Perform this command to reset a Linux account that has been locked out due to multiple login failures. This involves resetting the pam_tally back down to zero. Some systems use pam_tally2. First, check what’s the current tally.

Current tally:

pam_tally --user=username
pam_tally2 --user=username

To reset:

pam_tally --user=username --reset
pam_tally2 --user=username --reset