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Bug#1078871: installer: reserve first 16 MiB space in default recipes for ARM devices?

On 21/10/2024 at 10:26, Diederik de Haas wrote:

On Sun Oct 20, 2024 at 8:49 PM CEST, Pascal Hambourg wrote:

On 20/10/2024 at 16:28, Diederik de Haas wrote:


```
root@cs21:~# parted -s /dev/mmcblk1 print
Model: MMC NCard (sd/mmc)
Disk /dev/mmcblk1: 61.9GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number  Start   End     Size    File system  Name     Flags
   1      32.8kB  16.8MB  16.7MB               primary
   2      16.8MB  256MB   239MB   fat16        primary  boot, esp
   3      256MB   61.9GB  61.6GB  ext4         primary

root@cs21:~# lsblk -o +PARTFLAGS,FSTYPE /dev/mmcblk1
NAME        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS PARTFLAGS FSTYPE
mmcblk1     179:0    0 57.6G  0 disk
├─mmcblk1p1 179:1    0   16M  0 part
├─mmcblk1p2 179:2    0  228M  0 part /boot/efi             vfat
└─mmcblk1p3 179:3    0 57.4G  0 part /                     ext4
```


Partition 2 looks like a regular EFI partition mounted on /boot/efi as
expected by GRUB. With a size of 239MB it should be FAT32 instead of
FAT16, but maybe the UEFI firmware expects only FAT16 or does not care.


I don't care enough (about FAT) to look into it, but I think 'vfat' can
mean either FAT16 or FAT32?
Yes, but some UEFI firmware are picky about the combinations of FAT type and partition size they accept. 


So it looks like it just needs some indication (flag) of what the boot
device is, but it doesn't (seem to) matter which one.


Weird. Does it have to be on the boot/root partition or can it be on any
other partition ?


It appears to not matter if it's 'boot' or 'legacy_boot', but it (ofc?)
needs to be set on the partition with the kernel as that needs to be
started for the rest of the boot process.
But in cs21's partition table, the boot/esp flag is on the EFI partition, not the root partition. Does it mean that the kernel is installed in the EFI partition instead of the root partition ? Or is the "kernel" a secondary EFI boot loader such as GRUB ?
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