Re: [gentoo-user] UEFI booting

[Mick]

On Friday 26 Aug 2016 09:32:25 Peter Humphrey wrote:
> Hello list,
>
> In my search for a suitable boot method, I'm trying Mike G's systemd-boot
> ebuild. I've installed it with no problem, and now I reach the heart-in-
> mouth stage of actually replacing gummiboot with it. But first, the backup,
> including dd of what used to be called the MBR (what is it now?).
>
> # parted -l
> Model: Unknown (unknown)
> Disk /dev/nvme0n1: 256GB
> Sector size (logical/physical): 512B/512B
> Partition Table: gpt
> Disk Flags:
>
> Number  Start   End     Size    File system     Name       Flags
>  1      1049kB  3146kB  2097kB                  uefi       bios_grub
>  2      3146kB  144MB   141MB   fat32           boot       boot, esp
>  3      144MB   4504MB  4360MB  linux-swap(v1)  swap
>  4      4504MB  15.0GB  10.5GB  ext4            rescuesys
>  5      15.0GB  32.2GB  17.2GB  ext4            gentoo
>  6      32.2GB  36.5GB  4295MB  ext4            var
>  7      36.5GB  45.1GB  8590MB  ext4            home
> [...]
>
> That start block of the uefi partition looks odd to me.

The 'Name' of the 1st partition is the label you have provided when you 
created it.  It is NOT the type of the partition, which is shown under the 
'Flags' column as 'bios_grub'.  The 1st partition was created to accommodate 
Grub's boot code.   It starts on the first cylinder (change the units in parted 
to cyl and you'll see it starts at '0 cyl') and has no fs on it.

> I'm pretty sure I
> didn't specify a start position to parted when I was constructing the
> partition layout six months ago, preferring to let the program choose a
> value itself.

Parted and friends will create this partition for Grub at the very start of 
the disk, when you use GPT.  If you stay with a conventional msdos partition 
table, then the first partition starts at cylinder 63 allowing enough space for 
MBR to store its boot code in the unallocated cylinders 0 to 62.


> I do remember, though, that parted had a strange idea of what
> 2MB meant: it's turned out to be 2097kB.

You are mixing decimal and binary.  2MiB = 2 x 1024^2 = 2,097,152


> My question for the panel is whether I need to do anything about that
> partition layout. What do you think?

You don't have to do something about it, if you want to retain the ability to 
use Grub.  If you will no longer use grub then you probably do not need the 
first grub-specific partition.  


As shown above the second partition is your EFI partition. 141MB may not be 
enough to store many kernel images, but it depends on how many kernel images 
and initramfs you keep in there at any time.

-- 
Regards,
Mick