Friday, 4 April 2014

Setting up Environment variables before Apache starts

That was the third time I had to look this up, so I am putting it down for reference.

On Red Hat machines, apachectl sources /etc/sysconfig/httpd, so any variables you set there will be available to the apache runtime environment. Debian based systems use /etc/apache2/envvars for the same purpose.

Thursday, 3 April 2014

Linux (EL6) Required packages for installing the 64 bit Oracle 12c Client

The Oracle documentation has a list of the packages required in order to install the database client software for Enterprise Linux 6.

Since the minimum versions requirements are satisfied on an updated EL6 system, all one has to do is just copy and paste the names into a single yum command in order to complete the step. Did it once this morning and I hope that if I ever have to repeat it, I will just copy and paste the following:

yum -y install binutils compat-libcap1 compat-libstdc++-33.i686 compat-libstdc++-33.x86_64 \
gcc gcc-c++ glibc.i686 glibc.x86_64 glibc-devel.x86_64 glibc-devel.el6.i686 \
ksh libgcc.i686 libgcc.x86_64 \
libstdc++.x86_64 libstdc++.i686 libstdc++-devel.x86_64 libstdc++-devel.i686 \
libaio.x86_64 libaio.i686 libaio-devel.x86_64 libaio-devel.i686 \
libXext.x86_64 libXext.i686 libXtst.x86_64 libXtst.i686 \
libX11.x86_64 libX11.i686 \
libXau.x86_64 libXau.i686 \
libxcb.x86_64 libxcb.i686 \
libXi.x86_64 libXi.i686 \
make sysstat

PS: If not running this as root, remember to prefix this with sudo :)

Thursday, 20 March 2014

CakePHP-2 and AJAX The dependent list boxes problem (remake)


Back in 2010, I had written a post regarding the case of dependent list boxes in a CakePHP view. Back at those days CakePHP was at version 1.2 and support for Javascript and AJAX was very limited. Today I shall revise this using JQuery and JSON encoding which will make things simpler and easier to understand, implement and maintain.

The long story short

Suppose you have a page with two list boxes. One contains a standard set of values while the second one's list of values must be dynamically updated depending on the actual selected value of the first.

In our (sort of) real life example we have a list of commissions (aka production orders) that produce a series of products of varying lengths. The list of lengths for each commission is allowed to produce is available via a detail table and our goal is write an addProduct action and view that allows the user to specify the commission based on which the actual product was produced and the actual length of the product that should be one of the assigned commission lengths. The Product model has a commission_id and an actual_length fields. So each time the commission combo box changes the actual length field input options should also change in order to contain the commissions list of allowed lengths.

Getting Started

To begin with our tutorial make sure that your standard layout references the jQuery library. The easiest was to do this would be to open APP/View/Layout/default.ctp and make sure that a line like

<script src=""></script>

can be found somewhere in your html's head section.

The next thing that needs to be done is to add the RequestHandler component in our AppController. Add or modify your existing source so it looks more or less like this.

class AppController extends Controller {
    public $components = array(


Next we need to inform our routing system that it should also parse json URLs. So the line


should be added to the APP/Config/routes.php file right below the other Router::xxx() commands.

Create the AJAX method and view to return the JSON encoded list of lengths

The next thing to do is create the action that will return the list of lengths to be sent back to the view given commission id. The best place to put it will be the commissions controller. The code for the function looks a lot like the one baked by view. We just need to make sure that the data returned "contain" the correct detail information

    public function getRequestedLengths($id)
        if (!$this->Commission->exists($id)) 
            throw new NotFoundException(__('Invalid record'));
        $options = array(
            'conditions' => array(
                'Commission.' . $this->Commission->primaryKey => $id
            'contain' => array(
        $this->set('commission', $this->Commission->find('first', $options));

The view for the method should be placed in: APP/View/Commissions/json/get_requested_lengths.ctp.

 * Create and echo a json encoded list of the allowed lengths
$output = array();
if (!empty($commission['CommissionProduct']))
    foreach ($commission['CommissionProduct'] as $commissionProduct)
        $output[] = $commissionProduct['actual_length'];

echo json_encode($output);

So now if we point our browser towards http://yourserver/projectPath/Commissions/getRequestedLengths/7.json, we will receive a response with a JSON array containing all allowed lengths for commission id 7. The actual response will be something like ["45900","23400"].

Building the addProduct view

So far we have the mechanism to retrieve the required data. The final step will be to use it in the actual add product view, the PHP part of which should look more or less like this:

<div class="products form">
    <?php echo $this->Form->create('Product'); ?>
            <legend>Add Product</legend>
            <?php echo $this->Form->input('commission_id', array('empty' => __('Please select a commission'))); ?>
            <?php echo $this->Form->input('operator_id'); ?>
            <?php echo $this->Form->input('shift'); ?>
                echo $this->Form->input(
                    'type' => 'select',
                    'options' => $statusList
            <?php echo $this->Form->input('actual_length', array('type' => 'select')); ?>
            <?php echo $this->Form->input('gross_weight'); ?>
    <?php echo $this->Form->end('Save'); ?>

The final part will be the adding of Javascript code to make our form responsive.

