Air-gapped documentation describes how to use a mirrored operator image

[jeanfabrice]

Add a chapter how to run the ECK operator itself in an air-gapped environment

[kunisen]

Thanks @jeanfabrice for raising the doc PR!! 🙇
I built the docs and found {eck_version} is not reflected as the real version, as other sections in ECK docs.
Maybe you need to tweak the asciidoc and copy from other places to see if it can show the correct version.

---

# you can clone elastic/docs repository and run this command to build the ECK docs and show it in browser
# https://github.com/elastic/docs/blob/master/doc_build_aliases.sh
> docbldeck --open

[jeanfabrice]

Let me check. I naively thought this variable would be available cross doc page. Maybe the current doc page is missing some bits of configuration. Thanks!

[cla-checker-service]

💚 CLA has been signed

[jeanfabrice]

@kunisen According to https://docs.asciidoctor.org/asciidoc/latest/text/monospace/, asciidoc attributes, like {eck_version}, should resolve properly when used inside monospace code.
It doesn't work with our doc builder, and I don't know why. Note that the simple documentation example, E=mc^2^, doesn't work either.
I'm asking the doc team.

[jeanfabrice]

@kunisen the issue with the attribute resolution is now fixed

[kunisen]

Thank you Jean-Fabrice so much for the amazing effort!

[pebrc]

Looks good thanks for raising this.