update single jail app sections

if i understand correctly, when i add a new app section to Server Config-> Jailkit-> Jailkit chroot app sections:, this works for new jails and old ones (after jailkit maintenance cronjobs)
but how do we add a new chroot app section included in jk_init.ini (eg mysql-client, uidbasics) to a single existing jail or for a single new jail?

 

My understanding is it only applies to new jails. I may be mistaken, there was improvements to jailkit use in ISPConfig 3.2.

You can use the usual jailkit commands to modify jails.

 

which are the usual commands?
to add a single program i believe it is the following
$jk_cp -f -v -j /var/www/clients/client0/webXX/ /path/to/program
but if i want to add a section from jk_init.ini to the existing jail webXX? is it:
$jk_init -c /etc/jailkit/jk_init.ini -f -k -j /var/www/clients/client0/webXX mysql_client
Doesnt work

also, out of curiosity, hardlinks is the default option in ispconfig, right?
cause in server config i have "allow hardlinks within jail" and that translates to yes from this line git.ispconfig.org/ispconfig/ispconfig3/-/blob/3.2.5/server/plugins-available/shelluser_jailkit_plugin.inc.php#L316

 

Indeed it updates old jails too through the jailkit maintenance in 3.2.5
I verified it by adding mysql through server config and today after the midnight cron job every jail had mysql command.

The jk_init command above didnt work, actually i think i am not supposed to jk_init on an existing jail, but i am trying this on a test server.
Now i need to figure out if there is a way to add a section to a single jail or i am supposed to execute
$jk_cp -f -v -j <jail> <path>
for every file in the paths = ..., of the jk_init.ini