<script type="text/javascript">
    var commissionsCombo;
    var allowedLengthsCombo;

    jQuery(function() {
        commissionsCombo = jQuery('#ProductCommissionId');
        allowedLengthsCombo = jQuery('#ProductActualLength');

        commissionsCombo.change( function() {
            var selectedCommission = this.value;  // or $(this).val()
            // build the url that contained the selected commission code
            var ajaxUrl =
                    '<?php echo Router::url(array('controller' => 'Commissions', 'action' => 'getRequestedLengths', 'admin' => FALSE), TRUE)?>'
                    + '/'
                    + selectedCommission
                    + '.json';

            // do a "synchronous" AJAX call
                    async: false,
                    cache: false,
                    url: ajaxUrl,
                    success: function(response) {
                        // remove all options from the allowed metres per bobbin

                        // add all returned values
                        for (var i = 0; i < response.length; i++) {
                            var currentKey = response[i];
                            var currentKeyDescr = response[i] + ' metres';
                            var optionText = '<option value="'
                                    + currentKey
                                    + '">'
                                    + currentKeyDescr
                                    + '</option>';

As a last statement The code for manipulating the select input options comes from the very consise post from

Thursday, 13 March 2014

CentOS 6.5 does not like my handware or their combionation

Spent the whole morning trying to install CentOS 6.5 on a relatively new machine using a Gigabyte GA-B85-HD3 motherboard, with a NVIDIA GeForce GT 620. The message I got was that the hardware (or a combination of what) I 'm using is incompatible with CentOS.

As I had Fedora 20 already running on this very machine, I figured that the problem was related to UEFI and wasted a lot of time trying to the get rid of the EFI partition on the Linux disk. Eventually after updating the BIOS and trying all sorts of magic. I disabled the on board Intel graphics adapter and everything worked like a charm.

Friday, 31 January 2014

CakePHP 2.4: Saving paging data in the session

Quite some time ago I wrote a blog post about saving CakePHP 1.x paging data in the session so that they can be available at next page visit. The basic idea was that you could store the page, sort and direction named parameters in the session and restore them back when no paging parameters were available.

When I tried applying the same technique in CakePHP 2.4, I run into a very serious obstacle and that was the fact that the Paginator::numbers() function does not anymore include the page:1 named parameter when creating the link for the first (or previous) page. This created a phenomenon that when someone visited a page without any paging parameters, it was impossible to know whether they were there because of a link to the first page or as a result of a redirect from somewhere else, in which case the session had to be checked and paging data to be restored.

The thing had been puzzling me for some days now. I tried different remedies without any luck or results until I cried for help at It was there that Ilie Pandia shook things a bit and then I managed, thanks to his advice, to create the following component that mimics the original Cake 1.x PaginationRecallComponent by mattc found in the Bakery, from which I borrowed the name and structure.

App::uses('Component', 'Controller');

 * Pagination Recall CakePHP Component
 * CakePHP 2.x version Copyright (c) 2014 Thanassis Bakalidis
 * @author  thanassis 
 * @version  2.0
 * @license  MIT
class PaginationRecallComponent extends Component {
    const PREV_DATA_KEY = 'Pafinaion-PrevData';

    public $components = array('Session');
    private $_controller = NULL;
    private $_previousUrl;

    public function startup(Controller $controller)
        $this->_controller = $controller;        
        $sessionKey = "Pagination.{$this->_controller->modelClass}.options";

        // extract paging data from the request parameters
        $pagingParams = $this->_extractPagingParams();

        // if paging data exist write them in the session
        if (!empty($pagingParams)) {
            $this->Session->write( $sessionKey, $pagingParams);

        // no paging data.
        // construct the previous URL
        $this->_previousUrl = $this->Session->check(self::PREV_DATA_KEY)
            ? $this->Session->read(self::PREV_DATA_KEY)
            : array(
                'controller' => '',
                'action' => ''
        // and check if the current page is the same as the previous
        if ($this->_previousUrl['controller'] === $this->_controller->name &&
            $this->_previousUrl['action'] === $this->_controller->params['action']) {
            // in this case we have a link from our own paging::numbers() function
            // to move to page 1 of the current page

        // we are comming from a different page so if we have any session data
        if ($this->Session->check($sessionKey))
            // then restore and use them
            $this->_controller->request->params['named'] = array_merge(
    public function shutdown(\Controller $controller)
        // save the current controller and action for the next time
                'controller' => $this->_controller->name,
                'action' => $this->_controller->request->params['action']

    private function _extractPagingParams()
        $pagingParams = $this->_controller->request->params['named'];
        $vars = array('page', 'sort', 'direction');
        $keys = array_keys($pagingParams);
        $count = count($keys);

        for ($i = 0; $i < $count; $i++)
            if (!in_array($keys[$i], $vars))

        return $pagingParams;

Sunday, 12 January 2014

Enable MP3 on Fedora 20

A very short how to enable mp3 playback on your brand new fedora installation.

