Techmania

May 28, 2013

SSH must-haves for Productivity

Filed under: Development,FOSS,Linux,Uncategorized — mifan @ 9:21 am

Devops work with many different remote systems at once. For the lazy bunch ( a.k.a the truly productive bunch who look for ways to make their work easy – a.k.a the really bright ones ) there are ways to make life easier.

So instead of typing

ssh whitewizard@163.12.24.21

(or wait, was it 163.12.24.23??), and then entering the password that no one can remember given to us by the sysadmin, I’d now say

ssh devserver

and voila.

The steps to get there are:

SSH Passwordless Entry

Step one is to get rid of those pesky passwords required each time you SSH into a host. This can be achieved by setting up an RSA (public/private key). And besides, who’d say no to added security?

To generate a SSH key if you don’t have one already, run

mkdir ~/.ssh
chmod 700 ~/.ssh
ssh-keygen -t rsa

You will be prompted for a location to save the keys, and a passphrase for the keys. This passphrase will protect your private key while it’s stored on the system.

Generating public/private rsa key pair.
Enter file in which to save the key (/home/b/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/b/.ssh/id_rsa.
Your public key has been saved in /home/b/.ssh/id_rsa.pub.

Your public key is now available as .ssh/id_rsa.pub in your home folder.

Next, the little bit of magic where you’d copy your key over to the remote/host machine. If you can SSH into the machine, then this should be no problem. Run

ssh-copy-id whitewizard@163.12.24.21

Done. You can now login by saying

ssh whitewizard@163.12.24.21

And the system shouldn't ask you for a password.

SSH Hostname Shortcuts

But wait – we want more (or less, actually). The next step is to shorten this further. For this create a file .ssh/config with the following entries:

Host [shortcut]     
 Hostname [full-hostname]    
 User [username]

I’d use

Host devserver
     Hostname 163.12.24.21
     User whitewizard

And voila, now running the following will log you into the system

SSH devserver

Of course, replace the above hostnames and usernames with you own – else you’d be login into Saruman’s own server!

February 7, 2012

Creating Patches with SVN Diff

Filed under: Development,FOSS,Linux — mifan @ 12:33 am
Tags: , ,

I recently came across a situation where I had to generate a patch from SVN, where I was in a multi-developer environment, my code was committed in 2 batches, and there were changes from other developers in between. Thanks to the power of SVN, this is a breeze (of course, I’m not even going to start the version control debate here!!).
The format for SVN diff is as follows:

svn diff [-r N[:M]] [--old OLD-TGT] [--new NEW-TGT] [PATH...]

In this case, to generate a patch between revisions 1000 to 1020, only for files file1.php and file2.php would be as follows

svn diff -r 1000:1020 dir1/file1.php dir2/file2.php > mypatch.patch

For conventional patches, you would checkout the code, make your changes, and from the root locations run the svn diff, as

svn diff > mypatch.patch


October 5, 2011

Download Directories with wget

Filed under: Development,FOSS,Linux — mifan @ 6:53 am

wget is a non-interactive download utility available in the *nix OS, which can be used to remotely download files, amongst other things.

I’ve looked for the correct wget command to download a directory remotely, but couldn’t find the right one. This one, however, worked for me:

wget -r --level=3 -np -nH "<URL of Directory>"

where

r – recursive download (download recursively looping through sub directories

np – no parent directories (without this command, you get some weird results from the recursion working for the parent directory as well)

nH – no host (get rid of the host name – without this, your folder will be created with some weird name that includes the host/url

level=3 -upto what level/depth you want to recurse or go into. Change to an appropriate number

Check the man page of wget for more information

September 16, 2011

Multiple Terminals in the same Session with Screen

Filed under: Development,FOSS,Linux — mifan @ 8:30 am

As an administrator or unix user who has just SSH’d into a remote server, have you had the requirement to open multiple remote terminals without having to resort to re-logging in multiple times? I’ve had this one too many times, where I needed to run multiple apps, view logs etc. etc. in separate terminals, which can be made easy using GNU Screen.
GNU Screen is a screen multiplexer, which can be installed via a simple apt-get install screen on your linux server. This should be available by default as well. Once that is done, the following steps should suffice

  • Login to your remote terminal (e.g: via SSH)
  • Open Screen
 user@remote> screen
  • Use the following commands to create, navigate etc. CTRL+A (CTRL A) is the control key in my Ubuntu server by default, and this might be the case for you as well. Thus when I refer to CTRL A p, I mean holding CTRL + A down, press the ‘p’ key
  • Create a new terminal:
user@remote> CTRL A c
  • Move to the next terminal:
user@remote> CTRL A n
  • Move to the previous terminal:
user@remote> CTRL A p

