How to Install FFmpeg in Linux

                    FFmpeg is a very fast video and audio converter. It can also grab from a live audio/video source. FFmpeg is so important if you are planning to run a video website with streaming with conversion of video files to different video formats. This blog is intended for Centos/Redhat versions of Linux where any novice user can install ffmpeg without compiling the source which is a more traditional way of installing the FFmpeg software on linux servers. In this blog i will show you the easy way to install ffmpeg and ffmpeg-php (php extension) with just yum rather than compiling ffmpeg from source files.

Installation

First you need to add a file in yum repository directory for dag packages installation. For this edit the following file: 

Vi /etc/yum.repos.d/dag.repo 

add the following contents to the file, 

[dag] 
name=Dag RPM Repository for Red Hat Enterprise Linux 
baseurl=http://apt.sw.be/redhat/el$releasever/en/$basearch/dag 
gpgcheck=0 
enabled=1 

Then enter the command, 

yum install ffmpeg ffmpeg-devel 

To check what audi/video formats are supported 

ffmpeg -formats > ffmpeg-format.txt 

Open the ffmpeg-formats.txt to see the ooutput 

D means decode 
E means encode 
V means video 
A means audio 
T = Truncated

Installation of FFMPEG-PHP Extension

  FFmpeg-php is a very good extension and wrapper for PHP which can pull useful information about video through API interface. Inorder to install it you will need to download the source file and then compile and install extension in your server. 

For downloading the source tarball click here

or 

wget http://sourceforge.net/project/downloading.php?group_id=122353&filename=ffmpeg-php-0.6.0.tbz2&a=55737530 

Extract the souce tarball.

tar -xjf ffmpeg-php-0.6.0.tbz2 

cd ffmpeg-php-0.6.0/

 phpize 

./configure 

make 

make install

Editing PHP.INI

 Once you have done that without any problems then you will see the php extension file /usr/local/lib/php/extensions/no-debug-non-zts-20060613/ffmpeg.so and you will need mention that extension in php.ini file 

vi /usr/local/lib/php.ini 

Put the below two lines at the end of the php.ini file 

[ffmpeg] 
extension=ffmpeg.so 

Then restart the server
 
service httpd restart 

To check whether ffmpeg enabled with php, point your browser to test.php file. It should show the confirmation of installed ffmpeg php extension 

// #test.php

phpinfo();

?>

              

If any case the ffmpeg does not show in the phpinfo() test make sure that php.ini path to ffmpeg.so is correct. Still the problem occures, the reason could be you might be using older version of ffmpeg-php which is buggy. just download the latest version of ffmpeg-php sourse then complile it.

Common Errors

1. If you get command not found error for phpize, then you will need to do yum install php-devel

2. If you get error like "ffmpeg headers not found" while configuring the source.

configure: error: ffmpeg headers not found. Make sure ffmpeg is compiled as shared libraries using the --enable-shared option

then it means you have not installed ffmpeg-devel packages.

To Fix: Just install ffmpeg-devel using

yum install ffmpeg-devel

3. If you get an error like shared libraries not found problem and the program halts in the middle, then you must specify the ffmpeg installed path explicitly to the ./configure.

configure: error: ffmpeg shared libraries not found. Make sure ffmpeg is compiled as shared libraries using the --enable-shared option

To Fix:

1. First find out the ffmpeg path with ffmpeg --help command. The prefix default path should be like /usr/local/cpffmpeg
2. Configure the FFmpeg-php with --with-ffmpeg option

./configure --with-ffmpeg=/usr/local/cpffmpeg

That should resolve the problem!

Troubleshooting Nagios

There may be a number of potential problems while configuring Nagios. If you see an error like this,

1)Connection refused by host:

You get the above error, If you don't put the correct IP address in the nrpe.cfg file on the client, or if you do it correctly but forgot to restart NRPE on the client.

2) NRPE: Command 'check_users' not defined

Indicates that you didn't define the commands you wanted, again on the client, or you didn't restart NRPE on the client after you defined them.

3)NRPE: Unable to read output

Usually means that the path to the plugin to run is incorrect on the client. If you change it, remember to restart NRPE again.

