You can customize the standard ESXi installer ISO image with your own installation or upgrade script. This enables you to perform a scripted, unattended installation or upgrade when you boot the resulting installer ISO image.

Before you begin

  • Linux machine.

  • The ESXi ISO image VMware-VMvisor-Installer-5.x.x-XXXXXX.x86_64.iso,where 5.x.x is the version of ESXi you are installing, and XXXXXX is the build number of the installer ISO image.

  • Your custom installation or upgrade script, the ks_cust.cfg kickstart file.

About this task

See also About Installation and Upgrade Scripts and About the boot.cfg File.


  1. Download the ESXi ISO image from the VMware Web site.
  2. Mount the ISO image into a folder:

    mount -o loop VMware-VMvisor-Installer-5.x.x-XXXXXX.x86_64.iso /esxi_cdrom_mount

    XXXXXX is the ESXi build number for the version that you are installing or upgrading to.

  3. Copy the contents of cdrom to another folder:

    cp -r /esxi_cdrom_mount /esxi_cdrom

  4. Copy the kickstart file to /esxi_cdrom

    cp ks_cust.cfg /esxi_cdrom

  5. (Optional) : Modify the boot.cfg file to specify the location of the installation or upgrade script by using the kernelopt option.

    You must use uppercase characters to provide the path of the script, for example,

    kernelopt=runweasel ks=cdrom:/KS_CUST.CFG

    The installation or upgrade becomes completely automatic, without the need to specify the kickstart file during the installation or upgrade.

  6. Recreate the ISO image:

    mkisofs -relaxed-filenames -J -R -o custom_esxi.iso -b isolinux.bin -c -no-emul-boot -boot-load-size 4 -boot-info-table /esxi_cdrom


The ISO image now includes your custom installation or upgrade script.

What to do next

Install ESXi from the ISO image.