VMware Boot ISO Image: How to Boot from ISO Image in VMware

Booting VMware environments from an ISO image is a core skill for administrators working with both vSphere ESXi hosts and VMware Workstation. Whether you’re installing a fresh hypervisor, testing a new build, or recovering a lab setup, ISO booting provides a clean, flexible way to deploy VMware software without relying on physical media.

This guide explains how to boot from ISO in VMware ESXi and VMware Workstation, covering compatibility requirements, setup steps, and common pitfalls. By the end, you’ll know exactly how to mount and boot ISO images in VMware’s platforms with confidence.

What It Means to Boot a Virtual Machine from an ISO Image

Booting from an ISO image in VMware simply means starting a virtual machine using a disk image file instead of an already installed operating system. The ISO acts like a virtual CD/DVD, allowing you to run installers, recovery tools, or live environments directly inside ESXi or Workstation.

VMware ISO Boot vs Installed Operating System Boot

• ISO Boot: The VM loads its operating system or installer directly from the ISO file. This is typically used for OS installation, testing, or recovery.
• Installed OS Boot: The VM starts from its virtual disk, where the operating system is already installed and configured.

Common Use Cases for Booting from ISO in VMware

• Installing a new guest operating system (Windows, Linux, BSD, etc.).
• Running live environments for troubleshooting or recovery.
• Testing new OS builds or patches without affecting production VMs.
• Deploying hypervisors like ESXi itself from ISO in lab or production setups.

How to Boot VMware from ISO: Core Requirements

Before mounting an ISO in vSphere or Workstation, it’s important to understand the baseline requirements. Meeting these upfront eliminates most setup errors and ensures the VM boots cleanly from the image.

Supported ISO Formats and Bootable Media Requirements

1. 1. VMware supports standard ISO 9660 and bootable hybrid ISO images created by most OS vendors.
2. 2. The ISO must be bootable — not just a data image. Non‑bootable ISOs will mount but fail to start.
3. 3. Ensure the ISO is stored in a location accessible to the hypervisor:

• vSphere/ESXi: Datastore, content library, or accessible network share.
• Workstation: Local disk or mapped network drive.

VM Firmware Mode: BIOS vs UEFI

• BIOS mode: Required for older operating systems and legacy boot ISOs.
• UEFI mode: Necessary for modern OS installers (Windows Server 2016+, many Linux distributions) and secure boot scenarios.
• Mismatched firmware settings (e.g., UEFI ISO with BIOS VM) will prevent the VM from booting. Always align the VM’s firmware mode with the ISO’s boot requirements.

How to Boot from ISO in VMware Workstation

Booting from ISO in VMware Workstation is straightforward, but it requires correct device setup and timing to ensure the VM actually loads the ISO instead of the installed OS.

VMware Workstation Boot from ISO via Virtual CD/DVD

1. 1. Create or edit the VM in Workstation.
2. 2. In VM Settings → CD/DVD (SATA), select Use ISO image file and browse to the desired ISO.
3. 3. Ensure the CD/DVD device is set to Connected at power on.
4. 4. Save settings — the ISO is now mounted as a virtual boot device.

Boot Order and Power‑On Timing in VMware Workstation

1. 1. By default, Workstation boots from the virtual hard disk. To force ISO boot:

• Press ESC immediately after powering on the VM to access the boot menu.
• Select CD-ROM Drive to boot from the mounted ISO.

1. 2. Alternatively, adjust the VM’s BIOS/UEFI boot order in firmware settings to prioritize the CD/DVD device.
2. 3. Timing is critical — missing the ESC prompt means the VM will boot from the installed OS instead of the ISO.

How to Boot a Virtual Machine from ISO in vSphere / ESXi

Booting from ISO in vSphere or ESXi is slightly different from Workstation because the hypervisor runs on dedicated hosts and manages storage centrally. Administrators can mount ISO images either from datastores or directly from client devices.

vSphere Boot from ISO Using Datastore Files

1. 1. Upload the ISO to a datastore or content library accessible to the ESXi host.
2. 2. In the VM settings → CD/DVD Drive, select Datastore ISO file.
3. 3. Browse and attach the ISO, ensuring the device is set to Connect at power on.
4. 4. Power on the VM and press ESC during startup to select the CD/DVD drive as the boot device.

