• Download Flash Video Fragmented (F4F/F4M)

    Today, for network usage optimization purposes, a lot of videos are streamed and sent to the users as fragmented packets instead of one file. According to Adobe, F4F file is Flash MP4 Video Fragment created and used by Adobe Media Server for HTTP Dynamic streaming like CloudFront, Akamai, … If you want to download this video, you will have to download the script file KSV (download this script on Github) and execute it on a system with php enabled (install PHP on Windows).

    Once you’re on the page where video is loading, you have to look for manifest file in source code or network exchanges. This file has F4M extension, correspondig to manifest, which is the file containing the inventory of all the video fragments. It will be necessary for the script execution.

    Here is an example of how the command-line should look like (you can modify the quality parameter, and you have to specify the path for manifest file, and output file):

    php ksv.php --quality high --delete --manifest 'LINK_TO_MANIFEST.f4m' --outfile 'OUTPUT_FILE.flv'

    Here are the different options you can use to customize command-line:

     --help              displays this help
     --debug             show debug output
     --delete            delete fragments after processing
     --fproxy            force proxy for downloading of fragments
     --play              dump stream to stdout for piping to media player
     --rename            rename fragments sequentially before processing
     --update            update the script to current git version
     --auth      [param] authentication string for fragment requests
     --duration  [param] stop recording after specified number of seconds
     --filesize  [param] split output file in chunks of specified size (MB)
     --fragments [param] base filename for fragments
     --fixwindow [param] timestamp gap between frames to consider as timeshift
     --manifest  [param] manifest file for downloading of fragments
     --maxspeed  [param] maximum bandwidth consumption (KB) for fragment downloading
     --outdir    [param] destination folder for output file
     --outfile   [param] filename to use for output file
     --parallel  [param] number of fragments to download simultaneously
     --proxy     [param] proxy for downloading of manifest
     --quality   [param] selected quality level (low|medium|high) or exact bitrate
     --referrer  [param] Referer to use for emulation of browser requests
     --start     [param] start from specified fragment
     --useragent [param] User-Agent to use for emulation of browser requests

    All the original sources are available on GitHub : https://github.com/K-S-V/

  • Install VMware Tools on ESXi for Ubuntu Guest

    If you want to install VMware Tools on ESXi for an Ubuntu Guest, there is two possibilities:

    1. Use the package provided on distribution (but can be not up-to-date and so not approved)
    2. Install directly from official sources provided in vSphere Client (will be automatically recognized)

    Use the pre-package distribution

    This solution is the easiest way to install tools. You just have to use apt on your guest to install it:

    sudo apt-get install open-vm-tools

    Use the official sources available in vSphere Client

    This solution is not as simple as the previous one but is really sure and well-guided.

    1. Connect to your ESXi server using vSphere Client
    2. At this moment, ensure that you have a CDROM hardware available for your VM Guest (in Settings)
    3. Start your VM Guest running Ubuntu
    4. Check that you have already needed packages installed (most of time, they are not installed with a standard configuration):
      • gcc
      • build-essential
      • binutils

      You can use this command line to install them:

      sudo apt-get install gcc build-essential binutils
    5. You can now connect VMware Tools on your VM Guest using vSphere Client:
      • Right-click on your VM name
      • Select “Guest” > “Install/Upgrade VMware Tools”
      • Wait a few seconds

      This action will automatically (and transparently) mount the VMwre Tools CD into your VM Guest Ubuntu.

    6. Open a console on your VM Guest to mount the CDROM you just connected:
      sudo mount /dev/cdrom /mnt
    7. Copy the VMwareTools-x.x.x-xxxxxxx.tar.gz file from the CDROM to a local folder (‘x’ values depend on version used):
      cp /mnt/VMwareTools-9.0.5-1065307.tar.gz /tmp/
    8. Unzip the VMware tools package you just copied:
      cd /tmp/
      tar xzvf VMwareTools-9.0.5-1065307.tar.gz
    9. Go to the new folder created while unzipping file and run the installer script (perl script):
      cd /tmp/vmware-tools-distrib
      sudo ./vmware-install.pl
    10. From now, just follow the instructions displayed on the screen to install VMware tools.

