Guillermo Garron main site

iCloud beta released

2011-08-02T00:00:00-04:00

Varnishlog filter the records for debugging

2011-07-25T00:00:00-04:00

Varnish Logs

Varnish is a powerful reverse proxy that can balance the load of multiple web servers, and cache the required pages at the same time. You can read more about it at its home page

Now we all know that debugging is an important part of installing, configuring and fine tuning any piece of software, and that goes to varnish too, and varnishlog is a great utility to help you while debugging varnish.

varnishlog

As the name says, it display Varnish logs, but if you have a very busy site, and your run it with no parameters you will hardly follow the logs in the screen, so your first option to solve this, is to write the logs to a file and analyze them later.

varnishlog -w /home/user/varnishlogs.log

You can then use less to view the document. But you’ll have too much information to digest and it would be better to filter it by IP or some other field. We normally use grep to do that, but in the case of varnishlog the info is placed one field by line so grep is not useful.

Here an example, of the varnishlog output.

   17 SessionOpen  c 66.249.72.22 47013 :80
   17 ReqStart     c 66.249.72.22 47013 487860892
   17 RxRequest    c GET
   17 RxURL        c /find-Linux-command-to-find-files-on-your-disk
   17 RxProtocol   c HTTP/1.1
   17 RxHeader     c Host: www.go2linux.org
   17 RxHeader     c Connection: Keep-alive
   17 RxHeader     c Accept: */*
   17 RxHeader     c From: googlebot(at)googlebot.com
   17 RxHeader     c User-Agent: Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)
   17 RxHeader     c Accept-Encoding: gzip,deflate
   17 RxHeader     c If-Modified-Since: Sun, 24 Jul 2011 16:10:35 GMT
   17 VCL_call     c recv lookup
   17 VCL_call     c hash hash
   17 Hit          c 487859722
   17 VCL_call     c hit deliver
   17 VCL_call     c deliver deliver
   17 TxProtocol   c HTTP/1.1
   17 TxStatus     c 304
   17 TxResponse   c Not Modified
   17 TxHeader     c Date: Mon, 25 Jul 2011 16:28:26 GMT
   17 TxHeader     c Via: 1.1 varnish
   17 TxHeader     c X-Varnish: 487860892
   17 TxHeader     c Last-Modified: Sun, 24 Jul 2011 16:10:35 GMT
   17 TxHeader     c Cache-Control: public, max-age=300
   17 TxHeader     c Vary: Accept-Encoding, Accept-Encoding
   17 TxHeader     c Connection: keep-alive
   17 TxHeader     c X-Cache: HIT
   17 TxHeader     c X-Cache-Hits: 1
   17 Length       c 0
   17 ReqEnd       c 487860892 1311611306.344539404 1311611306.344666958 0.000112295 0.000054836 0.000072718

We can now filter for any of those fields, and only show the records that contain certain value for a specific field. Let’s see an example.

varnishlog -c -o RxRequest GET

Will show all records (like the one above) that have the field RxRequest with GET value. You can also list all records for an specific IP

varnishlog -c -o SessionOpen 11.22.33.44

You can also write everything to a file with

varnishlog -w /home/user/varnish.log

and then read from there filtering with:

varnishlog -r /home/user/varnish.log -c -o SessionOpen 11.22.33.44

As you can see varnishlog can be very useful, if you can filter the info you really need.

Remove spaces from file names with Linux

2011-07-25T00:00:00-04:00

I've been using this line to remove spaces from file names in Linux.

Usually Windows users like to add spaces in the file names, I prefer dashes (-) or under scores (_) instead, they are easy to manage in the console.

I've found this command a long time ago in a forum, and still have it on my personal notes.

Here posted for everybody:

  for file in *; do mv "$file" `echo $file | sed -e 's/  */_/g' -e 's/_-_/-/g'`; done

Use varnish to avoid hot linking or image leeching

2011-07-24T00:00:00-04:00

Introduction

Hot Linking

From Wikipedia we have:

The technology behind the World Wide Web, the Hypertext Transfer Protocol (HTTP), does not make any distinction of types of links—all links are functionally equal. Resources may be located on any server at any location. When a web site is visited, the browser first downloads the textual content in the form of an HTML document. The downloaded HTML document may call for other HTML files, images, scripts and/or stylesheet files to be processed. These files may contain <img> tags which supply the URLs which allow images to display on the page. The HTML code generally does not specify a server, meaning that the web browser should use the same server as the parent code (<img src="picture.jpg" />). It also permits absolute URLs that refer to images hosted on other servers (<img src="http://www.example.com/picture.jpg" />).

