VMware ESXi and vSphere Cluster Management
Configure Virtual Machine Boot Options in VMware ESXi
Learn how to configure VMware ESXi VM firmware, boot delay, firmware setup entry, boot recovery, and troubleshoot BIOS or UEFI startup issues in vSphere.
What VM boot options control
VM boot options are per-virtual-machine startup controls that determine which virtual firmware initializes the VM, how long startup pauses, whether firmware setup opens, and how the VM responds when it cannot find a bootable device.
Administrators commonly change these settings when installing an operating system, troubleshooting startup, changing firmware configuration, or needing more time to enter BIOS or EFI setup from the VM console.
These settings apply to the individual VM. They are different from:
- ESXi host boot settings, which control how the physical ESXi server starts.
- Guest operating system bootloader settings, which control startup after the VM firmware has handed control to the installed operating system.
The VM firmware initializes virtual hardware first. It then identifies a boot device and transfers control to the guest operating system's boot process.
Where to configure boot options
- Open the vSphere Client, the management interface for the vSphere inventory.
- Select the target virtual machine.
- Choose Edit Settings.
- Select VM Options.
- Expand Boot Options.
For most firmware and hardware-sensitive startup changes, power off the VM first. A powered-off VM also makes it easier to record the current configuration and apply changes without affecting a running guest.
For related configuration workflows, see Edit Virtual Machine Settings and Edit VM Options.
Virtual machine firmware: BIOS or EFI/UEFI
BIOS is legacy virtual machine firmware. It initializes virtual hardware and starts a traditional boot process.
EFI/UEFI is modern virtual firmware. It supports guest operating systems installed with UEFI boot files and commonly works with newer disk partitioning and boot configurations.
The firmware choice must match both the guest operating system and the way its boot disk was prepared. For a new installation, select the required firmware before installing the operating system. For an existing VM, inspect its current boot mode before changing anything.
| Consideration | BIOS | EFI/UEFI |
|---|---|---|
| Guest operating system compatibility | Use when the guest requires or supports legacy BIOS boot. | Use when the guest supports and is configured for UEFI boot. |
| Existing installation boot mode | Expected by a guest installed in legacy mode. | Expected by a guest installed in UEFI mode. |
| Disk partitioning and bootloader expectations | Typically aligns with legacy bootloader and partitioning requirements. | Typically aligns with UEFI boot files and the guest's UEFI-compatible disk configuration. |
| Suitability for a new installation | Choose when the operating system or application requires legacy firmware. | Choose before installation when the operating system requires UEFI. |
| Risk when changing an existing VM | May fail if the guest was installed for UEFI. | May fail if the guest was installed for legacy BIOS. |
Boot delay
Boot delay adds a pause after VM power-on and before the normal guest boot sequence begins. The value is measured in milliseconds.
Use a short delay when you need time to open the VM console and press the key or select the action that enters firmware setup. The delay is useful when firmware initialization proceeds too quickly for an administrator to interact with it.
Set the delay only as long as operationally necessary. Every power-on waits for the configured delay, so an unnecessarily large value increases VM startup time.
Force entry to BIOS or EFI setup
The firmware setup option makes the next VM startup open the applicable firmware configuration screen instead of immediately booting the guest. The interface depends on the selected firmware: a BIOS setup screen appears for a BIOS VM, and an EFI setup screen appears for an EFI/UEFI VM.
This option is useful for changing virtual boot order, reviewing firmware values, or diagnosing whether a virtual disk, optical device, or network source is detected.
- Power off the VM.
- Open Edit Settings > VM Options > Boot Options.
- Enable the option to force BIOS or EFI setup on the next startup.
- Power on the VM and open its console.
- Review the detected devices and boot priority.
- Save any firmware changes and restart the VM normally.
- Disable the forced-setup option if it remains enabled, so later starts return to normal guest boot.
Failed boot recovery
Failed boot recovery responds when the VM cannot locate a bootable device. When enabled, the VM retries startup after a failed boot-device detection attempt. The default retry interval is approximately 10 seconds.
Automatic retry can help when a boot device becomes available shortly after startup. For example, a temporarily delayed device may be detected on a subsequent attempt.
Repeated retries can also hide a persistent problem. During troubleshooting, monitor the console and consider disabling automatic retry temporarily so the original firmware error remains visible. Correct the underlying disk, boot order, firmware, or guest bootloader problem before relying on retries.
| Setting | What it controls | Typical use case | Operational caution |
|---|---|---|---|
| Firmware: BIOS | Uses legacy virtual firmware. | Running a guest installed for legacy boot. | Do not select it for a UEFI-only installation without preparing the guest. |
| Firmware: EFI/UEFI | Uses modern virtual firmware. | Installing or running a guest configured for UEFI. | Changing an existing BIOS installation may prevent boot. |
| Boot delay | Pauses startup for a value in milliseconds. | Opening the console and entering setup. | Increases startup time on every power-on. |
| Force BIOS/EFI setup | Opens firmware setup on the next startup. | Changing boot order or checking device detection. | Return it to normal after use if it remains selected. |
| Failed boot recovery | Retries after failure to locate a bootable device. | Recovering from a temporarily unavailable boot source. | Repeated retries can obscure a persistent failure. |
Safe change procedure
- Verify power state: Confirm whether the VM is powered on, powered off, or suspended. Power it off before changing firmware or other startup-sensitive settings.