    Once all of this is done, you will see on vSphere, in VM details, that the vMware Tools are correctly installed.

  • Unserialize web2py requests and allow concurrent access

    With a default configuration for your web2py application, you will notice that when you are launching an action, if this one is quite long to execute, you won’t be able to open a new tab to run another request on the same application. This can be explained because when you are launching an action, your browser is sending session informations to the server and your session file on server-side is so opened in writing mode for being updated. A lock is set on this file, blocking any other action to be executed for this session while the lock is not released.

    This problem is effectively not existing if you are using a database for your session management instead of a file system. To use a database system, you just need to declare your database:

    db = DAL(...)

    and initiate the connection to this database for sessions:

    session.connect(request, response, db)

    A table will so be automatically created, named web2py_session_appname and will contain following fields:

    Field('locked', 'boolean', default=False),
    Field('created_datetime', 'datetime', default=now),
    Field('modified_datetime', 'datetime'),
    Field('session_data', 'text')

    If you want to use the file system for your sessions, you will need to use the following command to allow the session file release:


    You will notice that this command must only be called if the action you want to execute do not require to session informations. For example, if you are loading dynamically some contents via Ajax calls on several parts of the page, you can add this command for each call to allow the concurrential execution knowing that the connection informations are saved while main page is loading.

    As testing, you can use following code:

    import time
    def session_lock():
        start = time.time()
        stop = time.time() - start
        return "Generated on %s - Took %s sec" % (request.now, int(stop))
    def session_lockall():
        a = LOAD('test', 'session_lock', ajax=True)
        b = LOAD('test', 'session_lock', ajax=True)
        c = LOAD('test', 'session_lock', ajax=True)
        d = LOAD('test', 'session_lock', ajax=True)
        e = LOAD('test', 'session_lock', ajax=True)
        f = LOAD('test', 'session_lock', ajax=True)
        g = LOAD('test', 'session_lock', ajax=True)
        h = LOAD('test', 'session_lock', ajax=True)
        return locals()

    If you’re calling previous code by deleting the session.forget() command call, you will get this as a result:

    a : Generated on 2014-03-14 20:35:25.830665 - Took 3 sec
    b : Generated on 2014-03-14 20:35:28.446957 - Took 3 sec
    c : Generated on 2014-03-14 20:35:31.433133 - Took 3 sec
    d : Generated on 2014-03-14 20:35:34.435814 - Took 3 sec
    e : Generated on 2014-03-14 20:35:37.438998 - Took 3 sec
    f : Generated on 2014-03-14 20:35:40.442821 - Took 3 sec
    g : Generated on 2014-03-14 20:35:43.446179 - Took 3 sec
    h : Generated on 2014-03-14 20:35:46.872932 - Took 3 sec

    If you’re calling the same code with the session.forget() command call, you will get:

    a : Generated on 2014-03-14 20:41:57.796238 - Took 3 sec
    b : Generated on 2014-03-14 20:41:57.798177 - Took 3 sec
    c : Generated on 2014-03-14 20:41:57.841212 - Took 3 sec
    d : Generated on 2014-03-14 20:41:57.835651 - Took 3 sec
    e : Generated on 2014-03-14 20:41:57.839484 - Took 3 sec
    f : Generated on 2014-03-14 20:41:57.837849 - Took 3 sec
    g : Generated on 2014-03-14 20:42:00.850737 - Took 3 sec
    h : Generated on 2014-03-14 20:42:00.878716 - Took 3 sec

    We can notice that between both cases, we have a concurrential execution thanks to the session.forget() function, and that we can hardly optimize the page loading time.

    Please note that most of browsers won’t allow you to execute more than 6 requests at the same time, hence the result we are getting with the last test where we can see that the six first requests are executed together whereas the following ones are executed afterwards (on a second flow but concurrent also).

  • Handling HTTP errors with Apache and Tomcat using mod_jk

    When you are working with web server in frontend (Apache in this example) and backend application servers (Tomcat here), you may wish to customize your error pages depending on the HTTP error code returned (either from the web server or application server).