This is good, if you own the server where the objects are stored, but if not, what you are doing is using someone else bandwidth.

And if somebody is using your bandwidth, you will not like it, and something needs to be done about it.

We’ll see now how to stop or prevent other from hot linking your content.

Block access to your media files from non authorized sites

We’ll use varnish, to block hot linking or image leeching.

This way, we’ll block the bandwidth thief before he really reach our web sever.

Here the code you may add to your varnish vcl

 sub hot_link {
        if (
                (req.http.host == "www.site1.com"
                ||
                req.http.host == "www.site2.com"
                ||
                req.http.host == "www.site3.com")

                &&
                req.url ~ "\.(js|css|jpg|jpeg|png|gif|gz|tgz|bz2|tbz|mp3|ogg|swf)$" 
                &&
                (req.http.referer 
                && (req.http.referer !~ "^http://www.site1.com/" && req.http.referer !~ "^http://www.site2.com/" && req.http.referer !~ "^http://www.site3.com"))
                )
                {
                        error 403 "No hot linking please";
                }
}

What is this code going to do?

First we define which host we are using as virtual hosts behind varnish, in this case I’m defining three you may add or take as you wish.
Next, we define the extension of files we do not want to be served unless our own site call them
Finally, we define the referrers that are authorized to call our content and load it in-page.
One last thing, we define what to do with those who do not comply with the requirements, in this case we are sending a 403 “forbidden error” with the message, “No hot linking please”.

You may change the behavior of this last call by sending other error or redirecting those calls to your homepage for example.

Once we have this sub-routine, we can call it in sub vcl_recv section.

Example of vcl_recv section

sub vcl_recv {
    call hot_link;

    ……
    #The rest of your rules come here
    …… 
}

Redirecting to your home page

If you want to redirect to an special page, instead of error 403, use error 302, and then create a vcl_error section like this:

sub vcl_error {
    if (obj.status == 302) {
        set obj.http.Location = "http://site.com/hot-linking.html";
        #set obj.status = 302;
        #return(deliver);
    }
}

Conclusion

Bandwidth is not cheap, and you should take care of it, there will always be not fairly people out there, and you should take care of them. This is just one method of doing this, there are others, and a lot of them more complex with more options, but this is a good place to start.

Secure Apache and PHP, hide version numbers

2011-07-21T00:00:00-04:00

Introduction

You may be concerned about security on your LAMP server, and you should hackers are always trying to break into your or anyone’s else system.

After finding this in slashdot, I have decided to show you how to to stop Apache and PHP sending their versions and other valuable info for hackers.

Hide Apache version

To make Apache stop sending its version number to any visitor do as follow:

Edit the file http.conf or apache2.conf and add the following lines.

ServerSignature Off
ServerTokens Prod

Restart Apache

Hide PHP version

Now the turn of PHP, we do not want those hackers out there to know which version of PHP we are running rig?

Edit the file php.ini, usually in /etc/php/ or /etc/php/apache2/` and add or change the following lines:

expose_php = Off
display_errors = Off

Restart Apache server.

You are done, now, your system is a little bit more secure. Remember that everybody have access to your server.

Create, edit and manage PDF documents really with Linux

2011-07-17T00:00:00-04:00

Introduction

Whenever you need to work with PDF documents, like when you need to merge documents, rotate them or put a lot of documents together in a single PDF file, you may need to work with PDF Mod, this great tool will let you do those things and more.

This is going to be just an introduction to its capabilities, you will then learn a lot more by yourself while working with it.

Installation

If you are using one of the major Linux distribution you will find it in the repositories of your distribution, or you can download from the homepage

I have installed it in Arch Linux from the AUR repositories using yaourt

If you want to install it in Ubuntu, use these commands.

sudo add-apt-repository ppa:pdfmod-team/ppa

To add the new PPA

sudo apt-get update

Update the repositories’ database

sudo apt-get install pdfmod

To install the software.

Using PDF Mod

Now that you have it installed, you can start editing your PDF documents, you can rotate pages, add or extract pages to final document.

One good scenario to use it is:

You need to present a report that need to include an introduction letter, some graphics, a spread sheet, and some pictures.

What you can do is:

Create the letter with LaTeX
Export your spreadsheets from LibreOffice to PDF (It has a function to do it)
Convert your JPG files to PDF (Use the opposite way that this tutorial use)

Now you can use PDF Mod to put all those pages together.

Just use the “+” (Plus) sign in the menu, to add documents to the master documents, and then you can change the order of the pages, by just moving them with the mouse in the main screen.

Conclusion

As you can see, this is powerful yet easy tool to create PDF documents, consisting of a lot of other documents, it is also very intuitive and you’ll find it really easy to use.

