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xinetd is a powerful replacement for inetd.
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Original site: http://www.xinetd.org
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xinetd has access control mechanisms, extensive logging capabilities,
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the ability to make services available based on time, can place
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limits on the number of servers that can be started, and has deployable
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defence mechanisms to protect against port scanners, among other things.
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There are a number of differences between xinetd and inetd. The
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largest difference to the end user is the config file. xinetd's
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config file format is more C like, and somewhat similar to bind 8's.
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xinetd's reconfig signal is now SIGHUP. SIGUSR2 still works for now,
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but should be considered deprecated. The state dump signal is now
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There are a couple of compile time options to xinetd:
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--with-libwrap : This option to the configure script tells xinetd
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to compile in support for tcp wrappers. You must already have libwrap
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installed on your system. This option will have xinetd pay attention
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to your /etc/hosts.{allow|deny} files. With this option turned on,
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xinetd will first look at your /etc/hosts.{allow|deny} files, then
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if access is granted, it goes through xinetd's internal access control
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mechanisms. Note that xinetd passes the server name if there is one,
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otherwise it uses the service id, *not* the service name to libwrap -
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this is a change from previous behaviour.
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--with-loadavg : This option to the configure script tells xinetd
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to compile in support for the max_load configuration option. This
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option allows you to have certain services disabled when the system
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load gets above a specified level. This is highly operating system
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specific. It currently has been tested on linux, and there is
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developmental support for solaris 2.6 and higher.
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--with-inet6 : Services default to IPv6 (PF_INET6) sockets.
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Now that IPv6 support is fully integrated into xinetd, this option
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is almost meaningless. IPv6 sockets are available with the "IPv6"
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service flag, even without this option.
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As of xinetd 2.1.8.8pre3 there is a change in the handling of
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names specified in the access control directives, only_from and
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no_access. For numerical entries in these fields, nothing has
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The way it used to be: When xinetd started, it would lookup the
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name(s) specified. It would then collect all the IP addresses
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associated with that name, and store them in the access control
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lists. This led to problems of acls being out of date, and
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access controls being messed up when names were specified. It did
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have the advantage of not waiting for a lookup to happen when you
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The way it is now: xinetd keeps all the names you specify on the
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access control directives. When a client attempts to connect to
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a service, a reverse lookup is performed on the client's IP address.
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The canonical name returned is compared with the specified names.
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If the first character of the name being specified in the config
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file is a '.', then all hosts within that domain are matched.
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For example, if I put .synack.net, all hosts with a reverse mapping
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that are in .synack.net domain, are matched.
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For libwrap access control, the access control is done by the
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server name for the service. So, if you have an entry like this:
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server = /usr/sbin/in.telnetd
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Your corresponding hosts.{allow|deny} entry would look something
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However, many services don't have a "server". Internal services
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and redirection services don't have a "server" line in the configuration
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file. For these services, the service name is used. For example:
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redirect = 10.0.0.1 23
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Your hosts.{allow|deny} entry would look something like this:
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So, in general, if a service has a "server" attribute to it, access
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control is performed based on that entry. If a service does not have
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a "server" attribute, (internal and redirection services) then access
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control is based on the service name.
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This is only for libwrap access control.
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I will continue to keep itox in the distribution, and fix any bugs or
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compatibility issues that come to my attention, but I probably won't
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get around to adding features. If someone else would like to pick this
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up, let me know and I'd be happy to incorporate changes.
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I have made a quick perl script (xconv.pl) to replace itox. xconv.pl
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does a straight translation of inetd.conf file syntax to xinetd.conf.
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It handles tcpd correctly, warns on the use of rpc services,
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sets the REUSE flag, and handles groups properly if your inetd.conf file
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xinetd was originally written by panos@cs.colorado.edu. At least one other
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version of xinetd has been seen floating around the net. This version is
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being maintained by Rob Braun (bbraun@synack.net) and bug reports for this
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version should be directed there.
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Known bugs: On some BSD's, you may need to set 'groups = yes' in your services.
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If you need this, and you don't specify 'groups = yes', you'll get a log
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message telling you it is needed, when you connect to a service.
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Bug reports/comments/suggestions/flames for this version should be sent
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