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
1cat /dev/null > /var/log/boot.log 2cat /dev/null > /var/log/btmp 3cat /dev/null > /var/log/cron 4cat /dev/null > /var/log/dmesg 5cat /dev/null > /var/log/dracut.log 6cat /dev/null > /var/log/lastlog 7cat /dev/null > /var/log/maillog 8cat /dev/null > /var/log/messages 9cat /dev/null > /var/log/secure 10cat /dev/null > /var/log/spooler 11cat /dev/null > /var/log/tallylog 12cat /dev/null > /var/log/wtmp 13cat /dev/null > /var/log/yum.log
CentOS 7系统
1cat /dev/null > /var/log/boot.log 2cat /dev/null > /var/log/btmp 3cat /dev/null > /var/log/cron 4cat /dev/null > /var/log/dmesg 5cat /dev/null > /var/log/firewalld 6cat /dev/null > /var/log/grubby 7cat /dev/null > /var/log/lastlog 8cat /dev/null > /var/log/mail.info 9cat /dev/null > /var/log/maillog 10cat /dev/null > /var/log/messages 11cat /dev/null > /var/log/secure 12cat /dev/null > /var/log/spooler 13cat /dev/null > /var/log/syslog 14cat /dev/null > /var/log/tallylog 15cat /dev/null > /var/log/wpa_supplicant.log 16cat /dev/null > /var/log/wtmp 17cat /dev/null > /var/log/yum.log