New wiki, mostly for car pc

I've created a wiki at wikispaces.com, to document things that are less transient than a blog entry.

Take a look at http://timwise.wikispaces.com/

I've started adding information about the car pc, and won't make any promises about what else I'll be adding (personal motto: under promise, over deliver).

I've made it open to all editors, and licensed under the GNU Free documentation licence to ensure the maximum value, reach and participation.

Nightly Shutdown, a new product from Proven Works

Congratulations to Joel Mansford, a good friend of mine, and his company Proven Works on getting the first release of Nightly Shutdown out of the door.

This looks to be a great product and hopefully will make system administrators' lives easier and greener. It's a utility for ensuring that the computers are off when you want them to be, and can be deployed through active directory making the sys admin's life easier. There's a 10 PC free trial available, so check it out at the download page.

Without even looking I know this will be a good product and fantastically well supported. Best of luck to all at Proven Works, and to all the potential users and buyers out there, don't forget to check it out and provide any feedback you can.

A vision of open in-car computing systems

I have a vision. A vision that puts you in control of your in car computing experience.

There are many superb appliances and embedded devices available for your in-car enjoyment, such as the sat navs, the dvd players, the built in games consoles. But they all share one thing in common, they are closed to you. You don't have the freedoms defined by Stallman because they are designed, intentionally or otherwise, to be hard for you to modify as you wish.

I feel deep in my heart that there is enormous potential for in-car computing. There are more possibilities than any individual or company can imagine or provide on their own. I'm sure my imagination is not big enough to list them here, so I leave the ideas for you to contemplate.

Add to this, the evidence and my experience that open source when done right produces the better engineered solution at a lower cost, and you have a compelling argument for such a system.

I have seen the freedom that open source and the GPL provide on the desktop computer, and I believe that this culture of openness and freedom for the users can be applied to the in-car computing market to the benefit of all.

My mission is to provide a basis for this innovation, and cultivate a thriving ecosystem in the way that only open systems can. And so, my vision is a range of affordable flexible and most importantly open computing devices for your car.

And so, I introduce to you in the above photo, the mark one of my in-car pc. It has no name, and the software and hardware needs some work to say the least, but in the tradition of openness on the internet, I will present here my ups and downs, successes and failures, genius and downright stupidity for your entertainment.

I have minimal spare time and numerous other projects, but there is no rush, as I think this plan will stand the test of time, and all the while hardware gets cheaper, smaller, faster and less power hungry. As I progress in fits and starts I will post photos to flickr under the tag carpc (first set) and progress updates to this blog under tag carpc.

All feedback welcome. I will announce new articles on my twitter feed, twitter.com/tim_abell, and can be contacted using the links at the bottom of my blog.

sharing work between computers with a usb flash drive and git

I couldn't find anything exactly matching this on the net when I was figuring it out, so here's what I did.

This is working against a remote svn (subversion) server, but applies even without one.

On the first computer, grab your git working copy from svn with git-svn clone (or clone a git repo, or just start a new one).

mkdir ~/project.git
cd ~/project.git
git-svn clone svn://project-server/trunk
git repack #for good measure

Plugin your usb flash drive/stick/external harddrive, I'll presume it's a vfat/fat32/fat16 formated device mounted at /media/flash.
Create an empty repository on the drive, I'll use a bare one as there's no need to keep the working copy as well.

mkdir /media/flash/project.git
git --bare init /media/flash/project.git

Then add the flash drive git repo as a remote source in your local git repo. "flash" is the name I've given to the remote branch reference, you can call it whatever you like.

git remote add flash /media/flash/project.git

If you push immediately it will fail (as I discovered) because fat doesn't support the execute flag on files, so all the hooks are automatically active. I deleted all the hooks as I wasn't planning on using them, this may be wrong so no promises, but it seems ok so far for me. So remove the hooks with:

rm /media/flash/project.git/hooks/*

Then push your current local copy to the flash drive with:

git push flash

This will copy all your committed work onto the flash drive, even if you haven't pushed it upstream to the svn server with "git-svn dcommit" yet. Bonus! It won't copy any of your branches across though, so you if you want them you can add those independently with:

git push flash mybranch

Now move over to the second computer and plug the flash drive in. I'm making the same assumptions on paths and devices. Do another completely independent svn checkout as above:

mkdir ~/project.git
cd ~/project.git
git-svn clone svn://project-server/trunk
git repack #for good measure