  1. Enable PRM Fusion repository.
  2. Install the vlc phonon-backend. (Fedora comes with GStreamer).
    . yum install phonon-backend-vlc
  3. Goto system settings → Multimedia → Audio and Video Settings. Select the backend tab. There should be two entries there: GStreamer and VLC. Select the VLC entry and click the Prefer buttom below the list. Finally click Apply. The final result should be something like this:
  4. Log out and back in for the changes to take effect.

After that you can play and kind of context directly from Dolphin, you can install additional music players like amarok, or vlc and enjoy the full music, audio and video experence.

yum install vlc
yum install amarok amarok-doc

Thursday, 7 November 2013

CakePHP New application database config (never forget the enconding)

Today I will put down the way to begin a new web application project using CakePHP.

The first part is database creation. Database charset must be utf-8 and collation: utf8_unicode_ci. The difference between general and unicode collations is explained in an excellent manner in this post on

Next, when you start a new CakePHP project the database config class looks like this

public $default = array(
  'datasource' => 'Database/Mysql',
  'persistent' => false,
  'host' => 'localhost',
  'login' => 'user',
  'password' => 'password',
  'database' => 'test_database_name',
  'prefix' => '',
  // 'encoding' => 'utf8',

My lesson today is: Before changing anything else, uncomment the last line!.

... in case you do not then Unicode (Greek in my case) text will still appear correctly in the web application, but phpMyAdmin and sqldump will display garbage. In addition searches with non-latin text will always fail. To make matters worse when I discovered the case of the problem, I realised that I would have to re-enter all my test data.

Friday, 1 November 2013

SchemaSync: An effective and simple way to synchronize MySQL databases

I have spend the last couple of days trying to find out a solution for migrating changes from a development database to the productive. I was looking for a clean, simple and reliable solution that (ideally) runs on Linux.

My first attempt was to to use the official MySQL mysqldiff command. It turned out that in my case, the only suggestion I got was to recreate indexes and drop primary keys every time there was a record number mismatch between tables. I also run into Windows GUI's with a 30 day evaluation period and a cost ranging from $90-$150.

My lack changes when I run into Schema Sync written in Python by Mitch Matuson. The page has everything you need and the setup (if you already have python) takes less that a minute.

Quoting from the utility's examples page, Sync the production db with the changes from the development db

 schemasync mysql://user:pass@dev-host:3306/dev_db mysql://user:pass@prod-host:3306/production_db

This will give you two files in your home directory, one to do the patching and one to revert back the changes if requested. A excellent piece of work, that I am very happy to use. Thumbs up for mr Matuson.

Saturday, 19 October 2013

Netbeans 7.x and Debian

Switched my laptop from Fedora 19 to Debian 7.1 for some peace, quiet and stability. It appears that the latest transitions to kernel 3.11 and the issues with the nvidia drivers were too much for it. So here I am, enjoying the Debian way of life without yum and gstreamer.

A goodie available only to Debian and Ubuntu users is the Oracle Java PPA available through this link. Andrew at webupd8,org has set up a PPA that downloads and installs the latest Oracle Java packages keeping your computer up to date along with the rest of normal updates.

So now it's Netbeans turn to get installed. I prefer to download the Java SE version and then manually add the PHP and CakePHP plugins that I require for my everyday use.

The first time I tried to install the normal way I ended up with an Exception: java.lang.NoClassDefFoundError thrown from the UncaughtExceptionHandler in thread "main". A little bit of digging revealed that that one way to install netbeans is to use the --silent installer option. The will install netbeans to the default /usr/local/netbeans-7.x location which is perfectly all right. After that you can run it from your desktop Development menu. So to start the installer just become root and type:

root@nb-thanassis:/home/thanassis/Downloads/Netbeans# ./ --silent

in a similar manner, in order to uninstall netbeans from your system, go to the installation directory and type

root@nb-thanassis:/usr/local/netbeans-7.4# ./  --slinent

There is one small thing that I noticed. in order for all this to work you must cd to the same directory as the installer script before issueing any commands. In my case -- hence the blog post -- all other attempts failed.


Monday, 7 October 2013

CakePHP locking tables

Here are my two cents on the issue.

