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Steve Kemp: We're all about storing objects

Sun, 21/06/2015 - 17:10

Recently I've been experimenting with camlistore, which is yet another object storage system.

Camlistore gains immediate points because it is written in Go, and is a project initiated by Brad Fitzpatrick, the creator of Perlbal, memcached, and Livejournal of course.

Camlistore is designed exactly how I'd like to see an object storage-system - each server allows you to:

  • Upload a chunk of data, getting an ID in return.
  • Download a chunk of data, by ID.
  • Iterate over all available IDs.

It should be noted more is possible, there's a pretty web UI for example, but I'm simplifying. Do your own homework :)

With those primitives you can allow a client-library to upload a file once, then in the background a bunch of dumb servers can decide amongst themselves "Hey I have data with ID:33333 - Do you?". If nobody else does they can upload a second copy.

In short this kind of system allows the replication to be decoupled from the storage. The obvious risk is obvious though: if you upload a file the chunks might live on a host that dies 20 minutes later, just before the content was replicated. That risk is minimal, but valid.

There is also the risk that sudden rashes of uploads leave the system consuming all the internal-bandwith constantly comparing chunk-IDs, trying to see if data is replaced that has been copied numerous times in the past, or trying to play "catch-up" if the new-content is larger than the replica-bandwidth. I guess it should possible to detect those conditions, but they're things to be concerned about.

Anyway the biggest downside with camlistore is documentation about rebalancing, replication, or anything other than simple single-server setups. Some people have blogged about it, and I got it working between two nodes, but I didn't feel confident it was as robust as I wanted it to be.

I have a strong belief that Camlistore will become a project of joy and wonder, but it isn't quite there yet. I certainly don't want to stop watching it :)

On to the more personal .. I'm all about the object storage these days. Right now most of my objects are packed in a collection of boxes. On the 6th of next month a shipping container will come pick them up and take them to Finland.

For pretty much 20 days in a row we've been taking things to the skip, or the local charity-shops. I expect that by the time we've relocated the amount of possesions we'll maintain will be at least a fifth of our current levels.

We're working on the general rule of thumb: "If it is possible to replace an item we will not take it". That means chess-sets, mirrors, etc, will not be carried. DVDs, for example, have been slashed brutally such that we're only transferring 40 out of a starting collection of 500+.

Only personal, one-off, unique, or "significant" items will be transported. This includes things like personal photographs, family items, and similar. Clothes? Well I need to take one jacket, but more can be bought. The only place I put my foot down was books. Yes I'm a kindle-user these days, but I spent many years tracking down some rare volumes, and though it would be possible to repeat that effort I just don't want to.

I've also decided that I'm carrying my complete toolbox. Some of the tools I took with me when I left home at 18 have stayed with me for the past 20+ years. I don't need this specific crowbar, or axe, but I'm damned if I'm going to lose them now. So they stay. Object storage - some objects are more important than they should be!

Categories: LUG Community Blogs

Andy Smith: F11 and F12 over serial

Fri, 19/06/2015 - 21:39

I always seem to forget this one.

To pass F11 or F12 over a serial connection (either real serial or Serial-over-LAN IPMI), it’s Escape followed by ! (Shift+1) or @ (Shift+') respectively.

Note that on a US keyboard ! and @ would be next to each other above the 1 and 2 keys so that would make some vague kind of sense as alternatives to F11 and F12. But it’s literally the @ that matters and since I’m using a UK keyboard then it is Shift+'.

(╯°□°)╯︵ ┻━┻)

Categories: LUG Community Blogs

Andy Smith: Fun with Supermicro motherboard serial headers

Fri, 19/06/2015 - 17:42
or, “LOL, standards”

TL;DR: Most motherboards have a serial header in an IDC-10 (5×2 pins) arrangement with the pins as a row of even numbered pins (2,4,6,8,X) followed by a row of odd numbered pins (1,3,5,7,9). Supermicro ones appear to have the pins in sequential order (6,7,8,9,X and then 1,2,3,4,5). As a result a standard IDC-10 to DB-9 cable will not work and you’ll need to either hack one about or buy the Supermicro one.

Are we sitting comfortably?

I bought a Supermicro motherboard. It doesn’t have a serial port exposed at the back. I like to use serial ports for a serial console even though I am aware that IPMI exists. IPMI on this board works okay but I like knowing I can always get to the “real” serial port as well.

