Re: Partition layout of ARM SD card images
- Reply: Mark Millard : "Re: Partition layout of ARM SD card images"
- In reply to: Mark Millard : "Re: Partition layout of ARM SD card images"
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Date: Sun, 10 Jul 2022 21:34:45 UTC
> Am 10.07.2022 um 17:48 schrieb Mark Millard <marklmi@yahoo.com>: > > On 2022-Jul-10, at 12:26, Dr. Rolf Jansen <freebsd-rj@cyclaero.com> wrote: > >> For example let's have a llok on the partition layout of, FreeBSD-13.1-RELEASE-arm64-aarch64-RPI.img (the others are similar): >> >> # mdconfig -a -u 0 -t vnode -f diskimg/FreeBSD-13.1-RELEASE-arm64-aarch64-RPI.img >> # gpart show md0 md0s2 >> >> => 63 6291393 md0 MBR (3.0G) >> 63 2016 - free - (1.0M) >> 2079 102312 1 fat32lba [active] (50M) >> 104391 6187041 2 freebsd (3.0G) >> 6291432 24 - free - (12K) >> >> => 0 6187041 md0s2 BSD (3.0G) >> 0 57 - free - (29K) >> 57 6186880 1 freebsd-ufs (2.9G) >> 6186937 104 - free - (52K) >> >> The start of the fat32 boot slice s1 (containing the u-boot) stuff is neither aligned to 1M nor to 4k, it starts on an odd base. The start of the BSD payload slice s2 and its size are odd as well. The padding of 57 blocks within s2 lets the UFS partition start on a globally even base, namely 104391+57 = 104448, which as a matter of fact is 4k aligned (104448*512/4096 = 13056) and 1M aligned as well (104448*512/1024/1024 = 51), however all this keeps looking strange. >> >> Are there reasons for this partition layout besides making it look more interesting? If yes, some insights would be good. > > The layout details are more specific to the aarch64 RPi* context > than to general aarch64 SD card images. For example, the Rock64 > image is different: > > # mdconfig -a -u 0 -t vnode -f FreeBSD-14.0-CURRENT-arm64-aarch64-ROCK64-20220708-a0b956f5ac5-256605.img > # gpart show md0 > => 40 6291376 md0 GPT (3.0G) > 40 32728 - free - (16M) > 32768 102400 1 efi (50M) > 135168 6156160 2 freebsd-ufs (2.9G) > 6291328 88 - free - (44K) This is a GPT table, while the others are still MBR. Images which come with u-boot must have a different layout.