[Linux] Screen

Hello there, this a 5 Minute Tutorial to screen.
What Screen is?
Well screen is an old unix / linux terminal programm with which you can create multiple virtual "screens".
You can switch between these screens and also can disconnect from them.
Especially useful: If you start an daemon within screen and disconnect from it,
you can reconnect anytime and see what its doing.
Or you can setup a screen session, detach and close your SSH.
If you reconnect, it will still be running.
Oh, and it will be also there and running if your connection drops.

My little list of important Screen Commands:

screen // Create a Screen
screen -ls // List active Screen sessions
screen -r // Resume Screen, if multiple, enter Screen Number from ls after r

CTRL A C - create new tab
CTRL A P - previous
CTRL A N - next
CTRL A D - detach from Screen

To close and exit a screen, just type exit within the screen session.
To start an script in the same folder "daemon like": screen -A -m -d -S SCREENSESSIONNAME ./SCRIPTNAME.sh

Easy, ain't it?

Webconverger - Install ISO to HDD

Just found some old notes, dunno wheter they still apply but its worth a try.

1. Make an Image of your choice by the creator. I made an post about that. Copy the resulting ISO to an USB Stick.
2. Boot in the new PC with Ubuntu or Knoppix Live DVD. Mount the USB Stick.
3. Copy the ISO to the Harddrive. With dd.
dd if=webconverger.iso of=/dev/sda
4. Reboot, thats it

Thank you!

I want to thank all the visitors for an amazing amount of 1277 visits last month!
Yesterday I saw links to pictures and posts of my gps stuff in an Russian Forum and was completly stunned.
Originally the blog started in August 2008 to be an private online notebook for writing down all the little scraps and pieces of code and notes I have had flying around - and never found when I needed it.
I'm happy to see that some people seem to make frequent use of this website and actually find use in the stuff I write.

Thank you very much.

If theres anything you want to see different, have questions or suggestions, don't hesitate to write an comment!

[OpenWRT] Build your own image on Ubuntu 10.03

I'm a huge geek when it comes down to OpenWRT.
I love the style of small little router boards with not much power consumption and still big impact and power.
I have been registred on OpenWRT Forums since 2006, and thats also the time I'm already working on it and doing (weird) stuff with it.
And actually I just plainly love that small debian derived linux.

And thats why most of you would be wondering why I never downloaded the build enviroment and build an image myself.
Actually, I have to face the same question. Because, In fact, its very easy to build an image from source to your own like.

I was thinking about writing an long big blog entry about this topic, but actually, its awesomly well documented within the OpenWRT Wiki, so I just give you the link and encourage you on building your own images: http://wiki.openwrt.org/doc/howto/build

But for all who want it short for Ubuntu 10.03, here are my notes:

install req:
apt-get install build-essential asciidoc autoconf binutils bison bzip2 \
flex gawk gettext libncurses5-dev libz-dev patch unzip zlib1g-dev subversion

download stable:
mkdir OpenWrt/
cd OpenWrt/
svn co svn://svn.openwrt.org/openwrt/branches/backfire

download and install feeds:
Before downloading feeds (additional predefined package build recipies for OpenWrt) you
can check which sources you want to include. Just edit feeds.conf.default in your base directory.
Then start the download with
./scripts/feeds update -a
install with
./scripts/feeds install -a

Building Process

1. Updating sources via Subversion
## Here, backfire is the directory name of the current release branch you're tracking
cd OpenWrt/backfire/
svn up

2. Updating package feeds
./scripts/feeds update -a
./scripts/feeds install -a

3. Creating a default configuration (if necessary)
make defconfig

4. Configuring the image(s) to build
make menuconfig

5. Building the image
make

copy images:
cd bin/
ls */

cleaning up
make clean

cleaing everything, erasing build images:
make distclean

If you need own files compiled into the image, put them to: OpenWrt/backfire/files

How to disable failsafe:

Edit "package/base-files/files/lib/preinit/30_failsafe_wait"
- FAILSAFE=
- pi_failsafe_net_message=true
- preinit_net_echo "Please press button now to enter failsafe"
- pi_failsafe_net_message=false
- fs_wait_for_key f 'to enter failsafe mode' $fs_failsafe_wait_timeout && FAILSAFE=true && export FAILSAFE
+ FAILSAFE=false
+ #pi_failsafe_net_message=true
+ #preinit_net_echo "Please press button now to enter failsafe"
+ #pi_failsafe_net_message=false
+ #fs_wait_for_key f 'to enter failsafe mode' $fs_failsafe_wait_timeout && FAILSAFE=true && export FAILSAFE

[ESXi4.1] Review

It has been sometime, but I still want to tell my experiences with ESXi 4.1.
In the beginning, I was very annoyed from the fact that you really need an 64 bit System and at least 2 Gigs of RAM.
But the rest just turned out fine, I have to admit.

Theres an upgrade path available, so you can upgrade your ESXi 3.5 Machine via an Upgrade to 4.1 without losing your Machines or the need to reinstall.
Actually - it worked, which did surprise myself in a good manner.

In Terms of Speed and Stabilty I did not recognize anything bad.
Especially the new features were downright awesome:
I just love the USB Virtualisation.
I really hit the top by plugin in an USB Videocard to my ESXi 4.1, and adding this Virtual Device to an Vmware Appliance: Awesome speed, had realtime video within my VM.
( I used it to virtualize a bunch of Servers, Firewalls, Routers, Asterisk and a Webcamserver... was really nice running ).

The only thing I really couldn't test and missed was the PCI Virtualization.
That feature *should* work - but you need some kind of state-of-the-Art Intel CPU / Board with Virtual I/O... and I had an old Tyan AMD Dual Core Board, only... ^^'.

So maybe sometime later.

But after all, I'm really happy with that System, I could migrate an running Windows XP Machine to the ESXi4U1 and the Converter was really doing alright...

Dropbox

So, another tool I'd like to present, Dropbox.
Dropbox is an online file synchronisation service which does take place on Amazon Servers.
The files are encrypted and stored securely, also with quite high performance.
Nice part? 2 GB of space are free.
You get 250 MB for doing the Tour,
and another 250 MB if you followed the invitation of another person.
( Oh, and yes the other person does get 250 MB as well.. )
Just in terms, heres my invitation link, would be nice if you would consider using it: http://db.tt/tIYzeey

So, how does it work?
In a nutshell: You create your account, download and install the client, enter the data and you're done.
You got an "Dropbox" Folder now on your Win / Mac / Linux Machine which is synchronized.
As soon as you move files to this folder, Dropbox starts to upload the data.
If you change data, these changes are also commited directly.
So far, so good.

The magic starts happening as soon as you install the client onto another pc:
From the moment you start copying files into the folder on one pc, these are also synchronized to the Dropbox Folder on the other one.

And to make the thing perfect:
There are also clients for Android and iPhone as well as an "GUI-less" Version:
Thats right, you're able to install Dropbox as "Backupmedium" to an Headless, Commandline only Linux Server.
( http://wiki.dropbox.com/TipsAndTricks/TextBasedLinuxInstall )

So - I really can recommend it after using it for some months already, so I would suggest you to test it.

Sorry for keeping you waiting

Sorry there, has been some time since the last post.
Nope, this blog ain't dead.
Problem was that I'm within a big project, taking place since June / July 2010 which didn't let me that much spare time.
Another thing I'm working on is my apprenticeship which will end in June this year.
And a lot of private stuff was going on.
So, I'm quite sorry and hope you're not disappointed.
Some new stuff will follow shortly.

Nico