Articles in the Uncategorized category

  1. Finding a Good Blu-Ray Player for Mac OS X

    Sun 22 September 2013

    I find playing a Blu-ray movie on my Mac cumbersome. I've been using Plex, XBMC and VLC but these free open-source products are all a usability nightmare.

    To play a Blu-ray movie, you have to perform these steps:

    1. right-click on the BDMV file
    2. choose 'show packet contents'
    3. go to the STREAM folder
    4. sort the files by size (from large to small)
    5. select the biggest m2ts file and open it in the appropriate player

    I got so fed-up with this process that I started searching for any product that just allows me to point it to a folder with Blu-ray content and friggin' play it. Fortunately, there is such a product for Mac OS X, it's called Mac Blu-ray Player and it's a paid application. I paid 36 euro (48 dollar) including taxes.

    Those 36 euros are well spend. No it is not free, no it is not open-source, but I don't care. It is a good product. If you value your time I highly recommend buying this software.

    I don't have anything against free or open-source software, but I do have a grudge against software that is not user-friendly. If software is not easy to use, something you would expect from a media player, it's broken.

    Fortunately, you don't have to trust me on my word, you can download a free trial that seems fully functional, it only shows a trial message when playing a movie.

    Tagged as : blu-ray Mac OS X
  2. Setting Up a Jabber Instant Messaging Server |_Http-Title: Site Doesn't Have a Title (Text/html; Charset=utf-8).

    Sat 05 February 2011

    I wanted to see how dificult it is to setup an instant messaging server based on open source software. Now I know that it is very easy, unless you are stubborn and do things your own way. In this example, I'm setting up a small IM server that is only for internal company use, but there is no difference if you want to expose the server to the internet.

    First a bit background information. There is an open IETF standard for instant messaging called "XMPP" which stands for "Extensible Messaging and Presence Protocol". This protocol originated as part of the open source Jabber IM server software.

    Setting up ejabberd

    I decided to use ejabberd which is part of the Debian software archive. It is written in Erlang, but I can live with that. This blog posts documents how to setup the IM server with two accounts that can chat with each other. The configuration I use also enforces the use of SSL/TLS so authentication and all messages are encrypted.

    Steps to get things running:

    • apt-get update
    • apt-get install ejabberd
    • cd /etc/ejabberd
    • edit ejabberd.cfg

    Change the following line to your needs:

    %% Hostname
    {hosts, ["localhost", "jabber.domain.local"]}.

    Also enforce the use of encryption like this:

    starttls, {certfile, "/etc/ejabberd/ejabberd.pem"}

    Must be changed to:

    starttls_required, {certfile, "/etc/ejabberd/server.pem"}

    Generating a custom SSL certificate

    Security wise, it is very wrong to use the default SSL certificate as provided by the installation package for the server certificate. Anyone with access to this key material can decrypt encrypted communication. So you must generate your own server certificate. This is also required because IM clients may verifiy the certificate against the domain name used within the certificate. If there is no match, it will not work or it will at least complain.

    openssl req -new -x509 -newkey rsa:2048 -days 365 -keyout privkey.pem \ 
    -out server.pem

    So this creates a public key (server.pem) and a private key (privkey.pem) which are valid for a year. Feel free to make the certificate valid for a longer period, this is an example. You will have to fill in some stuff, the most important part is this part:

    Common Name (eg, YOUR name) []:jabber.domain.local

    You are forced to set a password on the private key, but we want to remove this because otherwise the ejabberd service will not start automatically.

    openssl rsa -in privkey.pem -out privkey.pem

    Just enter the password you entered earlier and you're done. We now have separate files for the public and private key, but ejabberd expects them in one single file.

    cat privkey.pem >> server.pem
    rm privkey.pem

    Set proper file system permissions:

    chown ejabberd server.pem
    chmod 600 server.pem

    Now we are done. Restart ejabberd to use the new settings.

    /etc/init.d/ejabberd restart

    Security caveats

    Please note that the ejabberd daemon provides a small build-in web interface for administration purposes on TCP port 5280. By default it is not protected by SSL or TLS and cannot be used unless you add users to this part of the confiuration file:

    {acl, admin, {user, "", "localhost"}}.


    {acl, admin, {user, "admin", "localhost"}}.

    The user must also be registered as a normal IM user as described in the next section.

    Warning: it seems to me that this interface is not very secure, for example, there is no logout button.

    Furthermore, you might consider disabling the following section:


    This prevents your IM server from communicating with other IM servers source. But we are not finished. When you install ejabberd, some other services are also started on the system. It is thus very important that you configure your firewall to block these ports. This small nmap port scan output shows some interesting services:

    4369/tcp  open  epmd?
    5222/tcp  open  jabber  ejabberd (Protocol 1.0)
    5269/tcp  open  jabber  ejabberd
    5280/tcp  open  http    ejabberd http admin
    |_http-methods: No Allow or Public header in OPTIONS response (status code 400)
    36784/tcp open  unknown

    Port 4369, 36784 and 5280 should be blocked by your firewall and not accessible from the internet.

    Adding users

    It is now time to create some IM users. A user account always looks like an email addres, for example:


    To add accounts, use the ejabberdctl utiliy:

    ejabberdctl register peter jabber.domain.local <password>

    Please note that passwords that are entered on the command line end up in your bash_history file, so beware. Also, users running ps aux may be able to see the command for a brief moment. So be carefull.

    By registering two account, you can test your new server.

    Additional resources

    Nice to know: the domain names used for your accounts can differ from the domain used for the IM server.

    If you have a Windows Active Directory domain, you could consider authenticating your users against LDAP.

    Other resources: - tutorial 1 - tutorial 2

  3. 'Linux: Using Disk Labels to Counter Storage Device Name Changes'

    Mon 22 November 2010

    My router decided to change the device name for some USB storage devices. So /dev/sdc was swapped for /dev/sdd and vice versa. The result was some file system corruption on /dev/sdc, because it was used on a remote system through iSCSI, using a different file system from /dev/sdd.

    With regular internal disks, attached with PATA, SATA or SAS, the chances are very small that such an event will occur, but it is possible, especially if you start adding/subtracting disks. With USB devices the risk is substantially bigger.

    To prevent your system from mixing up drives because there device names change, use file system labels. All information that follows have been stolen from this location. Since this blog is also my personal notepad, the relevant bits are reproduced here.

    There are three steps involved, the third being optional:

    1. add a label to the file system
    2. add the label to /etc/fstab
    3. update grub boot manager (optional)

    Add a label to the file system

    Setting a label when the file system is created:

    mkfs.ext3 -L ROOT /dev/sda1
    mkfs.xfs -L BIGRAID /dev/sde

    Set label for existing file system


    e2label /dev/sda1 PRIMARY_ROOT
    e2label /dev/sda1


    xfs_admin -L DATA1 /dev/sdf
    xfs_admin /dev/sdf

    Set label for swap partition

    mkswap -L SWAP0 /dev/sdb5

    add the label to fstab

    Example of contents of fstab:

    LABEL=ROOT          /         ext3    defaults        1 1
    LABEL=BOOT          /boot     ext3    defaults        1 2
    LABEL=SWAP          swap      swap    defaults        0 0
    LABEL=HOME          /home     ext3    nosuid,auto     1 2

    Update the grub boot manager

    title server
    root (hd0,0)
      kernel (hd0,0)/vmlinuz ro root=LABEL=SERVER_ROOT0 rhgb quiet
      initrd (hd0,0)/initrd.img
    Tagged as : Uncategorized

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