Hi All,
could you please tell in layman language how ansible different from Shell or pearl scripting apart from Ansible Orchestration and Ansible Tower
Regards
Kanna
One way to think about this is to examine a non-trivial Ansible playbook
and try to imagine how much work would be required to duplicate what
it does in bash or perl. It's important to include the capabilities
of inventory management, access control, and other features of Ansible.
Jon Forrest
When done right, Ansible is "idempotent", which means if you run the same script multiple times on the same host, it will only do what it needs to do to configure the host. It will check the state of the thing you have told it to change to determine if it needs to make the change. If not, it moves on to the next step. With shell scripts, you have to write that check in yourself, which can be rather complex. Example: you want to enable a service. The "service" module will do this for you, and you can "enable" it (configure it to start on boot) AND start it in a single task. The module will check if the service is already enabled and enable it if it needs to, and it will detect if the service is already running and only start it if it's not running. With a shell script, unless you specifically write in the logic to check if the service is already running and just tell it to start the service, you'll probably get an error. Similarly, if you tell it to REstart the service, the module will do what it needs to do. If it's not running, it will start it. If it is running, it will stop it first, then start it. In Red Hat, if you just do "service X restart" it might handle that fine if it's not running already, or it might not, depending how the start script was written. Also, by using the "service" module, you don't have to worry about what the correct command is to do that on Red Hat (or even RHEL 6 initd vs RHEL 7 systemd) vs Debian vs Suse. The module will figure that out for you and you only have to write one task to work on all three. (Note: this doesn't help if the name of the service is different on all three, it only covers knowing the correct service restart command. Apache is "httpd" on RHEL, but may be "apache" on Debian for instance. In this case you'd need to account for this, but again, not hard to do in Ansible.)
Also, though not necessarily an intentional part of the design, I find it useful if I want to run the same command / script on multiple servers. I don't have to write a complicated for loop in a shell script to log into each host and run a command. If I want to gather a piece of information from a dozen hosts, I can do a quick Ansible specifying the hosts I want from my inventory and it will log into each of them and run the command.
ex: I want to start Postfix on all my mail servers. I already have a "group" in my inventory file called, appropriately "mailservers".
ansible -i inventoryfile mailservers -b -m service -a "name=postfix state=started"
With a shell script I'd have to do something like:
for server in server1 server2 server3 server4 server5; do ssh $server "if [! $(sudo service postfix status); then sudo service postfix start; fi"; done
And I'm only about 85% confident that will work right without testing it, and it will probably only work on a RHEL system, and assumes the "postfix" init script accepts "status" as an argument.