    For the following example, you will need as pre-requisites at least those versions:

    • Web Server Apache >= 2.2.x
    • Mod JK >= 1.2.27 (rule extensions are not available in earlier versions)

    Apache configuration

    If you want to handle any error coming from your web server or from your application servers, you will need to perform some changes in your configuration to allow the handling. First of all you will need to set up some parameters in your Apache configuration file (in apache2.conf file directly or in your VirtualHost definitions).

    In my example, I am handling any HTTP error code between:

    • HTTP 400 and HTTP 405
    • HTTP 500 and 504

    I am using an only file (written in PHP) allowing me to send back a simple HTML page to the user depending on the HTTP error code received.

    Here is what I’ve configured in my apache2.conf file for handling any error listed above:

    ErrorDocument 400 /errorhandler.php?error=400
    ErrorDocument 401 /errorhandler.php?error=401
    ErrorDocument 402 /errorhandler.php?error=402
    ErrorDocument 403 /errorhandler.php?error=403
    ErrorDocument 404 /errorhandler.php?error=404
    ErrorDocument 405 /errorhandler.php?error=405
    ErrorDocument 500 /errorhandler.php?error=500
    ErrorDocument 501 /errorhandler.php?error=501
    ErrorDocument 502 /errorhandler.php?error=502
    ErrorDocument 503 /errorhandler.php?error=503
    ErrorDocument 504 /errorhandler.php?error=504

    The errorhandler.php file could be like that (feel free to customize it as you want with a beautiful CSS theme, for the example I’ve used a basic configuration ;)):

    The HTTP request could not be understood by the server due to malformed syntax.
    The web browser may be too recent, or the HTTP server may be too old.";
                    $errorcode = "Error 401";
                    $errormessage = "The request requires user authentication.
    This means that all or a part of the requested server is protected by a password that should be given to the server to allow access to its contents.";
                    $errorcode = "Error 402";
                    $errormessage = "Payment Required
                    $errorcode = "Error 403";
                    $errormessage = "The HTTP server understood the request, but is refusing to fulfill it.
    This status code is commonly used when the server does not wish to reveal exactly why the request has been refused, or when no other response is applicable (for example the server is an Intranet and only the LAN machines are authorized to connect).";
                    $errorcode = "Error 404";
                    $errormessage = "The server has not found anything matching the requested address (URI) ( not found ).
    This means the URL you have typed or cliked on is wrong or obsolete and does not match any document existing on the server (you may try to gradualy remove the URL components from the right to the left to eventualy retrieve an existing path).";
                    $errorcode = "Error 405";
                    $errormessage = "This code is given with the Allow header and indicates that the method used by the client is not supported for this URI.
                    $errorcode = "Error 500";
                    $errormessage = "The HTTP server encountered an unexpected condition which prevented it from fulfilling the request.
    For example this error can be caused by a serveur misconfiguration, or a resource exhausted or denied to the server on the host machine.";
                    $errorcode = "Error 501";
                    $errormessage = "The HTTP server does not support the functionality required to fulfill the request.
    This is the appropriate response when the server does not recognize the request method and is not capable of supporting it for any resource (either the web browser is too recent, or the HTTP server is too old).";
                    $errorcode = "Error 502";
                    $errormessage = "The gateway server returned an invalid response.
    The HTTP server, while acting as a gateway or proxy, received an invalid response from the upstream server it accessed in attempting to fulfill the request.";
                    $errorcode = "Error 503";
                    $errormessage = "The HTTP server is currently unable to handle the request due to a temporary overloading or maintenance of the server.
    The implication is that this is a temporary condition which will be alleviated after some delay.";
                    $errorcode = "Error 504";
                    $errormessage = "This response is like 408 (Request Time-out) except that a gateway or proxy has timed out.
    else {
            $errorcode = "Error";
            $errormessage = "An error has occured while trying to contact the website. Please contact support.";


    mod_jk configuration

    Once you’re done with the main configuration of Apache, you will have to specify to Apache that you want to handle any HTTP error coming from the application servers. For that, you will have to use the rule extension use_server_errors when mounting an access point to a worker through mod_jk.