Boot VM from ISO via Client Device Mapping

• In VM settings, configure the CD/DVD Drive to use the Client Device option.
• When powering on the VM through the vSphere Client, mount the ISO from your local machine.
• The VM will treat the client‑mapped ISO as a bootable CD/DVD.
• This method is useful for one‑off installs or testing without uploading the ISO to a datastore.

VMware Boot to ISO: One‑Time vs Persistent Configuration

Booting from ISO in VMware can be configured either as a temporary setup for installation or as a persistent attachment. Understanding the difference prevents accidental misconfiguration and avoids long‑term stability risks.

Temporary ISO Boot for OS Installation

• Attach the ISO to the VM’s CD/DVD drive and enable Connect at power on.
• Boot once from the ISO to install or repair the operating system.
• After installation, detach the ISO to ensure the VM boots from its virtual disk.
• This is the recommended workflow for clean OS deployments and avoids unnecessary boot delays.

Persistent ISO Attachment Risks

• Leaving an ISO permanently attached can cause the VM to repeatedly attempt booting from the image, leading to failed startups if the ISO is unavailable.
• Persistent ISO mapping may also introduce dependency risks: datastore moves, client device disconnections, or ISO file deletions can break VM boot behavior.
• In production environments, persistent ISO attachment is considered a misconfiguration and can complicate troubleshooting.

Common Problems When Booting VMware from ISO

Even with correct setup, ISO booting in VMware can fail due to configuration mismatches or firmware restrictions. These are the most frequent issues administrators encounter.

VM Does Not Detect ISO at Startup

• The ISO file is not bootable (data‑only image).
• The CD/DVD device is not set to Connect at power on.
• ISO path is invalid or inaccessible (datastore move, client device not mounted).

Virtual Machine Skips ISO and Boots from Disk

• Boot order prioritizes the virtual hard disk over the CD/DVD drive.
• ESC prompt missed during power‑on, preventing manual boot selection.
• Persistent ISO attachment misconfiguration causing fallback to disk.

UEFI Secure Boot Blocking ISO Boot

• Secure Boot enforces signed bootloaders; unsigned ISOs fail to load.
• Many Linux distributions and custom recovery ISOs are not Secure Boot compliant.
• Solution: disable Secure Boot in VM firmware settings or use a signed ISO image.

VMware Boot ISO vs Network Boot (PXE)

Recovering VMFS and VMDK Data After Boot or Install Errors

ISO boot failures or misdirected installations can cause serious damage to VMware storage. When a VM is accidentally reinstalled or a datastore is overwritten, administrators need to act quickly to preserve data.

When OS Installation Corrupts Virtual Disks

• Accidental overwrite of VMDK files: Installing an OS to the wrong virtual disk can erase guest data and render snapshots unusable.
• VMFS metadata damage: Misconfigured ISO boots may reinitialize datastore partitions, breaking VMFS structures and hiding all VMs.
• Recovery urgency: Once overwritten, data recovery becomes more complex and time‑sensitive, requiring specialized tools rather than simple rollback.

DiskInternals VMFS Recovery™ as a Recovery Example

• Purpose‑built for VMware: DiskInternals VMFS Recovery™ is designed to handle VMFS volumes and VMDK files damaged by failed installs or boot errors.
• Metadata reconstruction: The software can rebuild VMFS headers and RAID configurations logically, avoiding destructive rebuilds.
• VMDK extraction: Even when VMFS is corrupted, it can locate and recover virtual disks for re‑import into ESXi or Workstation.
• Pre‑replacement recovery: Ideal for extracting data before swapping controllers, disks, or reinstalling ESXi, minimizing downtime and data loss.

Best Practices for Booting VMware Virtual Machines from ISO

ISO booting is a powerful tool in VMware environments, but it must be handled carefully to avoid wasted time or accidental data loss. Following best practices ensures smooth installs and safe operations.

Pre‑Boot Checklist for ISO‑Based Operations

• Verify the ISO is bootable and matches the VM’s firmware mode (BIOS vs UEFI).
• Confirm the CD/DVD device is set to Connect at power on.
• Check datastore or client device accessibility before powering on.
• Adjust boot order so the VM prioritizes the ISO when needed.
• Disable Secure Boot if the ISO is unsigned or incompatible.

When to Detach ISO After Installation

• Once the OS installation or recovery task is complete, detach the ISO from the VM.
• Leaving the ISO attached can cause repeated boot attempts, failed startups, or accidental overwrites.
• For production workloads, always ensure the VM boots from its virtual disk, not a lingering ISO mapping.