protective-mbr · shipping · also PMBR, protective Master Boot Record

Protective MBR

A protective MBR is a legacy-format record at LBA 0 of a GPT disk that uses partition type 0xEE to discourage GPT-unaware tools from treating its space as unused.

Related Observatory article: Protective MBR on hesela.com

The protective record starts at LBA 1 and describes the remaining disk, capped at 0xFFFFFFFF logical blocks when its size field cannot represent that span. It is a compatibility marker, not a duplicate list of the GPT partitions. [1]

A recognizable 0xEE entry alone is not a complete GPT validation. Linux v6.18 treats protective-MBR checks separately from GPT header and entry-array checks. Preserve original acquisition bytes; partition repair belongs on a separate working copy. [2]

Relations

related
GUID Partition Table (GPT), Partition type GUID, ddrescue mapfile

Limitations

  • The marker cannot prevent arbitrary writes or substitute for an independent recovery copy. [1]

Citations

  1. UEFI 2.10, chapter 5: GPT layout, headers and partition entries (accessed 2026-10-21)
  2. Linux v6.18 GPT parsing: is_gpt_valid and compare_gpts (accessed 2026-10-21)
Sources & caveats
  • UEFI 2.10 protective layout; no claim that all partition tools honor the marker.

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Hesela team. Protective MBR. Hesela. 2026-10-21. https://hesela.dev/terms/protective-mbr/