这是systemctl status dnsmasq.service的内容：
● dnsmasq.service - dnsmasq - A lightweight DHCP and caching DNS server
Loaded: loaded (/lib/systemd/system/dnsmasq.service; enabled; vendor preset: enabled)
Active: failed (Result: exit-code) since Sat 2019-06-29 12:37:37 CEST; 23s ago
Process: 24641 ExecStart=/etc/init.d/dnsmasq systemd-exec (code=exited, status=2)
Process: 24638 ExecStartPre=/usr/sbin/dnsmasq --test (code=exited, status=0/SUCCESS)
以下是日记内容：
-- Logs begin at Tue 2019-06-25 11:49:21 CEST, end at Sat 2019-06-29 12:48:50 CEST. --
Jun 25 11:49:29 EddLinux kernel: nouveau 0000:01:00.0: preinit failed with -22
Jun 25 11:49:29 EddLinux kernel: nouveau: DRM:00000000:00000080: init failed with -22
Jun 25 11:49:32 EddLinux avahi-daemon[297]: chroot.c: open() failed: No such file or directory
Jun 25 11:49:33 EddLinux systemd-rfkill[421]: Failed to open device: No such device
Jun 25 11:49:35 EddLinux dhclient[502]: Failed to get interface index: No such device
Jun 25 11:49:35 EddLinux dhclient[502]:
Jun 25 11:49:35 EddLinux dhclient[502]: If you think you have received this message due to a bug rather
Jun 25 11:49:35 EddLinux dhclient[502]: than a configuration issue please read the section on submitting
Jun 25 11:49:35 EddLinux dhclient[502]: bugs on either our web page at www.isc.org or in the README file
Jun 25 11:49:35 EddLinux dhclient[502]: before submitting a bug. These pages explain the proper
Jun 25 11:49:35 EddLinux dhclient[502]: process and the information we find helpful for debugging..
Jun 25 11:49:35 EddLinux dhclient[502]:
Jun 25 11:49:35 EddLinux dhclient[502]: exiting.
Jun 25 11:49:35 EddLinux systemd[1]: Failed to start Raise network interfaces.
Jun 25 11:49:44 EddLinux wpa_supplicant[571]: nl80211: Unexpected encryption algorithm 5
Jun 25 12:17:49 EddLinux wpa_supplicant[571]: nl80211: Unexpected encryption algorithm 5
Jun 25 13:32:38 EddLinux wpa_supplicant[571]: nl80211: Unexpected encryption algorithm 5
Jun 25 13:32:43 EddLinux wpa_supplicant[571]: nl80211: Unexpected encryption algorithm 5
Jun 25 17:36:10 EddLinux wpa_supplicant[571]: nl80211: Unexpected encryption algorithm 5
Jun 25 18:29:26 EddLinux kernel: ACPI Error: No installed handler for fixed event - PowerButton (2), disabling (20160831/evevent-291)
Jun 25 18:46:36 EddLinux wpa_supplicant[571]: nl80211: Unexpected encryption algorithm 5
Jun 25 18:50:57 EddLinux kernel: ACPI Error: No installed handler for fixed event - PowerButton (2), disabling (20160831/evevent-291)
Jun 26 12:29:22 EddLinux wpa_supplicant[571]: nl80211: Unexpected encryption algorithm 5
Jun 26 13:08:52 EddLinux anacron[4522]: Can't find sendmail at /usr/sbin/sendmail, not mailing output
Jun 26 14:20:05 EddLinux wpa_supplicant[571]: nl80211: Unexpected encryption algorithm 5
Jun 26 14:31:18 EddLinux kernel: ACPI Error: No installed handler for fixed event - PowerButton (2), disabling (20160831/evevent-291)
Jun 26 15:38:34 EddLinux wpa_supplicant[571]: nl80211: Unexpected encryption algorithm 5
Jun 26 15:38:47 EddLinux kernel: sd 6:0:0:0: [sdb] No Caching mode page found
Jun 26 15:38:47 EddLinux kernel: sd 6:0:0:0: [sdb] Assuming drive cache: write through
Jun 26 15:42:56 EddLinux kernel: ACPI Error: No installed handler for fixed event - PowerButton (2), disabling (20160831/evevent-291)
Jun 26 15:52:46 EddLinux wpa_supplicant[571]: nl80211: Unexpected encryption algorithm 5
Jun 26 16:21:11 EddLinux kernel: ACPI Error: No installed handler for fixed event - PowerButton (2), disabling (20160831/evevent-291)