My new personal blog

2011-07-11T00:00:00-04:00

I'm thinking about letting go2linux as a place only for tutorials and how to. All my opinions editorials may be moving to my personal blog. I think that will may easier to anyone only interested in my tips and tutorials not to be messed with my opinion posts. What do you think?
Find my personal blog at http://garron.me

If I finally decide to do that I'll let you know.

Thanks.

Drupal and Wordpress first impressions

2011-07-11T00:00:00-04:00

Well,

I now have two sites, this one and http://garron.me.

This one is using Drupal, and the other is with Wordpress, I'll write about them later, but my first impressions are: Wordpress is easier...

Drupad module and iPhone app

2011-07-11T00:00:00-04:00

If you blog on drupal, you'll really love this module and drupad app for the iPhone and iPod touch.

Wordpress dashboard problem with Ajax, CSS and Javascript

2011-07-09T00:00:00-04:00

Introduction

I'm still kind of playing with http://garron.me and for the last three days I've been switching from Movable Type to Wordpress, but I have faced a weird problem.

And while searching in the forums and using Google to solve it, I've found that a lot of people is facing somehow the same problem, and in all forum's threads people is guiding them to the same possible solutions time after time and lots of them have not found the real solution.

Well, I hope this post may help anybody who may face this issue, like me.

Dashboard Ajax / CSS/ Java not working

That is some of the queries I've used in Google to find the solution, and the problem is that in a fresh new install of Wordpress the dashboard did not worked as it should, somehow Ajax, Javascripts and CSS where not working, as none of the drop down / pull down menus worked in some of the pages.

I've been reading and almost all solutions point in these directions

Disable all plugins
Restore the 20 11 default theme
Upload again the wp-admin and wp-includes files from a fresh download

Also others more technical were:

Increase the size of PHP, using php.ini or .htaccess or wp-config.php
Add this statement define( 'CONCATENATE_SCRIPTS', false ); in wp-config.php file

But none of them solved my problem, I have even installed WP again and again, even recreating the database from scratch.

[Solved] Wordpress Dashboard problem version 3.2"

All that I have needed to do was to enable json.so library in the php.ini file.

Edit php.ini and uncomment this line.

; extension=json.ss

Just delete the semicolon ";" and restart Apache. (You may need to install json first, Google about it for your Linux distribution).

Hope this helps someone.

Share your music library using a Linux server, with DAAP and iTunes

2011-07-07T00:00:00-04:00

Introduction

If you want to share you iTunes library with your family or maybe (for private use) in you office, you can set up a Linux server with mt-daap, it uses the DAAP protocol to share music within your network.

As far as I know the music can not be downloaded by the clients, only streamed, if this is not true please let me know.

Be aware that according to Apple the music you buy in iTunes can only be shared with your family.

Install mt-daap in Slackware

I have a printer server in my office and have decided to use it to share my music collection with my colleagues.

The installation in Slackware is really easy, you can find mt-daap in slackbuilds.org (13.37 version).

And then follow the instruction in this post to install from slackbuild. How to install sofware from slackbuilds

Configure mt-daap

The /etc/mt-daap.conf file only needs one change, and that is the folder where you music is.

Look for this section

#
# mp3_dir (required)
#
# Location of the mp3 files to share.  Note that because the
# files are stored in the database by inode, these must be
# in the same physical filesystem.
#

mp3_dir         /var/cache/mp3

And change the path, according to your configuration.

Start the server

Now is time to start enjoying your Music server.

/etc/rc.d/rc.mt-daap start

If it is not executable make it so, with:

chmod 755 /etc/rc.d/rc.mt-daap

You are done, in all iTunes clients on the same network this should be seen.

For Linux clients

For all the fortunate users that are running Linux, can use Amarok or Banshee as DAAP clients.

Here a list of DAAP clients

Dropbox for Debian

2011-07-07T00:00:00-04:00

Introduction

Dropbox is according to Wikipedia:

Dropbox is a Web-based file hosting service operated by Dropbox, Inc. that uses cloud computing to enable users to store and share files and folders with others across the Internet using file synchronization. It was founded in 2007 by Drew Houston and Arash Ferdowsi as a Y Combinator startup.

It is really useful, at it has clients for iPhones, Blackberries, Android and others, as well as Windows and Macs, so Debian is a must.

How to install Dropbox in Debian Linux

Thanks to my friend Raphael Hertzog, we now have Debian dropbox packages.

So, if you need to install it on your Debian, check this page

Burn an ISO image in Mac OS X

2011-07-07T00:00:00-04:00

If you are new to Mac like me, you may find it hard to do a simple task like burning an ISO image.

