Why to install and configure Ansible in Linux.
Using configuration management systems we can control large numbers of servers which makes system administrators life easy. In a nutshell we can control or manage huge number of server or systems from single central server with the help of automation tools.
There are many such tools are available for automation such as Chef or Puppet. However these tools are some what complex in nature. We have got great alternative to these options which is Ansible. Since its very much easy to install and configure Ansible in Linux.
This guide will quickly guide you on how to install and configure Ansible in Linux.
How Ansible Works!
Ansible does not use any agents for carrying out the automation tasks, which means that there are no background processes runs on the clients. Instead Ansible makes connection using SSH for carrying out its operations.
Setup details for Ansible installation.
Ansible management server details:
OS: Red Hat Enterprise Linux Server release 7.2 (Maipo) Hostname: ansimgmt IP: 172.31.15.60 User: lradmin
Client machine details:
client 1 Hostname: web1 IP: 172.31.7.221 Client 2 Hostname: web2 IP: 172.31.25.35
Step1: Installing Ansible on management server.
For Linux Mint,Ubuntu and Debian
#apt-add-repository ppa:ansible/ansible #apt-get update && sudo apt-get install ansible
For RHEL,CentOS and Fedora
#yum install ansible
Please note that there are no official Ansible repository for RedHat , howerver we can still install Ansible by enabling epel repository under RHEL or Centos.
After installing the Ansible you can check the version using below command.
[root@ansimgmt ~]# ansible --version ansible 2.3.1.0 config file = /etc/ansible/ansible.cfg configured module search path = Default w/o overrides python version = 2.7.5 (default, Oct 11 2015, 17:47:16) [GCC 4.8.3 20140911 (Red Hat 4.8.3-9)] [root@ansimgmt ~]#
Step2: Setting up ssh for configuring Ansible.
For deployment or managing the client machine from our management server “ansimgmt” we need to setup password less ssh between them. In this demo we have configured lradmin user for password less ssh.
Generate the ssh keys on the management server for the user lradmin.
[root@ansimgmt root]# id uid=0(root) gid=1001(lradmin) groups=1001(lradmin) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 [root@ansimgmt root]# ssh-keygen Generating public/private rsa key pair. Enter file in which to save the key (/root/.ssh/id_rsa): /root/.ssh/id_rsa already exists. Overwrite (y/n)? y Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /root/.ssh/id_rsa. Your public key has been saved in /root/.ssh/id_rsa.pub. The key fingerprint is: 5e:a3:5b:4c:dc:15:7d:96:59:a8:85:97:43:03:70:a2 root@ansimgmt The key's randomart image is: +--[ RSA 2048]----+ | o.o+++=| | . o. *=+| | E +.o.| | . ... | | S = . | | . = . | | o o | | o | | . | +-----------------+
Here we are done with generating the keys now in the next step we need to copy the contents of “/root/.ssh/id_rsa.pub” to client system for the user lradmin. Please follow the steps in this post , so that password less communication between management server and client machine web1 and web2 can be configured.
Once you are done with password less configuration you can cross check the same by doing ssh as below. System should not ask any password during the procedure.
[root@ansimgmt ~]# id uid=0(root) gid=1001(lradmin) groups=1001(lradmin) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 [root@ansimgmt ~]# ssh lradmin@172.31.25.35 Last login: Mon Jun 19 02:03:34 2017 from ip-172-31-15-60.ap-south-1.compute.internal [root@web2 ~]# hostname web2 [root@web2 ~]# logout Connection to 172.31.25.35 closed. [root@ansimgmt ~]# ssh lradmin@172.31.7.221 Last login: Mon Jun 19 04:18:19 2017 from ip-172-31-15-60.ap-south-1.compute.internal [root@web1 ~]# hostname web1 [root@web1 ~]# logout Connection to 172.31.7.221 closed. [root@ansimgmt ~]#
Step3: Create inventory file for Ansible.
In the next step we need to create inventory file for the list of clients. Basically its list of client ip or hostname for machines which are being used for automation.
Please add below lines of code under file “/etc/ansible/hosts” on our management server.
[web] 172.31.7.221 ansible_user=lradmin 172.31.25.35 ansible_user=lradmin
The above lines of code describes that , list of client machines which comes under web category having Ansible user as lradmin.
Step4: Check the connection.
Now its time to check whether our configuration is properly setup or not. To do this we will be using ping module within Ansible.
#ansible -m ping web
In the above command we have used ping module for our web category server. You can also check all the modules within Ansible here.
System should respond with below messages if everything is Ok.
[root@ansimgmt ~]# ansible -m ping web
172.31.25.35 | SUCCESS => {
"changed": false,
"ping": "pong"
}
172.31.7.221 | SUCCESS => {
"changed": false,
"ping": "pong"
}
[root@ansimgmt ~]#
Step4: Executing remote commands on the client machines.
Now we can able to run random commands on our client machines to pull out some information about them. So to do this we need to use “command” module within Ansible.
- In case you wanted to have file-system utilisation of the client machine.
[root@ansimgmt ~]# ansible -m command -a "df -h" web 172.31.25.35 | SUCCESS | rc=0 >> Filesystem Size Used Avail Use% Mounted on /dev/xvda2 10G 946M 9.1G 10% / devtmpfs 478M 0 478M 0% /dev tmpfs 496M 0 496M 0% /dev/shm tmpfs 496M 13M 484M 3% /run tmpfs 496M 0 496M 0% /sys/fs/cgroup tmpfs 100M 0 100M 0% /run/user/1000 tmpfs 100M 0 100M 0% /run/user/0 172.31.7.221 | SUCCESS | rc=0 >> Filesystem Size Used Avail Use% Mounted on /dev/xvda2 10G 1.6G 8.5G 16% / devtmpfs 478M 0 478M 0% /dev tmpfs 496M 0 496M 0% /dev/shm tmpfs 496M 13M 484M 3% /run tmpfs 496M 0 496M 0% /sys/fs/cgroup tmpfs 100M 0 100M 0% /run/user/1000 tmpfs 100M 0 100M 0% /run/user/0 [root@ansimgmt ~]#
-
Checking the uptime of the client machines.
[root@ansimgmt ~]# ansible -m command -a "uptime" web 172.31.25.35 | SUCCESS | rc=0 >> 04:48:37 up 3:42, 2 users, load average: 0.00, 0.01, 0.05 172.31.7.221 | SUCCESS | rc=0 >> 04:48:37 up 3:57, 2 users, load average: 0.00, 0.01, 0.05 [root@ansimgmt ~]#
Conclusion:
Need for Automation within IT industry is getting increased day by day for reducing the cost as well time for carrying out the various tasks. There are tools or applications available in the market like Chef or Puppet. Ansilble is easy to install and configure. Also its agent less meaning that it does run any background process on clients.
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