在我的服务器上，我设置了 dnsmasq；它被配置为另一台服务器，它可以在那里工作（尽管与其他硬件和操作系统一起）。
但是在这个特定的主机上，dnsmasq 在启动后不起作用（客户端无法解析名称），但如果我手动重新启动它（service dnsmasq restart），它就可以工作。
我无法从日志中找出任何东西，日志没有显示任何问题。启动后立即提取系统日志：
15:Apr 13 12:31:39 <server_hostname> systemd[1]: Stopping dnsmasq - A lightweight DHCP and caching DNS server...
276:Apr 13 12:32:22 <server_hostname> systemd[1]: Starting dnsmasq - A lightweight DHCP and caching DNS server...
285:Apr 13 12:32:22 <server_hostname> dnsmasq[592]: dnsmasq: syntax check OK.
511:Apr 13 12:32:22 <server_hostname> dnsmasq[622]: started, version 2.75 cachesize 150
512:Apr 13 12:32:22 <server_hostname> dnsmasq[622]: compile time options: IPv6 GNU-getopt DBus i18n IDN DHCP DHCPv6 no-Lua TFTP conntrack ipset auth DNSSEC loop-detect inotify
513:Apr 13 12:32:22 <server_hostname> dnsmasq[622]: DNS service limited to local subnets
514:Apr 13 12:32:22 <server_hostname> dnsmasq[622]: warning: ignoring resolv-file flag because no-resolv is set
515:Apr 13 12:32:22 <server_hostname> dnsmasq-dhcp[622]: DHCP, IP range 192.168.166.2 -- 192.168.166.254, lease time 1h
516:Apr 13 12:32:22 <server_hostname> dnsmasq[622]: using nameserver 209.222.18.218#53
517:Apr 13 12:32:22 <server_hostname> dnsmasq[622]: using nameserver 209.222.18.222#53
518:Apr 13 12:32:22 <server_hostname> dnsmasq[622]: read /etc/hosts - 5 addresses
558:Apr 13 12:32:22 <server_hostname> systemd[1]: Started dnsmasq - A lightweight DHCP and caching DNS server.
568:Apr 13 12:32:24 <server_hostname> dnsmasq-dhcp[622]: DHCP packet received on eth1 which has no address
575:Apr 13 12:32:27 <server_hostname> dnsmasq-dhcp[622]: DHCP packet received on eth1 which has no address
589:Apr 13 12:32:32 <server_hostname> dnsmasq-dhcp[622]: DHCPDISCOVER(eth1) 192.168.166.129 <client_mac>
590:Apr 13 12:32:32 <server_hostname> dnsmasq-dhcp[622]: DHCPOFFER(eth1) 192.168.166.129 <client_mac>
591:Apr 13 12:32:32 <server_hostname> dnsmasq-dhcp[622]: DHCPREQUEST(eth1) 192.168.166.129 <client_mac>
592:Apr 13 12:32:32 <server_hostname> dnsmasq-dhcp[622]: DHCPACK(eth1) 192.168.166.129 <client_mac> <client_hostname>
执行后添加的条目service dnsmasq restart：
625:Apr 13 12:33:39 <server_hostname> systemd[1]: Stopping dnsmasq - A lightweight DHCP and caching DNS server...
626:Apr 13 12:33:39 <server_hostname> dnsmasq[622]: exiting on receipt of SIGTERM
627:Apr 13 12:33:39 <server_hostname> systemd[1]: Stopped dnsmasq - A lightweight DHCP and caching DNS server.
628:Apr 13 12:33:39 <server_hostname> systemd[1]: Starting dnsmasq - A lightweight DHCP and caching DNS server...
629:Apr 13 12:33:39 <server_hostname> dnsmasq[875]: dnsmasq: syntax check OK.
630:Apr 13 12:33:39 <server_hostname> dnsmasq[885]: started, version 2.75 cachesize 150
631:Apr 13 12:33:39 <server_hostname> dnsmasq[885]: compile time options: IPv6 GNU-getopt DBus i18n IDN DHCP DHCPv6 no-Lua TFTP conntrack ipset auth DNSSEC loop-detect inotify
632:Apr 13 12:33:39 <server_hostname> dnsmasq[885]: DNS service limited to local subnets
633:Apr 13 12:33:39 <server_hostname> dnsmasq[885]: warning: ignoring resolv-file flag because no-resolv is set
634:Apr 13 12:33:39 <server_hostname> dnsmasq-dhcp[885]: DHCP, IP range 192.168.166.2 -- 192.168.166.254, lease time 1h
635:Apr 13 12:33:39 <server_hostname> dnsmasq[885]: using nameserver 209.222.18.218#53
636:Apr 13 12:33:39 <server_hostname> dnsmasq[885]: using nameserver 209.222.18.222#53
637:Apr 13 12:33:39 <server_hostname> dnsmasq[885]: read /etc/hosts - 5 addresses
638:Apr 13 12:33:40 <server_hostname> systemd[1]: Started dnsmasq - A lightweight DHCP and caching DNS server.
服务器是 Ubuntu 16.04；dnsmasq 版本是2.75-1ubuntu0.16.04.4。
配置（下/etc/dnsmasq.d/）是：
bind-interfaces
dhcp-range=eth1,192.168.100.2,192.168.100.254
server=<dns_server_1>
server=<dns_server_2>
no-resolv
我该如何调试此问题？可能的原因是什么？
答案1
这实际上是 systemd 和 dnsmasq 之间的竞争条件，在 Raspbian 上也可能发生。
解决方案是确保在 dnsmasq 启动之前网络接口已启动：
sudo systemctl edit dnsmasq
并添加：
[Unit]
After=network-online.target
Wants=network-online.target