To do it in a Mac, just follow these steps.

Insert a blank disc.
Start Disk Utility. (Under Applications/Utitilities)

From the File menu, choose Open Disk Image and select the ISO to be burned.
In the list of volumes, you will now see an item representing the ISO file. Select it.
Click the Burn button and follow the instructions.

Install, list, uninstall, delete perl modules with easy

2011-07-06T00:00:00-04:00

Introduction

A Perl module is a discrete component of software for the Perl programming language. Technically, it is a particular set of conventions for using Perl's package mechanism that has become universally adopted.[discuss] A module defines its source code to be in a package (much like a Java package), the Perl mechanism for defining namespaces, e.g. CGI or Net::FTP or XML::Parser; the file structure mirrors the namespace structure (e.g. the source code for Net::FTP is in Net/FTP.pm). Furthermore, a module is the Perl equivalent of the class when object-oriented programming is employed

Now we'll see an easy way to manage them, install, list, delete (uninstall) from the command line.

Perlmod

Perlmod is a program that will help you manage Perl Modules.

You can download it from here

Here you have the INSTALL file that comes with the package.

*******************************************
PERL MODULE MANAGER - perlmod Version 1.2.0 
*******************************************

-------------------
Installation Steps:
-------------------
a) chmod 655 installer

b) ./installer

Note: Always run as a root user


------------------------------------------------
Syntax:
------------------------------------------------
Usage: perlmod [options] [module1] [module2] ...

Options:
-i, install, --install      Install perl modules automatically
-d, delete, --delete        Uninstall perl modules from the system
-f, file, --file        Print all files related to a module
-h, help, --help        Print help about perlmod
-l, list, --list        List all perl modules installed in system
-m, module, --module        List version of module installed in system
-c, cpan, --cpan        Search for a perl module in cpan.org
-s, search, --search        Search for a perl module installed in system
-v, version, --version      Shows perlmod version

Example:
install             => perlmod -i Date::Calc SOAP::Parser Authen::NTLM::HTTP
uninstall           => perlmod -d Date::Calc
module files            => perlmod -f Date::Calc
module details          => perlmod -m Date::Calc
list all modules        => perlmod -l
search in cpan.org      => perlmod -c Date::Calc
search for a module         => perlmod -s Date::Calc
perlmod help            => perlmod -h
perlmod version         => perlmod -v

---------------------------------------------------------------------
For any help about this script, Please contact to sendtogeo@gmail.com

Developed By Geo Varghese (www.seofreetools.net)
---------------------------------------------------------------------

As you can see, it will help you a lot.

How to flush / clear Varnish cache

2011-07-06T00:00:00-04:00

If you are new to Varnish, here is what Wikipedia says about ti:

Varnish is an HTTP accelerator designed for content-heavy dynamic web sites. In contrast to other HTTP accelerators, such as Squid, which began life as a client-side cache, or Apache, which is primarily an origin server, Varnish was designed from the ground up as an HTTP accelerator.

You can also read Varnish Cache homepage, and here is what I've written about varnish.

Well today I want to show you how to purge all the cache without the need to restart the daemon.

varnishadm -T 127.0.0.1:6082 url.purge .

That will flush the cache.

Crossposting from posterous to Drupal and Movable Type

2011-07-06T00:00:00-04:00

I just wanted to test how auto post from Posterous to both Drupal and Movable Type works.

This short post should appear at:

How good or bad crossposting is to SEO? well there is a lot of debate about that out there.

One more thing, I’m using Markdown on this email/post

Arch Linux perl upgrade problems

2011-07-06T00:00:00-04:00

Introduction

Yesterday, while upgrading Perl in Arch Linux to host my Personal Blog, I run into some errors.

While installing I've got this warning.

- The directories /usr/lib/perl5/current, /usr/lib/perl5/site_perl/current,
  /usr/lib/perl5/site_perl/5.10.1, and /usr/share/perl5/site_perl/5.10.1
  have been removed from @INC.
- The script/binary directories are now /usr/bin/*_perl instead of
  /usr/lib/perl5/*_perl/bin which will be eventually removed.

And after the upgrade, no perl script was able to run in my server.

