check.proc.writable.markdown

The context behind all the 'check proc writable' stuff.

It all started with this P/R

When provisioning Riak via Ansible in a constrained container environment, like modern version of Docker, access to /proc and /sys is locked down, which prevents sysctl from operating.

As far as I can tell, the sysctl commands here (and in ansible-riak-common) don't affect the installation, but are performance improvements.

So, ignoring errors here seems safe.

Let me know if this is reasonable (or if there is a better way). If so, I can make a similar pull request on ansible-riak-common.

So... simple enough. In the somewhat less common use case where the role is applied in a restricted environment, and it is not possible to tune sysctl.. don't fail the entire role.. just continue on.

But we went for a more complicated approach with lots of checks, and callbacks and handlers, with a result that the entire role broke under Ubuntu because of a missing callback.