使用CentOS系统的时候，经常会遇到系统日志文件非常大的情况，如果直接删除，会导致日志错误，不再生成日志，这时，我们可以使用下面的方法清空日志。
CentOS 6系统
cat /dev/null > /var/log/boot.log
cat /dev/null > /var/log/cron
cat /dev/null > /var/log/dmesg
cat /dev/null > /var/log/dracut.log
cat /dev/null > /var/log/lastlog
cat /dev/null > /var/log/maillog
cat /dev/null > /var/log/messages
cat /dev/null > /var/log/secure
cat /dev/null > /var/log/spooler
cat /dev/null > /var/log/tallylog
cat /dev/null > /var/log/wtmp
cat /dev/null > /var/log/yum.log
CentOS 7系统
cat /dev/null > /var/log/boot.log
cat /dev/null > /var/log/btmp
cat /dev/null > /var/log/cron
cat /dev/null > /var/log/dmesg
cat /dev/null > /var/log/firewalld
cat /dev/null > /var/log/grubby
cat /dev/null > /var/log/lastlog
cat /dev/null > /var/log/mail.info
cat /dev/null > /var/log/maillog
cat /dev/null > /var/log/messages
cat /dev/null > /var/log/secure
cat /dev/null > /var/log/spooler
cat /dev/null > /var/log/syslog
cat /dev/null > /var/log/tallylog
cat /dev/null > /var/log/wpa_supplicant.log
cat /dev/null > /var/log/wtmp
cat /dev/null > /var/log/yum.log