The code below is a function from a behaviour that tries to create an additional unique key on a field named code, by counting the number of records created this year. The important part in the locking procedure is that we must specify the AS clause in the LOCK TABLES statement or otherwise the $model->find() function will not work complaining that the table is locked.

    public function getNextCode(&$model)
        $thisYear = date('Y');
        $dbo = $model->getDataSource();
            sprintf('LOCK TABLES %s AS %s WRITE;',
        $recordsThisYear = $model->find(
                'recursive' => -1,
                'conditions' => array(
                    $model->alias .'.code LIKE' => $thisYear.'%'
        $dbo->execute('UNLOCK TABLES');
        return sprintf('%d-%06d', $thisYear, $recordsThisYear + 1);

The original idea for the post and function cake from a doWeb posting available through here.

Friday, 14 June 2013

Using a raspberrypi as an sftp server

Following a previous post regarding how to use your raspberry-pi device as a file server, we are going to continue amd set up sftp service on the same pi device, so that it may be accessible over WAN.

The complete guide comes from a Mark Van den Borre posting available through this link.In our case however the steps are fewer, since raspberry has already the openssh server set up and running and if you have followed from the previous port we already have a user (bill) and a group (microsoft) to use for sftp service.

To get started let;s give our friend Bill a password:

pi@xena ~ $ sudo passwd bill 
Enter new UNIX password: 
Retype new UNIX password: 
passwd: password updated successfully

Next step will be to prevent Bill from interactively logging in. The usual remedy to this problem to use the sftp server as a login shell. After the post is over bill will not be able to access our pi from ssh either

pi@xena ~ $ sudo chsh bill 
Changing the login shell for bill
Enter the new value, or press ENTER for the default
        Login Shell [/usr/lib/tftp-server]: /usr/lib/sftp-server
pi@xena ~ $ 

Now for the sftp configuration itself. (Copying, pasting and adjusting from Mark's post we have something like this:) Open the default OpenSSH server configuration for editing:

pi@xena ~ $ sudo vi /etc/ssh/sshd_config

: and change the default sftp server from:

Subsystem sftp /usr/lib/openssh/sftp-server


Subsystem sftp internal-sftp

Some users can only use sftp, but not other OpenSSH features like remote login. Let's create a rule for that group of users. Add the following section to the bottom of /etc/ssh/sshd_config:

Match group microsoft
ChrootDirectory /mnt/SFTP-Data
X11Forwarding no
AllowTcpForwarding no
ForceCommand internal-sftp

Thursday, 23 May 2013

CakePHP and AJAX submitting a form with jQuery

A couple of years back I wrote an article about how to handle the dependent drop down lists problem using CakePHP's Ajax facilities. Today i will put down a trivial example of how to submit a CakePHP created form using jQuery as a small reference that can be easily pasted.

Let me remind you of the CakePHP ajax way. You start by creating a controller method that will "return" the ajax content. For our trivial example, the following controller will be more than enough.

class AjaxController extends AppController {
   var $name = 'Ajax';
   var $uses = NULL;

   public function helloAjax()
       // result can be anything coming from $this->data
       $result =  'Hello Dolly!';
       $this->set("result", $result);

The corresponding view file view/ajax/hello_ajax.ctp should contain just the following:

<?php echo $result; ?>

Setting up our Ajax call is now as easy as, creating a link or a button that will invoke the asynchronous call and then setting the id of the field that will receive the result. A typical setup would be that the link looks something like this :

<a href="#" id="performAjaxLink">Do Ajax </a>

And then the target field can be created using:

<?php echo $this->Form->input('your_field', array('id' => 'resultField')); ?>

Finally a little script at the end of the file ...

                    async: true,
                    cache: false,
                    url: '<?php echo Router::Url(array('controller' => 'ajax','admin' => FALSE, 'action' => 'helloAjax'), TRUE); ?>',
                    success: function(response) {
                return false;

The jQuery Ajax API is available here.

Wednesday, 10 April 2013

Using a raspberry-pi as a UPS server with nut

In this post we will try to install the Network UPS tools on a Raspberry-Pi device, attach a USB connected UPS and use it as a UPS server that will allow all machines sharing the same UPS to shut-down correctly when the UPS runs out of power. Our server will look after two clients; one running EL5 and the other openSUSE 11.4.

At the end of the post we will demonstrate how easy it is to set up your clients once the server is up and running and provide additional instructions for setting up the client software on Fedora 18 and EL6.

Update 2014-02-02: Meanwhile things here at the office have changed. The openSUSE machine is now gone and has been replaced by one running Debian 7. I have now revised the client setup guides for Fedora and EL5, 6 and I also have added one for Debian. The openSUSE "howto" is left as is but I can no longer verify if it works or not :) ..