Etc. Some more commands are as follows

  • Move to a specific terminal: CTRL A “
  • Move to the last used terminal: CTRL A A
  • Move to terminal number 0 (0-9) : CTRL A 0

These commands were enough to get me going. For even further commands and to explore the power of screen in depth, here are some useful resources:

Resource 1, Resource 2

July 2, 2008

Debugging PHP in Eclipse using XDebug

Filed under: Development,FOSS,Linux — mifan @ 12:44 pm

My previous post touched upon the basics of getting Eclipse PDT (PHP Development Tools) up and running for PHP development. In this post, we’ll be looking at getting PHP debugging capabilities into our PHP dev environment. Again, I’ll be focusing on Ubuntu Linux – 8.04 LTS to be specific: however, with minor changes, this can be used on any platform.

Of course, there are simpler methods of debugging PHP scripts: a var_dump is quite handy in terms of simple debugging – however, having the right tools at hand for development means that we can spend more time in actual development than writing debug statements every once in a while – anyways, that’s my take.

XDebug is a remote debugger. Here we’ll take a look at getting XDebug working with Eclipse PDT providing a full debugging client. The first step would of course be to get Eclipse PDT up and running (refer previous post if needed). Once done, the next step would be to get Xdebug for our PHP environment set up – in my case, PHP5. On Ubuntu, this can be achieved by:
apt-get install php5-xdebug
This should install Xdebug for PHP5. Next, we’d configure Xdebug by editing the PHP configuration file. Most systems require the configuration items be added to the main php.ini, or the appropriate conf file. In Ubuntu 8.04 LTS, a separate configuration file,xdebug.ini, is created for Xdebug. Open this file using your favorite text editor (vim in my case):
sudo vim /etc/php5/conf.d/xdebug.ini
Add the following lines after the zend_extension= or zend_extension_ts= conf value.

xdebug.remote_enable=On
xdebug.remote_host="localhost"
xdebug.remote_port=9000
xdebug.remote_handler="dbgp"

And restart your web-server. In my case, Apache:
/etc/init.d/apache2 restart
To try out the debugger, open a PHP project in Eclipse (if you are importing an existing project via CVS, remember to add it as a PHP project using the New Project Wizard). In Window->Preferences->General->Web Browser, select external web browser, and set it to point to your default web browser. Next go into the debug section, by Window->Preferences->PHP->Debug, and set the PHP Debugger option to XDebug (by default this is set to the Zend Debugger). Note the chekbox “Break at first line” in this page as well – you can change this later on, as required. After you’ve applied your changes, go into the Debug menu, by Run->Open Debug Dialog… Here, make sure the Server Debugger is set to XDebug, and that the PHP server points to http://localhost or an appropriate server location. The file section should point to the file to be debugged, relative to your workspace (Note: if your project is missing from the list, check whether you’re project is configured as a PHP project – I’ve noticed that non-PHP projects fail to appear on this list). Thus if your file is index.php, the relative path maybe something/www/index.php etc.
Next, check the URL section to see whether it points to the correct location – if not, make sure you uncheck the “Auto-Generate” check box, and enter in the correct location. Apply the changes and close the dialog box.
A view of the Debug dialog is here:
EclipsePDT Debug Dialog
You should now be ready to debug your application. Click on Run->Debug or F11 to enable debugging – Eclipse should switch to the Debug View, and the page should start loading in your external browser. If “Break at First Line” checkbox was checked previously, then the program would have “stopped” at the first line – you can step into or step over subsequent lines using the controls on your top left corner. Alternatively, you can place breakpoints at various locations and stop code execution there as well. The variables tab should give you the variables and their values at various times. I good guide from which I borrowed from is here. Get creative – start debugging.
A view of the debugger in operation is here:
EclipsePDT XDebug for PHP

