为树莓派配置dhcp服务器（isc-dhcp-server），启动服务时出现：
Job for failed. See 'systemctl status ' and 'journalctl -xn' for details.
运行
# systemctl status
得到
● - LSB: DHCP server
Loaded: loaded (/etc//isc-dhcp-server)
Active: failed (Result: exit-code) since Sun 2017-09-03 16:47:49 CST; 2min 18s ago
Process: 1145 ExecStart=/etc//isc-dhcp-server start (code=exited, status=1/FAILU)
Sep 03 16:47:47 NanoPi3 dhcpd[1152]: to which interface usb0 is attached. **
Sep 03 16:47:47 NanoPi3 dhcpd[1152]:
Sep 03 16:47:47 NanoPi3 dhcpd[1152]:
Sep 03 16:47:47 NanoPi3 dhcpd[1152]: Not configured to listen on any interfaces!
Sep 03 16:47:47 NanoPi3 dhcpd[1152]:
Sep 03 16:47:49 NanoPi3 isc-dhcp-server[1145]: Starting ISC DHCP server: dhc...!
Sep 03 16:47:49 NanoPi3 isc-dhcp-server[1145]: failed!
Sep 03 16:47:49 NanoPi3 systemd[1]: : control proces...=1
Sep 03 16:47:49 NanoPi3 systemd[1]: Failed to start LSB: DHCP server.
Sep 03 16:47:49 NanoPi3 systemd[1]: Unit entered fa...e.
Hint: Some lines were ellipsized, use -l to show in full.
很明显，interface设备错了，被设置为了usb0
解决：
# vi /etc/default/isc-dhcp-server
修改默认的设备（eth0, wlan0 ....)