4)The check_nrpe plugin returns "CHECK_NRPE: Socket timeout after 10 seconds" or"Connection refused or timed out"

This error can indicate several things:

The command that the NRPE daemon was asked to run took longer than 10 seconds to execute. This is the most likely cause if the error message was "CHECK_NRPE: Socket timeout after 10 seconds". Use the -t command line option to specify a longer timeout for the check_nrpe plugin. The following example will increase the timeout to 30 seconds:

/usr/local/nagios/check_nrpe -H localhost -c somecommand -t 30

The NRPE daemon is not installed or running on the remote host. Verify that the NRPE daemon is running as standalone daemon or under inetd/xinetd with one of the following commands:

ps axuw | grep nrpe
netstat -at | grep nrpe

There is a firewall that is blocking the communication between the monitoring host (which runs the check_nrpe plugin) and the remote host (which runs the NRPE daemon). Verify that the firewall rules (e.g. iptables) that are running on the remote host allow for communication and make sure there isn't a physical firewall that is located between the monitoring host and the remote host.

5)The check_nrpe plugin returns "CHECK_NRPE: Received 0 bytes from daemon. Check the remote server logs for an error message."

First thing you should do is check the remote server logs for an error message. Seriously. :-) This error could be due to the following problem:

The check_nrpe plugin was unable to complete an SSL handshake with the NRPE daemon. An error message in the logs should indicate whether or not this was the case. Check the versions of OpenSSL that are installed on the monitoring host and remote host. If you're running a commercial version of SSL on the remote host, there might be some compatibility problems.

6)The check_nrpe plugin returns "NRPE: Command 'x' not defined"

This error means that you didn't define command x in the NRPE configuration fileon the remote host. On the remote host, add the command definition for x. See the existing command definitions in the NRPE configuration file for more information on doing this. If you're running the NRPE daemon as a standalone daemon (and not under inetd or xinetd), you'll need to restart it in order for the new command to be recognized.

7)The check_nrpe plugin returns "NRPE: Command timed out after x seconds"

This error indicates that the command that was run by the NRPE daemon did not finish executing within the specified time. You can increase the timeout for commands by editing the NRPE configuration file and changing the value of the command_timeout variable. If you're running the NRPE daemon as a standalone daemon (and not under inetd or xinetd), you'll need to restart it in order for the new timeout to be recognized.

Adding more services to the Nagios

Monitoring Host Configuration:

Define the remote host name in client.cfg
Edit /usr/local/nagios/etc/objects/remotehost.cfg and append the following lines:

define host{
use linux-box
host_name remote_host
address ipaddress of remote_host
check_command check-host-alive
contacts nagios admin,cliectcontact
}
Next define contact name and contact goup name inn same file

define contact{
contact_name clientcontact
host_name remote_host
use generic-contact
alias Nagios client
email remotehost@gmail.com
}
define contactgroup{
contactgroup_name groupname
host_name remote_host
alias Nagios group
members clientcontact,membersof remote_host
}

Next add more services to monitor remote host,for this:

define service{
use generic-service
host_name remote_host
service_description CPU Load
check_command check_nrpe!check_load
}
define service{
use generic-service
host_name remote_host
service_description HyperVM
check_command check_nrpe!check_http
}
define service{
use generic-service
host_name remote_host
service_description Procs
check_command check_nrpe!check_procs
}
define service{
use generic-service
host_name remote_host
service_description Zombie Processes
check_command check_nrpe!check_zombie_procs
}
define service{
use generic-service
host_name remote_host
service_description / Partition
check_command check_nrpe!check_disk1
}
define service{
use generic-service
host_name remote_host
service_description /storage partition
check_command check_nrpe!check_disk2
}
define service{
use generic-service
host_name remote_host
service_description Current Users
check_command check_nrpe!check_users
}

define service{
use generic-service
host_name remote_host_name
service_description controlpanel check
check_command check_tcp!-H $HOSTADDRESS$ -p 2082
}
define service{
use generic-service
host_name remote_host
service_description ssl
check_command check_nrpe!check_ssl
}

Restart nagios daemon

/etc/init.d/nagios restart

Remote Host Configuration:

