Mar 28

Executing a linux command in background/foreground using terminal

 

Executing a Linux command silently or in background

While working on terminal we can make a command to execute in background, so that we can work something else on that terminal.

There are two ways to do so:

1. Directly executing the command using “&” operator.

Command will be executed like
$ COMMAND &

2. Other way is like this

$ COMMAND
Press CTRL+Z //This will pause(stop) the command
To view the number assigned to the above command, use “jobs” command
$ jobs
[n]+   Stopped             COMMAND &
It will show the number assigned to that job/command(it would be n here)
Now execute the command to run it in background
$bg %n
Now you can check that it is running, using job command
$ jobs
[1]+  Running                 COMMAND &

Lets take an example of executing VLC:
1. Using first method
$ vlc &

2. Using Second method
$ vlc
CTRL+Z
$ jobs
[1]+  Stopped                  vlc &
$ bg %1
$ jobs
[1]+  Running                  vlc &

Executing command in foreground

Now when we execute a command silently, i.e, in background, Sooner or later we need to bring it back to foreground.

So a job can be brought back to foreground as follows:
Check its job id
$ jobs
[n]+   Running                      COMMAND &
Now bring it to foreground
$ fg %n

Lets see an example
$ jobs
[1]+    Running                   vlc &
$ fg %1

This will bring VLC back to foreground.

Mar 20

Koding – Now develop in your browser

 

Koding  provides cloud development environment where developers can come and code in a browser. It provides real servers (Virtual Machines) in which you can create and execute your code.

You can do almost everything one can do on a real server. You can code in Ruby, C, C++, Java, Python, PHP ,i.e., in any programming language you want. You can even install WordPress, Laravel, Django, Bootstrap and much more.  You can even manage your database using MySQL.

That is it provides complete programming environment which one can desire. Moreover it provides a VM of 3 GB,  which can be extended up to 20 GB free of cost.

You can access koding from here:

Visit Koding

Mar 14

Tor in Android – Orbot

 

Tor is a network of virtual tunnels that allows people to access internet anonymously without compromising their privacy. Tor bounces your encrypted traffic several times through computers around the world, instead of connecting you directly like VPNs and proxies.

It might take longer but security provided by it is  worth waiting. Tor is considered to be the strongest privacy and identity protection providing tool.

New York Times writes “when a communication arrives from Tor, you can never know where or whom it’s from.”

Orbot is an proxy app that uses Tor to encrypt internet traffic and bounces it through a series of computers around the world. You can use it in your smartphone in the same way you use Tor in PC.

 

You can download Orbot from here:

Download Orbot

Mar 08

VMware player installation in OpenSuse

Follow the following steps  to install VMware Player

 

1.  Download VMware Player

 

2. Install the required packages

[root]#zypper install kernel-desktop

[root]#zypper install kernel-desktop-devel

[root]#zypper install gcc make kernel-source

 

3. Go to the directory containing VMware-Player-[VERSION].bundle

[root]#cd PATH_TO_VMware-Player-[VERSION].bundle

 

4. Make VMware player Bundle EXECUTABLE

[root]#chmod +x VMware-Player-[VERSION].bundle

 

5.  Execute the package

[root]#./VMware-Player-[VERSION].bundle

 

Note :

This same procedure works for VMware Workstation also.

You can download VMware Workstation from here:

DOWNLOAD VMware Workstation

 

Feb 27

Unknown OS type hvm

After fresh installation of  Virtual Machine Manager, when I created a new VM it displayed this error

                      unknown os type 

 

This was because all qemu packages were not installed

So I installed all qemu packages

[root]#zypper install qemu*                           (in opensuse)

you can use

[root]#yum install qemu*                                (in fedora or centos)

It should have installed all the packages, but somehow it didn’t installed qemu-kvm,

due to which it displayed this error

Cannot check QEMU binary /usr/bin/qemu-kvm: No such file or directory

while creating new VM.

It was all because qemu-kvm was not installed.

So to install qemu-kvm I followed following steps :             (IN OPENSUSE)

1.  Start yast.

2. Choose Virtualization -> Install Hypervisor and Tools.

3. Select KVM and confirm with Accept

4. Confirm to the list of packages that is to be installed with Install.

5. Agree to set up a network bridge by clicking Yes. It is recommended using a bridge on a VM Host Server (virtual machine host). If you prefer to manually configure a different network setup, you can safely skip this step by clicking No.

6. After the setup has been finished, reboot the machine as YaST suggests. Alternatively load the required kernel modules manually and start libvirtd to avoid a reboot:

[root]#modprobe kvm-intel                                    // on Intel machines only
[root]#modprobe kvm-amd                                    // on AMD machines only
[root]#modprobe vhost-net
[root]#rclibvirtd start

 

Feb 12

Active ports on your system

To check active ports on a system we use netstat command.

 

To check active TCP ports, command is :

$netstat -tnlp

 

To check active UDP ports, command is :

$netstat -unlp

 

Further if you want to check kernel’s routing table, command is :

$netstat -r

 

To view active interfaces, command is :

$netstat -i

 

Here flags used represent:

-t : tcp

-u : udp

-l : listing

-p : process id and process name

-n : nolookup (it shows IP rather than HostName)

-r : routing table

-i : interfaces

Feb 07

How to check whether your system supports Virtualization or Not

To check whether your system supports virtualization or not, open the file /proc/cpuinfo under flag section check if following flags are present :

svm       :        Applicable for AMD processor

vmx       :       Applicable for Intel processor

If any of these flags is present it means your processor supports virtualization .

 

Cpuinfo

 

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