I have added this in the blog to help a newbie land in a page that is easy to follow. The steps cover

i) Adding rpmforge
ii) Adding adobe repo
iii) Installation command to install libraries, flash plugin and other streaming medias
iv) MPlayer codec installation

For e.g. lets find where “samba” is located in a CentOS server

$ which samba
which command searches the list of programs listed down through the PATH settings

$ whereis samba
whereis command also searches for programs that are not present in the PATH setting

First create a folder in your Windows system, right click the folder and share the folder for network access. Let say that you have created a folder for share as “xpshare” and that the name of your windows machine is “windowsxp” (right click “My Computer” and select properties. Under the tab “Computer Name” you can note the name of the machine)

Now go to your Linux box.

Check the rpm package to ensure if samba, samba client got installed
$ rpm -qa ‘samba*’

If it is not installed, then install it using yum installer
$ yum install samba samba-client

Note the current directory
$ pwd
/tmp

Now issue the samba command to connect to windows box as
$ smbclient //windowsxp/xpshare
password:

Enter the password of your linux box and you will be connected to the windows machine and the command prompt will be changed to

smb: \>

To know the commands that you can use with samba,
smb :\> help
You can use the commands like dir, get, put, chmod, rmdir within the samba share

smb :\> get New File.txt (wrong)
smb :\> get “New File.txt” (correct)

In windows you can easily create and move file with names which has space in it. In order to get a file from windows with spaces, enclose the file name within quotes. Else you will get an error which would state “NT_STATUS_OBJECT_NAME_NOT_FOUND opening remote file \New” as it fails to go beyond the first space in the file name “New File”

smb :\> quit
Now the file “New File.txt” will be in the directory from where you initially connected to the samba share
$ ls -l (to list the file that was brought down from the samba share)

To know the version of samba that you are using , type
$ smbd -V

$ apache2 -v

In CentOS, it is

$ httpd -v

To find out where apache2 or httpd program is installed you can do the
$ whereis apache2 or,
$ locate httpd

Virtual Hosting is a technique by which web servers can serve more than one domain name on the same server. It can also be a variation of serving different sites on the same IP but on different ports.

If Ubuntu, you may need to edit
i) /etc/hosts

ii) /etc/apache2/conf.d/vhosts.conf (or /etc/apache2/sites-available/default) depending on how you have configured the virtual host environment

If CentOS, you may need to edit

i) /etc/hosts

ii) /etc/httpd/conf/httpd.conf

For listening to different ports Listen directive should be added to /etc/httpd/conf/httpd.conf file

References:

http://httpd.apache.org/docs/2.0/vhosts/examples.html (Apache’s virtual host configuration documentation)

http://en.wikipedia.org/wiki/Virtual_host

http://apptools.com/phptools/virtualhost.php (For configuring Apache server on Windows)

To install Ruby Gems
$ wget http://rubyforge.org/frs/download.php/45905/rubygems-1.3.1.tgz
$ tar xvf rubygems-1.3.1.tgz
$ cd rubygems-1.3.1
$ ruby setup.rb

To install Radrails IDE
RadRails is one of the tools that can be used to develop scripting languages like Ruby, PHP. Thought it is preferred to hand code programs, knowledge of using an IDE comes in handy at times. The following steps should help you install RadRails on CentOS

$ wget http://prdownloads.sourceforge.net/radrails/radrails-0.6.2-linux.zip?download

Extract the files and then you can open the RadRails by executing the command
$ ./radrails/radrails

To check if ruby, rails is installed you can check their versions numbers to ensure that it got installed.

$ ruby -v
$ rails -v

Hope this gives a good installation intro for Ruby on Rails. Hope it saved your some time

Download nagios plugin and nagios-nrpe plugin in the server host (client that talks with nagios host) from nagios website. The files comes as .tar files and you need to configure them for their use. Move the files to /usr/src

$ cd /usr/src
$ tar zxvf nagios-plugins-1.4.13.tar.gz
$ cd nagios-plugins-1.4.13

$ ./configure –prefix=/usr/local/nagios
$ make
$ make install

Now nagios-plugin is successfully installed. Go back to /usr/src

$ cd ..
$ tar zxvf nrpe-2.12.tar.gz
$ cd nrpe-2.12
$ ./configure –enable-ssl

By default, you will get the following list of information. If you want to change these values you can go ahead and change them.

General Options:
————————-
NRPE port: 5666
NRPE user: nagios
NRPE group: nagios
Nagios user: nagios
Nagios group: nagios

$ make all

If the nrpe client compiled without any error then you can continue with installation settings to make these two comptuers talk to each other.

$ make install-plugin
$ make install-daemon
$ make install-daemon-config
$ make install-xinetd

$ cp src/nrpe /usr/local/nagios/libexec/
$ cp src/check_nrpe /usr/local/nagios/libexec/

Now the executables are in place and we can configure the NRPE daemon on the remote system.

Search for the string “allowed_hosts” in /etc/nagios/nrpe.cfg and change it to the nagios host IP address (this restricts the server host to listen only from the above IP)

# Set this to listen only from nagios host
allowed_hosts=127.0.0.1

Restart nagio nrpe in ubuntu

* Identify where nrpe.cfg and make the necessary changes to that configuration file. Save it. Then restart the nrpe server by
$ /etc/init.d/nagios-nrpe-server restart

From centos, if you want to start xinetd
$ /etc/init.d/xinetd restart

From the server host execute telnet to see if you can communicate with nagios host

telnet remote-nagios-host 5666

If you get the following message then everything sounds fine until now

Escape character is ‘^]’.

