snap prevents disk devices from being accessed

i wanted to backup the device my /boot partition is mounted on using mozilla. but snap seems to prevent me from doing that.

i use fsck here to illustrate what is happening - clonezilla seems to work when fsck works.

i started by unmouning /boot:

sudo umount /boot/efi sudo umount /bootsudo fsck /dev/sda2  # which is the device for /boot

from that i get the error message

fsck from util-linux 2.37.2e2fsck 1.46.5 (30-Dec-2021)/dev/sda2 is in use.e2fsck: Cannot continue, aborting.

my question is: how can i get fsck to run.

the current workaround is:

• snap disable all installed snaps
• sudo systemctl stop snapd
• reboot

then everything works.

but there must be a simpler way of accessing /dev/sda2! how can i access it without the interference of snap?