Jail is a chrooted environment using bash. its main use is to put it as shell for any user you want to be chrooted. Their primary goals is to be simple, clean, and highly portable.
Changes: Path splitting was removed since it is not necessary. The user directory and its shell are now chosen from the data stored in the /etc/passwd inside the chrooted environment. The "no such file or directory" bug has been removed. mkenv.sh has been fully rewritten, and it now supports the different platforms within it. mkenv.sh supports guessing the libraries needed for the executable files being copied into the chrooted environment. Also, mkenv.sh protects you from overwriting the customized files (/etc/passwd /etc/group and /etc/shadow) so you can have multiple users in a single chrooted environment.