Red Hat Enterprise Linux 5 Administration Unleashed

The xinetd Super Server 385. A pattern that begins with a period specifies all hostnames that end with thepattern. For example, the pattern .example.com matches the hostnamehost.example.com.. A pattern that ends with a period specifies all IP address that begin with the pattern.For example, the pattern 192.168. includes 192.168.0.2.. A pattern that begins with the @ character is used to specify an NIS netgroup name.. A pattern in the form of a netmask pair such as 192.168.1.0/255.255.255.0 can beused to specify a subnet.. A pattern in the form of a [net]/prefixlen pair or [n:n:n:n:n:n:n:n]/m can be used tospecify a network.. A pattern is considered a filename if it begins with a forward slash (/). The fileshould contain zero or more lines with zero or more hostname or address patternsseparated by whitespace.. Some patterns can use the * or ? character as a wildcard. It can’t be used in conjunctionwith the following patterns: netmask matching, hostname pattern that beginswith a period, or IP address pattern that ends with a period.In the daemon_list and client_list, the following wildcards can be used:. ALL: The universal wildcard, always matches.. LOCAL: Any hostname that doesn’t contain a dot character.. UNKNOWN: Any user whose name is unknown and any host whose name or address isunknown.. KNOWN: Any user whose name is known and any host whose name and address areknown. Use this pattern with caution: Hostnames may be temporarily unavailabledue to DNS issues.. PARANOID: Any hostname that doesn’t match its address.In both daemon_list and client_list, the EXCEPT operator can be used to exclude namesfrom the list. However, use caution with this operator because it makes it more difficultfor administrators to read the access rules.19TIPUse the command man 5 hosts_access to learn more about the hosts.allow andhosts.deny files.Individual Access Control for xinetdThe default /etc/xinetd.conf file lists most of the access control attributes. They can begiven default values in /etc/xinetd.conf and can also be given values per individualservice in the individual service files in the /etc/xinetd.d/ directory.