Then add the flash drive's repo to the git repo on the second pc and pull all changes from the flash drive, optionally including any branches:

git remote add flash /media/flash/project.git
git pull flash master
git pull flash mybranch #if you like

When you've committed changes to git or pulled the latest changes from svn on either pc, you can then update the flash drive with the simple command:

git push flash

Which pushes all your changes on your master branch on to the flash drive. You are now ready to run the pull command on the other computer to get back in sync:

git pull flash master

If you don't push changes to the flash drive before committing to svn then things will be very simple. If you push changes to the flash drive, and then commit them to the svn server you will need to do a little more work. This is because when you run "git svn dcommit" it pushes your latest git commits to the svn server, deletes your locally committed changes, and then fetches them back from the svn server. This means that git won't recognise your local changes as being the same as the ones on the flash drive because they have different commit message and SHA1 hash. Attempting to push to the flash drive fails with the message "! [rejected] master -> master (non-fast forward)" as the old copy of the commits are still there.

To resolve this you need to throw away the matching set of changes on the flash drive. To do this you can use git reset as follows, where HEAD~1 should be the number of commits you need to throw away (eg HEAD~3 to throw away the last 3 commits that were pushed to the flash drive):

cd /media/flash/project.git
git --bare log #to see how many changes don't have svn information
git --bare reset HEAD~1

You can then push your changes as above.

cd ~/project.git
git push flash

I've glossed over subtleties with fetch vs pull, but hopefully you will find this useful.

This howto makes use of git's ability to pull from multiple sources, and I've found that git quite happily copes with changes that were checked in to svn coming via the flash drive, even when later running "git-svn rebase".

Please do comment or contact me with any problems, errors, extra info and feedback, and let me know if it was useful.

Removing the execute flag from many files

Here's how to recursively remove execute permissions on files that have been copied from a windows system.

find * -type f -exec chmod -x {} \;

ie, find all files (not directories), and execute a command to remove all execute permissions for each file.

My bash prompt

I like a new line in my prompt so that if I'm deep in a path I don't end up with 10 characters left to type in, and pretty colours so that it's easy to spot the prompt when scrolling through lots of output.

Update 26/04/2008, added red for root.

From my ~/.bashrc
# Comment in the above and uncomment this below for a color prompt
if [ $UID = 0 ] ;then
PS1='${debian_chroot:+($debian_chroot)}\[\033[00;31m\]\u@\h\[\033[00m\]:\[\033[00;34m\]\w\[\033[00m\]\n\$ '
else
PS1='${debian_chroot:+($debian_chroot)}\[\033[00;32m\]\u@\h\[\033[00m\]:\[\033[00;34m\]\w\[\033[00m\]\n\$ '
fi

The result (more or less):
tim@lap:~/Documents
$ echo "That's better"

Enjoy.

stop motion animation on linux

A quick howto...

1. Take a series of photos on your digital camera.
2. Copy them onto your linux box.
3. shrink the photos to a more managable size:
   mogrify -verbose -resize 600x400 -quality 60% *.JPG
4. Preview the animation with animate:
   animate -delay 8 *
5. Optionally rotate the image to match the exif information from your camera (mine was sideways):
   exiftran -ai *
6. Convert the jpg files to png:
   mogrify -format png *.JPG
   
7. Create the flash animation from the PNG files:
   png2swf -r 15 -o flower2.swf -v -X 399 -Y 600 *.png
8. Create an html file to hold the animation containing the following:
   

   <object>
   <param name="movie" value="flower2.swf" />
   <param name="loop" value="true" />
   <param name="quality" value="high" />
   <embed src="flower2.swf" width="399" height="600" />
   </object>
   

9. Write a blog article to tell everyone about it ;-)
   "history" is a handy command for reviewing your activities for writing up your achievements.
   

And here it is, providing I've kept up with my hosting fees and not been slashodotted: