1. Filtering is determined by looking in the /etc/hosts.deny and /etc/hosts.allow files, respectively. A suggested method to help secure a system is to deny all services to everyone by adding a line to /etc/hosts.deny with the following line:

ALL: ALL

Access should then be granted on a service, machine or subnet basis in the /etc/hosts.allow file thusly:

ftp: .fnal.gov @dcdsv0.fnal.gov
ALL: .fnal.gov

The first line will allow anyone in the fnal.gov subnet and anyone in the netgroup dcdsv0.fnal.gov to ftp to the machine. The second line will allow all services to anyone in the fnal.gov domain.

2. Logs of access go to /var/log/messages and other files in /var/log/.

B. xntp is a time client to sync the system to other systems in the subnet or other servers in the world.

C. xntp is run at boot time so a symbolic links should reside in the /etc/rc.d/rc3.d and rc5.d directories pointing to /etc/rc.d/init.d/xntpd. Look at the startup script in the init.d dir and make sure that the daemon is started with the -b option. This will set xntpd to listen mode. It will then sync the system clock from periodic time broadcasts from the routers on site.