The motherboard has a COM1 serial header, and I wasn’t using the PCI expansion slot on the back of the chassis, so I decided to put a serial port there. I bought a typical IDC-10 / DB-9 cable and plate:

Didn’t work. Serial-over-LAN (IPMI) worked alright. On COM1 I would get either nothing or a run of garbage characters from time to time. I wasted a good number of hours messing with BIOS settings, baud rates, checking if my USB serial adaptor actually worked with another device (of which I only have one in my home), before I decided to sit down and check the pin numbering for both the header and the cable.

Looking at the motherboard manual we see this:

And the cable?

Notice anything amiss?

The cable’s pins go in a row of odd numbers and then a row of even numbers:

2 4 6 8 X 1 3 5 7 9 -

The X is the missing pin (serial uses 9 pins) and the - indicates where the notch for the connector would be: next to pin 5 in this case.

The header’s pins go in sequential order:

6 7 8 9 X 1 2 3 4 5 -

As a result all but pin 1 are incorrect.

You actually need a Supermicro cable for this. CBL-0010L is the part number in my case. CBL-0010LP would be the low profile version. Good luck finding it mentioned on Supermicro’s site, but your favourite reseller will probably know of it. As it was I found one on Ebay for £1.58+VAT, and it works now.

After knowing what to search for I also found someone else having a similar issue with a Supermicro board.

You could of course instead hack any existing cable’s pins about or fit an adaptor in between (as the person in the above link did).

Thanks Supermicro. Thupermicro.

Categories: LUG Community Blogs

Steve Kemp: I'm still moving, but ..

Sat, 13/06/2015 - 01:00

Previously I'd mentioned that we were moving from Edinburgh to Newcastle, such that my wife could accept a position in a training-program, and become a more specialized (medical) doctor.

Now the inevitable update: We're still moving, but we're no longer moving to Newcastle, instead we're moving to Helsinki, Finland.

Me? I care very little about where I end up. I love Edinburgh, I always have, and I never expected to leave here, but once the decision was made that we needed to be elsewhere the actual destination does/didn't matter too much to me.

Sure Newcastle is the home of Newcastle Brown Ale, and has the kind of proper-Northern accents I both love and miss but Finland has Leipäjuusto, Saunas, and lovely people.

Given the alternative - My wife moves to Finland, and I do not - Moving to Helsinki is a no-brainer.

I'm working on the assumption that I can keep my job and work more-remotely. If that turns out not to be the case that'll be a real shame given the way the past two years have worked out.

So .. 60 days or so left in the UK. Fun.

Categories: LUG Community Blogs

Andy Smith: OneRNG kickstarter arrived!

Sat, 06/06/2015 - 12:43

My OneRNG kickstarter arrived today. I had five units, so I chose three external models and two internal ones. The finish of the external model isn’t really up to the quality of an Entropy Key. Here’s a picture of them together.

Given that the external model looks rather flimsy — I could imagine it getting snapped in half if someone bumped into it — I think I’d probably prefer the internal model in practice. Here’s what that looks like:

The three different connectors are to try to ensure you can find a useful connection angle no matter how your motherboard’s internal USB headers are laid out.

I haven’t yet plugged them in to check out how they work. This is probably going to have to wait a few weeks as I have quite a lot on.

Assuming they work about as well as the Entropy Keys then I only need to keep two of these for myself, so if anyone wants one I would be willing to sell it on to you at cost plus postage.

Categories: LUG Community Blogs

Anton Piatek: Bye bye big blue

Thu, 04/06/2015 - 11:00

After nearly 10 years with IBM, I am moving on… Today is my last day with IBM.

I suppose my career with IBM really started as a pre-university placement at IBM, which makes my time in IBM closer to 11 years.  I worked with some of the WebSphere technical sales and pre-sales teams in Basingstoke, doing desktop support and Lotus Domino administration and application design, though I don’t like to remind people that I hold qualifications on Domino :p

I then joined as a graduate in 2005, and spent most of my time working on Integration Bus (aka Message Broker, and several more names) and enjoyed working with some great people over the years. The last 8 months or so have been with the QRadar team in Belfast, and I really enjoyed my time working with such a great team.

I have done test roles, development roles, performance work, some time in level 3 support, and enjoyed all of it. Even the late nights the day before release were usually good fun (the huge pizzas helped!).

I got very involved with IBM Hursley’s Blue Fusion events, which were incredible fun and a rather unique opportunity to interact with secondary school children.

Creating an Ubuntu-based linux desktop for IBM, with over 6500 installs, has been very rewarding and something I will remember fondly.

I’ve enjoyed my time in IBM and made some great friends. Thanks to everyone that helped make my time so much fun.

 

Categories: LUG Community Blogs

Steve Kemp: A brief examination of tahoe-lafs

Thu, 28/05/2015 - 01:00

Continuing the theme from the last post I made, I've recently started working my way down the list of existing object-storage implementations.

tahoe-LAFS is a well-established project which looked like a good fit for my needs:

  • Simple API.
  • Good handling of redundancy.

