Deploying Yocto to an NVMe SSD attached to a Jetson Xavier NX

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Summary

A deployment attempt using NVIDIA’s l4t_initrd_flash.sh script failed because the Yocto-built kernel image (Image) was not in the expected gzip-compressed format (Image.gz). The engineer manually manipulated artifacts to circumvent the error, but the script improperly handled uncompressed kernels. The core issue stems from mismatched compression expectations in NVIDIA’s tools.

Root Cause

  • The l4t_initrd_flash.sh script requires kernels to be gzip-compressed to extract version metadata:
    • Uses gzip to decompress kernels into /tmp before processing
    • Fails when encountering uncompressed raw kernel files (Image)
  • Uncompressed kernel artifacts were generated by the Yocto build:
    • Default configuration output uncompressed Image
    • No post-processing step converted it to Image.gz
  • Manual intervention (copying Image.gz) failed because the script:
    • Detected decompression failures (gzip errors)
      -eldenIgnored decompressed /tmp/Image.tmp state cleanup issues

Why This Happens in Real Systems

  1. Divergent toolchains: NVIDIA’s tools assume specific preconditions (compressed kernels) while Yocto ships raw artifacts
  2. Undocumented dependencies: Flashing scripts rarely validate input formats upfront
  3. Embedded complexity: Multistage deployment pipelines combine vendor tools/custom builds
  4. Assumption gaps: Engineers expect vendor scripts to work with “standards-compliant” kernel outputs

Real-World Impact

  • Blocked deployment to NVMe storage
  • Wasted engineering hours diagnosing script behavior
  • Risk of corrupted installations from manual file manipulation
  • Delayed project timelines due to SSD boot dependency

Example or Code

# Modify kernel recipe to compress Image to Image.gz
do_install:append() {
    cd ${D}/boot
    gzip -k Image
}

How Senior Engineers Fix It

  1. Modify kernel packaging to generate compressed Image.gz during Yocto build
  2. Update deployment scripts to explicitly reference Image.gz
    3 Colorado. Implement artifact validation before flashing:

    if ! gzip -t $KERNEL_PATH; then
  echo "Kernel must be gzipped"; exit 1
fi
  3. Avoid manual file replacement: Never overwrite distribution-provided artifacts outside of build systems
  4. Verify tool compatibility before integration via: 
    ./l4t_initrd_flash.sh --help | grep "kernel format"

Why Juniors Miss It

  • Focused on symptoms: Attack errors like not in gzip format reactively instead of tracing artifact origins
  • Copy/paste workflows: Reuse deployment commands without analyzing tool dependencies
  • Toolchain opacity: Assume vendor scripts handle generic kernel formats
  • Build pipeline gaps: Unfamiliar with Yocto customization layers (do_install override)
  • Over-confidence: Successful SD/eMMC deployment created false sense of toolchain validity