The protective MBR for GPT partitioning must be at

sector 0. No EBR qualifies.

diff --git a/sbin/fdisk/mbr.c b/sbin/fdisk/mbr.c
index 16e21da..f2b6859 100644 (file)
--- a/sbin/fdisk/mbr.c
+++ b/sbin/fdisk/mbr.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: mbr.c,v 1.70 2021/05/14 21:11:15 krw Exp $    */
+/*     $OpenBSD: mbr.c,v 1.71 2021/05/21 19:09:46 krw Exp $    */
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -42,6 +42,9 @@ MBR_protective_mbr(struct mbr *mbr)
        struct dos_partition dp[NDOSPART], dos_partition;
        int i;
 
+       if (mbr->offset != 0)
+               return (-1);
+
        for (i = 0; i < NDOSPART; i++) {
                PRT_make(&mbr->part[i], mbr->offset, mbr->reloffset,
                    &dos_partition);