Make Skype Icon Visible in Gnome Desktop Ubuntu 12.04

If you are using Ubuntu 12.04 with Gnome - Classic Desktop , you may experience a problem with not displaying SKYPE icon in the system tray. This can be solved in an easy method. You need to install Status NotifierItem plugin. If you are using 64Bit install of Ubuntu , you need to install i386 version of sni-qt.

sudo apt-get install sni-qt:i386

Thats it !!! login to skype and skype icon will be displayed in your system tray.

Reverse SSH Tunneling OR "Poor mans VPN"

In corporate networks , the servers will be placed behind a NAT for security reasons. Its not possible to access the server behind the NAT from outside network. And here comes a way to access servers behind NAT through SSH , its called Reverse SSH Tunneling OR Poor Mans VPN.

Scenario.

IP Address of the Server you need to access 192.168.20.55
IP Address of the Client from which you are trying 150.57.9.9


1. SSH from the destination to the source (with public ip) using command below:

ssh -R 2080:localhost:22 sourceuser@150.57.9.9

2. Now you can SSH from source to destination through SSH tuneling:

ssh localhost -p 19999

KVM (Virtualization) Tips

KVM Tips.


Assumptions

1.You should have a working KVM Environment
2.You should have knowledge in Linux and little Networking.
3.You should have basic level knowledge in Virtualisation

1.To Check whether KVM has been installed

virsh -c qemu:///system list

You will see the following...

[root@server1 ~]# virsh -c qemu:///system list
 Id Name                 State
----------------------------------

[root@server1 ~]#

Which means your KVM server is up and running.

2.To View all the running Guests

virsh --connect qemu:///system

virsh# list -all

Id Name                 State
----------------------------------
  3 vm11                 running
  - vm10                 shut off

virsh #

3.Start a Virtual Machine
virsh# start vm10

4.Stop a Virtual Machine
virsh# shutdown vm10

5.Suspend a Virtual Machine

virsh# suspend vm10

6.Forcefully Shutdown a virtual Machine (ie remove power plug)

virsh# destroy vm10

7.Exit the Virtual shell
virsh# Exit

Static Route in Linux

Static Route is using for improving the overall performance of your network. Also you can use static route for implementing Sub Networks. Suppose you are having different branch office to be connected with a Head office who is linked with a T1 line , Static route will be use full.

1.To View the routes in your system

ip route show

route -n

2.Adding a route in the Linux Machine.

route add default gw 10.10.100.1 eth0

This will create a ROUTE in the interface eth0 for a gateway to 10.10.100.1

This will be lose once you restart the network. For Adding a static route , you should follow the below steps.

vi /etc/sysconfig/network-scripts/route-eth0

Append the following

10.10.1.0/8 via 10.120.194.5

This will byepass all the traffic to 10.120.194.5 router through eth0


DTMF Issue With Asterisk - Solution.

Asterisk is nothing but a Software implementation of Private Branch Exchange. Mark Spencer of Digium  has wrote this application once he is not able to find a PBX for his company. Now this application is using by lot of people for medium , and large scale enterprises.

ISSUE

The signals from a DTMF system is not recognised by the Asterisk. Specifically key press from Smart phones and Mobile phones who is sending DTMF signals.

ASSUMPTION

You have a working Asterisk system

Add the following line in chan-dahdi.conf file

relaxdtmf=yes
toneduration=300

Save and Exit.

Reload the Asterisk.

Now you will be able to receive the Signals from DTMF devices.

VLAN With Hypervisor - KVM

IDEA.

Some times we need a VLAN inside the Linux machine to communicate with outside network. Specifically when we are dealing with Blade Servers. KVM Hypervisor only allows outside traffic through this VLAN only OR Management IP. We are not considering management NIC here.

The traffic from BladeS erver is allowed to main switch only through this VLAN. When a packet come from the Blade , the particular port of the switch will ask challenge to the packet for VLAN information. So we need to create a separate VLAN inside the Linux machine.

HowTO

cp /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth0.300

vi /etc/sysconfig/network-scripts/ifcfg-eth0.300

Find the Word DEVICE and change its name to eth0.300 (Normally that should be eth0)

Add the Line       VLAN=yes

Restart the Network    /etc/init.d/network restart.

Adding a new VLAN

vconfig add eth0 5

Assigning an IPAddress to the VLAN

ifconfig eth0.5 192.168.1.100 netmask 255.255.255.0 broadcast 192.168.1.255 up

For Shutting down a VLAN

ifdown eth0.300

For Remove a VLAN

vconfig rem eth0.300