Chapter 6. Completing post customization tasks

Procedure

1. Navigate to a working directory such as /tmp, and create a subdirectory named product/:

   $ cd /tmp

2. Create a subdirectory product/

   $ mkdir product/

3. Create a directory structure identical to the location of the file you want to replace. For example, if you want to test an add-on that is present in the /usr/share/anaconda/addons directory on the installation system, create the same structure in your working directory:

   $ mkdir -p product/usr/share/anaconda/addons

   Note

   To view the installer’s runtime file, boot the installation and switch to virtual console 1 (Ctrl+Alt+F1) and then switch to the second tmux window (Ctrl+b+2). A shell prompt that can be used to browse a file system opens.

4. Place your customized files (in this example, custom add-on for Anaconda) into the newly created directory:

   $ cp -r ~/path/to/custom/addon/ product/usr/share/anaconda/addons/

5. Repeat steps 3 and 4 (create a directory structure and place the custom files into it) for every file you want to add to the installer.

6. Create a .buildstamp file in the root of the directory. The .buildstamp file describes the system version, the product and several other parameters. The following is an example of a .buildstamp file from Red Hat Enterprise Linux 8.4:

   [Main]
   Product=Red Hat Enterprise Linux
   Version=8.4
   BugURL=https://bugzilla.redhat.com/
   IsFinal=True
   UUID=202007011344.x86_64
   [Compose]
   Lorax=28.14.49-1

   The IsFinal parameter specifies whether the image is for a release (GA) version of the product (True), or a pre-release such as Alpha, Beta, or an internal milestone (False).

7. Navigate to the product/ directory, and create the product.img archive:

   $ cd product

   $ find . | cpio -c -o | gzip -9cv > ../product.img

   This creates a product.img file one level above the product/ directory.

8. Move the product.img file to the images/ directory of the extracted ISO image.

Procedure

1. Make sure that all of your changes are included in the working directory. For example, if you are testing an add-on, make sure to place the product.img in the images/ directory.
2. Make sure your current working directory is the top-level directory of the extracted ISO image, for example, /tmp/ISO/iso/.

3. Create a new ISO image using the genisoimage:

   # genisoimage -U -r -v -T -J -joliet-long -V "RHEL-8 Server.x86_64" -volset "RHEL-8 Server.x86_64" -A "RHEL-8 Server.x86_64" -b isolinux/isolinux.bin -c isolinux/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table -eltorito-alt-boot -e images/efiboot.img -no-emul-boot -o ../NEWISO.iso .

   In the above example:

   • Make sure that the values for -V, -volset, and -A options match the image’s boot loader configuration, if you are using the LABEL= directive for options that require a location to load a file on the same disk. If your boot loader configuration (isolinux/isolinux.cfg for BIOS and EFI/BOOT/grub.cfg for UEFI) uses the inst.stage2=LABEL=disk_label stanza to load the second stage of the installer from the same disk, then the disk labels must match.

     Important

     In boot loader configuration files, replace all spaces in disk labels with \x20. For example, if you create an ISO image with a RHEL 8.0 label, boot loader configuration should use RHEL\x208.0.

   • Replace the value of the -o option (-o ../NEWISO.iso) with the file name of your new image. The value in the example creates the NEWISO.iso file in the directory above the current one.

     For more information about this command, see the genisoimage(1) man page.

4. Implant an MD5 checksum into the image. Note that without an MD5 checksu, the image verification check might fail (the rd.live.check option in the boot loader configuration) and the installation can hang.

   # implantisomd5 ../NEWISO.iso

   In the above example, replace ../NEWISO.iso with the file name and the location of the ISO image that you have created in the previous step.

   You can now write the new ISO image to physical media or a network server to boot it on physical hardware, or you can use it to start installing a virtual machine.