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Friday, June 25, 2010

Clock synch on Ubuntu 10.04 Lucid on

Running Ubuntu 10.04 Lucid on a

What do we need to do to make the clock time be right?

I tried running without ntp and letting it take the time from the host machine (dom0). This didn't seem to be too bad. Over a few weeks we seemed to build up an error of about 0.3 seconds. I don't know why or how it can be off by such a small amount. Surely it should either be off by more than that, or bang on. Strange.

Anyway I have now turned on the ntp configuration again. We now seem to be running within a handful of milliseconds of the right time and ntpdc -c kerninfo is saying the we are synched. We will have to leave it a few weeks to see how it gets on.

Wednesday, June 16, 2010

Setting up a default locale under Ubuntu 10.04 Lucid

Do you do Perl? If so, you might like to try It's like, only it's not, so when goes down, stays up. Plus it's UK based, so for people in the UK and the rest of Europe, it should be quicker.

Had a problem where I had a VM running Ubuntu 10.04 Lucid but we did not have a suitable locale set to make it "work in UTF-8".

What is normally required is for the environment variable LANG to be set to something sane like en_GB.UTF-8.

On the system in question, which was derived from a bare-bones VM Ubuntu, LANG was empty. Pasting a smiley face ☺ into a PuTTY window just made it go bing. Typing a pound sign £ didn't work.

Now back in the good old days we would do something like

sudo aptitude install locales
sudo dpkg-reconfigure locales

But on my Ubuntu 10.04 Lucid system that did nothing.

Some googling around showed up remarkably little. It seems everyone just uses the GUI installer and it does everything for you. There is not much help for the command-line user.

Anyway, eventually the answer did start to become clear. The locale data is kept in separate language packs. These are represented by various packages in the standard repository, with meta-packages to link things together.

The upshot is that you need to install the relevant language pack

sudo aptitude install language-support-en

Then set the default locale as desired

update-locale LANG=en_GB.UTF-8

Log out and log in again to pick up the default locale. Then check it with

echo $LANG

This should show the default locale set earlier.

I can now paste a smiley face ☺ into PuTTY and type a pound sign £ and that all works.

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Monday, June 14, 2010

Unison seems to be interesting

Humyo turned out to be not as good as I'd hoped for.

I was still looking for a way to synchronise my lappy (or at least bits of it) with a server.

So I thought I would have a go with Unison.

So far it seems to be working out OK.

The old Unison 2.27 that you get with your average Linux distro is a bit pants because it does not support Unicode filenames. You need something a bit newer like 2.32.

At the minute I seem to be ending up with Unison 2.40 everywhere.

Unison comes with an X.Y.Z version number and you need to have the same X.Y at both ends of the link for it to work.

So I am using the standard pre-built Windows GTK build of 2.40.something, and building my own one on the Linux side.

For some reason, Unison 2.40 insists that it needs Ocaml 3.11.2, which is the latest released version. Ocaml is a big old beast to build yourself. You really want to be using a pre-built package version. So I have ended up going to Ubuntu 10.04 Lucid which includes Ocaml 3.11.2.

To get Unison on Windows to be able to call up the Linux box, I use "plink" out of PuTTY. I was previously using SSH out of cygwin, but using plink seems to involve less overall weirdness. To get Unison to be able to invoke plink (relatively) smoothly, I used a shim script called ssh2plink.bat.

Unison is quite neat in the way it synchronises. It seems to be able to spot files with the same content, even if they have different name. So you can happily pick up a tree and move it somewhere else, and Unison will synchronise it quickly without having to re-upload or re-download the whole tree. This also seems to work with tree copies.

One thing I have been doing is having two lappies synchonised with the server. This, coupled with the fact of having all e-mail accessed by IMAP meant I could switch from working on one lappy to the other lappy with ease.

I eventually stumbled across the fact that Unison does not propagate file modified timestamps by default. There is an option ("times") which can be turned on easily enough, but for some unknown reason it is not enabled by default.

Humyo: ghastly

On the face of it, Humyo looks like quite a good idea. About £4 per month for 100GB storage.

After using it for a few days I started to run into what turned out to be a show-stopping problem.

The Humyo software takes an age "working out what has changed", and does not provide any progress indication.

I thought this was just some funny little thing about the way it worked.

That was until I tried to get my data off of Humyo again.

And he we find the rub, and it's a biggy: Humyo is slow. Deathly slow.

Retrieving a file through the DAV interface runs at about 1 Mbit/s (one megabit per second). Not even 1 Mbyte/s. Really, 1 Mbit/s (125 kbyte/s). This is even slower than my out-in-the-sticks 2 Mbit/s broadband connection.

Reporting this to Humyo tech support, at first they claimed there was "packet loss near my host". This was fine except I had run my tests from 3 different co-lo boxes, all with proved excellent connectivity. Humyo then ran tests through the HTTP (public file sharing interface) which ran more quickly. Yeeeesss, but that is public file sharing. I was talking about the private authenticated DAV interface.

If we mount up Humyo using Davfs2, and try and do any operation which enumerates the directory hierarchy, we can only go through it at about one directory per second. And this is with empty directories.

No. Humyo is utterly ghastly.

At the present time AWS S3 seems to be quite a good idea. Access to AWS S3 seems to be reasonably good from the co-lo machine.

Thursday, June 10, 2010

LG 37LH5000 red button prompt dismissal

When you're watching a programme on the LG 37LH5000 via the integrated Freeview receiver, you sometimes get an overlay at the top right of the screen telling you that you could press the red button.

On Sky Digital, you get similar prompts and you can dismiss this prompt by pressing the 'back' button.

But this does not work on the LG 37LH5000.

So can you do the same thing another way, and if so, how?

Yes, press the green button.