Many UNIX system administrators are accustomed to using TCP
wrappers to manage access to certain network services. Any network
services managed by xinetd (as well as any
program with built-in support for libwrap)
can use TCP wrappers to manage access. xinetd can use the /etc/hosts.allow and /etc/hosts.deny files to configure access to system
services. As the names imply, hosts.allow
contains a list of rules that allow clients to access the network
services controlled by xinetd, and
hosts.deny contains rules to deny access.
The hosts.allow file takes precedence
over the hosts.deny file. Permissions to
grant or deny access can be based on individual IP address (or
hostnames) or on a pattern of clients. Refer to the Red Hat Enterprise Linux Reference Guide and
hosts_access in section 5 of the man
pages (man 5 hosts_access) for
details.
To control access to Internet services, use xinetd, which is a secure replacement for inetd. The xinetd daemon
conserves system resources, provides access control and logging,
and can be used to start special-purpose servers. xinetd can be used to provide access only to
particular hosts, to deny access to particular hosts, to provide
access to a service at certain times, to limit the rate of incoming
connections and/or the load created by connections, and more
xinetd runs constantly and listens on
all ports for the services it manages. When a connection request
arrives for one of its managed services, xinetd starts up the appropriate server for that
service.
The configuration file for xinetd is
/etc/xinetd.conf, but the file only
contains a few defaults and an instruction to include the
/etc/xinetd.d directory. To enable or
disable an xinetd service, edit its
configuration file in the /etc/xinetd.d
directory. If the disable
attribute is set to yes, the service
is disabled. If the disable
attribute is set to no, the service is
enabled. You can edit any of the xinetd
configuration files or change its enabled status using the
Services Configuration Tool, ntsysv, or chkconfig.
For a list of network services controlled by xinetd, review the contents of the /etc/xinetd.d directory with the command ls /etc/xinetd.d.