Here some of the error I found in the logs:

[Tue Jul 05 22:50:42 2011] [error] [client 97.107.133.237] Premature end of script headers: mt-check.cgi
[Tue Jul 05 22:57:55 2011] [error] [client 97.107.133.237] /usr/bin/perl: symbol lookup error: /usr/lib/perl5/site_perl/auto/Cwd/Cwd.so: undefined symbol: Perl_Gthr_key_ptr
[Tue Jul 05 22:57:55 2011] [error] [client 97.107.133.237] Premature end of script headers: mt-check.cgi

Solved

I do not know if this is the best solution, and also do not know if it can break something in your system, but it worked with me.

mv /usr/lib/perl5/site_perl /usr/lib/perl5/site_perl.bak

Save laptop battery with Linux and bumblebee (Nvidia Cards)

2011-07-04T00:00:00-04:00

Introduction

We all know that one of the biggest problems with equipments that work with batteries is the need to charge them usually more often that we would like to do it, this applies to smartphones and laptops.

The problem is more or less the same with them both, and it is the display, in the case of laptops the more powerful your graphics card is, the faster you'll need to recharge your laptop's battery.

We also know that we do not need all that power all the time, we may need it if we are using our laptop to play games, but for normal uses, like surfing the web, reading emails or creating a document.

Nvidia has come with a great feature the "Nvidia optimus technology".

Nvidia optimus Technology

Optimus technology is completely automatic allowing you to experience longer battery life and amazing visuals without having to manually change settings. Behind the scenes and with no interference to what you're doing, Optimus seamlessly figures out how to best optimize your notebook computing experience. NVIDIA graphics you've come to expect, with more than 10x better performance¹ with NVIDIA® CUDA™ technology, allowing you to enjoy your applications and games without interruption or worry.

This is not completely true with Linux, where you will need to adjust manually how much power your card will give you, but anyway, it will save battery juice.

Bumblebee

bumblebee is Optimus support for Linux, with real offloading, and not switchable graphics.. More important.. it works on Optimus Laptops without a graphical multiplexer..

You can install it on Ubuntu using this PPA:

ppa:mj-casalogic/bumblebee

You may also read how to install it and configure it at Arch Linux Wiki

And you will find the project at GitHub

Reeder first class news reader, for the iPhone/iPad and the Mac

2011-07-04T00:00:00-04:00

Introduction

What do you do first time in the morning?. Let me guess, no, I'm not going to go into your private life, I mean what do you do first time in the morning technologically speaking.

I think you check your tweeter stream, and check your RSS list to find the news of the day.

Now, If you are using some Apple device, let's say your iPhone, iPod Touch, iPad or your Mac, you might want to know about this.

Reeder

Reeder is not a free app, but it really worth the price, Reeder is a newsreader application available for the iOS and Mac OS platforms.

It syncs with a free Google reader account, and keeps all your reading devices in sync, and if you are not in front of one of your Apple devices, you can always use the Google site to read your news, and everything you may mark read there will appear read-marked in your Reeder app.

In fact, Reeder syncs in two ways, from the cloud to the app and from the app to the cloud.

Reeder has a neat and very intuitive interface, you will easily learn about it, and I'm sure you will love it from the very first day.

Some of the features I love include:

Support for twitter
Support for Instapaper
Support for ReadItLater
Google reader star support

Here you can see and screenshot of it in action.

iPad changed a nine-year old girl life

2011-06-30T00:00:00-04:00

We all remember how just a simple difference in our clothes or look may be such a big problem in school. Kids tend to put aside anyone who is a little bit different from the group.

Now imagine how hard it is for a nine year old girl with albinism to go to school everyday, also imagine how could it be if that little girl also needs the teachers to magnify all text in the photocopy for to be able to read with the rest of the class, just because albinism affected her eyes.

Well that girl is Holly Bligh, from Australia, but one thing changed her life, and gave her some relief, that thing is an iPad.

The Australian Herald Sun says

The iPad has replaced a weighty magnifying glass as Holly's classroom companion, and a simple swipe of her finger now zooms in on text that once had to be enlarged by teachers on the photocopier.

Her mother, Fiona was so impressed about how the iPad helped her daughter, wrote an email to Steve Jobs, and amazingly in just a matter of few hours he respond her back.

In the email Ms. Bligh said

"Holly's enthusiasm to read has grown so much, and it's definitely increased her independence," Ms Bligh said.

"All the other kids think it's awesome that she gets an iPad!"

"Sometimes in the past Holly has found her extra equipment embarrassing ... But the iPad has a coolness factor!"

Mr. Jobs asked her permission to share Holly's story.

"Thanks for sharing your experience with me. Do you mind if I read your email to a group of our top 100 leaders at Apple?"

Another thing I would like to share with you, is a comment in the macrummors blog.

"The iPad is nice but it's just a giant iPod." "Tablets are still toys, you can't do anything serious." "Apple's iPad is too simple. Not enough buttons and flashing lights."

And yet it still manages to change lives. Amazing.

Nice right?