Pádraig Brady <[email protected]> writes:
> On 04/09/2026 10:22, ii via GNU coreutils Bug Reports wrote:
>> if dd is used to write block device, would destroy in-use devices, or LVM,
>> partition tables on devices.
>> Before opening the output, probe with libblkid and warn if content is
>> recognized, prompting for confirmation.
>
> Checking whether a device is mounted does seem potentially useful.
>
> Checking whether to overwrite existing file system structures seems less
> useful,
> as that would be a very common scenario. Also that functionality adds the
> libblkid dependency which isn't ideal.
Wouldn't this change break common instructions people use to create
flash drives for installing GNU/Linux, or other operating systems? At
least, I remember 'dd' commonly being recommended for that. Asking one
of the major slop bots:
How do I write a Fedora ISO to a usb?
Resulted in an answer involving the following steps:
$ sudo umount /dev/sda*
$ sudo dd if=Fedora-Workstation.iso of=/dev/sda \
bs=4M status=progress oflag=sync
If I understand correctly, the above steps would now give a warning with
this change if the drive has an MBR/GPT partition table, e.g., if I
previously used the drive to install FreeBSD using a memstick image:
$ od -Ax -tx1 -j 510 -N 2 FreeBSD-15.1-RELEASE-amd64-memstick.img
0001fe 55 aa
000200
$ fdisk -l FreeBSD-15.1-RELEASE-amd64-memstick.img | tail -n 3
Device Boot Start End Sectors Size
Id Type
FreeBSD-15.1-RELEASE-amd64-memstick.img1 1 66584 66584 32.5M
ef EFI (FAT-12/16/32)
FreeBSD-15.1-RELEASE-amd64-memstick.img2 * 66585 3032424 2965840 1.4G
a5 FreeBSD
While I am sympathetic to making things safer, I worry that this
behavior might come as welcome surprise to others.
Collin
