VMware ESXi USB Passthrough and Mount USB Drive ESXi: Complete Admin Guide

USB passthrough in VMware ESXi allows administrators to connect physical USB devices directly to virtual machines, enabling access to removable storage, license dongles, or specialized hardware inside the guest OS. Unlike VMware Workstation, ESXi runs on bare‑metal servers and enforces stricter hardware abstraction, so mounting and using USB drives requires proper configuration at the host level.

This guide explains how to enable USB passthrough in ESXi, mount USB drives inside VMs, and avoid common pitfalls such as device mapping limitations and host‑level restrictions. By the end, you’ll know how to safely attach and use USB devices in ESXi for tasks like data transfer, backup, and testing.

VMware ESXi USB Passthrough and Mount USB Drive ESXi: The Direct Answer

USB passthrough in ESXi is a powerful feature, but it behaves differently than in VMware Workstation. To use it effectively, administrators need to understand how devices are handled at both the hypervisor and VM levels.

• ESXi supports USB passthrough to virtual machines. You can assign physical USB devices directly to a VM, allowing the guest operating system to interact with them as if they were locally attached. This is commonly used for license dongles, removable storage, or specialized hardware.
• USB devices can be mounted at the hypervisor level for file operations. ESXi itself can mount USB drives for host‑level tasks such as copying files, transferring backups, or importing/exporting data. This bypasses the VM entirely and treats the USB as part of the host’s storage environment.
• NTFS mounting requires manual CLI configuration. ESXi does not natively support NTFS file systems. If you attach a Windows‑formatted USB drive, you’ll need to use the ESXi shell or CLI tools to manually mount and access the data. FAT32 and VMFS are supported more seamlessly, but NTFS requires extra steps.
• USB controller passthrough differs from device passthrough. Passing through an entire USB controller exposes all devices connected to that controller to the VM. Device passthrough, on the other hand, targets a single USB drive. Controller passthrough is useful for specialized hardware but carries higher risk, while device passthrough is safer for general storage use.
• Improper handling can corrupt VMFS datastores or VMDK files. If a USB device is incorrectly mapped or removed unsafely, it can damage VMFS volumes or corrupt virtual disk files. This risk is especially high when experimenting with raw device mappings or when mounting USB drives directly on the host. Always validate mappings and disconnect devices gracefully.

Understanding USB Access Methods in ESXi

VMware ESXi offers several ways to work with USB devices, but each method has different implications for performance, visibility, and risk. Choosing the right approach depends on whether you want the USB accessible inside a VM, at the host level, or through full hardware passthrough.

USB Device Passthrough to VM

• Attach USB storage directly to guest OS: A single USB device can be mapped to a VM, allowing the guest operating system to use it as if it were locally connected.
• Managed through VM settings: This is configured in the VM’s hardware settings, where you select the specific USB device to passthrough.
• No host‑level file visibility: Once the device is passed through, ESXi itself cannot access the files on it — only the VM sees the device. This makes it ideal for isolated use cases like license dongles or removable storage.

USB Controller Passthrough (PCI Passthrough)

• Entire USB controller assigned to VM: Instead of mapping a single device, you can passthrough the entire USB controller. This exposes all devices connected to that controller to the VM.
• Requires IOMMU/VT‑d support: Hardware virtualization features (Intel VT‑d or AMD‑Vi) must be enabled in the server BIOS for controller passthrough to work.
• Removes controller access from ESXi host: Once a controller is passed through, ESXi can no longer use it. This method is powerful but risky, as it hands full control of the hardware to the VM.

USB Drive Passthrough for Backup or Transfer

• External drive mapped to VM: A USB drive can be connected to a VM for tasks like offline backup, data extraction, or temporary file transfer.
• Used for offline backup or data extraction: This is a practical way to move large datasets in and out of a VM without relying on network transfers.
• Best for short‑term use: While convenient, USB drive passthrough should not replace proper datastore storage, as performance and stability are limited compared to VMFS volumes.

ESXi Mount USB Drive at Host Level

Mounting a USB drive directly on the ESXi host is useful for tasks like transferring files, importing backups, or staging ISO images. Unlike passthrough to a VM, this method gives the hypervisor itself access to the USB device.

Step 1 — Enable SSH Access

To work with USB devices at the host level, you need shell access.

1. 1. Access ESXi shell: Enable SSH or use the local ESXi shell via the DCUI (Direct Console User Interface).
2. 2. Identify USB device:

• Run lsusb to list connected USB devices.
• Use esxcli storage core device list to confirm the device ID and check how ESXi recognizes the drive.

This ensures you know exactly which device you’re about to mount, avoiding accidental operations on production datastores.

Step 2 — Identify Filesystem Type

ESXi can interact with USB drives, but support varies depending on the filesystem:

• FAT32: Fully supported and can be mounted easily for file transfers.
• VMFS: Native VMware filesystem; ESXi can mount VMFS volumes directly.
• NTFS: Not supported natively. Mounting requires manual CLI configuration or third‑party tools, making it more complex.
• exFAT limitations: ESXi does not support exFAT, so drives formatted this way must be reformatted or accessed via a VM instead.

ESXi Mount NTFS USB Drive

Mounting NTFS‑formatted USB drives on an ESXi host is possible, but it comes with important limitations and risks. ESXi is designed primarily for VMFS and FAT32 filesystems, so NTFS support is restricted and requires manual configuration.

ESXi does not natively support NTFS write operations

• NTFS volumes can be detected, but ESXi cannot reliably write to them.
• Attempting write operations may lead to corruption or metadata inconsistencies.

