The dirname argument is the address of the pathname of a directory, terminated by an ASCII NUL. The chroot system call causes dirname to become the root directory, that is, the starting point for path searches of pathnames beginning with /.
In order for a directory to become the root directory a process must have execute (search) access for that directory.
It should be noted that chroot has no effect on the processs current directory.
This call is restricted to the super-user.
Depending on the setting of the kern.chroot_allow_open_directories sysctl variable, open filedescriptors which reference directories will make the chroot fail as follows:
If kern.chroot_allow_open_directories is set to zero, chroot will always fail with EPERM if there are any directories open.
If kern.chroot_allow_open_directories is set to one (the default), chroot will fail with EPERM if there are any directories open and the process is already subject to the chroot system call.
Any other value for kern.chroot_allow_open_directories will bypass the check for open directories
Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned and errno is set to indicate an error.
The chroot system call will fail and the root directory will be unchanged if: