init system discovery script fails with: [[: not found

[Dimiter Naydenov]

On 1.24 after https://github.com/juju/juju/pull/2359 has landed (surprisingly not on master, despite the same fix was ported as https://github.com/juju/juju/pull/2358) I see errors during the cloud-init phase: http://paste.ubuntu.com/11243099/ that's due to two things I've discovered:
1. the runcmd script cloud-init generates from the given user-data starts with a "#!/bin/sh" shebang.
2. the init_system=$(...) line contains a bash-specific script, which is just inlined (see an excerpt of the user-data - http://paste.ubuntu.com/11243163/), but the "#!/usr/bin/env bash" shebang coming from juju/utils/shell/bash.go's RenderScript is getting ignored in this case (treated as a comment), and the script actually executes using /bin/sh (the system non-interactive shell dash rather than bash, since 2006).

If I apply the following patch it works without errors: http://paste.ubuntu.com/11243524/

We need to be careful when using "bashisms" in scripts and only do so when we're generating a script file to run, not when inlining scripts run (most likely) by /bin/sh in cloud-init runcmds.

UPDATE: #2359 was reverted from 1.24, but the problem is still there I believe, and master should be affected as well.

[Eric Snow (ericsnowcurrently)]

For 1.23: http://reviews.vapour.ws/r/1737/
For 1.23/master: http://reviews.vapour.ws/r/1738/

[Eric Snow (ericsnowcurrently)]

That should have been 1.24/master.