Installing python3 and pip3 on Centos7

Here I have no python3 installed

The most simplest way to install python3
=================
sudo yum install python3

Make python 3.6 as default one
=================
sudo alternatives --install /usr/bin/python python /usr/bin/python3.6 60
sudo alternatives --config python

Check the python version
==================

Check the pip version
==================

Check the pip3 version
==================

Upgrade pip3
=================
pip3 install --upgrade pip --user

 

Check the pip version

==================

Bonus: Fixing yum package manager

Now lets try to install a random package to check the yum package manager

Install nano
=============
sudo yum install nano
you will get following error

To fix this, Open the /usr/bin/yum file and in the first line, change python to python2
OLD:

NEW:

If again you got similar issue with different file, for example:

Open this file (sudo vi /usr/libexec/urlgrabber-ext-down ) and in the first line change "python" to "python2"

 

Here is the Youtube demo:

 

 

-That's all for now

Ansible: Installation and Configuration

Ansible is an open-source software provisioning, configuration management, and application deployment tool. It runs on many Unix-like systems, and can configure both Unix-like systems as well as Microsoft Windows. Before proceeding for the installation, it is necessary to get yourself comfortable with basic knowledge.

Ansible Wikipedia: https://en.wikipedia.org/wiki/Ansible_(software)
Official Documentation: https://docs.ansible.com/ 

1. Ansible installation

1.1.  Through pip

The easy way to install ansible is through pip, which is a python package manager.

Prerequisite:

> For before installing ansible, make sure that python3 is already installed.  

> Once Python3 is installed go ahead to install pip

    Sudo easy-install pip3

> Now install ansible through pip3

    pip3 install ansible

1.2.  Through apt (ubuntu)

$ sudo apt-get update

$ sudo apt-get install software-properties-common

$ sudo apt-add-repository --yes --update ppa:ansible/ansible

$ sudo apt-get install ansible

[src]: https://docs.ansible.com/ansible/latest/installation_guide/intro_installation.html#latest-releases-via-pip

2.  Basic Configuration:

If ansible is installed manually through pip, the ansible_host inventory file needs to be created manually. Following this you also need to check the reachability of remote servers.

2.1. Adding host file if NOT present

If the ansible is installed using pip3, you will not find any host inventory in the directory /etc/ansible/hosts

if you execute the command ansible webservers --list-hosts this will give an error something like "unable to parse the inventory file in /etc/ansible/hosts". This means that no directory named ansible in /etc/ directory is present. For this follow steps below:

1: cd /etc/

2: sudo mkdir -p ansible/hosts/

3: vim ansible_host

[localhost]

127.0.0.1

[webservers]

foo.example.com

bar.example.com

[dbservers]

one.example.com

two.example.com

three.example.com

[myhomepage]

www.chinmayadehury.in

[testservers]

www.google.com

www.chinmayadehury.in

4: now enter the command ansible testservers --list-hosts

This will list the webservers that are listed in the group called [testservers]

2.2. Connecting to remote host using ssh

1: open the ansible_host inventory file

vim /etc/ansible/hosts/ansible_host

2: add the following host group or host

[myhomepage]

160.153.137.40 ansible_port=<sshport#> ansible_user=username1 ansible_ssh_pass=user1password

It is assumed that you are able to login to that remote using ssh and using above credentials.

3: now save the ansible_host file

4: enter following command

ansible myhomepage -m ping

2.3. Disabling ssh key host checking

Open the config file in /etc/ansible/ansible.config

Find for #host_key_checking = false. Uncomment the line to make it enable.
[src]: https://docs.ansible.com/ansible/latest/installation_guide/intro_installation.html#latest-releases-via-pip

-Thats all for now.

Installing OpenCV and Python in Windows

1. Download and install Python 2.7.x in windows
             windows install : http://python.org/ftp/python/2.7.5/python-2.7.5.msi
2.  The default installation directory C:\Python27


3. Download and install python package manager pip if NOT installed
                  A. Download get-pip.py script from  https://bootstrap.pypa.io/get-pip.py
                  B. Open command prompt
                  C. Enter following command to run the downloaded script
                                    python <path to get-pip.py file>

4.  Go to http://www.lfd.uci.edu/~gohlke/pythonlibs/ to download and install python packages

5.  Now, Download Numpy python package (choose the .whl file based on your requirement)
                  A. Open command prompt
                  B. Go to the local directory where numpy-1.11.2+mkl*.whl file is present
                  C. Enter following command to Install Numpy
                                    pip install numpy-1.11.2*.whl
6. You can repeat Step-5 to install other required packages


7. Download and install OpenCV
                  A. Folllow the link to download OpenCV-3.1.0
                  B. Open the .exe file to install (in C drive)
                  C. Goto C:\opencv\build\python
                  D. Copy cv2.d to C:\Python27\Lib\site-packages

Please comment if you encounter any error....

-Thank you