vyos@lagg-vyos-01# set system login user vyos authentication plaintext-password  $MYPASSWORD
[edit]
vyos@lagg-vyos-01# commit
[ system login ]
usermod: existing lock file /etc/passwd.lock without a PID
usermod: cannot lock /etc/passwd; try again later.
Attempt to change user vyos failed: can´t update password file

[[system login]] failed
Commit failed
[edit]

vyos@lagg-vyos-01:~$ sudo su
root@lagg-vyos-01:/home/vyos# passwd vyos
passwd: Authentication failure
passwd: password unchanged