When I am trying to add a user, the following error occurs: mismatch in /etc/passwd and /etc/shadow. What does this mean?

This can occur when there is inconsistencies between the /etc/passwd and /etc/shadow files. The offending account needs to either be modified or removed. To find out which account is causing the issue run the following command as root:

pwck

All entries in the /etc/passwd and /etc/shadow are checked to see that t...