How to get into linux gentoo on the server if it does not let you under any user?

Question

linux

Good afternoon.
The server with gentoo stopped letting me in.
As far as I understand, after updating the /etc/shadow/ file, it was updated
in turn. when changing the password, passwd user showed an error:
passwd: Authentication token manipulation error
Colleagues help, as usual, someone who is not strong with Linux writes to you.
Thank you.

Answer 1

This error occurs when you do not have write permissions. Check the permissions on the file and how the root partition is mounted.
And it's better to log into the server using ssh keys.

Answer 2

Didn't do very well, but still.
Booted from liveCD.
Edited shadow
After that it turned out to go.
Then I returned the backup shadow and ok.
It remains to solve the problem with passwd.
passwd: Authentication token manipulation error