Server Setup

Before we begin I would like to confess that my first attempt to install a no-name made in China UPS resulted to total failure, so eventually I got an expensive APC BackUPS Pro, that worked without any problems from the beginning, so unless your UPS is one supported by the UPS network tools project drivers, don't even try to follow the tutorial.

root@raspbx:~# apt-get install nut-client nut-server
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following extra packages will be installed:
Suggested packages:
  nut-cgi nut-snmp nut-dev nut-xml
The following NEW packages will be installed:
  libupsclient1 nut-client nut-server
0 upgraded, 3 newly installed, 0 to remove and 0 not upgraded.
Need to get 1,583 kB of archives.
After this operation, 3,217 kB of additional disk space will be used.
Do you want to continue [Y/n]? y
Get:1 wheezy/main libupsclient1 armhf 2.6.4-2.3 [106 kB]
Get:2 wheezy/main nut-client armhf 2.6.4-2.3 [191 kB]
Get:3 wheezy/main nut-server armhf 2.6.4-2.3 [1,286 kB]
Fetched 1,583 kB in 2s (562 kB/s)     
debconf: delaying package configuration, since apt-utils is not installed
Selecting previously unselected package libupsclient1.
(Reading database ... 37855 files and directories currently installed.)
Unpacking libupsclient1 (from .../libupsclient1_2.6.4-2.3_armhf.deb) ...
Selecting previously unselected package nut-client.
Unpacking nut-client (from .../nut-client_2.6.4-2.3_armhf.deb) ...
Selecting previously unselected package nut-server.
Unpacking nut-server (from .../nut-server_2.6.4-2.3_armhf.deb) ...
Processing triggers for man-db ...
Setting up libupsclient1 (2.6.4-2.3) ...
Setting up nut-client (2.6.4-2.3) ...
[info] nut-client disabled, please adjust the configuration to your needs.
[info] Then set MODE to a suitable value in /etc/nut/nut.conf to enable it.
Setting up nut-server (2.6.4-2.3) ...
[info] nut-server disabled, please adjust the configuration to your needs.
[info] Then set MODE to a suitable value in /etc/nut/nut.conf to enable it.

Don't worry about the nut-server information we shall deal with it later on. Now an optional step that will allow us to to use the lsusb utility will be to install the usbutils package, assuming that it is not already there. So:

root@raspbx:~# apt-get install usbutils

.. and then -- blame me for my Windows habits, I firmly suggest a reboot. When the system is back on, we will make sure that out USB device is nιcely plugged in...

root@raspbx:~# lsusb
Bus 001 Device 002: ID 0424:9512 Standard Microsystems Corp. 
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp. 
Bus 001 Device 004: ID 051d:0002 American Power Conversion Uninterruptible Power Supply

Our UPS is there so let's set up the driver for the nut server. Open file /etc/nut/ups.conf and append the following lines at the end.

        driver = usbhid-ups
        port = auto
        desc = "APC Back UPS Pro 1200VA supporting the two network servers"

You can name your ups anything you like, as far as the driver is concerned my advice is to browse through the official Network UPS Tools drivers list.

Setting up the UPS name and driver is not enough. I have not tested this on any other Debian box, but on raspberry-pi we need an extra step in order to create the /var/run/nut folder and set correct permissions to it.

root@raspbx:~# mkdir /var/run/nut
root@raspbx:~# chown root.nut /var/run/nut/
root@raspbx:~# chmod 770 /var/run/nut/

Now we are ready to test the UPS driver.

root@raspbx:~# upsdrvctl start
Network UPS Tools - UPS driver controller 2.6.4
Network UPS Tools - Generic HID driver 0.37 (2.6.4)
USB communication driver 0.31
Using subdriver: APC HID 0.95

Our next step will be to configure upsd and upsmon. The network UPS tools design dictates that upsd communicates with the UPS driver that we just started and upsmon communicates with upsd and actually shuts down the machine in the event of a power failure. By providing this extra level of indirection, nut allows for multiple instances of upsmon to run on different machines. That way they can allow share the same physical UPS and this is what we said that we are going to demonstrate in this posting.

So to enable accessing the upsd via the network, edit the file /etc/nut/upsd.conf and place the following LISTEN directives.

LISTEN 3493, is my pi's IP address -- replace that with your own. Next, we will need to add some kind of security and the next file that we will need to tamper with will be the /etc/nut/upsd.users. Edit it with your text editor and set up the following users

        password = myadmpass
        actions = SET
        instcmds = ALL

# --- Configuring for a user who can execute tests only
        password  = pass  
        instcmds  = test.battery.start
        instcmds  = test.battery.stop

# --- Configuring for upsmon
# To add a user for your upsmon, use this example:
        password  = local_pass
        upsmon master
        password  = remote_pass
        upsmon slave

Finally the local UPS monitor daemon will need to specify the UPS to monitor and the user credentials from upsd.users file. Open the /etc/nut/upsmon.conf file, locate the monitor section and add the following line:

MONITOR apc1200@localhost 1 upsmon_local local_pass master 

The number 1 after the ups name and host is the power value. The man page for upsd states clearly that:

The "current overall power value" is the sum of all UPSes that are currently able to supply power to the system hosting upsmon. Any UPS that is either on line or just on battery contributes to this number. If a UPS is critical (on battery and low battery) or has been put into "forced shutdown" mode, it no longer contributes.
A "power value" on a MONITOR line in the config file is the number of power supplies that the UPS runs on the current system.