Edit the nrpe configuration file and add the folowing lines:

vi /etc/nrpe.conf

command[check_pop]=/usr/local/nagios/libexec/check_pop -p 110 -4 -w 10 -c 20
command[check_imap]=/usr/local/nagios/libexec/check_imap -p 143 -4 -w 10 -c 20
command[check_smtp]=/usr/local/nagios/libexec/check_smtp -p 25 -4 -w 10 -c 20
command[check_http]=/usr/local/nagios/libexec/check_http -H 127.0.0.1 -w 5 -c 10
command[check_mysql]=/usr/local/nagios/libexec/check_tcp -p 3306 -w 10 -c 20
command[check_dns]=/usr/local/nagios/libexec/check_dns -H www.eglueweb.com
command[check_ftp]=/usr/local/nagios/libexec/check_ftp -w 10 -c 20
command[check_procs]=/usr/local/nagios/libexec/check_procs -w 150 -c 200
command[check_total_procs]=/usr/local/nagios/libexec/check_procs -w 150 -c 200
command[check_ping]=/usr/local/nagios/libexec/check_ping -H $ARG1$ -w $ARG2$ -c $ARG3$ -p 5
command[check_ssl]=/usr/local/nagios/libexec/check_tcp -H 67.228.194.218 -p 443
command[check_mailq]=/usr/local/nagios/libexec/check_exim -w 10 -c -20

restart the nrpe damon

/etc/init.d/nrpe restart

How to install and configure NRPE in Nagios

The NRPE addon is designed to allow you to execute Nagios plugins on remote Linux/Unix machines. The main reason for doing this is to allow Nagios to monitor "local" resources (like CPU load, memory usage, etc.) on remote machines. Since these public resources are not usually exposed to external machines, an agent like NRPE must be installed on the remote Linux/Unix machines.


The NRPE addon consists of two pieces:
The check_nrpe plugin, which resides on the local monitoring machine
The NRPE daemon, which runs on the remote Linux/Unix machine

INSTALLATION:
Remote Host Setup:
Create a new nagios user account and give it a password.
/usr/sbin/useradd nagios
passwd nagios
Download nrpe and nagios-plugin.

wget http://osdn.dl.sourceforge.net/sourceforge/nagiosplug/nagios-plugins-1.4.11.tar.gz

tar xvzf nagios-plugins-1.4.11.tar.gz

cd nagios-plugins-1.4.11/

Compile and install the plugins.
./configure --prefix=/usr/local/nagios
make
make install

The permissions on the plugin directory and the plugins will need to be fixed at this point, so run the following commands.
chown nagios.nagios /usr/local/nagios
chown -R nagios.nagios /usr/local/nagios/libexec

Install the NRPE daemon

Download the source code tarball of the NRPE addon (visit http://www.nagios.org/download/ for links to the latest versions) and execute:

mkdir ~/downloads
cd ~/downloads/
wget http://osdn.dl.sourceforge.net/sourceforge/nagios/nrpe-2.12.tar.gz
tar xzf nrpe-2.12.tar.gz
cd nrpe-2.12/

Compile the NRPE addon.

./configure
make all
Install the NRPE plugin (for testing), daemon, and sample daemon config file.
make install-plugin
make install-daemon
make install-daemon-config

Add the following entry for the NRPE daemon to the/etc/services file.

nrpe 5666/tcp# NRPE

Next we have to add init script for nrpe.For this,

cd nrp-2.12/
cp ./src/nrpe /usr/sbin/
cp ./sample-config/nrpe.cfg /etc /

cat init-script.in > /etc/init.d/nrpe

mod a+x /etc/init.d/nrpe

open the /etc/init.d/nrpe file and edit lines:

NrpeBin=/usr/sbin/nrpe
NrpeCfg=/etc/nrpe.cfg

Then restart nrpe services

/etc/init.d/nrpe restart

Next you have to edit the nrpe configuration file and allow the monitoring of host ipaddress with:
vi /etc/nrpe.cfg

allowed_hosts=127.0.0.1,ipaddress of monitoring host

Then open nrpe port in the remote server firewall. Here I am using apf firewall.

vim /etc/apf/conf.apf
edit the follwing section and add port number 5666

IG_tcp_cports="5666,20...........etc"

restart the services

/etc/init.d/apf restart

Make sure the nrpe daemon is running under xinetd.

netstat -at | grep nrpe

The output of this command should show something like this:

tcp 0 0 *:nrpe *:* LISTEN

Monitoring Host Setup

We have to install nrpe plugin to the monitoring host.

cd ~/downloads
wget http://osdn.dl.sourceforge.net/sourceforge/nagios/nrpe-2.12.tar.gz
tar xzf nrpe-2.12.tar.gz
cd nrpe-2.12/
Compile the NRPE addon.
./configure
make all
Install the NRPE plugin.
make install-plugin

Create a command definition

You'll need to create a command definition in one of your Nagios object configuration files in order to use the check_nrpe plugin. Open the sample commands.cfg file for editing...

