I want to use a socket (mysql) in multiple jails. Using nullfs to mount it in each jail where you want to use it does not work (bug in nullfs?). Using a hardlink (if the jails reside on the same FS) works. I hope this info safes a little bit of time in case someone tries to do the same.
The hostname MySQL sees in such a connection is “localhost”. Maybe this is obvious to one or another, but because jails don’t have a 127.0.0.1 it was not obvious to me.