    By default, for a mounting point you are using:

    JkMount /myapp/* worker1

    But if you want to handle any HTTP 40x error coming from this worker, you will have to add the use_server_errors extension to your mounting point:

    # Use web server error page for any error
    JkMount /myapp/* worker1;use_server_errors=400

    To handle any HTTP 50x error:

    # Use web server error page only for technical errors
    JkMount /myapp/* worker1;use_server_errors=500

    Or another option to handle both errors using just one command:

    JkMount /myapp/* worker1;use_server_errors=400,500

    You are now handling any error received from your application server with your web server allowing you to customize it as you want.

    Feel free to read more about this rule extension on the official website.

  • How to compile and install its own Linux kernel

    The Linux Kernel is the operating system kernel. It is the core of the system and provide an interface between the hardware and the software layers.

    Most of Linux distributions are coming with a pre-compiled and ready-to-use kernel for most of standard usage. However, some functionalities are sometimes missing in the kernel to allow the execution of specific functions or the support of some hardware (cards, …). In these cases, you will need to use the source code of the needed kernel, recompile it and reinstall it to replace the existing one. All the official soruces of the different kernels are available for free on the website kernel.org.

    I will show you here how to modify the source code, compile and install your own kernel for your system (command-lines provided are working under Debian/Ubuntu based system, you will probably need to adapt them depending on the system you are running).


    In a first time, check that you got the different packages necessary for the operation:

    sudo apt-get install build-essential make libncurses5-dev lzma initramfs-tools bc

    Once these packages are correctly installed, you can go on the official website to retrieve the source and the configuration files for the kernel you want to use: http://www.kernel.org. In our example, we will use the kernel on version 3.13.5 (latest stable version available today).

    Let’s move to the /usr/src directory and then download the kernel archive that we will uncompress immediately:

    cd /usr/src/
    sudo wget https://www.kernel.org/pub/linux/kernel/v3.x/linux-3.13.5.tar.gz
    sudo tar xzvf linux-3.13.5.tar.gz

    Kernel sources are now uncompressed in the /usr/src/linux-3.13.5 folder and we can go ahead with its configuration.


    Let’s move in the directory you just created and start with the use of command make menuconfig to launch the configuration tool:

    cd linux-3.13.5
    sudo make menuconfig

    At this time, you can activate any feature you want on the kernel. For example:

    • To activate the virtualization and its specific functions, move on Virtualization and then press the Space bar to get access to the different available functionalitiesuis  (that you can activate/deactivate as you want)
    • To activate the modules support, move on Enable loadable module support and choose the modules you want to enable by pressing the Space bar (activated items will be checked)


    Once you’re done with this configuration, choose Exit and confirm the save of your configuration. This one will be saved in the current directory under the .config file (that you can manually edit with a simple text editor if necessary).


    Now that the kernel is configured, you will have to compile it so that it can be used on your system. For that, you will need to execute several commands for the different compilation steps:

    • Dependencies compilation (now useless with latest versions)
      sudo make dep
    • Kernel image compilation
      sudo make bzImage
    • Modules compilation
      sudo make modules
    • Modules installation
      sudo make modules_install

    At this time, your kernel has been compiled and is ready to be set up on your system.


    To install your own kernel, you just need to execute the command-line below:

    sudo make install

    This command will create the following files in the /boot start directory:

    • vmlinuz-3.13.5 : the current kernel
    • config-3.13.5 : the kernel configuration file
    • System.map-3.13.5 : the symbol table exported by the kernel
    • initrd.img-3.13.5 : the root file used temporarily during the boot process

    This command should update automatically the Grub configuration file (grub.cfg). You won’t need to perform the update manually.

    If it’s not done automatically, you can execute it manually with the command-line below:

    sudo update-grub2


    In order to check that your kernel has correctly been loaded and is used, you need to reboot your system. Once restarted, you can check which kernel is used with the uname command:

    sudo reboot
    uname -r
    > 3.13.5

    You are now using your own kernel with the functionalities you wanted.