CentOS
cat /dev/null > /var/log/wtmp cat /dev/null > /var/log/btmp cat /dev/null > /var/log/lastlog cat /dev/null > /var/log/secure history -cw
Ubuntu
cat /dev/null > /var/log/wtmp cat /dev/null > /var/log/btmp cat /dev/null > /var/log/lastlog cat /dev/null > /var/log/auth.log history -cw