Getting one of your Five-a-Day – connecting Remotely to a Raspberry Pi from Linux Mint

It’s Christmas. To mark the occasion, my son bought me a top-of-the-range computer…


Christmas has come early ! Er, hang, on…

Yes, a Raspberry Pi 2 b-spec, complete with 900 MHz Quad-core ARM processor and 1 GB RAM.

Getting it up and running was a bit more of a challenge than I had anticipated.
The Pi uses HDMI for Video output and my ageing monitor is not equipped for HDMI…


The best program on TV – NOOBS doing it’s thing.

In the end, I had to “borrow” the TV.
This arrangement was, of necessity, extremely temporary. The TV had to be back in it’s usual place ready for The Strictly-TOWIE-Dancing-Get-Me-Out-Of-Here Christmas Special, on pain of pain.
Therefore, my first Pi project was to connect to it remotely from another machine, namely, my Linux Mint Laptop.
This will enable me to run the Pi headless (i.e. without a monitor/keyboard/mouse attached to it).

I’m going to cover two different methods of connecting to the Pi.
The first is using ssh to connect to the command line.
The second is to connect remotely to the Raspbian desktop itself.

Just to avoid any confusion, I will be referring to the Raspberry Pi as “the Pi” and the machine I’m connecting from as “Mint”.
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Gits and Giggles – Getting onto Github from Mint

“Github ?” said Deb, “sounds like a chat room for grumpy old men. You should fit right in !”
To be fair, neither of us were in a particularly good mood at the time.
Deb had just been made to sit through the Rugby World Cup Final whilst my emergency backup nationality had finally born fruit.
All I said to her was that it’s nice to be able to support a real country rather than a mere principality, like Wales. Honestly, some people are so touchy.

For my part, I had just discovered that Github, based on the Git source control system written by Linus Torvalds himself, has integrated clients for Windows and Mac, but not for Linux.

No matter. If you want to interact with Github, you’ll need to have Git installed on your client machine anyway and, mine being Linux, there are a number of GUIs available for Git.

Aside from the Git documentation itself, which is extensive, there are a number of excellent guides to both Git and Github available.
Rather than re-hashing these – although I will link some of them – I’m going to look at things from a slightly different perspective.

Throughout my career, I’ve been, first and foremost, a database developer.
Way back when, choices of version control systems were rather limited. In a professional sense, I grew up with PVCS and Visual Source Safe.
Even later on, the fact that Oracle Forms and Reports were binary source code meant that the Edit-Merge paradigm of source control was something that tended not to gain traction in the Oracle Shops that I worked in.

Later on, in larger organisations, Perforce was the tool of choice, although always with the comforting P4Win ( and later P4V) front-end.

So, I’d rather like the comfort of a GUI, if only to see that the files I think I’ve checked in are actually there.

Additionally, Github uses an enhanced version of the Markdown language for text files. It would be nice to be able to preview these files before uploading them to the repository.

First things first then…. Continue reading

Keep your Database Tidy – making sure a file exists before DBMS_DATAPUMP makes a mess

There are times when I wonder whether DBMS_DATAPUMP isn’t modelled on your average teenager’s bedroom floor.
If you’ve ever tried to start an import by specifying a file that doesn’t exist ( or that DBMS_DATAPUMP can’t see) you’ll know what I mean.
The job fails, which is fair enough. However, DBMS_DATAPUMP then goes into a huff and refuses to “clean up it’s room”.
Deb has suggested that this sort of thing is also applicable to husbands.
Not that I have any idea of whose husband she’s talking about.
Anyway, you may consider it preferable to check that the export file you want to import from actually exists in the appropriate directory before risking the wrath of the temperamental datapump API.
This apparently simple check can get a bit interesting, especially if you’re on a Linux server…
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The Ping of Mild Annoyance Attack and other Linux Adventures

Sometimes, it’s the simple questions that are the most difficult to answer.
For example, how many votes does it take to get an MP elected to the UK Parliament ?
The answer actually ranges from around 20,000 to several million depending on which party said MP is standing for.
Yes, our singular electoral system has had another outing. As usual, one of the main parties has managed to win a majority of seats despite getting rather less than half of the votes cast ( in this case 37%).

Also, as has become traditional, they have claimed to have “a clear instruction from the British People”.
Whenever I hear this, can’t help feeling that the “instruction” is something along the lines of “don’t let the door hit you on the way out”.

Offering some respite from the mind-bending mathematics that is a UK General Election, I’ve recently had to ask a couple of – apparently – simple questions with regard to Linux… Continue reading

Getting a File Listing from a Directory in PL/SQL

It’s General Election time here in the UK.
Rather than the traditional two-way fight to form a government, this time around we seem to have a reasonably broad range of choice.
In addition to red and blue, we also have purple and – depending on where you live in the country, multiple shades of yellow and green.
The net effect is to leave the political landscape looking not so much like a rainbow as a nasty bruise.

The message coming across from the politicians is that everything that’s wrong in this country is down to foreigners – Eastern Europeans…or English (once again, depending on your location).
Strangely, the people who’ve been running our economy and public services for the last several years tend not to get much of a mention.
Whatever we end up choosing, our ancient electoral system is not set up to cater for so many parties attracting a significant share of support.

The resulting wrangling to cobble together a Coalition Government will be hampered somewhat by our – equally ancient – constitution.

That’s largely because, since Magna Carta, no-one’s bothered to write it down.

In olden times, if you wanted to find out what files were in a directory from inside the database, you’re options were pretty undocumented as well.
Fortunately, times have changed…

What I’m going to cover here is how to use an External Table pre-process to retrieve a file listing from a directory from inside the database.
Whilst this technique will work on any platform, I’m going to focus on Linux in the examples that follow…
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Installing VirtualBox on Mint with a CentOS Guest

Christmas is almost upon us. Black Friday has been followed by Small Business Saturday and Cyber Monday.
The rest of the month obviously started on Skint Tuesday.
Fortunately for all us geeks, Santa Claus is real. He’s currently posing as Richard Stallman.
I mean, look at the facts. He’s got the beard, he likes to give stuff away for free, and he most definitely has a “naughty” list.

Thanks to Santa Stallman and others like him, I can amuse myself in the Holidays without putting any more strain on my Credit Card.

My main machine is currently running Mint 17 with the Cinnamon desktop. Whilst I’m very happy with this arrangement, I would like to play with other Operating Systems, but without all the hassle of installing/uninstalling etc.
Now, I do have Virtualbox on a Windows partition, but I would rather indulge my OS promiscuity from the comfort of Linux… sorry Santa – GNU/Linux.

So what I’m going to cover here is :

  • Installing VirtualBox on a Debian-based distro
  • Installing CentOS as a Guest Operating System
  • Installing VirtualBox Guest Additions Drivers on CentOS

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