This article provides a basic understanding of Ansible technology along with steps to install it. Ansible is an open source IT automation software for configuring, managing and installing software’s on the clients or nodes without any downtime and agent installed on the nodes. It uses SSH to communicate with the clients.
Currently, most of the IT Automation tools runs as an agent in remote host, but Ansible needs only an SSH connection, a user and a Python (2.4 or later).
Environment Setup Details
Server
Operating System: Centos 6.7
IP Address: 192.168.87.140
Host-name: ansible.hanuman.com
User: root
Remote Nodes
Node 1: 192.168.87.156
Node 2: 192.168.87.157
Operating System: Centos 6.7
IP Address: 192.168.87.140
Host-name: ansible.hanuman.com
User: root
Remote Nodes
Node 1: 192.168.87.156
Node 2: 192.168.87.157
Installing Ansible Server
There is no official Ansible repository for RPB based clones, but we can install Ansible by enabling epel repository using RHEL/CentOS 6. X, 7. X using the currently supported fedora distributions.
# rpm -Uvh http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm Output: Retrieving http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.no arch.rpm warning: /var/tmp/rpm-tmp.nHoRHj: Header V3 RSA/SHA256 Signature, key ID 0608b89 5: NOKEY Preparing... ########################################### [100%] package epel-release-6-8.noarch is installed
After configuring epel repository, you can now install Ansible using yum with the below command.
# sudo yum install ansible -y Output: Loaded plugins: fastestmirror, security Setting up Install Process Determining fastest mirrors epel/metalink | 4.3 kB 00:00 * base: centosmirror.go4hosting.in * epel: epel.mirror.net.in * extras: centosmirror.go4hosting.in * updates: centosmirror.go4hosting.in Resolving Dependencies . . . Installed: ansible.noarch 0:1.9.4-1.el6 Dependency Installed: PyYAML.x86_64 0:3.10-3.1.el6 libyaml.x86_64 0:0.1.3-4.el6_6 python-babel.noarch 0:0.9.4-5.1.el6 python-crypto2.6.x86_64 0:2.6.1-2.el6 python-httplib2.noarch 0:0.7.7-1.el6 python-jinja2.x86_64 0:2.2.1-2.el6_5 python-keyczar.noarch 0:0.71c-1.el6 python-pyasn1.noarch 0:0.0.12a-1.el6 python-simplejson.x86_64 0:2.0.9-3.1.el6 sshpass.x86_64 0:1.05-1.el6 Complete!
Verifying the Installation
After configuring epel repository, you can now install Ansible using yum with the below command.
# ansible --version ansible 1.9.4 configured module search path = None
Preparing SSH Keys to Remote Hosts
To perform any deployment or up-gradation from the ansible server, for every host, there should be a user account to communicate. Also, we need to copy the ssh keys from the Anisble server to the remote host for password-less connection.
First, let us create an SSH key using the below command and copy the key to remote hosts.
# ssh-keygen -t rsa -b 4096 -C "ansible.hanuman.com"
Generating Public/Private rsa Key Pair
Enter file in which to save the key (/root/.ssh/id_rsa): Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in ansible_key. Your public key has been saved in ansible_key.pub. The key fingerprint is: 28:ae:0c:8d:91:0a:fa:ac:2f:e2:8c:e5:fd:28:4b:c6 ansible.hanuman.com The key's randomart image is: +--[ RSA 4096]----+ | | | | | | | . . | |+ . . S | |+= . . | |= E . | |=X.o . | |=*Ooo.. | +-----------------+
After creating SSH Key success, now copy the created key to all the two remote servers, We need a user to do ansible here for a demo and I am using root user from where we can perform the ansible tasks.
# ssh-copy-id root@192.168.87.156 Output: root@192.168.87.156's password: Now try logging into the machine, with "ssh 'root@192.168.87.156'", and check in: .ssh/authorized_keys to make sure we haven't added extra keys that you weren't expecting. # ssh-copy-id root@192.168.87.157 Output: root@192.168.87.157's password: Now try logging into the machine, with "ssh 'root@192.168.87.157'", and check in: .ssh/authorized_keys to make sure we haven't added extra keys that you weren't expecting.
