Installing ansible on a management server

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To install ansible first configure rpmfusion, epel and rpmforge repositories. Then ansible can be installed using:

   yum -y install ansible

To check ansible installation, first try to connect to localhost itself and check if ansible can manage localhost. To manage localhost using ansible use following steps:

1. Ansible uses a hosts file to determine which hosts it can connect to, their addresses, their groupings, etc. By default ansible will use /etc/ansible/hosts but for this simple test we can create a test hosts file using:

   echo "localhost" > ansible_hosts

2. Now pings all hosts mentioned in ansible hosts file using:

   ansible all -m ping -i ansible_hosts

3. Since ssh public-key based access is not allowed the connection will fail. To solve the problem we can either supply password or setup ssh-public key based trusted ssh.

   To supply password use following additional steps:

   1. Install sshpass using:

      yum -y install sshpass

      This helps in supplying password for remote hosts, if key based authentication is not setup

   2. Now ping all hosts mentioned in ansible_hosts file by supplying root password using:

      ansible all -m ping -i ansible_hosts --ask-pass

   Other option is to setup key based access using following steps:

   1. Create a ssh-public and private key pair for current host, if not already present, using:

      ssh-keygen

   2. Copy current hosts key to remote machine using appropriate method. In case of localhost we can simply use:

      cp ~/.ssh/id_rsa.pub ~/.ssh/authorized_keys
      chmod 400 ~/.ssh/authorized_keys

      For other machines use:

      ssh-copy-id root@<remote-machine>

      and supply root password just once.

   3. Now try to ping all machines specified in ansible_hosts file using:

      ansible all -m ping -i ansible_hosts

Note that if ping is successful you would see output similar to:

     localhost | success >> {
         "changed": false, 
         "ping": "pong"
     }

On CentOS 6.5 you may see following warning whenever ansible command is used:

   [WARNING]: The version of gmp you have installed has a known issue regarding
   timing vulnerabilities when used with pycrypto. If possible, you should update
   it (i.e. yum update gmp).

Please ignore the warning.

Note that using --ask-pass will cause password to be asked even when ssh public key based trusted ssh is established. Hence use --ask-pass only if trusted ssh is not already setup.

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