vi /usr/local/nagios/etc/commands.cfg

and add the following definition to the file:

define command{
command_name check_nrpe
command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
}

Now you can add services to your system for monitoring them in the remote system.
You can insert each remote system services in one file.For that you have to edit the configuration file

vim /usr/local/nagios/etc/nagios.cfg

and append the following line.

cfg_file=/usr/local/nagios/etc/objects/remotehost.cfg


Before adding services, create a new template for each different type of host you'll be monitoring. Let's create a new template for linux boxes.
vi /usr/local/nagios/etc/objects/templates.cfg
add the following lines.

define host{
name linux-box ; Name of this template
use generic-host ; Inherit default values
check_period 24x7
check_interval 5
retry_interval 1
max_check_attempts 10
check_command check-host-alive
notification_period 24x7
notification_interval 30
notification_options d,r
contact_groups admins
register 0 ; DONT REGISTER THIS - ITS A TEMPLATE
}

Next you have to edit /usr/local/nagios/etc/objects/remotehost.cfg and add the following definitions and services

Define a new host for the remote Linux/Unix box that references the newly created linux-box host template.
define host{
use linux-box ; Inherit default values from a template
host_name remotehost ; The name we're giving to this server
alias Fedora Core 6 ; A longer name for the server
address 192.168.0.1 ; IP address of the server

}

Then, define a new contact for the remote Linux/Unix box that references the generic-contact template.

define contact{
contact_name remote
use generic-contact
alias Nagios client
email remotehost@gmail.com
}
The following service will monitor the CPU load of the remote host. The "check_load" argument that is passed to the check_nrpe command definition tells the NRPE daemon to run the "check_load" command as defined in the
nrpe.cfg file.
define service{
use generic-service
host_name remotehost
service_description CPU Load
check_command check_nrpe!check_load
}
The following service will monitor the the number of currently logged in users on the remote host.
define service{
use generic-service
host_name remotehost
service_description Current Users
check_command check_nrpe!check_users
}
The following service will monitor the free drive space on /dev/hda1 on the remote host.
define service{
use generic-service
host_name remotehost
service_description /dev/hda1 Free Space
check_command check_nrpe!check_hda1
}
The following service will monitor the total number of processes on the remote host.
define service{
use generic-service
host_name remotehost
service_description Total Processes
check_command check_nrpe!check_total_procs

}

The following service will monitor the number of zombie processes on the remote host.

define service{
use generic-service
host_name remotehost
service_description Zombie Processes
check_command check_nrpe!check_zombie_procs
}


Remote Host Configuration

You have to insert the following command definitions in /etc/nrpe.conf

command[check_users]=/usr/local/nagios/libexec/check_users -w 5 -c 10
command[check_load]=/usr/local/nagios/libexec/check_load -w 15,10,5 -c 30,25,20
command[check_hda1]=/usr/local/nagios/libexec/check_disk -w 20% -c 10% -p /dev/hda1
command[check_zombie_procs]=/usr/local/nagios/libexec/check_procs -w 5 -c 10 -s Z

Then restart the nrpe daemon

/etc/init.d/nrpe restart

How to setup and configure nagios

Nagios

Nagios is a popular open source computer system and network monitoring software application. It watches hosts and services, alerting users when things go wrong and again when they get better.It allows you to gain insight into your network and fix problems before customers know they even exist. It's stable, scalable, supported, and extensible. Most importantly, it works.

It will do the Comprehensive Network Monitoring in the following

* Windows
* Linux/Unix
* Routers, Switches, Firewalls
* Printers
* Services
* Applications


Installation of Nagios in localhost

Before installing nagios,you have to install the following packages
* Apache
* GCC compiler
* GD development libraries

if you are using rpm based packages,

yum install httpd
yum install gcc
yum install glibc glibc-common
yum install gd gd-devel

If you are using ubuntu,

sudo apt-get install apache2
sudo apt-get install build-essential
sudo apt-get install libgd2-xpm-dev

1) Create Account Information

Create a new nagios user account and give it a password.

/usr/sbin/useradd -m nagios
passwd nagios

Create a new nagcmd group for allowing external commands to be submitted through the web interface. Add both the nagios user and the apache user to the group.