Final steps: Open the /etc/nut/nut.conf file and change the value of Mode to netserver -- making sure that there are no spaces between each side of the = sign. (See NOTE at end of file) and issue the following commands:

root@raspbx:/etc/nut# service nut-server start
[ ok ] Starting NUT - power devices information server and drivers:  driver(s). upsd.
root@raspbx:/etc/nut# service nut-client start
[ ok ] Starting NUT - power device monitor and shutdown controller: nut-client.

As a last check, verify that both services will start automatically on system (using the update-rc.d command) reboot and yes, our server is ready! ...

root@raspbx:~# ps -ef | grep ups
nut       3275     1  0 Apr09 ?        00:08:24 /lib/nut/usbhid-ups -a apc1200
nut       3278     1  0 Apr09 ?        00:00:19 /sbin/upsd
root      3312     1  0 Apr09 ?        00:00:00 /sbin/upsmon
nut       3314  3312  0 Apr09 ?        00:00:09 /sbin/upsmon
root      4721  4711  0 18:44 pts/1    00:00:00 grep ups


Client setup requires more or less three things: One will be to edit the nut.conf file and set the mode variable value to netclient. Next will be to place the correct MONITOR line in the upsmon.conf file and the third will be to start the upsmon daemon.


Our first client is an openSUSE 11.4 machine that I keep saying that I must upgrade. To install nut on openSUSE we need to issue the following command as root.

zypper install nut

openSUSE nut stores the configuration files /etc/ups. By the way the file /usr/share/doc/packages/nut/README.SUSE offer excellent detailed and precise information on how to do things right. So to get things started:

  • Add the line MODE=netclient at the end of the /etc/ups/nut.conf file
  • Add MONITOR apc1200@asterisk "UPS supporting the main Servers" to /etc/hosts.conf
  • Comment out any reference to any UPS at the end of /etc/ups/ups.conf
  • Add MONITOR apc1200@asterisk 1 upsom_remote remote_pass slave
  • Start the service with etc/init.d/upsd start. (The reload option can be used to reread updated configuration files
  • Finally change the system config so that the service starts every time you start your system using the following command: chkconfig upsd on

Reboot and verify :

atlas:~ # ps -ef | grep ups
root      2958     1  0 18:06 ?        00:00:00 /usr/sbin/cupsd -C /etc/cups/cupsd.conf
root      3374     1  0 18:06 ?        00:00:00 /usr/sbin/upsmon
upsd      3376  3374  0 18:06 ?        00:00:00 /usr/sbin/upsmon
root      4776  4732  0 18:13 pts/0    00:00:00 grep ups

You might probably want to test the configuration and whether the upsmon daemon can shut-down your server, so go ahead and ...

atlas:~ # upsmon -c fsd
Network UPS Tools upsmon 2.6.0
Broadcast Message from upsd@atlas                                              
        (somewhere) at 13:57 ...                                               
Executing automatic power-fail shutdown                                        

Broadcast message from root@atlas (Wed Apr 10 13:57:06 2013):

The system is going down for system halt NOW!


Perhaps the easiest setup is on a Debian system. You only need four steps:

  1. Install just the client:sudo apt-get install nut-client.
  2. Edit the file/etc/nut/nut.conf and set the mode to netclient. MODE=netclient (mind that there must be no spaces around the equals sign).
  3. Add the monitor MONITOR apc900@xena 1 upsom_remote remote_pass slave command in the /etc/nut/upsmon.conf.
  4. Restart the nut-client service
    service nut-client restart
  5. Update the system to start the service automatically update-rc.d nut-client defaults

Fedora and CentOS versions 5 & 6

Fedora also stores the nut related data in /etc/ups. Again here we need to perform the three steps we mentioned before, but this time we will need to start the upsmon daemon by hand. So to set up our fedora box as a network client:

  • Install the software using yum install nut-client
  • Add MONITOR apc1200@asterisk 1 upsom_remote remote_pass slave
  • Add /usr/sbin/upsmon start in /etc/rc.d/rc.local to verify that the monitor program will start again after reboot.
    Note: On my Fedora 20 system the file was not present so I had to create it, turn it into a shell script by adding !/bin/sh at the first line and make it executable.