- Check guest requirements: Determine whether the guest operating system expects BIOS or EFI/UEFI and whether its installed bootloader matches that mode.
- Record the baseline: Document the current firmware, delay, forced-setup state, failed boot recovery state, and any known boot order.
- Apply the change: Use Edit Settings > VM Options > Boot Options to change only the required setting.
- Observe startup: Open the VM console before powering on when early firmware interaction may be needed.
- Verify the result: Confirm that the expected boot device is detected and that the guest operating system starts successfully.
- Document and revert safely: Record the final configuration. If the VM does not boot, restore the prior firmware or boot setting where possible, then investigate before making another permanent change.
Example: install an operating system that requires UEFI
- Create or select the new VM and power it off.
- In Boot Options, set the firmware type to EFI/UEFI.
- Attach the installation image or other installation media to the virtual CD/DVD device.
- Power on the VM and open the console.
- Verify that the installer starts in the intended firmware mode.
The expected result is an operating system installation whose boot configuration is compatible with UEFI. For the broader installation workflow, see Install a Guest Operating System.
Example: open firmware setup to change the boot source
- Enable forced entry to BIOS or EFI setup for the next start.
- Open the VM console before powering on the VM.
- Power on the VM and review the firmware screen.
- Choose the desired virtual disk, optical device, or network source in the boot order.
- Save the firmware setting and restart normally.
The VM should attempt to start from the selected bootable device.
Example: give an administrator time to enter setup
- Configure a short boot delay in milliseconds.
- Open the console and power on the VM.
- Use the delay to enter BIOS or EFI setup if needed.
- Remove or reduce the delay after the administrative task.
This provides reliable access to early startup controls without permanently slowing normal VM starts.
Example: retry a temporarily unavailable boot device
- Enable failed boot recovery when delayed device availability is expected.
- Power on the VM and observe whether the boot device appears on a retry.
- If retries continue to fail, inspect disk connectivity, boot order, firmware compatibility, and guest bootloader status.
The expected result is automatic recovery from a transient detection issue while persistent failures remain identifiable.
Boot troubleshooting workflow
Use the VM console to identify where startup stops:
- Before firmware initialization: Check VM power behavior and configuration. The problem may occur before the firmware can display its normal startup screen.
- During firmware device detection: Check whether the expected virtual disk, CD/DVD device, or network source is visible and whether firmware boot priority selects it.
- Within the guest bootloader: Check the guest's boot files, partitioning, and operating system recovery procedures. VM boot options may have already completed their work.
Also verify that the expected virtual disk is attached, available, and configured to connect at power on. Check virtual CD/DVD and network-device state when those devices are possible boot sources.
Use a boot delay or forced setup entry when you need access to startup controls. Confirm that the selected firmware is compatible with the guest installation mode.
| Symptom | Likely cause | Relevant boot option | Suggested check |
|---|---|---|---|
| No bootable device found | Disk is missing, disconnected, not bootable, selected after another device, or incompatible with the firmware mode. | Firmware, forced setup, failed boot recovery | Confirm disk attachment and connection at power on, then inspect firmware boot priority and guest installation mode. |
| Unable to access firmware setup in time | Firmware initialization is too fast or the console opened too late. | Boot delay or force setup | Open the console before power-on and use a short delay or one-time forced setup. |
| Guest fails after a firmware change | Bootloader and disk layout match the previous firmware type. | Firmware | Restore the previous type, plan a supported conversion or reinstall, and test in a clone first. |
| VM repeatedly retries startup | Failed boot recovery is retrying a persistent boot-device failure. | Failed boot recovery | Review the original console error and temporarily disable retry while correcting the problem. |
| VM starts from an unexpected device | Firmware boot order prioritizes another disk, optical device, or network source. | Force setup | Enter the applicable BIOS or EFI setup and correct boot priority. |
Common failure resolution paths
No bootable device is available
- Open the VM console and read the firmware message.
- Confirm that the intended virtual disk is attached and connected at power on.
- Force entry into BIOS or EFI setup and verify boot priority.
- Confirm whether the guest was installed for BIOS or EFI/UEFI.
The guest no longer starts after changing firmware
The most likely cause is that the guest bootloader and disk layout were created for the prior firmware type. Restore the prior firmware type to recover service where possible. Plan a supported guest conversion or reinstall, and validate it in a clone or test environment before changing the production VM.
The setup key cannot be pressed quickly enough
Set a boot delay, or enable forced BIOS/EFI setup entry for the next boot. Open the console before powering on the VM.
The VM repeatedly attempts to boot
Review the console to identify the original failure. Temporarily disable failed boot recovery if repeated retries prevent examination of the error. Then correct disk attachment, boot order, firmware compatibility, or guest bootloader issues.
Exam-relevant notes
- Boot options are configured per VM, not as a replacement for ESXi host boot configuration or the guest bootloader.
- The navigation path is VM > Edit Settings > VM Options > Boot Options.
- BIOS and EFI/UEFI are firmware choices; they must match guest operating system support and the existing installation's boot mode.
- Boot delay is measured in milliseconds and increases every startup.
- Forced firmware setup affects the next startup and should be returned to normal behavior after use.
- Failed boot recovery retries after failure to locate a bootable device; its default retry interval is approximately 10 seconds.
For safe testing before changing a production VM, review Clone a Virtual Machine. For virtual disk and hardware checks, see Add Virtual Hardware to VM.