[wishlist] bootloader-configuration, avoid use of /dev/sd?

Hello,

Following a recent discussion on Guix-devel [1] I'm "forwarding here" a

proposal to switch from /dev/sd? to (target (uuid ...)) in

bootloader-configuration operating-system declaration

This is a recap of current situation: the installer usually uses

/dev/sda as target for grub-install (and bootloader-cofiguration) but it

happened to me that on a machine /dev/sda was the USB media, not the

target HD

The fact is that it's not guaranteed that /dev/sd? always corresponds to

the same device

This is where we are with the discussion:

Ludovic Courtès <ludo@gnu.org> writes:

[1] Message-ID: <87o93mwr4b.fsf@gnu.org>

http://lists.gnu.org/archive/html/guix-devel/2019-05/msg00454.html

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Giovanni Biscuolo

Xelera IT Infrastructures

Hello Tobias and Ludo'

I've opened a bug report for this, WDYT if we go on there?

Tobias Geerinckx-Rice <me@tobias.gr> writes:

Grub supports quite a number of ways to specify devices [1] but I cannot

find something suitable for this purpose: am I missimg something

obvious?

AFAIU on ther distros (e.g. Debian) (the installer?) populates a device

map [2] using the grub-mkdevicemap utility (grub-common package in

Debian) but I cannot find that in our grub package

This is an example on one of my Debian hosts:

(the map is not updated)

We could use (hd?) in grub config - that's grub specific, not Linux/udev

specific - **but** we should find a way to automate the selection of the

device corresponding to our target (the one mounted as /mnt)

Thanks for working on this!!!

Happy hacking. Gio'.

[1] https://www.gnu.org/software/grub/manual/grub/html_node/Device-syntax.html

[2] https://www.gnu.org/software/grub/manual/grub/html_node/Device-map.html

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Giovanni Biscuolo

Xelera IT Infrastructures

Grub already can search by uuid or label (via "search --fsuuid" and

"search --label", respectively). IF you specify an uuid or label

in your operating-system configuration it will use that.

The only part missing is: The Guix installer's config generator should

find out the uuids and print those instead of the /dev nodes.

If nothing else, we can just use blkid to find out which is which.

For example: blkid -d -s UUID -o value /dev/sda1

But T G-R is right, Guix already does what is required at other places.

Care has to be taken that parted also uses GUIDs for GPT partition TYPES

and also for partitions as such (not their contents). Those are something

else.

Hi Danny,

Danny Milosavljevic <dannym@scratchpost.org> skribis:

These are concerned with file system UUIDs/labels, whereas this issue is

about disk IDs, AIUI. Or am I missing something?

Ludo’.

Ludovic Courtès wrote:

This. Also, this only affects grub-install—not ‘grub

run-time’—which runs under the Hurd/Linux/…, unless I, too, am

missing something, and this entire thread collapses in a cacophony

of confusion.

G'night,

T G-R

Yeah, but disk ids are not uuids.

/dev/disk/by-id seems to be a good way to find those disk ids in order to pass

them to grub-install. I doubt that this can be made OS-independent--even the

udev rules specify different variables for different devices, sometimes it's

bus id and serial number, sometimes it's name and serial number, sometimes it's

ieee1394_id, sometimes ID_WWN_WITH_EXTENSION.

Alternatively, grub also works from a boot-active partition--it nothing else

works, we can install grub to a partition (for example the root partition).

Then, migration would be difficult, though (if people had grub installed on

the MBR, that destroyed the previous loader that would have loaded from the

boot sector of the partition).

Hello,

I think this bug has been fixed in bug #51878:

Pushed as b90504cdb5ce3d1981c8d7bc8a9cc918b0d60af7 (26 Nov 2021).

Closing! :-)

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Giovanni Biscuolo

Xelera IT Infrastructures