The host that I am executing the Ansible commands from is a standard RHEL 7.2 install. The remote nodes however are booting a read-only root file system (RHEL 7.3), with a layer of writable directories that I can specify, and are copied into tmpfs. I added /root/.ansible to the writable directories, which has allowed me to execute ad-hoc Ansible commands, and some playbooks, but some playbooks are failing, such as when I try to use async with poll value other than 0. For example:
try enabling pipelining, which avoids most writes.
I found that if i enabled read-write to ~/.ansible_async, I was able to execute a playbook with async and a non-zero value for poll. It would be very helpful to know if there are any additional directories that need write access.
I can also look into enabling pipelining, but if it avoids most writes, then I will still need to know which directories will need to be writable in that case as well.
Ansible uses tmp directories, different ones depending on
circumstance, ~/.ansible_async is for when tasks are async, normally
it is an ~/.ansible/tmp (you can change in config) in the user's dir,
but in some cases it falls back to /tmp or /var/tmp.
Pipelining eliminates the file copies or need for tmp dir for the
modules themselves, but if doing actions like copy, assemble or
template, a dir is still needed to transfer the files to the target,
but uses same temps as modules themselves normally do.