/usr/sbin/groupadd nagcmd
/usr/sbin/usermod -a -G nagcmd nagios
/usr/sbin/usermod -a -G nagcmd apache(or www-data)

2) Download Nagios and the Plugins
mkdir ~/downloads
cd ~/downloads

for downloading Nagios click here

or in terminal type the following line

wget http://osdn.dl.sourceforge.net/sourceforge/nagios/nagios-3.0.2.tar.gz

Extract the Nagios source code tarball.

tar xvzf nagios-3.0.2.tar.gz

cd nagios-3.0.2

Run the Nagios configure script, passing the name of the group you created earlier like so:

./configure --with-command-group=nagcmd

3) Compile the Nagios source code.

make all

Install binaries, init script, sample config files and set permissions on the external command directory.

make install
make install-init
make install-config
make install-commandmode

4) Configure the Web Interface

Install the Nagios web config file in the Apache conf.d directory.

make install-webconf

Create a nagiosadmin account for logging into the Nagios web interface. Remember the password you assign to this account - you’ll need it later.

htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin
If you want to add more users then

htpasswd /usr/local/nagios/etc/htpasswd.users username

Edit the file in /usr/local/apache/conf/includes/pre_virtualhost_global.conf and append the following line in to the virtual host directories
AuthName "Nagios Access"
AuthType Basic
AuthUserFile /usr/local/nagios/etc/htpasswd.users
Require valid-user

/etc/init.d/apache2 restart(or service httpd restart)

5) Download, Compile and Install the Nagios Plugins

For downloading Nagios-plugins click here

or in terminal we can download using the wget command,its shown below:

wget http://osdn.dl.sourceforge.net/sourceforge/nagiosplug/nagios-plugins-1.4.11.tar.gz

cd ~/downloads
tar xvzf nagios-plugins-1.4.11.tar.gz
cd nagios-plugins-1.4.11/

Compile and install the plugins.

./configure --with-nagios-user=nagios --with-nagios-group=nagios
make
make install

6) Start Nagios

Configure Nagios to automatically start when the system boots.

ln -s /etc/init.d/nagios /etc/rcS.d/S99nagios

Verify the sample Nagios configuration files.

/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

If there are no errors, start Nagios.

/etc/init.d/nagios start (service nagios start)

Add Nagios to the list of system services and have it automatically start when the system boots.

chkconfig --add nagios
chkconfig nagios on

you can check the Nagios in your browser typing the following url:

http://localhost/nagios

You should now be able to access the Nagios web interface at the URL below. You'll be prompted for the username (nagiosadmin) and password you specified earlier.

Installation and configuration of of Nagios with NRPE for both remote hosts and local host will be posted on next session

Let's start with Some Tricks & Tips

A cat with Twist

We use cat command to view a text file from top to bottom.If you want to read a text file from bottom to top you can use tac command.

How to mount Windows share on Linux

Most of them needs to frequently access windows from your Linux system.Most of you probably manually mount the  partition every time you require it.You can mount windows partion permenantly  by adding following in /etc/fstab file.

//server/sharename  /home/mountpoint  smb        userrname=user,password=password   1 2 

Change the variables in the above line to the real values, the way it is in your case.

It would work in a home environment, where  you don't mind putting password in a /etc/fstab file.If you want to be cautious,have a script ask for your password and mount the stuff using the smbmount command.However,if you would like to do this as the non-root user,specify the mount point option in /etc/fstab along with th noauto and user options.

  Execute a command at a specific time

The at command is used to run a command at a specific time or date.For example,inorder to remove a directory after one minute, issue the following commands:

#at now+1 min

at>rm -rf dirname

at>updatedb

at>

To remove a directory on a particular day,say on MM/DD/YYYY, use the code below:

#at MM/DD/YYYY

at>rmdir dirname

at>updatedb

at>

  Play Music in VLC without a GUI

In your terminal promp, type the following 

vlc -I ncurses /home/kingfisher/filename.mp3

Where the -I option is, specify the interface-in our case,it's ncurses.It will open a ncurses interface in the termnal,where you can increase or decrease the volume by using A or Z keys and press H for further options.

 Also note that /home/kingfisher/filename.mp3 is an example of a music file.You can open any number of files by using a wild card such as *.mp3.

How to get Server e-mail Alerts on the root login

Append the following line at the end of your ~/.bash_profile

echo ‘ALERT - Root Shell Access on:’ `date` `who` | mail -s “Alert: Root Access from `who | awk ‘{print $6}’`” your@email.com

Replace your@email.com with the actual email account address that you want to the root access alert notification been sent to.