In order to start Pure-FTPd at boot-time, add something like this to
/etc/rc.local:

if [ -x ${PREFIX}/sbin/pure-ftpd ]; then
  echo Starting pure-ftpd
  ${PREFIX}/sbin/pure-ftpd -4 -A -B -H -u1000
fi

By default, Pure-FTPd will only listen to IPv6 addresses unless you
explicitely add the -4 switch to the command-line.