Defaults in jail.conf not applied if jail block is not existing

[James Gritton]

If I'm reading it right, then yes the behavior on creating jails if
intended.  The defaults in jail.conf are only defaults to the jails listed
in jail.conf, not defaults to command-line-generated jails.  So even if you
only include an empty block for the jail, it then is a jail.conf jail and
not a command-line jail.

For the non-persistent jail poststop scripts, the only way to run them
outside the jail is to have a process outside the jail to run them from.
Cron isn't a perfect solution, but a pretty workable one.  If your jail has
a single process that runs from start to finish (i.e. not something like a
typical "command=sh /etc/rc"), then you could simply have a subshell that
runs the jail and then runs the poststop script itself:
# (jail -c name=foo command=sleep 10; echo doing cleanup) &

You may be interested in the suggested patch for jail notifications in
devctl.  That way, a jail-watch process can tell when jails start and stop.

- Jamie

On Fri, Jul 19, 2019 at 10:29 AM Luca Pizzamiglio <pizzamig at freebsd.org>
wrote:

> Hi all,
>
> I have 2 silly questions and I think I know the answer.
> I'd like to use the command line jail tool start and configure my jails;
> however, I'd like to have defaults set up in a central place.
>
> I thought I could put those defaults in /etc/jail.conf and then dynamically
> create my jails with the cli tool.
> However, if the jail create (or stop) is not explicitly listed in
> jail.conf, the defaults are not applied.
> If I add an empty configuration block, then the default values are applied.
>
> Is this an intended behavior?
>
> The second question is about not persistent jails.
> Once all processes in the jail exits, the jail is automatically destroyed.
> However, without invoking jail -r , there is no way (that I'm aware of) to
> invoke a poststop script automatically.
> Is there a workaround or a suggested way to have a callback/script invoked
> when a jail disappear? (currently, I'm not happily considering a cronjob as
> a solution)
>
> Thanks in advance for the support!
>
> Best regards.
> pizzamig@
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