Installed it on the Raspberry Pi and it was good to go.

I definitely recommend buying a case which makes it a lot more fun to play with it. I also bought a 3.5” display. I think small screen goes well with the small device. If I’m going to plug something in to my 23” LED monitor, I’d prefer it to be my desktop. The display I bought can be found on Amazon. It doesn’t come with a power supply so you also have to buy a 12V – 2A DC power supply. I also needed a male – male RCA cable to connect the display to the Pi.

The result is the smallest computer I have ever had:

Raspberry Pi

I hope I can do something useful with it too.

dev nosql

Couch is one of move most popular databases in NOSQL movement. When I first started playing around with Couch I was a bit confused by the naming. I had thought there was one product but turns out there are two actually.

CouchDB vs. Couchbase

Apache CouchDB was created by Damien Katz who then started a company called CouchOne Inc. After some time they decided to merge their company with Membase Inc. which developed another open-source distributed key-value database called Membase. They merged the two products so that it would use Membase as storage backend and some portions were rewritten. The end result was called Couchbase. So even though it’s based on Apache CouchDB it’s a different product and is being developed by a different company. But it’s still open source and licensed under the Apache 2.0 license.

Which one to use?

They serve different needs. Couchbase has a built-in memcached-based caching technology whereas Apache CouchDB is a disk-based database. Therefore Couchbase is better suited low latency requirements. Couchbase has built-in replication which allows data to be spread across all the nodes in the cluster automatically. Apache CouchDB supports peer-to-peer replication. I find auto-replication feature of Couchbase marvellous and it’s extremely easy to manage. When you create a new node it can be a new cluster on its own or it can be added to an existing cluster. Adding it to a cluster consists of just providing the IP address/hostname and administrator credentials of a machine in that cluster and the rest is automagically taken care of. I’m using Couchbase in my test applications.

What’s new in Couchbase 2.0

Couchbase released a new major version recently. Highlights of the new features are:

  • Cross Data-Center Replication (XDCR) enhancements
  • 2 cool sample buckets (beer-sample and gamesim-sample)
  • A new REST-API
  • New command-line tools
  • Querying views during rebalance

In the next post I’ll go into more technical details.

security network, wireshark

When I saw this gadget, I knew I had to have it. Didn’t exactly know what to use it for but it looked and sounded cool. So I ordered one along with a pro version. Unfortunately only the pro version arrived as the other one was out of stock. It would be more fun to build it myself but just seeing it in action is fun too. Of course it’s not as cool as a throwing star but functionality is exactly the same.

LAN Tap Throwing Star

The idea is instead of directly connecting your computer to a switch, you connect the machine to this gizmo and connect the port across to the switch. So essentially getting between the target machine and its final destination for network traffic. The other 2 ports are for monitoring. One of them is for received packets and the other is for the transmitted. Connect a monitoring device to one of these ports and it’s done. The rest is firing WireShark in the monitoring machine and watching the traffic of the other machine. A few cool things about it:

  • It doesn’t require any power source
  • It’s unobtrusive and undetectable

If you want to learn more, here is a nice video about it from Hak5:

Hak5–Throwing Star LAN Tap

I learned that it is commonly used for Intrusion Detection Systems (IDS) so it would be nice to one handy if I can start using one finally. The limitation is of course it only can be used to monitor one target device only. To listen to whole network I’ll need a switch with port mirroring or SPAN support. But for now let’s make sure this device is working properly first. The problem with the pro version is that it doesn’t have any indicators of which ports are for monitoring. So I randomly selected one, connected it between my desktop and the router, connected the laptop to one of the remaining ports. To test it I’m simply pinging google.com. With this confiugration I got nothing, Let’s change the ports and give in another try.. and voila! I filter the packets by my desktop’s IP and ICMP protocol so it’s easy to observe the sniffed packets.


But as you can in the above screenshot there’s a problem: This is only one-way traffic. Let’s use the other monitoring port to see what’s going to change. Another ping to Google and this is what we get:


Now we receive only ping reply packets.As Darren Kitchen mentioned in the Hak5 video we can overcome this problem by using a USB Ethernet adapter with multiple ports. I don’t have one of those so I’ll just take his word for it. Verdict: Only monitoring one machine in one direction makes it a bit useless for me. I was planning to use something to see everything in both directions but overall it was a valuable  experience. After all, before I heard about LAN tapping in a TWIET episode (http://twit.tv/twiet) I didn’t even know such thing existed. Hearing about it in a podcast is nice but nothing beats hands-on experience.