man ftpchroot (Formats) - file which lists users who need to be chrooted
NAME
ftpchroot - file which lists users who need to be chrooted
DESCRIPTION
/etc/ftpchroot is used by ftpd(8); the file contains a list of users who need to be chrooted before the ftp service is offered. Blank lines and lines beginning with "#" are ignored. Remember that the whole line will be used for the username, so please don't use the "#" character after a name to comment this entry.
EXAMPLES
/etc/ftpchroot
may contain the following entries:
#
# /etc/ftpusers
#
not_so_anonymous
FILES
/etc/ftpchroot