FROM NAGIOS HOST

Add the following entries in developer-host.cfg (the name of the file is configurable from nagios.cfg file)

define host{
use linux-server ; Name of host template to use
host_name developer-host
alias developer-host
normal_check_interval 2
retry_check_interval 1
address 10.4.8.48
}

define service{
use generic-service
host_name developer-host
service_description HTTP
check_command check_http
notifications_enabled 1
normal_check_interval 2
retry_check_interval 1
}

Restart nagios from nagios host and you are ready to go.

Note: If you have custom commands that you need to run or configure certain perl files, then you can add the entry for the command in nagios.cfg and about the execution entry

in the custom defined .cfg file for that host. This custom defined entry needs to be configured in the nrpe.cfg file that is to be located in the server host (client listening to nagios host)

For configuring the nagios nrpe host, client on Ubuntu check the following resources

http://sysbible.org/x/2008/11/10/how-to-install-nagios-nrpe-under-debian-linux/

http://debianclusters.cs.uni.edu/index.php/Nagios_NRPE_Addon_Installation_and_Configuration

In your terminal, issue the following command (by default, httpd is installed). This will install apache if it was not installed.

Step 1:
[root@user Desktop]# yum install httpd

Step 2: To start apache as a service on boot, issue the following command
[root@user Desktop]# chkconfig –levels 255 httpd on

Step 3: If you want to edit Apache server configuration settings open the httpd.conf (configuration file) to make changes by issuing the following command
[root@user Desktop]# /etc/httpd/conf/httpd.conf

Step 4: Restart apache server if you have made changes to apache server settings in httpd.conf
[root@user Desktop]# /sbin/service httpd restart

Step 5: Visit http://localhost in your web browser and you should be able to see the Apache Test Page

When we want to connect to Office network from an external location or from home, then we need to setup our Linux box to establish communication with the server at the office via a secured link over the internet. In this part, I will list down the steps needed to establish a client communication.

For you to connect to your Office network where VPN is installed, your server administrator would have given you the following files:

- a .csr file (like for e.g. yourname.csr)
- a .crt file (like for e.g. yourname.crt)
- a .key file (like for e.g. yourname.key)
- a .conf file (like for e.g. yourname.conf)

A sample <<yourname.conf>> file:

[root@computer /]# vi yourname.conf

#yourname.conf
tls-client
client
dev tun
proto udp
tun-mtu 1400
remote vpn_server_ip_address 1194
resolv-retry infinite
nobind
persist-key
persist-tun
ca /etc/openvpn/ca.crt
cert /etc/openvpn/yourname.crt
key /etc/openvpn/yourname.key
cipher BF-CBC
comp-lzo
verb 3

As you can see from the above file, you need to COPY the file <<yourname.csr>>, <<yourname.crt>>, <<yourname.key>>, <<yourname.conf>> to the location /etc/openvpn/. If you want to setup a different folder for having these files separately, then give the appropriate path inside <<yourname.conf>> file.

Inside <<yourname.conf>> file, replace vpn_server_ip_address with the IP address given by your server administrator.

Now you are good to go. Issue the command

[root@computer /]# openvpn –config yourname.conf

Once the connection is established you will get a line stating that “Initialization sequence completed” which signals that client communication with the remote location is instantiated. Now you can browse through the files in the remote server wherever you are.

Notes:
- Inside <<yourname.conf>>  file, DO NOT have ~ (tilde) mark to signify the root. This is not recognized from within the .conf file and it will return an error.
- Check the line that states ‘cipher’ in <<yourname.conf>>. Here I have stated that BF-CBC as my 128 bit cypher encryption algorithm for establishing my connection. Depending on the information given by your server admin, you may need to change this part.

VPN – Short Intro

VPN is an acronymn for Virtual Private Networks which facilitates extending of networks beyond horizons shortening the gap between remote offices with the head office. It is a private network over internet which is a public medium providing a “virtual” office environment.

After a few comparisons with other open source products and after digging through Internet I found steps related to openVPN installation on Linux CentOs 5 and few hints related to possible sources of errors during installation which I would like to share with others who face similar problems and are newbies like me

Installation Steps
==================

1. Download the following package files
[root@computer /]# wget http://openvpn.net/release/openvpn-2.0.9.tar.gz
[root@computer /]# wget http://openvpn.net/release/lzo-1.08-4.rf.src.rpm
Note: Sources for LZO RPM Package file downloads
http://openvpn.net/release/
http://dag.wieers.com/rpm/packages/lzo/

To check if OpenVPN is already installed you can issue the command
[root@computer /]# rpm -q openvpn

2. Setting up the LINUX CentOS environment
[root@computer /]# yum install rpm-build
[root@computer /]# yum install autoconf.noarch
[root@computer /]# yum install zlib-devel
[root@computer /]# yum install pam-devel
[root@computer /]# yum install openssl-devel
3. Building the Linux CentOS environment
[root@computer /]# rpmbuild –rebuild lzo-1.08-4.rf.src.rpm
[root@computer /]# rpm -Uvh /usr/src/redhat/RPMS/i386/lzo-*.rpm
[root@computer /]# rpmbuild -tb openvpn-2.0.9.tar.gz
[root@computer /]# rpm -Uvh /usr/src/redhat/RPMS/i386/openvpn-2.0.9-1.i386.rpm