Resolving VFAT CORRUPTION ERROR During vSAN/ESXi 8.0.3 Upgrade

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Resolving VFAT_CORRUPTION_ERROR During vSAN/ESXi 8.0.3 Upgrade

When upgrading an ESXi host (e.g., from 7.0.3 to 8.0.3) using esxcli software profile update, esxcli software vib update, or via ISO/ZIP file installation, the upgrade fails with the following error: 

Hardware precheck of profile ESXi-8.0U3e-24674464-standard failed with errors:
<VFAT_CORRUPTION_ERROR: A problem with one or more vFAT bootbank partitions was detected. Please refer to KB 91136 and run dosfsck on bootbank partitions.>

This indicates that the VFAT (FAT32) filesystem on one or more of ESXi's bootbank partitions is corrupted, preventing the upgrade from proceeding. The bootbank partitions contain essential hypervisor OS files, so their corruption blocks upgrade and re-partitioning operations.

Prerequisites

  • Ensure all running VMs on the host are migrated off or shut down.
  • Place the ESXi host into Maintenance Mode.
  • Enable SSH access to the ESXi host.
  • Login as root.

Step-by-Step Resolution

1. List Mounted Filesystems

Run the following command to identify the mounted filesystems and locate the vFAT bootbank partitions: 

# esxcli storage filesystem list

Typical output includes entries like: 

Mount Point                                        Size          Free          Volume Name               UUID                                  Mounted Type
-------------------------------------------------  ------------  ------------  ----------------  ------------------------------------ ------- -----
/vmfs/volumes/63984c6c-9424ef71-9e85-00620b52c270  12850538432   12201537952   OSDATA-63984c6c   63984c6c-9424ef71-9e85-00620b52c270   true    VMFS-L
/vmfs/volumes/017539ad-6545f12b-efbc-46d1ab1fda48  4293591040    4062117888    BOOTBANK1         017539ad-6545f12b-efbc-46d1ab1fda48   true    vfat
/vmfs/volumes/65a809d6-04d6993c-7a80-7c7dd5dfd89a  4293591040    4065787904    BOOTBANK2         65a809d6-04d6993c-7a80-7c7dd5dfd89a   true    vfat
/vmfs/volumes/vsan:52d24081123c03ed-3c0c7b3bdd3a86d8  00700932096  1845180947568 vsanDatastore     vsan:52d24081123c03ed-3c0c7b3bdd3a86d8 true   vsan

Note the paths of the BOOTBANK1 and BOOTBANK2 partitions.

2. Print Partition Details of Bootbank Volumes

For each vFAT bootbank volume identified, run: 

# vmkfstools -P /vmfs/volumes/<UUID_or_volume_path>

Example: 

[root@splkolesx04:~] vmkfstools -P /vmfs/volumes/017539ad-6545f12b-efbc-46d1ab1fda48

vfat-0.04 (Raw Major Version: 0) file system spanning 1 partitions.
File system label (if any): BOOTBANK1
Mode: private
Capacity 4293591040 (65511 blocks) 4062117888 (61983 blocks) avail, max supported file size 0
Disk Block Size: 512/0/0
UUID: 017539ad-6545f12b-efbc-46d1ab1fda48
Partitions spanned (on "disks"):
t10.ATA_____DELLBOSS_VD_____________________________________________
616d4606701600100000000005
Is Native Snapshot Capable: NO

This outputs details such as:

  • File system label (e.g., BOOTBANK1)
  • Disk and partition ID (e.g., t10.ATA_____DELLBOSS_VD____________________616d460670160010000000000:5)
  • Capacity and block size

Note the disk and partition ID, which will be used in the next step.

3. Repair VFAT Filesystem Using dosfsck

Run the dosfsck command against the device ID found in Step 2 to check and repair the VFAT filesystem: 

# dosfsck -Vv /dev/disks/<disk-and-partition-id>

Example: 

# dosfsck -Vv /dev/disks/t10.ATA_____DELLBOSS_VD____________________616d460670160010000000000:5

The command will scan the filesystem and report errors.

When prompted for action:

  • Select Delete to remove corrupted entries.
  • Then select Keep the Changes to write the repair results.

4. Repeat Repair for All Bootbank vFAT Partitions

If multiple vFAT partitions (e.g., BOOTBANK1 and BOOTBANK2) are found, run the above dosfsck repair command on each.

5. Verify Repair

Re-run the dosfsck -Vv command to ensure no further errors are reported.

Reboot the ESXi host to reload the repaired partitions and clear cached errors.

6. Retry ESXi Upgrade

Once the host is back online and stable, retry the upgrade process via esxcli or vSphere Lifecycle Manager. The VFAT_CORRUPTION_ERROR should no longer occur.

For upgrading ESXi through CLI using offline bundle ZIP files, please follow the detailed steps described here: Install ESXi patch via depot zip file

Refer:




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