May 26, 2008

Python for Series 60 Upgrade

Filed under: Development,FOSS,Mobile — mifan @ 10:41 am

The newer version of Python for Series 60, 1.4.3, is out, and I’ve upgraded my Nokia 7610 with it. This is an Open Source project to port the beautiful Python programming language to Symbian Series 60 phones, which goes under the name of pys60. The advantage is that you’ve now got a scripting solution to access the Symbian Series 60 C++ APIs. Python provides the power of accessing underlying layers compared to J2ME, whilst remaining easier in terms of learning curve than Symbian C++. The python interpreter cum shell allows code to be executed directly on the phone – and the shell can be accessed via bluetooth from a PC, which means code written on the PC can be executed on the Phone real-time ! – More on that later though…
Installing Python on Series 60 devices is as simple as sending the relevant .SIS file of the interpreter to the phone. The SIS files are available on the project site: be sure to check the category of your Phone OS, and download the specific version. For Nokia phones, the version can be obtained at Forum Nokia. For instance, my Nokia 7610 is a Series 60 Feature Pack2, so I’ll be downloading Python for Series 60 FP2.
Now to check whether my previous code snippets are backward-compatible…. And yes, they are :)
Python Series 60

February 18, 2008

Tuning the Guitar on Linux

Filed under: FOSS,Linux,Music — mifan @ 6:36 pm

Unfortunately, the manual tuner for my guitar ended up with one of my guitars, so I had to look for something to tune the other acoustic one. And hey presto, Linux to the rescue again :). GtkGUITune is an application to tune guitars: it obtains the note played via the mic interface and shows the frequency measurement: And unlike other methods, the measurement is shown in 1/10th of a second. So all you have to do is to tune your guitar to match your required notes/frequencies.
GTKGuiTune Home Page

GTKGuiTune

November 10, 2007

Drivel: Offline blogging client

Filed under: FOSS,Linux — mifan @ 12:59 pm

Finally, I’ve crash landed on a single offline blogging client, and I hope this would be the start of a long lasting friendship. Drivel, an apt-get away on Ubuntu, is a desktop blogging client which allows you to post/blog to multiple blogs, from the comfort of your dektop (literally). It supports various types of Journals: LiveJournal, Atom, Blogger, MovableType and Advogato, and thus any blog that supports one of these types, including WordPress and Drupal using MovableType. Users have the ability to store their username, password for various accounts, and work offline saving blog posts for delayed posting. And the simple, uncluttered, spartan-looking user interface gives that polished look to the client. All in all, lets hope I blog more (ok…at least I’m hoping I do :) )

Drivel Client

July 27, 2007

Using Gmail SMTP server to send mails

Filed under: Development,FOSS,Linux — mifan @ 8:49 pm

The last couple of weeks I had a horrid time. My favourite past-time: sending emails, was cut short due to some problem in my email client, coupled with our SMTP server, which kept giving me this error message:
Error while performing operation.
Welcome response error: Transaction failed

A number of Googling searches led me knowhere, so I turned to a solution of another sort from Google: The GMail SMTP server. Luckily, I could setup my Evolution Client on my Linux box within no time, to use and send mail via the GMail SMTP server. The steps are below:

  • In your GMail account, goto settings>Accounts
  • Add another email address there, in this case my email addy that complains.. :)
  • Verify the email address in GMail
  • In Evolution (or whatever client you use), Edit your mail preferences
  • Under server, add smtp.gmail.com
  • Enable TLS encryption
  • Under authentication, add <yourgmailusername> as your username
  • Click Ok, enter the password when required, and cross your fingers :)

Thus, with some simple steps and some faith, I started sending emails again, thus becoming a nuisance to the world once again :p

June 28, 2007

FOSS-Ed for Windows..

Filed under: Development,FOSS,Life,Linux — mifan @ 9:20 pm

Today was the 3rd and final day of the amazingly different FOSS-Ed for Windows. Why amazingly different? Well, for starters, we had a hard time finding speakers from our community of merry fellows, for the simple reason that most of us do NOT use Windows regularly. Thus, this was something totally different for some of us, but all in all, the event progressed well. Actually, all credit to the organizing committee, consisting of Karthigha, Lohitha, Gunith, Gayal, Dr. Sanjiva, Hasmin and the zillions of others hanging around for a job very well done.

Day one at HNB towers was for total tech stuff. My presentation on “Thunderbird,Evolution and Firefox” was an eye opener for me as well, and I got to know of quite a few new cool FF addons as well :) Lighting talks of day2 was something else though: I paired up with Suchetha to moderate the session, and it was nothing short of pure fun, and for a change, I guess the audience enjoyed it too (for those in the dark: lighting talks are where people come on stage and talk for 5 mins on some non-tech subject. Being unaware of the time, they are booed away at the end of 5 mins). The event ended with a very *interesting* panel discussion on IPR, with the panel consisting of Brian Behlendorf, and representatives from Microsoft Sri Lanka and the ICTA Sri Lanka.

All in all, another successful FOSS event underway, and now we look forward to the next one, which is :)

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