Do not specify '-F 16' for mkfs.vfat and also no '-o fat=16' when mounting it

[jsmeix]

• Type: Minor Bug Fix / Enhancement / Cleanup

• Impact: Low

• Reference to related issue (URL):
  Possibly obsolete '-F 16' for mkfs.vfat and 'fat=16' mount option in 700_create_efibootimg.sh and 200_mount_bootimg.sh #2575

• How was this pull request tested?
  Not tested by me but SUSE user reported that it is ok, see
  Possibly obsolete '-F 16' for mkfs.vfat and 'fat=16' mount option in 700_create_efibootimg.sh and 200_mount_bootimg.sh #2575

• Brief description of the changes in this pull request:

Do no longer specify '-o fat=16' when loop mounting efiboot.img file
but rely on the automatic FAT type detection when mounting
cf. #2575
plus some general generic code cleanup in
output/ISO/Linux-i386/700_create_efibootimg.sh

[jsmeix]

@gdha @gozora
could you have a look here if that change looks OK to you?

I wonder if -F 16 is actually needed for mkfs.vfat ?

output/ISO/Linux-ia64/200_mount_bootimg.sh
indicates -F 16 was specified because 'size >30MB'

# make sure we select FAT16 instead of FAT12 as size >30MB
mkfs.vfat $v -F 16 $TMP_DIR/boot.img

but on my openSUSE Leap 15.2 "man mkfs.vfat" reads (excerpt)

-F FAT-SIZE
  Specifies the type of file allocation tables used (12, 16 or 32 bit).
  If nothing is specified, mkfs.fat will automatically select between
  12, 16 and 32 bit, whatever fits better for the filesystem size.

so also for mkfs.vfat it seems to be better to
rely on what "mkfs.fat will automatically select".

[jsmeix]

@rmetrich
could you have a look here if that should be OK for Red Hat
in particular for older Red Hat versions, see also
#2575 (comment)
how things look on SLES11 according to what the man pages tell there.

[gozora]

Your changes looks OK to me.
Unfortunately I don't have currently time to test them.

V.

[jsmeix]

@gozora
thank you for having a look!
I did not expect that you test it.
But perhaps you had known a reason why FAT16 was enforced with -F 16
(there was no comment that could have explained why that -F 16 was there).

What do you think about
#2575 (comment)

[gozora]

Hello @jsmeix,

What do you think about

I think that changing defaults to 512MB is OK. 400MB is not a nice number and I'm not surprised that some UEFI versions might have problems with.

V.

[jsmeix]

From my point of view this pull request is now sufficiently complete
so I would like to merge it tomorrow afternoon
unless there are objections.

[jsmeix]

@OliverO2 @gozora
thank you for your help with this issue!
It is much appreciated because I am really not an expert in that area.