This article will help to lock and unlock user on linux system
root@server [~]#passwd -l gthomas
Locking password for user gthomas.
passwd: Success
passwd: Success
root@server [~]# grep user /etc/shadow
gthomas:!!$1$YKoF7EbU$zXqSSlKelclFLn0LDR/YM0:16063:0:99999:7:::
root@server [~]#passwd -u gthomas
Unlocking password for user gthomas.
passwd: Success
passwd: Success
root@server [~]#grep gthomas /etc/shadow
gthomas:$1$YKoF7EbU$zXqSSlKelclFLn0LDR/YM0:16063:0:99999:7:::
