There are many ways to boot an ESXi 7 host from different media or from a network. The topic of boot options for VMware ESXi is one that you need to master in order to pass the datacenter certification exam. In this post, we can cover only the fundamentals.

VMware has changed the storage requirements and completely changed the partition layout in ESXi 7. VMware has increased the bootbank sizes, and it has consolidated the system partitions and made them expandable.

The layout of system-storage boot media was changed mainly to prepare for the future, since VMware is planning to add new features and capabilities in later releases. The partition layout can now consume up to 138 GB of disk space, which limits the space available to create a VMFS datastore.

These are the media options for booting the ESXi installer:

  1. Boot from a CD or DVD.
  2. Boot from a USB device.
  3. Boot from a network using the Preboot Execution Environment (PXE).
  4. Boot from a remote location using a remote management application: HP Integrated Lights-Out (iLO), Dell Remote Access Card (DRAC), IBM management module (MM), and Remote Supervisor Adapter II (RSA II).

Boot from a CD, a DVD, or a USB device

Booting from a CD or DVD is pretty straightforward. It is an interactive process in which you choose the disk or partition where you would like to install the ESXi 7 hypervisor. Other steps, like networking or password configuration, are also easy; so we won't go into much detail here. You can also use a script.

You can create an installer ISO that includes the installation script. With an installer ISO image, you can execute a scripted, unattended installation when you boot the resulting installer ISO image. The installation is then completely automated.

For further details, see "VMware ESXi Installation and Setup," a reference document that is studied to prepare for the VCP-DCV certification exam.

Boot from PXE

In this network environment, in which you can use the TFTP server to PXE-boot the ESXi installer, you usually choose whether the target host supports a UEFI boot or just the legacy BIOS. Most environments now support UEFI, which was not always the case.

Overview of PXE boot installation process

Overview of PXE boot installation process

What's happening in the background:

  • The user boots the target ESXi host.
  • The target ESXi host makes a DHCP request.
  • The DHCP server responds with the IP information and the location of the TFTP server.
  • The ESXi host contacts the TFTP server and requests the file that the DHCP server has specified.
  • The TFTP server sends the network boot loader, and the ESXi host executes it. There is an additional boot loader that can be loaded after the initial boot; it is also from the TFTP server.
  • The boot loader searches for a configuration file on the TFTP server, downloads the kernel and other ESXi components from the HTTP server or the TFTP server, and boots the kernel on the ESXi host.
  • The installer runs interactively or by using a kickstart script, as specified in the configuration file.

This, in essence, is all the magic of the process.

Scripted ESXi 7 installation

ESXi Installation scripts provide an efficient way to deploy multiple hosts and to deploy hosts remotely. You can use an installation script that includes the settings for installing ESXi. The script can be applied to all of the hosts that need to have the same configuration. Only supported commands can be used in the installation script. This script can be modified to specify settings that need to be unique for each host. The installation script can be stored on an FTP server, an HTTP or HTTPS server, an NFS server, or a USB flash drive.

To start the installation script, enter boot options at the ESXi installer boot command line. At boot time, press Shift+O in the boot loader, enter boot options, and access the kickstart file.

Press Shift plus O during the boot process

Press Shift plus O during the boot process

If you are using a PXE boot to install, options can be passed through the kernelopts line of the boot.cfg file. The location of the installation script is set with the ks=filepath option, where filepath is the location of the kickstart file. If ks=filepath is not included in the script, the text installer is executed.

For example, at the runweasel command prompt, you could enter ks= along with the path to the installation script and the command-line options. You could enter the following options to boot the host from a script named esxi-script residing on the server 192.168.1010.10 and set the IP address of the host to 192.168.100.101:

ks=http://192.168.100.10/kickstart/esxi-script.cfg

nameserver=192.168.1.100 ip=192.168.100.101

netmask=255.255.255.0 gateway=192.168.100.101

Check the documentation to see all the different options. There is a default installation script included with the ESXi installer that can be used to install ESXi onto the first disk that is detected.

Using Auto Deploy

VMware vSphere Auto Deploy makes it possible to install ESXi 7 on hundreds of physical hosts. By using Auto Deploy, experienced administrators can manage large environments efficiently. However, your vCenter server needs to be up; otherwise, Auto Deploy does not work.

ESXi 7 hosts use network booting to boot from a central Auto Deploy server. Hosts can be configured with a host profile created from a reference host. This host profile can be created to prompt for input. After the hosts boot and are configured, they are managed by vCenter Server, as other ESXi hosts are.

Auto Deploy can be configured for either stateless caching or stateful installations:

Stateless caching. Auto Deploy does not store ESXi config or state data within the host (which is why it is "stateless"). Auto Deploy uses image profiles and host profiles to maintain the host configuration.

If a network boot fails, the ESXi host can use a local cache to boot from the last known ESXi 7 image.

Stateful installations. Auto Deploy is used to boot the host, but the installation and configuration are written to a local disk. During boots, the host boots from the local disk where this host configuration is stored.

Auto Deploy can be configured and managed using a graphical user interface (GUI) in vSphere 6.5 and later.

There is also a PowerCLI method, but the GUI option is easier to use. You must activate Image builder and Auto Deploy services (which are disabled by default) within the vSphere client.

Enable Auto Deploy and Image Builder in vSphere 7

Enable Auto Deploy and Image Builder in vSphere 7

The Image Builder feature in the GUI enables you to download ESXi images from the VMware public repository or to upload ZIP files containing ESXi images or drivers.

You can customize the images by adding or removing components, and you can export images to ISO or ZIP files for use elsewhere.

You can compare two images to see how their contents differ. Use the Deployed Hosts tab to view hosts that are provisioned with Auto Deploy and to perform tests and remediations.

Auto Deploy and Image Builder configuration screen

Auto Deploy and Image Builder configuration screen

Conclusion

Previous releases of vSphere included only the PowerCLI option for configuring Auto Deploy. But in vSphere 6.5 and vSphere 7, the Auto Deploy and Image Builder options are visible in the GUI, allowing you to create custom ISOs from which you can then boot ESXi 7 hosts on your network.

In many cases, administrators simply deploy the first ESXi host and then deploy vCenter Server and use vCenter Server together with other tools to deploy other hosts and avoid manual configs. These other tools include vSphere host profiles, which can facilitate the deployment and configuration of the remaining ESXi hosts.

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