Getting the system up and running, on four nodes, was very simple. Setup a single/simple "introducer" which is a well-known node that all hosts can use to find each other, and then setup four deamons for storage.

When files are uploaded they are split into chunks, and these chunks are then distributed amongst the various nodes. There are some configuration settings which determine how many chunks files are split into (10 by default), how many chunks are required to rebuild the file (3 by default) and how many copies of the chunks will be created.

The biggest problem I have with tahoe is that there is no rebalancing support: Setup four nodes, and the space becomes full? You can add more nodes, new uploads go to the new nodes, while old ones stay on the old. Similarly if you change your replication-counts because you're suddenly more/less paranoid this doesn't affect existing nodes.

In my perfect world you'd distribute blocks around pretty optimistically, and I'd probably run more services:

  • An introducer - To allow adding/removing storage-nodes on the fly.
  • An indexer - to store the list of "uploads", meta-data, and the corresponding block-pointers.
  • The storage-nodes - to actually store the damn data.

The storage nodes would have the primitives "List all blocks", "Get block", "Put block", and using that you could ensure that each node had sent its data to at least N other nodes. This could be done in the background.

The indexer would be responsible for keeping track of which blocks live where, and which blocks are needed to reassemble upload N. There's probably more that it could do.

Categories: LUG Community Blogs

Adam Trickett: Bog Roll: Rhubarb Jam

Mon, 25/05/2015 - 19:40

Over the bank holiday weekend I made two batches of jam: rhubarb & ginger and rhubarb & orange. I made a small batch last year - which we've not yet eaten - but it's quite a while since I've made so much and for sale.

This year I remembered to grade the rhubarb first, so that each batch was made from stems of similar diameter, which means that they cook evenly and you don't end up with a heterogeneous mixture - which is bad.

Categories: LUG Community Blogs

Anton Piatek: Customise your linux prompt

Fri, 22/05/2015 - 13:47

If you use a Linux or Unix box with bash or zsh, and you haven’t come across Liquid Prompt, then I suggest you head there right now to install it. I’m loving having more info on the status line, especially near code version control, but even having cpu load and temperature along with battery life right under where I am typing is really useful

Categories: LUG Community Blogs

Anton Piatek: Raspberry pi cloud print server

Mon, 18/05/2015 - 13:43

It turns out that a raspberry pi does a very good job of being a print server for a google cloud printer. Thanks to https://matthew.mceachen.us/blog/add-google-cloudprint-wifi-access-to-your-older-printer-with-a-raspberry-pi-1342.html I can now print at home directly from my phone!

Categories: LUG Community Blogs

Andy Smith: Has your CurrentCost ever done this?

Fri, 15/05/2015 - 20:35

Update: Replacing the battery and retraining the receiver fixed it. I suppose it must have had enough juice to flash the LED but not transmit.

A few days ago my CurrentCost starting reading just dashes. There’s also no transmitter icon, so I think it’s not receiving anything from the transmitter. It looks like this:

I went and fished the transmitter box out of the meter closet expecting its batteries to be dead, but it still has its red LED flashing periodically, so I don’t think it’s that.

I did the thing where you hold down the button on the transmitter for 9 seconds and also hold down the V button on the display to make them pair. The display showed its “searching” screen for a while but then it went back to how it looks above.

Anyone had that happen before? It’s otherwise worked fine for 4 years or so (batteries replaced once).

Categories: LUG Community Blogs

Debian Bits: Debian Ruby team sprint 2015

Mon, 11/05/2015 - 23:01

The Debian Ruby Ruby team had a first sprint in 2014. The experience was very positive, and it was decided to do it again in 2015. Last April, the team once more met at the IRILL offices, in Paris, France.

The participants worked to improve the quality Ruby packages in Debian, including fixing release critical and security bugs, improving metadata and packaging code, and triaging test failures on the Debian Continuous Integration service.

The sprint also served to prepare the team infrastructure for the future Debian 9 release:

  • the gem2deb packaging helper to improve the semi-automated generation of Debian source packages from existing standard-compliant Ruby packages from Rubygems.

  • there was also an effort to prepare the switch to Ruby 2.2, the latest stable release of the Ruby language which was released after the Debian testing suite was already frozen for the Debian 8 release.

Left to right: Christian Hofstaedtler, Tomasz Nitecki, Sebastien Badia and Antonio Terceiro.

A full report with technical details has been posted to the relevant Debian mailing lists.

Categories: LUG Community Blogs