build image 4/5 part B fails with bad superblock with Beta-12

[mperino]

I've updated the build image script for 12, but it's failing at 4/5 Part B.

The changes:

> IMAGE_URL=""https://github.com/LimelightVision/systemcore-os-public/releases/download/limelightosr-beta-12-184/limelightsystemcorebetacm5-limelightosr-beta-12.zip
> IMAGE_ZIP="${SCRIPT_DIR}/cache/limelightsystemcorebetacm5-limelightosr-beta-12.zip"
> BUILD_IMG="${SCRIPT_DIR}/systemcore-pi5b-beta12.img"
> OUTPUT_IMG="${SCRIPT_DIR}/systemcore-pi5b-beta12-${PI5B_VERSION}.img"
> 
> # Beta 12 partition layout:
> #   p1: boot selector (FAT32, 16M)  — autoboot.txt, config.txt (empty)
> #   p2: boot A (FAT32, 64M)         — config.txt, cmdline.txt -> rootfs p5
> #   p3: boot B (FAT32, 64M)         — config.txt, cmdline.txt -> rootfs p6
> #   p4: extended
> #   p5: rootfs A (ext4, 7G)
> #   p6: rootfs B (ext4, 7G)
> BOOT_A_OFF=$((34816 * 512))
> BOOT_B_OFF=$((165888 * 512))
> ROOT_A_OFF=$((299008 * 512))
> ROOT_B_OFF=$((4495360 * 512))

The line:
echo "mount -o loop,offset=${ROOT_B_OFF} " "$BUILD_IMG" "$ROOT_B_MNT"

fails with bad super block.

Running file -s shows that I have the right offsets?

(base) mperino@Aku:~/dev/systemcore/systemcore-rpi5-guide$ file -s /home/mperino/dev/systemcore/systemcore-rpi5-guide/systemcore-pi5b-beta12.img

/home/mperino/dev/systemcore/systemcore-rpi5-guide/systemcore-pi5b-beta12.img: DOS/MBR boot sector; partition 1 : ID=0xc, active, start-CHS (0x0,32,33), end-CHS (0x2,42,40), startsector 2048, 32768 sectors; partition 2 : ID=0xc, start-CHS (0x2,42,41), end-CHS (0xa,83,9), startsector 34816, 131072 sectors; partition 3 : ID=0xc, start-CHS (0xa,83,10), end-CHS (0x12,123,41), startsector 165888, 131072 sectors; partition 4 : ID=0xf, start-CHS (0x12,123,42), end-CHS (0x11b,230,11), startsector 296960, 4263936 sectors
(base) mperino@Aku:~/dev/systemcore/systemcore-rpi5-guide$ fdisk -l /home/mperino/dev/systemcore/systemcore-rpi5-guide/systemcore-pi5b-beta12.img
Disk /home/mperino/dev/systemcore/systemcore-rpi5-guide/systemcore-pi5b-beta12.img: 2.14 GiB, 2300576256 bytes, 4493313 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x00000000

Device Boot Start End Sectors Size Id Type
/home/mperino/dev/systemcore/systemcore-rpi5-guide/systemcore-pi5b-beta12.img1 * 2048 34815 32768 16M c W95 FAT32 (LBA)
/home/mperino/dev/systemcore/systemcore-rpi5-guide/systemcore-pi5b-beta12.img2 34816 165887 131072 64M c W95 FAT32 (LBA)
/home/mperino/dev/systemcore/systemcore-rpi5-guide/systemcore-pi5b-beta12.img3 165888 296959 131072 64M c W95 FAT32 (LBA)
/home/mperino/dev/systemcore/systemcore-rpi5-guide/systemcore-pi5b-beta12.img4 296960 4560895 4263936 2G f W95 Ext'd (LBA)
/home/mperino/dev/systemcore/systemcore-rpi5-guide/systemcore-pi5b-beta12.img5 299008 4493311 4194304 2G 83 Linux
/home/mperino/dev/systemcore/systemcore-rpi5-guide/systemcore-pi5b-beta12.img6 4495360 4560895 65536 32M 83 Linux

what am I missing?