isc-dhcp-server log

    ddns-update-style none;
    option domain-name-servers 125.219.192.2,222.88.88.88,202.102.224.68,211.84.208.2;
    default-lease-time 86400;
    max-lease-time 172800;
    log-facility local7; //日志发送给local7
    ping-check true;
    ping-timeout 2;
    authoritative;

在rsyslog.conf中，指定local7记录到那里

local7.*            -/var/log/dhcpd/dhcpd.log
之后：service rsyslog restart

在查看：/var/log/dhcpd/dhcpd.log