Jun 26 17:39:35 EddLinux wpa_supplicant[571]: nl80211: Unexpected encryption algorithm 5
Jun 26 18:16:05 EddLinux kernel: ACPI Error: No installed handler for fixed event - PowerButton (2), disabling (20160831/evevent-291)
Jun 26 18:25:44 EddLinux wpa_supplicant[571]: nl80211: Unexpected encryption algorithm 5
Jun 26 20:30:11 EddLinux kernel: ACPI Error: No installed handler for fixed event - PowerButton (2), disabling (20160831/evevent-291)
Jun 27 16:39:10 EddLinux wpa_supplicant[571]: nl80211: Unexpected encryption algorithm 5
Jun 27 17:06:50 EddLinux anacron[11980]: Can't find sendmail at /usr/sbin/sendmail, not mailing output
Jun 27 17:38:13 EddLinux kernel: ACPI Error: No installed handler for fixed event - PowerButton (2), disabling (20160831/evevent-291)
Jun 27 18:11:44 EddLinux wpa_supplicant[571]: nl80211: Unexpected encryption algorithm 5
Jun 27 18:12:28 EddLinux wpa_supplicant[571]: nl80211: Unexpected encryption algorithm 5
Jun 27 18:50:12 EddLinux kernel: ACPI Error: No installed handler for fixed event - PowerButton (2), disabling (20160831/evevent-291)
Jun 28 11:46:18 EddLinux wpa_supplicant[571]: nl80211: Unexpected encryption algorithm 5
Jun 28 11:48:33 EddLinux kernel: sd 6:0:0:0: [sdb] No Caching mode page found
Jun 28 11:48:33 EddLinux kernel: sd 6:0:0:0: [sdb] Assuming drive cache: write through
Jun 28 11:48:55 EddLinux kernel: FAT-fs (sdb1): unable to read boot sector to mark fs as dirty
Jun 28 11:53:31 EddLinux kernel: sd 6:0:0:0: [sdb] No Caching mode page found
Jun 28 11:53:31 EddLinux kernel: sd 6:0:0:0: [sdb] Assuming drive cache: write through
Jun 28 11:53:41 EddLinux wpa_supplicant[571]: nl80211: Unexpected encryption algorithm 5
Jun 28 12:08:31 EddLinux anacron[17533]: Can't find sendmail at /usr/sbin/sendmail, not mailing output
Jun 28 12:52:24 EddLinux kernel: ACPI Error: No installed handler for fixed event - PowerButton (2), disabling (20160831/evevent-291)
Jun 29 12:13:35 EddLinux anacron[21404]: Can't find sendmail at /usr/sbin/sendmail, not mailing output
Jun 29 12:35:05 EddLinux dnsmasq[24574]: failed to create listening socket for port 53: Address already in use
Jun 29 12:35:05 EddLinux dnsmasq[24574]: FAILED to start up
Jun 29 12:35:05 EddLinux systemd[1]: Failed to start dnsmasq - A lightweight DHCP and caching DNS server.
Jun 29 12:37:37 EddLinux dnsmasq[24641]: failed to create listening socket for port 53: Address already in use
Jun 29 12:37:37 EddLinux dnsmasq[24641]: FAILED to start up
Jun 29 12:37:37 EddLinux systemd[1]: Failed to start dnsmasq - A lightweight DHCP and caching DNS server.
我已经重新安装了。欢迎任何帮助！
答案1
问题
无法为端口 53 创建监听套接字：地址已被使用
就是这样。
DNS 使用在端口 53 上发送数据的查询（大多数时候是 UDP，但也可以使用 TCP）。
dnsmasq是（除其他外）所谓的转发 DNS服务器，因为它是服务器，所以它想要听至少在 53/UDP 上，也可能在 53/TCP 上。
只有一个进程（正在运行的程序）能够侦听特定 IP 地址上具有特定编号的端口。因此，该错误意味着其他某个程序已在侦听端口 53，但dnsmasq未能做到这一点，并退出。
该怎么办？
首先，弄清楚 53/UDP 上正在监听什么。
安装
iproute2：# apt install iproute2查看谁在使用 53/UDP：
# ss -nlup这些选项的含义是：
- 展示n数字地址，不要尝试进行 DNS 解析。
- 只显示升监听套接字。
- 只显示你dp 插座（实际上是端点，但没关系）。
- 展示页打开这些套接字的进程。
（请注意，您必须以
root—maybe via的身份运行该程序sudo；这取决于您如何配置系统上的提升权限的方式。）现在在输出中找到一个包含类似内容的记录
[::]:53— — 确切的读数可能有所不同，比如说，0.0.0.0:53但您:53肯定会看到那个后缀 — — 那是端口号，— — 然后看到“用户”列 — — 它应该列出打开该套接字的程序的名称。比如说，在我的系统上，相关的类似内容看起来像
UNCONN 0 0 [::]:53 [::]:* users:(("dnsmasq",pid=601,fd=6))（为了简洁，我压缩了一些空格）。请注意，用户是dnsmasq；在您的系统上，这将有所不同。
好的，一旦你弄清楚了谁是罪魁祸首，就试着想想如何卸载该程序。这样做之后，一切# systemctl restart dnsmasq就都简单了。