Re: Disk Structures

From: Daniel Anderson <development_at_kd2ycu.com>
Date: Sun, 14 Dec 2025 02:17:22 UTC
Raspberry Pis have a weird partition system.  IIRC the first partition has to be under 256MB.  I did a quick google and found the below link.  I should mention that you can download a Raspberry Pi imager that will let you do more customizations than is available with dd https://www.raspberrypi.com/software/ 

https://github.com/raspberrypi/noobs/wiki/NOOBS-partitioning-explained
NOOBS partitioning explained
github.com


> On Dec 13, 2025, at 8:38 PM, Doug Hardie <bc979@lafn.org> wrote:
> 
> dd if=FreeBSD-14.2-RELEASE-arm64-aarch64-RPI.img of=/dev/da1 bs=10M
> 
> or 15.0 as appropriate
> 
> When I did this with 14.0, the Pi came up just fine.  Also the Pi5 did also.  I am confident what I see below is correct, I just don't understand it.
> 
> -- Doug
> 
>> On Dec 13, 2025, at 17:25, Daniel Anderson <development@kd2ycu.com> wrote:
>> 
>> Right but how are you getting it to the micro SD card?
>> 
>>> On Dec 13, 2025, at 5:24 PM, Doug Hardie <bc979@lafn.org> wrote:
>>> 
>>> The original installation was from FreeBSD-14.2-RELEASE-arm64-aarch64-RPI.img and I have been trying FreeBSD-15.0-RELEASE-arm64-aarch64-RPI.img
>>> 
>>> -- Doug
>>> 
>>>> On Dec 13, 2025, at 14:09, Daniel Anderson <development@kd2ycu.com> wrote:
>>>> 
>>>> Are you using the official Raspberry Pi images or imager?  I believe there’s a few specific requirements for the partitions...
>>>> 
>>>>> On Dec 13, 2025, at 4:54 PM, Doug Hardie <bc979@lafn.org> wrote:
>>>>> 
>>>>> I have a couple of Raspberry Pi 5s.  One of which is a production server for mail.  It works just fine.  However, the disk structure is quite confusing.  I only noticed this because of trying to bring up another similar server.  
>>>>> 
>>>>> If I list the dev entries for mmcsd, I get the following.
>>>>> 
>>>>> mail# ll /dev/mmcs*
>>>>> crw-r-----  1 root operator 0x49 Nov 26 15:47 /dev/mmcsd0
>>>>> crw-r-----  1 root operator 0x4a Nov 26 15:47 /dev/mmcsd0s1
>>>>> crw-r-----  1 root operator 0x4b Nov 26 15:47 /dev/mmcsd0s2
>>>>> crw-r-----  1 root operator 0x4e Nov 26 15:47 /dev/mmcsd0s2a
>>>>> crw-r-----  1 root operator 0x4f Nov 26 15:47 /dev/mmcsd0s2b
>>>>> 
>>>>> This looks like the drive was partitioned using GPT.  However, gpart list shows MBR.  I removed the non-relevant entries:
>>>>> 
>>>>> mail# gpart list mmcsd0
>>>>> Geom name: mmcsd0
>>>>> entries: 4
>>>>> scheme: MBR
>>>>> Providers:
>>>>> 1. Name: mmcsd0s1
>>>>> Mediasize: 52428800 (50M)
>>>>> type: fat32lba
>>>>> 2. Name: mmcsd0s2
>>>>> Mediasize: 128124452864 (119G)
>>>>> type: freebsd
>>>>> 
>>>>> There are the two partitions I expected.  A boot partition, and a data partition.  Looking at the df output:
>>>>> 
>>>>> mail# df -h
>>>>> Filesystem          Size    Used   Avail Capacity  Mounted on
>>>>> /dev/ufs/rootfs     108G    9.1G     90G     9%    /
>>>>> devfs               1.0K      0B    1.0K     0%    /dev
>>>>> /dev/msdosfs/EFI     50M     25M     25M    50%    /boot/efi
>>>>> tmpfs                12G     85M     12G     1%    /tmp
>>>>> /dev/da0s2           25G    1.3G     22G     6%    /mailbkup
>>>>> mail# 
>>>>> 
>>>>> The entries for / and /boot/efi are not at all what I expected.  The /mailbkup seems normal.  How do I make sense of all this?
>>>>> 
>>>>> I duplicated the microSD card but it doesn't boot the new machine.  I believe that is caused by a hardware failure in the Pi.  It does some strange rebooting before ever reading the SD card.  Never the less, I should be able to mount the copied SD card on a working machine, but can't figure out how to do that.  Messages shows the new disk is da1.
>>>>> 
>>>>> mail# mount /dev/da1s2 /mnt
>>>>> mount: /dev/da1s2: No such file or directory
>>>>> mail# mount /dev/mmcsd1s2b /mnt
>>>>> mount: /dev/mmcsd1s2b: No such file or directory
>>>>> 
>>>>> I would like to verify that the new SD card is good.
>>>>> 
>>>>> 
>>>>> -- Doug
>>>>> 
>>>>> 
>>>> 
>>> 
>> 
> 
>