On Mon, Jul 17, 2017 at 07:21:49PM +0200, ingegneriafore...@alice.it wrote:
> CAN GRUB IMPLICITLY WRITE TO A DRIVE ATTACHED TO A COMPUTER ?
>
> Implicitly means: without an explicit command from a user.
Please stop SHOUTING; it's generally considered rather rude.
GRUB intentionally has no general filesystem writing support. As far as
I'm aware there are exactly four ways for it to send any write commands
to disks:
1) The "save_env" command (grub-core/commands/loadenv.c) which writes
key/value pairs to a small preallocated region of disk. This is
used to communicate small amounts of information to the OS, such as
whether the last request to boot a particular menu entry on only the
next boot has been completed.
2) The "gptsync" command (grub-core/commands/gptsync.c), which does
some MBR/GPT partition table mangling needed on some Apple models.
3) The similar "mactelbless" and "macppcbless" commands
(grub-core/commands/macbless.c), which configure a file/directory on
some Apple filesystems to be the 'blessed' boot image for that
filesystem.
4) The "parttool" command (grub-core/commands/parttool.c,
grub-core/parttool/), which can be used to make various
modifications to MBR partition table entries.
GRUB is scriptable, so it isn't possible to give a general answer to
your question for all systems that might have custom configurations, but
the default configuration files only use the "save_env" and "parttool"
commands, the latter only in the case where a chainloadable operating
system was detected on a disk using the MBR partition table format. In
either case, it isn't going to write to a random USB device that's
attached to a machine, although save_env might write to the device it
believes holds /boot/grub/grubenv.
The low-level disk handling code is in grub-core/disk/.
--
Colin Watson [cjwat...@ubuntu.com]
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