[thanassis@skymnos ~]$ ps -ef | grep upsmon
root      1898     1  0 17:37 ?        00:00:00 /usr/sbin/upsmon start
nut       1900  1898  0 17:37 ?        00:00:00 /usr/sbin/upsmon start
500       2142  2118  0 17:38 pts/0    00:00:00 grep upsmon

NUT Monitor

A very good GUI based tool to help test the ups servers. It can be easily installed using the package manager of your distribution -- just search for the nut-monitor package and after you install and run it, it looks like this:


Winnut is a Windows client, that runs as a 32bit service on Windows 7. The project has not been updated since February 24, 2011. I did install the software on a Windows machine but have not been able to do any serious testing. The program's configuration follows the same rules as the Linux clients. The only thing you have to is click the edit configuration file button

and then add the correct MONITOR Line in the upsmon.conf file that will appear loaded into notepad. On 64bit systems you will also need to change the line

NOTIFYCMD "\"c:\\Program Files\\WinNUT\\alertPopup.exe\""


NOTIFYCMD "\"c:\\Program Files (x86)\\WinNUT\\alertPopup.exe\""

Thursday, 28 February 2013

NVidia on Centos 6

The post documents the steps I followed in order to install the NVidia drivers using kmod-nvidia and ELPrepo on a fresh CentOS installation.

We begin by importing the ELRepo Project's public key

sudo rpm --import

The people at ELRepo suggest that this should also be present, so unless you already have it ...

sudo yum install yum-fastestmirror

The next step is to install the ELRepo repo itself

sudo rpm -Uvh

... and finally the NVidia drivers, which is what we aimed for in the first place.

sudo yum install kmod-nvidia

An optional step would be to install the 32bit compatibility drivers and files

sudo yum install nvidia-x11-drv-32bit

What else is there... ahh yes, reboot!

Wednesday, 16 January 2013

Fedura 18 update with fedup

After updating two fc17 x86_64 KDE PCs over the network using FedUp, I thought that I would put down my experience and prepare anyone trying to do the same.

To get things started, fedup will probably not exist on your system, so, before starting the actual update process you will probably have to install it using the simple sudo yum install fedup command.

An other thing to mention here is that the current version of google-earth does not install on fedora 18.The actual error message is file /usr/bin from install of google-earth-stable- conflicts with file from package filesystem-3.1-2.fc18.x86_6. So the only way to do a descent update -- at least for the moment, Jan-16-2013 -- is to remove it: (sudo yum erase google-earth-stable) I am certain that the problem will be fixed, but right now we cannot have them both.

For the sake of completion, after installing fedup and removing google-earth, perform a full system update.

sudo yum -y update

After updating and rebooting, start the actual update process with the command:

sudo fedup-cli --network 18 --debuglog fedupdebug.log

This process (depending on your internet speed) will take quite some time. In the case of my desktop development machine, it downloaded 1755 packages plus an additional 728. When it will eventually be over, we will need to reboot and start the system from a specific "System Update (FedUp)" grub menu entry. FedUp will then do it's magic (press the Escape key if you want to see what it;s doing) and then you 'll have to reboot. The tricky part afterwards, is that KDE does not start complaining about various dependencies being let unsatisfied. The solution is start the system in text mode, make sure that you have an active network connection and then run:

yum distro-sync

This will downgrade approximately 90 packages but things will work out. As the fedora wiki advices, try running package-cleanup --orphans to determine packages left over that will receive no further updates and if possible remove them. (speaking of which a package-cleanup --oldkernels wouldn't hurt either...)

Saturday, 15 December 2012

xmllint : Command line XML parser and formatter

So you were given a XML file that came straight out of a windows system with no indentation and incorrect line endings. The simplest way out is xmllint.

The program does much more than formatting its input. Additional functions include: parsing, verifying, dropping empty nodes and many more.

Installing it on CentOS, Fedora and like, is performed via :

sudo yum -y install libxml2

openSUSE users may use yast or type something like:

zypper install libxml2

... while Debian and Ubuntu users will have to go like:

sudo apt-get install libxml2-utils

after you have it on your system, the easy way to fix the badly formated xml file would be :

xmllint --format badlyFormated.xml > wellFormated.xml

Thursday, 13 December 2012

Gnome2 Default Keyring location

Just a quick note for me -- and anyone else out there -- The location of the keyring in gnome2 is in ~/gnome2/keyrings. And if you forget your keyring password then the easy way to start all over with a new keyring is:

rm ~/.gnome2/keyrings/default.keyring 

Thursday, 6 December 2012

Using a raspberrypi as a file server

The idea came to me from a friend. I wanted to install a small network storage system to use merely as a file exchange repository at the office and I was looking to buy some kind of Ethernet disk, when he said to me why don't you do it with a raspberry and a USB flash drive?. The thought was intriguing -- to say the least, so here I am with all the little details:

I am not going to go through the entire process of downloading and preparing the raspberry SD card from the Raspberry Pi Downloads page. The cool thing with raspberry is that once you get it running for the first time, you get a real Debian Linux that does all you expect a descent OS to do.

A pleasant surprise with the raspberry image was that the default set-up registered itself to my dynamic DNS and I was able to log into raspberrypi the moment I plugged it into my LAN without touching a thing.

The first thing that I needed to do was change the hostname of the device. That way there would be no name conflicts when I add a fresh one for the next God knows what project that will come up...

