Download Safari Books Online apps: Apple iOS | Android

Entire Site

Safari Books Online

    Free Trial

    Safari Books Online is a digital library providing on-demand subscription access to thousands of learning resources.


    • Create BookmarkCreate Bookmark
    • Create Note or TagCreate Note or Tag
    • DownloadDownload
    • PrintPrint
    Share this Page URL
    Help

    Chapter 19. Network Services > Xinetd: The Master Service

    Xinetd: The Master Service

    As a system administrator, you will most likely need to provide your users with network and Internet services. These services may include FTP, HTTP, or Telnet. Although some software packages like Apache provide a single service (HTTP), there is also a master service called xinetd that can run multiple services at the same time. Although the Red Hat Exam Prep Guide doesn’t specify any particular xinetd service, you may need it to configure basic services on the exam. It is also a widely used service in the real world, particularly when it comes to automating the installation of Red Hat. There are really only a few things that you need to know to be able to use the xinetd service. This package doesn’t always come installed by default, so first let’s install it.

    Step 1.
    Install the xinetd package:

    # yum install –y xinetd

    Step 2.
    Verify that the package is installed correctly:

    # rpm -qa | grep xinetd
xinetd-2.3.14-29.el6.x86_64

    With the service installed, you can shift your focus to the config files. The xinetd service has a master config file (/etc/xinetd.conf), which inherits all the settings of the services that it controls. Aside from this master config file, a single directory (/etc/xinetd.d) contains individual config files for each service you would like xinetd to run. As an example, let’s set up a TFTP server, which can be used to back up config files for Cisco switches or to deliver data to clients during a PXE boot process (also known as a network installation). We looked at PXE boot earlier in Chapter 8, “Network Installs.” To get started, you just need to install the TFTP server package.

    Step 3.
    Install the required package:

    # yum install -y tftp-server

    Step 4.
    Verify that the package is installed correctly:

    # rpm -qa | grep tftp
tftp-server-0.49-5.1.el6.x86_64

    Now that the package is installed, you can go into the /etc/xinetd.d directory and see the config file for the new service. By default, the TFTP service is disabled. Let’s look at the config file, which is small and simple to understand.

    # cat /etc/xinetd.d/tftp
service tftp
{
        socket_type             = dgram
        protocol                = udp
        wait                    = yes
        user                    = root
        server                  = /usr/sbin/in.tftpd
        server_args             = -s /tftpboot
        disable                 = yes
        per_source              = 11
        cps                     = 100 2
        flags                   = IPv4
}

    Here, you can see the basics, such as which protocol it uses, whether the service is disabled, and what arguments are passed to the service during startup. For this example, all the defaults work fine. You may be wondering why I suggest leaving the service disabled if you want to use it. Services that are controlled by xinetd can be enabled in the config file when you enable them during the boot process.

    Step 5.
    Enable the TFTP server to start when the system boots:

    # chkconfig tftp on

    Step 6.
    Verify that the service will start during boot:

    # chkconfig tftp --list
tftp            on

    Looking back in the config file now, notice that the service has been automatically enabled to start. You can verify this by checking the file:

    # cat /etc/xinetd.d/tftp | grep disable
         disable = no

    Step 7.
    At this point, you should also enable the xinetd service itself to start on system boot:

    # chkconfig xinetd on

    Step 8.
    Verify that the service will start during boot:

    # chkconfig xinetd --list
xinetd          0:off   1:off   2:off   3:on    4:on    5:on    6:off

    There is also one other thing you can verify. You can get a list of all services enabled during boot by using the chkconfig command. The difference here, though, is that the xinetd service lists not only its boot levels, but also those of all the services that it controls.

    Step 9.
    Use chkconfig to view all the xinetd services:

    # chkconfig --list
xinetd          0:off   1:off   2:on    3:on    4:on    5:on    6:off
xinetd based services:
         chargen-dgram: off
         chargen-stream: off
         daytime-dgram: off
         daytime-stream: off
         discard-dgram: off
         discard-stream: off
         echo-dgram:    off
         echo-stream:   off
         tcpmux-server: off
         tftp:           on
         time-dgram:    off
         time-stream:   off

    You can see here that the xinetd service is set to start on boot and that the TFTP service is the only service it will start.

    Step 10.
    To get the service up and running without a system reboot, just adjust any config file options you’d like and restart the xinetd service:

    # service xinetd restart
Stopping xinetd:                                          [  OK  ]
Starting xinetd:                                          [  OK  ]

    Step 11.
    Verify that the xinetd service is now running on the system and listening on UDP port 69 for connections:

    # netstat -a | grep tftp
udp        0      0 *:tftp                      *:*


      

    You are currently reading a PREVIEW of this book.

                                                                                            

    Get instant access to over
    $1 million worth of books and videos.

      

    Start a Free Trial