can't boot up

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Joined: 12/03/2019

Taurinus x200 running Trisquel:
After I downloaded an update, at boot-up says DMAR: failed to map dmar2
unable to read hardware clock.
Busybox v1.22.1 (Ubuntu 1:1.22.0-15ubuntu1.4) built in shell (ash)
Enter "help" for list ofbuilt-in commands.
Then a prompt after (initramfs).
What can I do to get it to boot up?