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NOTE: CentOS Enterprise Linux is built from the Red Hat Enterprise Linux source code. Other than logo and name changes CentOS Enterprise Linux is compatible with the equivalent Red Hat version. This document applies equally to both Red Hat and CentOS Enterprise Linux.

2.5. Preparing for a Network Installation

NoteNote
 

Make sure an installation CD (or any other type of CD) is not in your hosting partition's drive if you are performing a network-based installation. Having a CD in the drive may cause unexpected errors.

The Red Hat Enterprise Linux installation media must be available for either a network installation (via NFS, FTP, or HTTP) or installation via local storage. Use the following steps if you are performing an NFS, FTP, or HTTP installation.

The NFS, FTP, or HTTP server to be used for installation over the network must be a separate machine which can provide the complete RedHat/ directory. Both the RedHat/base/ and RedHat/RPMS/ directories must be available and populated with all files from all installation CD-ROMs.

NoteNote
 

The directory specified in the following refers to /location/of/disk/space/. This means it is the directory up to, but not including, the RedHat/ distribution directory. For example, if you have Red Hat Enterprise Linux 4 installation files located in /export/rhel/ on the installation staging server, /location/of/disk/space/ would be /export/rhel/.

To copy the RedHat/ directory from the installation CD-ROMs to a Linux machine which acts as an installation staging server, perform the following steps:

  • For each binary CD-ROM, execute the following commands:

    • mount /mnt/cdrom

    • cp -var /mnt/cdrom/RedHat /location/of/disk/space

      where /location/of/disk/space/ is a directory you create such as /export/rhel/

    • umount /mnt/cdrom/

  • Note that the Release Notes are not included in the RedHat directory. Unless they are specifically copied over, the Release Notes will not be available during your installation of Red Hat Enterprise Linux. The Release Notes are formatted in HTML files located at the root of the disc. Copy the files to your installation directory. For example:

    cp /mnt/cdrom/RELEASE-NOTES*.html /location/of/disk/space/

    The Release Notes are also available online from https://www.redhat.com/docs/.

  • Next, make /location/of/disk/space/ available for network installation via NFS, FTP, or HTTP and verify access from a client system.

  • For NFS, export the directory by adding an entry to /etc/exports to export to a specific system:

    /location/of/disk/space client.ip.address(ro,no_root_squash)

    To export to all machines (not appropriate for all NFS systems), add:

    /location/of/disk/space *(ro,no_root_squash)

    Start the NFS daemon (on a Red Hat Enterprise Linux machine, use /sbin/service nfs start). If NFS is already running, reload the configuration file (on a Red Hat Enterprise Linux system, use /sbin/service nfs reload).

    Be sure to test the NFS share following the directions in the Red Hat Enterprise Linux System Administration Guide.

    If the RedHat/ directory does not appear in the NFS shared directory, the wrong path may have been mounted and/or exported.

  • FTP and HTTP installations also support a second type of tree structure. To make it easier to access the contents of the installation CD-ROMs, mount each CD-ROM or ISO image with the following mount point on the FTP or HTTP server (where X is the number of the CD-ROM or ISO image):

    /location/of/disk/space/discX/

    For example:

    mount -o loop CD1.iso /location/of/disk/space/disc1/

2.5.1. Using ISO Images for NFS Installs

NFS installations can use ISO (or CD-ROM) images rather than copying an entire installation tree. After placing the required ISO images (the binary Red Hat Enterprise Linux CD-ROMs) in a directory, choose to install via NFS. You will then point the installation program at that directory to perform the installation.

Verifying that the ISO images are intact before you attempt an installation will help to avoid problems that are often encountered during an NFS installation. To verify the ISO images are intact prior to performing an installation, use an md5sum program (many md5sum programs are available for various operating systems). An md5sum program should be available on the same server as the ISO images.

NoteNote
 

The Red Hat Enterprise Linux installation program has the ability to test the integrity of the installation media. It works with the CD, DVD, hard drive ISO, and NFS ISO installation methods. Red Hat recommends that you test all installation media before starting the installation process, and before reporting any installation-related bugs (many of the bugs reported are actually due to improperly-burned CDs). To use this test, type the following command at the boot: prompt (prepend with elilo for Itanium systems):

linux mediacheck

Additionally, if a file called updates.img exists in the directory from which you install, then it will be used for installation program updates. Refer to the file install-methods.txt in the anaconda RPM package for detailed information on the various ways to install Red Hat Enterprise Linux, as well as how to apply the installation program updates.

NoteNote
 

You can only have the ISO images for one release and one variant of Red Hat Enterprise Linux in the directory.

 
 
  Published under the terms of the GNU General Public License Design by Interspire