I've just started to learn the basics of Ansible which is a powerful automation tool. The first step of any automation is to setup the environment on which we are working. I'm referring Frits Hoogland's blog which is very easy to understand the basics of Ansible.
The first step is to set up your hosts file and test the connectivity between the servers. We have an inbuilt Ansible ping module to do this. Here is how my hosts file looks like
1 2 3 4 5 6 7 8 9 10 11 12 | [oracle@linux-8 ansible-project]$ cat hosts192.168.56.131192.168.56.151[l7]192.168.56.151[l8]192.168.56.131192.168.56.181[oracle@linux-8 ansible-project]$ |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | [oracle@linux-8 ansible-project]$ ansible l8 -m ping -u oracleSSH password:[WARNING]: Unhandled error in Python interpreter discovery for host 192.168.56.131: unexpected output from Python interpreter discovery192.168.56.131 | FAILED! => { "msg": "failed to transfer file to /home/oracle/.ansible/tmp/ansible-local-32681q1m7n_gx/tmpzvfmvwgz /home/oracle/.ansible/tmp/ansible-tmp-1617045011.6527164-32687-33868194395919/AnsiballZ_ping.py:\n\nOracle Home set as /u01/db/122 and SID=orcl\n"}192.168.56.181 | SUCCESS => { "ansible_facts": { "discovered_interpreter_python": "/usr/libexec/platform-python" }, "changed": false, "ping": "pong"}[oracle@linux-8 ansible-project]$ |
This "\n\nOracle Home set as /u01/db/122 and SID=orcl\n" is a environment info message I have set in the server when we login as Oracle user using .bashrc file.
Normal ssh works without any issues.
1 2 3 4 5 6 | [oracle@linux-8 ansible-project]$ ssh 192.168.56.131Web console: https://linux75.selvapc.com:9090/ or https://10.0.2.15:9090/Last login: Mon Mar 29 14:46:24 2021 from 192.168.56.181Oracle Home set as /u01/db/122 and SID=orcl[oracle@linux75 ~]$ |
We can see the info message line once we login.
The answer lies in how the connection is being established to the server. There are 4 types of shells in Unix.
- Interactive login - Login session started using graphical interface or by providing username/password via ssh
- Interactive non-login - Sessions started by opening another terminal in a server
- Non interactive non-login - Sessions started by scripts execution where the commands are run and exits the shell. We can't interact with these shells
- Non interactive login - Providing a command to run using ssh like "echo "some command" |ssh servername". Here instead of login, the session will run the "some command" and exits
So now, the difference in these shells is that the Login shells (shells started by the login system process, or by your X display manager) uses or reads .profile or .login files to set your environment or initialize your environment
Non interactive login/non-login shells, such as scripts started by shell or the Ansible ping that we are using now reads .bashrc or .kshrc files to initialize environment. Hence we should not set up any echo statements which would then become stdout to the shell initialization (which the shell won't expect) and errors out as a result.
My .bashrc file looked like the below which was causing the issue with the non interactive session from Ansible ping.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | [oracle@linux75 ~]$ cat .bashrc# .bashrc# Source global definitionsif [ -f /etc/bashrc ]; then . /etc/bashrcfi# Uncomment the following line if you don't like systemctl's auto-paging feature:# export SYSTEMD_PAGER=# User specific aliases and functionsexport ORACLE_BASE=/u01/dbexport ORACLE_HOME=/u01/db/122export PATH=$PATH:$ORACLE_HOME/binexport ORACLE_SID=orclecho "Oracle Home set as $ORACLE_HOME and SID=$ORACLE_SID" |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | [oracle@linux-8 ansible-project]$ ansible l8 -m ping -u oracle -kSSH password:192.168.56.181 | SUCCESS => { "ansible_facts": { "discovered_interpreter_python": "/usr/libexec/platform-python" }, "changed": false, "ping": "pong"}192.168.56.131 | SUCCESS => { "ansible_facts": { "discovered_interpreter_python": "/usr/libexec/platform-python" }, "changed": false, "ping": "pong"}[oracle@linux-8 ansible-project]$ |
Hope you have learnt regarding different types of Unix shells and the different initialization files they use.
References:
Happy Shelling!!! :)
