retain jail startup output (with high enough --log-level)

[igalic]

currently, a lot of generated scripts are discarding the output of the scripts ran in the jail startup & teardown.

This makes it quite hard to develop new provisioners or just debug a jail's startup.

[gronke]

The reasons to put the entire start and stop hooks into shell scripts are performance and the missing exec.created jail hook that will be available in 12-CURRENT. We need to configure the network right after starting the jail before the services start. To achieve this only the poststart hook is used that executes all host and jail commands at once. By doing so libiocage indeed looses the relation between command execution and failures. Right now there's not much we can do about it unless we want to maintain two code paths (for releases before 12-CURRENT and after).

[igalic]

what i mean is this: setting a high enough debug level should make it so that the generated exec hooks do not have >/dev/null in them

[gronke]

There was another issue related to it. The async execution does not read from STDERR, so that any occasion of output would just let the process hang. Please feel free to contribute a patch to the iocage.helpers.exec_generator() method that adds another layer of multi-threading to deal with STDERR in addition to STDOUT.

I'm re-opening this issue until the method has been enhanced and the >/dev/null occasions were removed from the hook scripts.