Changing the host name is as simple as editing the file /etc/hostname, changing the single line with the word raspeberrypi to xena (Yes i wanted an ... epic name) and then rebooting. The DNS picked up the name change and logging into xina was as easy as typing ssh -l pi xena -X. (An even easier way to accomplish the task is to use raspi-config. Check the advanced options menu)

Next thing would be a plug the USB disk and make sure it gets mounted every time the system boots. I suppose that the proper way to make this work would be to tamper with /etc/fstab. I chose to do it a bit differently and ended up creating a file containing the last things that the system should do right after booting.

First create a mount point and mount the USB disk. In my case, I created /mnt/SFTP-Data and tested it with a:
mount /dev/sda1 /mnt/STFP-Data

The idea with executing commands right after boot is that we need to create a file, let's call it that contains the above mount command, plua the necessary LSB comments, place it in /etc/init.d, make it executable and then run insserv to add this command as the last default runlevel action. The format of the comments section is :

#! /bin/sh
# Provides:
# Required-Start: $remote_fs $syslog
# Required-Stop: $remote_fs $syslog
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Start up script after boot
# Description: Enable service provided by daemon.
mount /dev/sda1 /mnt/STFP-Data

...and the actual command to make this work is:
sudo insserv /etc/init.d/

Finally, it time to install and configure Samba. The Debian Administrator's handbook says it all. Just remember that raspebrry-pi only has 256MB of actual RAM so keep away from web configuration tools like swat and go with the debconf and manually editing the the smb.conf file option.

After Samba is up and running edit the file /etc/samba/smb.conf and fix the basic staff like work group name and server description. Mine looks like this:

## Browsing/Identification ###

# Change this to the workgroup/NT-domain name your Samba server will part of
   workgroup = aryballos

# server string is the equivalent of the NT Description field
   server string = %h Raspberry-PI Server

# Windows Internet Name Serving Support Section:
# WINS Support - Tells the NMBD component of Samba to enable its WINS Server
  wins support = yes

In order to create a read write share that anyone can use, we need to create a new user that has read/write access to the disk and then force that use and group everytime that someone accesses data through the Samba share.

pi@xena /etc/samba $ groupadd microsoft
pi@xena /etc/samba $ useradd -c "Samba user" -m -d /mnt/mdz-disk/shared/ -g microsoft bill

There are two things here. First Bill does not have a password so he can not log in interactively. Second Bill's home is the directory on the disk where I want everybody to have full read/write access. Telling this to the Samba server requires that the following section be placed at the end of the smb.comf file ...

   comment = Public data in the USB drive for our work-group
   read only = no
   path = /mnt//mnt/STFP-Data/public
   guest ok = yes
   force user = bill
   force group = microsoft

... the directory is made and permissions are set

pi@xena /mnt/SFTP-Data $ sudo mkdir public
pi@xena /mnt/SFTP-Data $ sudo chown public/

... and finally the samba service is restarted...

pi@xena /etc/samba $ sudo service samba restart
[ ok ] Stopping Samba daemons: nmbd smbd.
[ ok ] Starting Samba daemons: nmbd smbd.
pi@xena /etc/samba $ 

Thursday, 18 October 2012

PHP: Workaround for the mailbox is empty imap error

If you are in the process of learning how to use the PHP imap* family of functions in order to manage a remote mailbox, here is a little hint to let you get away with the first annoying error warning you are likely to run into.

So here is how the story goes. You open am empty mailbox. Do something with it and then when you close it you get a PHP warning like :

Notice (8): Unknown: Mailbox is empty (errflg=1) [Unknown, line ??]

I have read many ways for handling this. The bottom line is that this is only a warning and due to the nature of the PHP imap functions, it will eventually be flashed when you call imap_close() or when your script exits. Fortunately each call to imap_errors() flashes the internal error log, so a simple way to avoid the entire hassle would be to code something like ...

    function connect()
        $mailBoxx = @imap_open($this->server, $this->username, $this->password);

        if ($mailBox) {
            // call this to avoid the mailbox is empty error message
            if (imap_num_msg($mailBox) == 0)
                $errors = imap_errors();
            return TRUE;
        // imap_errors() will contain the list of real errors
        return FALSE;

Sunday, 15 April 2012

bash scrupt to copy all songs in an m3u list into a folder

This is not the first time I thought about it and it took a lot of digging and googling in order to get the right command line to do it. So, all credit goes to the who is the initial poster and my only contribution is turning the initial command line into a script.


# ------------------------------------------------------------------------------------
# Copy all files from a playlist to a dest folder
# ------------------------------------------------------------------------------------
if [ "$#" != 2 ]; then
 echo usage $0 playlist.m3u dest-dir
 exit 1

if [ ! -d "$2" ]; then
    mkdir $2
    echo Creating directory `pwd`"/"$2

if [ -z "$1" ]; then
 echo  $1 is not a valid file
 exit 2

cat "$1" | grep -v '#' | while read i; do cp "${i}" "$2" ; echo "${i}"; done

Thank you the thefekete