# First, added `root` group via System Preferences > Users & Groups
# (`/sbin/groupadd` is not present on macOS)

$ sudo chown root:root /Users/jail
$ ls -ld /Users/jail
drwxr-xr-x+ 13 root  root  442 Jan 12 15:21 /Users/jail
$ sudo /usr/local/Cellar/jailkit/2.19/sbin/jk_init -v /Users/jail basicshell
ERROR: /Users/jail is not owned by root:root!

ERROR: jail directory /Users/jail is not safe