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Initrd Flash Fails on ZFS Host (mount.nfs access denied)

Introduction​

When you flash a Seeed Jetson device with NVIDIA’s initrd workflow (l4t_initrd_flash.sh with --network usb0), the Ubuntu host PC temporarily shares flash files to the Jetson over NFS (Network File System). If your host was installed with a ZFS root filesystem (Ubuntu installer option Erase disk and use ZFS), flashing may fail with:

mount.nfs: access denied by server while mounting [fc00:1:1:0::1]:/path/to/mfi_xxx/rootfs
Flash failure
Either the device cannot mount the NFS server on the host or a flash command has failed.

This is not a defect of your Seeed carrier board or Jetson module. It is a known interaction between ZFS and NVIDIA’s default temporary NFS export used during initrd flashing.

Applicable products

Any Seeed Jetson product flashed with l4t_initrd_flash.sh --flash-only --massflash 1 --network usb0 (or similar initrd + network flash), including but not limited to:

  • reComputer Classic / Mini / Super (J401 series)
  • reComputer Industrial / reServer J401
  • reComputer Robotics J401 / J501 / J501 Mini
  • reServer J501

It is not specific to a single SKU. Root cause is the host filesystem, not the target device.

What is NFS in this context?​

During initrd flashing:

  1. You extract the Seeed mfi package on the Ubuntu host.
  2. The Jetson boots a small initrd image over USB.
  3. The host exports folders such as rootfs and tools/kernel_flash/images over NFS.
  4. The Jetson mounts those folders and writes the system image.

NFS here is only a host ↔ Jetson transfer mechanism during flashing. It is unrelated to NFS features on the carrier board.

Why ZFS hosts fail​

NVIDIA’s script (tools/kernel_flash/l4t_network_flash.func) uses exportfs -o to create temporary, in-memory NFS exports.

On ext4 (default Ubuntu install), this usually works.

On ZFS, the Linux NFS server cannot auto-assign a stable fsid for the dataset. The export may appear to succeed on the host, but the Jetson receives access denied when mounting.

Ubuntu has offered ZFS as a root option since 19.10, so this can affect any user who chose ZFS during installation.

Copy the entire mfi directory to an ext4 filesystem, then run the flash command from there.

# Example: copy mfi folder to an ext4 mount (adjust paths)
cp -a /path/on/zfs/mfi_recomputer-orin-super-j401 /mnt/ext4-flash/
cd /mnt/ext4-flash/mfi_recomputer-orin-super-j401

sudo ./tools/kernel_flash/l4t_initrd_flash.sh --flash-only --massflash 1 --network usb0 --showlogs

Tips:

  • Use a dedicated ext4 partition, external USB drive formatted as ext4, or an ext4 loopback image.
  • Ensure enough free space for the full extracted mfi package.
  • Install flash prerequisites on the host (nfs-kernel-server, sshpass, etc.) as in your product’s Getting Started guide.

Advanced workaround (stay on ZFS)​

If you must flash from a ZFS path, configure persistent exports in /etc/exports with explicit fsid= values, and ensure permissions are correct. You may also need to patch enable_nfs_for_folder() in l4t_network_flash.func so the script uses /etc/exports + exportfs -ra instead of exportfs -o.

Example export lines (adjust paths and IPv6 network to match your mfi directory):

/path/to/mfi_xxx/rootfs fc00:1:1::/48(rw,nohide,insecure,no_subtree_check,async,no_root_squash,fsid=1)
/path/to/mfi_xxx/tools/kernel_flash/images fc00:1:1::/48(rw,nohide,insecure,no_subtree_check,async,no_root_squash,fsid=2)

Then:

sudo chmod 755 /path/to/mfi_xxx/rootfs /path/to/mfi_xxx/tools/kernel_flash/images
sudo chown root:root /path/to/mfi_xxx/rootfs /path/to/mfi_xxx/tools/kernel_flash/images
sudo systemctl restart nfs-kernel-server
sudo exportfs -rav

Full details and a sample patch are in wiki-documents #4148.

Verify your host filesystem​

df -T /
findmnt -no FSTYPE /

If the output shows zfs, use the ext4 workaround above before flashing.

Resources​

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