Click the Apply Changes button to make the program active.

15.6 Configuring the Internet Services and Protocols Module

To access the configurable options of the Internet Services module, click on the Module Config link in the top left corner of its main page. This will take you to the standard configuration form, on which you can change the options shown in Table 15.3.

Table 15.2 Common RPC Programs and Their Purposes Program name Purpose

rquotad Remote disk quota retrieval. If a system is NFS-exporting a filesystem with quo- tas, this program can be used by the quota command on the client to display used and available blocks and files on the NFS-mounted filesystem.

rusersd _{Requesting the list of users logged into a system. The} rusers command can be used to display users logged into one or more servers.

walld _{Broadcasting a message to users on a server. Like the} wall command for sending a message to local users, the rwall command sends to users on another system by calling this RPC program.

Configuring the Internet Services and Protocols Module 137

The rest of the module configuration options under System configuration are set automati- cally by Webmin based on your operating system type, and so should not be changed.

Figure 15.3 The RPC program editing form. Table 15.3 Module Configuration Options

Show services with no program If set to Yes, the main page will show only Internet services that have an enabled or disabled server program assigned. On most distributions the default is No, but some have so many known ser- vices that this option has to be turned on to limit the size of the services list.

Sort services and programs by Controls the ordering of Internet and RPC services on the main page. If Name is selected, they will be ordered by service name. If Assignment is selected, all those that have an enabled server program will be listed first, followed by those with a disabled pro- gram and finally those that are unassigned.

If Order in file is chosen, the services will be displayed in the same order as they are stored in /etc/services, which is usu- ally by port number.

15.7 Other Operating Systems

Almost all versions of UNIX include inetd as standard, and use it to launch infrequently run server programs in the same way that Linux does. However, its configuration file format and capabilities are slightly different on other operating systems, which means that the module’s user interface will not be exactly the same. The main page will always show lists of Internet and RPC services, but when editing or creating a service, different fields and options will be avail- able depending on the UNIX variant you are running:

Sun Solaris

• When editing an Internet service, the Max Per Minute and Execute as Group fields are not available.

• Solaris versions 8 and above support IPv6 TCP and UDP protocols, as well as the standard IPv4 that Linux uses.

• Many RPC services exist in the disabled state by default, for things like NFS quotas and locking.

FreeBSD

• RPC services cannot have programs assigned. All you can do is edit the service names and program numbers.

• When editing or creating a service, you can control the number of server programs that can be active at any one time with the Max Child Processes field.

• Also when editing, you can set the login class that the server program runs as with the Execute as Login Class field.

NetBSD

• As on FreeBSD, the Max Child Processes and Execute as Login Class fields are available when editing or creating a service.

• As with Solaris, Internet services can use IPv6 TCP and UDP protcols. OpenBSD, Compaq Tru64/OSF1, IBM AIX, SCO OpenServer, and SCO UnixWare

• As on Solaris, the Max Per Minute and Execute as Group fields are not available. SGI Irix

• The Max Per Minute and Execute as Group fields are not available when editing a service.

• There is an additional checkbox below the server program Command field labeled Command may not exist? If this is set, it tells inetd to ignore the service if the server program is not installed. By default, this is turned on for many services related to Irix packages that are not installed by default.

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HP/UX

• On HP/UX, the module has exactly the same options as on Linux. Apple MacOS X

• As on Solaris, the Max Per Minute and Execute as Group fields are not available. • RPC services cannot have programs assigned, as on FreeBSD.

• Instead of being stored in the /etc/services file, service names and ports are in a NetInfo table. Webmin dumps and re-loads this table to read and edit services.

15.8 The Extended Internet Services Module

This module allows you to configure xinetd, a super server that is similar in purpose to inetd

but has several additional features. Like the Internet Services and Protocols module, this one can also be found under the Networking category. However, its icon will appear only if Webmin detects that xinetd is installed, which it does by looking for the /etc/xinetd.conf file. If you have compiled and installed it manually, you may need to create a symbolic link to the real location of xinetd.conf.

The main page lists all services that have server programs assigned, their port numbers, pro- tocol, program, and active status—see Figure 15.4 for an example. Services with no programs are never shown, unlike in the Internet Services module.

On Linux distributions that use xinetd, most server program packages include a file that adds an appropriate service to the list shown on the main page. These are generally disabled by default, so that services are not unexpectedly enabled the moment you install them.

If you are using a different operating system on which you have installed xinetd, the user interface will be exactly the same as on Linux. However, server program packages will probably not set up services when installed.

15.9 Enabling or Editing an Extended Internet Service

If you want to allow users to fetch mail from your system using the POP3 protocol or login via telnet it is necessary to turn on the appropriate service in this module, assuming it is listed on the main page. If not, you will need to first install the appropriate package from your distribution website or CD, which should add an entry for the service. If not, see Section 15.10 “Creating an Extended Internet Service”.

Existing services can also be changed in other ways—for example, to restrict the allowed cli- ent IP addresses or number of concurrent connections. To edit a service, the steps to follow are:

1. On the main page of the Extended Internet Services module, click on the name of the ser-