Copy SSH Key Second Remote Host
After copying all SSH Keys to remote host, now perform an ssh key authentication on all remote hosts to check whether authentication working or not run below commands to test.
# ssh root@192.168.87.156 [ansible@localhost ~]# Connection to 192.168.87.156 closed. # ssh root@192.168.87.157 [ansible@localhost ~]#
Creating Inventory File for Remote Hosts
Inventory file, This file has information about the hosts for which host we need to get connected from local to remote. The default configuration file will be under /etc/ansible/hosts.
Now, we will add the two nodes to configuration file. Open and edit file using your favorite editor, Here we are using vim.
# sudo vim /etc/ansible/hosts Add the following two hosts IP address.. [webservers] 192.168.87.156 192.168.87.157
Note: [webservers] in the brackets indicates as group names, it is used to classify the nodes and group them and to controlling at what times and for what reason.
To Test if Ansible is Working or Not
Now time to check our all server by just doing a ping from our Ansible server. To perform the action we need to use the command ‘ansible’ with options ‘-m‘ (module) and ‘-all‘ (group of servers).
# ansible -m ping webservers
Output:
[root@localhost ~]# ansible -m ping webservers
192.168.87.157 | success >> {
"changed": false,
"ping": "pong"
}
192.168.87.156 | success >> {
"changed": false,
"ping": "pong"
}
OR
# ansible -m ping -all
Output:
[root@localhost ~]# ansible -m ping webservers
192.168.87.157 | success >> {
"changed": false,
"ping": "pong"
}
192.168.87.156 | success >> {
"changed": false,
"ping": "pong"
}
Now, here we are using another module called ‘command’, which is used to execute a list of shell commands (like, df, free, uptime, etc.) on all selected remote hosts at one go. For demo you can execute the below commands.
Check the Partitions on all Remote Hosts
# ansible -m command -a "df -h" webservers Output: 192.168.87.156 | success | rc=0 >> Filesystem Size Used Avail Use% Mounted on /dev/mapper/VolGroup-lv_root 18G 2.0G 15G 12% / tmpfs 491M 0 491M 0% /dev/shm /dev/sda1 477M 42M 411M 10% /boot 192.168.87.157 | success | rc=0 >> Filesystem Size Used Avail Use% Mounted on /dev/mapper/VolGroup-lv_root 18G 2.0G 15G 12% / tmpfs 491M 0 491M 0% /dev/shm /dev/sda1 477M 42M 411M 10% /boot
Check Memory Usage for all Webservers
# ansible -m command -a "free -mt" webservers Output: 192.168.87.156 | success | rc=0 >> total used free shared buffers cached Mem: 981 528 453 0 39 322 -/+ buffers/cache: 166 815 Swap: 2047 0 2047 Total: 3029 528 2501 192.168.87.157 | success | rc=0 >> total used free shared buffers cached Mem: 981 526 455 0 39 322 -/+ buffers/cache: 164 817 Swap: 2047 0 2047 Total: 3029 526 2503
Redirecting the Output to a File
# ansible -m shell -a "service httpd status" webservers > service_status.txt Output: # cat service_status.txt 192.168.87.156 | FAILED | rc=3 >> httpd is stopped 192.168.87.157 | FAILED | rc=3 >> httpd is stopped
To Shut down the Remote Servers
#ansible -m shell -a "init 0" webservers OutPut: 192.168.87.157 | success | rc=0 >> 192.168.87.156 | success | rc=0 >>
Ansible is a Powerful IT automation tool which is mostly used by every Linux Admins for deploying applications and managing servers at one go. Among any other automation tool such as Puppet, Chef, etc., Ansible is quite very interesting and very easy to configure and good for a simple environment.
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