Ansible: [WARNING]: Platform linux on host web1 is using the discovered Python
Ansible had to guess which Python to run modules with on the managed host, and warns because a later package install could change the answer. It is harmless on its own, but the same guessing is behind confusing failures elsewhere: a module that says a library is missing when you installed it for a different Python, or a playbook that works on one host and not another with the same OS.
Quick fix
Read the commands before running them. Anything that restarts a service, deletes data or changes permissions should be tried on a non-production system first.
# What did Ansible pick on each host?
ansible all -m setup -a 'filter=ansible_python*'
# Pin it per group in the inventory, so it never guesses
# [webservers:vars]
# ansible_python_interpreter=/usr/bin/python3
# Or pin it for a single host on the command line
ansible web1 -m ping -e ansible_python_interpreter=/usr/bin/python3
# Keep discovery but silence the warning (ansible.cfg, [defaults])
# interpreter_python = auto_silent
# Install module dependencies for the interpreter Ansible actually uses
ansible web1 -m pip -a 'name=docker' -e ansible_python_interpreter=/usr/bin/python3How to diagnose Ansible errors
Ansible errors split cleanly between transport problems (it cannot reach or authenticate to the host) and execution problems (it reached the host but the play failed). The message header tells you which: UNREACHABLE! is transport, FAILED! is execution. Transport issues are SSH issues wearing an Ansible hat and should be debugged with plain ssh first.
If the quick fix above does not resolve it, work through these steps. They apply to this whole class of error, not just to this one message, which is usually what saves the time.
- Run
ansible -m ping allbefore running any playbook. It isolates connectivity and privilege escalation from your task logic. - Raise verbosity progressively:
-vshows results,-vvvshows the SSH command line,-vvvvshows connection debugging. Most unreachable errors are solved at-vvv. - Use
--check --diffto see what a play would change without changing it. This turns a destructive debugging loop into a safe one. - For undefined-variable errors, dump the actual scope with a
debugtask (var: hostvars[inventory_hostname]) rather than reasoning about precedence from the docs. - Remember variable precedence order: extra vars (
-e) beat everything, role defaults lose to everything. Surprising values are nearly always a precedence surprise.
Tools worth reaching for
ansible -m pingansible-playbook --check --diffansible-lintssh -vvv
Authoritative references
Primary documentation for this error, worth reading before applying any fix in production.
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Something missing or wrong?
This entry is maintained by hand. If the fix is out of date, incomplete, or you have a better one, email a correction and it will be reviewed.