On 23/04/2024 13:21, Thomas Schmitt wrote:
Max Nikulin wrote:
Out of curiosity, does the requirement of specific GUID exist for removable
drives?
It is disputed, whether the specs say that the partitions must be marked
by 0xEF in legacy MBR tables and by C12A7328-F81F-11D2-BA4B-00A0C93EC93B
in GPT.
It happened so that I had locally a file with UEFI spec Version 2.3.1,
Errata C June 27, 2012. I tried to search it for "removable" and for
"0xef". Since I am not familiar with context of the following snippets,
my interpretation may be wrong. Later versions may have some updates.
12.3.3 Number and Location of System Partitions
... Further, UEFI implementations may allow the use of conforming FAT
partitions which do not use the ESP GUID. Partition creators may prevent
UEFI firmware from examining and using a specific partition by setting
bit 1 of the Partition Attributes (see 5.3.3) which will exclude the
partition as a potential ESP.
From my point of view it is opposed to "must be" for strict partition
type checks.
I have noticed that FAT12 and FAT16 are allowed for removable media. The
restriction is that while a fixed media may have multiple ESP, a
removable one must have single EFI partition.
A USB drive may be formatted without partition table.
The specs only talk of partitions.
12.3.1 System Partition
... For a diskette (floppy) drive, a partition is defined to be the
entire media.
Some details are in 12.3.4.2 Diskette
USB pen drive is not a diskette, but it increases probability that
superfloppy formatting style is supported. Of course, singe FAT
partition is more portable.
7z and bsdtar can extract content of ISO files without mounting images.
But mounting needs no special software and gives you the opportunity
to use many different ways of copying, which may be decisive when the
target is a heavily restricted filesystem like FAT.
I usually have p7zip-full installed to be able to extract files from
various archives, so I do not consider it as a too special. I did not
need extra flexibility, with 7z there was no need for extra mount/umount
commands, just extracting as a regular user was enough. So in some cases
it is more convenient.
