Uncompressing the lazy way

Always forgetting what options you need to pass to tar to decompress a tar.gz or tar.bz2 or some other archiving tool?

Was it  -zxvf  or  -jxvf  ?

For the lazy Sysadmin or the people who just want to get going with their work right away without having to google for the right options or read through the man pages, there is unp

unp (1)              – a shell frontend for uncompressing/unpacking tools

Available in a repo near you.

Got some devolo’s

At home I have a special situation when it comes down to having internet.

My current ISP is Belgacom, and their service (VDSL) relies on the telephone line which comes from the street into my home.

The situation I’m in, is that, instead of the primary cable, or local loop, coming from the street into the wall at the ground floor, my cable does quite some distance, all the way to the first floor.

Not that there’s anything really special about that, except that it’s a bit of an inconvenience as I also have Digital Tv in the living room downstairs.

The decoder needs to have a UTP cable connected into the tv ethernet port on my modem, the bbox2 provided by my ISP. The only way for me to have both internet and digital tv at the same time, was to place the modem downstairs on a secondary RJ11 jack.

This situation isn’t optimal, as the advertised speeds I should get are 30Mbps down and 3,5Mbps up, while in reality, I only get 20Mbps down and 3,5Mbps. That’s only getting 66% out of my line.

The ideal situation would be to plug the modem upstairs, directly on the splitter connected to my local loop, and have the decoder in some way connected to it.

These are some of the options I had:

  • Drill holes in the wall to extend the Ethernet cable of the decoder to the first floor where the modem is.
  • Cut the local loop and place it somewhere on the ground floor.
  • Connect the modem upstairs on the local loop and use Powerline communication for the decoder

Making holes and other things were out of the question, which led me to try out the third option: Powerline communication.

Belgacom sells sets of 2 at 80€ (current prices when this was posted).


They are a white-labelled product from a well known German company who specialises in making Powerline solutions.

In case you haven’t checked yet what Powerlines are, it’s basically a technology to use your household electric circuit as your LAN Network.

This is ideal in houses or small offices where there are many rooms with network devices that can’t be connected through conventional networking like Ethernet cables or WiFi.

This is a very elegant solution although it comes with a speed trade-off.

If you would connect 2 computers together who have 100baseTX network cards, the theoretical speed should be 100Mbps. In reality, the effective speed you’ll achieve is about 96,5Mbps.

To test the speed over the powerline, I’ve connected my home pc running Ubuntu in one such adaptor, and my laptop in the second one, each in a power outlet.

I’ve installed a network speed measuring tool on both systems called iperf.

sudo apt-get install iperf

I’ve given a static IP address to my fixed home pc so that I didn’t have to wait or mess with DHCP, so I could just plug the cable in anywhere I wanted, wait for the signal to be green and go ahead and test.

On the fixed pc, I ran the following command:

iperf -s -D -p 65000

This tells iperf to run in server mode (-s), listen for connections on port 65000 (-p), and run as a daemon service (-D) (this is optional).

On my laptop, I just run this command every time I’m plugged on another power outlet when the light turns green:

iperf -c <ip_of_fixed_pc> -p 65000

Here’s a sample output:

Client connecting to, TCP port 65000
TCP window size: 23.5 KByte (default)
[ 3] local port 33421 connected with port 65000
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.0 sec 114 MBytes 95.5 Mbits/sec

Here are some speed measurements I made:

Direct connection with pc’s:      96,6Mbps

Plugs next to eachother:          49Mbps

Outlet in the next room(5m):     25Mbps

Further in the next room(11m):  47Mbps

Downstairs kitchen (8m):          46Mbps

Downstairs dining room(14):      46Mbps

Of course this isn’t really significant for your situation, let alone the distances in meters as that actually depends on the electrical wiring inside your house.

One thing we can see from these measurements, is that the speeds are pretty much consistent around my house:  ~47Mbps

While you can certainly say that those speeds are pretty low for connecting computers with each other, one mustn’t forget that the idea is that only the Decoder gets connected that way to the modem!

In fact, Digital Tv doesn’t require a lot of speed to operate as intented ( about 4-8Mbps ), let alone that my maximum internet connection speed is 30Mbps.

So now I have the modem upstairs connected directly on the local loop and being able to surf at full speed while the decoder downstairs is connected to the modem over the powerline with enough bandwidth to spare!