Mount via vmkfstools or esxcli storage filesystem mount

• Administrators can use ESXi CLI tools to mount USB drives.
• Example: esxcli storage filesystem list to identify devices, then esxcli storage filesystem mount to attach.
• NTFS drives will typically mount in read‑only mode, allowing safe file extraction but not modification.

Read‑only behavior considerations

• NTFS drives are best used for data import/export rather than active workloads.
• For write access, reformat the USB drive to FAT32 or VMFS before use.

Risk of metadata inconsistency

• Because NTFS is not fully supported, metadata such as journaling or permissions may not be interpreted correctly.
• This can cause unexpected behavior if the drive is later reattached to a Windows system.

ESXi Mount External USB Drive for Data Transfer

Mounting an external USB drive directly on the ESXi host is a practical way to move large datasets, perform offline backups, or handle special scenarios like forensic acquisition. Unlike passthrough to a VM, this method gives the hypervisor itself direct access to the USB device.

1. 1. Copy VMDK files from datastore

• Administrators can mount an external USB drive and copy virtual disk files (VMDKs) directly from a datastore.
• This is useful for archiving VMs or migrating them to another environment without relying on network transfers.

1. 2. Export VM backups

• USB drives can serve as a temporary backup destination when network storage is unavailable.
• ESXi can copy VM configuration files, snapshots, and disk images to the external drive for safekeeping.

1. 3. Offline migration scenarios

• In environments without fast network connectivity, USB drives provide a portable medium for moving VMs between hosts.
• This is especially relevant in remote sites or air‑gapped systems.

1. 4. Forensic acquisition use cases

• Investigators can mount USB drives on ESXi to extract VM data for forensic analysis.
• Read‑only mounting is recommended to preserve evidence integrity and avoid altering metadata.

USB Passthrough vs Host-Level Mount: What to Choose

Risks of USB Operations in ESXi

While USB passthrough and host‑level mounting can be useful in VMware ESXi, they also introduce risks that administrators must carefully manage. Improper handling can lead to corruption, data loss, or instability in the virtual environment.

Accidental overwrite of VMDK

• Raw device mapping or misconfigured passthrough can overwrite virtual disk files.
• Always double‑check device IDs before attaching or writing to a USB drive.

Mounting wrong device

• ESXi identifies devices by unique IDs, which can be confusing if multiple USB drives are connected.
• Mounting the wrong device may overwrite or corrupt production datastores.

Incomplete file copy

• USB transfers are slower and less reliable than datastore operations.
• Interruptions or unsafe removal can leave files partially copied, causing VM boot failures or data loss.

Datastore lock issues

• Mounting USB drives incorrectly can interfere with VMFS datastore locks.
• This may prevent VMs from accessing their disks or cause snapshot inconsistencies.

VMFS corruption during unsafe removal

• Removing a USB drive without unmounting it properly can corrupt VMFS metadata.
• Always unmount the filesystem before physically disconnecting the device.

VMFS Datastore and VMDK Recovery After USB‑Related Incidents

USB operations in ESXi can sometimes lead to corruption or data loss, especially when devices are removed unsafely or file copies are interrupted. Recovery requires careful steps to protect the datastore and restore virtual disk integrity.

Common Failure Scenarios

Interrupted VMDK copy

• Large file transfers to or from USB may fail mid‑operation, leaving incomplete or corrupted VMDK files.

USB removal during write

• Detaching a USB drive while ESXi is writing data can damage both the VMDK and the datastore metadata.

Damaged VMFS metadata

• Improper mounting or unsafe removal can corrupt VMFS structures, preventing access to stored VMs.

Corrupted snapshot chain

• If snapshots are active during a failed USB operation, the chain may break, making rollback impossible.

Recovery Workflow

1. 1. Stop datastore activity: Immediately halt VM operations on the affected datastore to prevent further corruption.
2. 2. Prevent overwrite: Avoid writing new data to the datastore until recovery is complete.
3. 3. Scan VMFS volume: Use ESXi tools or third‑party utilities to analyze the datastore for damaged metadata and lost files.
4. 4. Recover lost or damaged VMDK: Attempt to restore virtual disk files from backups or recovery tools before re‑attaching them to VMs.

DiskInternals VMFS Recovery™

• Deep scan corrupted VMFS datastore to locate damaged or deleted files.
• Recover deleted or damaged VMDK files even after severe corruption.
• Restore full virtual machine structure including VMX configuration and snapshot chains.
• Extract critical data before rebuilding environment, ensuring business continuity while repairs are underway.

Best Practices for Safe USB Use in ESXi

USB operations in VMware ESXi can be convenient for data transfer, backup, or testing, but they carry risks if not handled carefully. Following these best practices helps ensure stability and protect datastore integrity:

Avoid using USB for production storage

• USB drives are not designed for continuous, high‑performance workloads.
• Rely on VMFS datastores on enterprise storage for production VMs, and reserve USB for temporary transfers or offline backups.

Always verify device identifier before mount

• ESXi identifies devices by unique IDs, which can be confusing if multiple USB drives are connected.
• Double‑check the device path with esxcli storage core device list before mounting to avoid accidental overwrites.

Safely unmount before removal

• Removing a USB drive without unmounting can corrupt VMFS metadata or leave incomplete file copies.
• Use esxcli storage filesystem unmount or the vSphere client to disconnect safely before unplugging.

Maintain datastore backups

• Even with careful handling, USB operations can fail.
• Keep regular backups of VMFS datastores and VMDK files to ensure recovery options are available after incidents.

Use VMFS‑formatted drives when possible

• VMFS is the native filesystem for ESXi and offers the most reliable compatibility.
• FAT32 is supported but limited in file size, while NTFS and exFAT require manual workarounds and are prone to metadata issues.