ssh.service 启动失败；端口 22 已在使用

Question

全新的ubuntu安装：

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.1 LTS
Release:        20.04
Codename:       focal

ssh.service 由于端口 22 已在使用，无法启动：

$ sudo service ssh status
? ssh.service - OpenBSD Secure Shell server
     Loaded: loaded (/lib/systemd/system/ssh.service; enabled; vendor preset: enabled)
     Active: failed (Result: exit-code) since Thu 2021-02-04 14:10:27 CST; 11min ago
       Docs: man:sshd(8)
             man:sshd_config(5)
    Process: 2041 ExecStartPre=/usr/sbin/sshd -t (code=exited, status=0/SUCCESS)
    Process: 2042 ExecStart=/usr/sbin/sshd -D $SSHD_OPTS (code=exited, status=255/EXCEPTION)
   Main PID: 2042 (code=exited, status=255/EXCEPTION)

Feb 04 14:10:27 ubu20a systemd[1]: Starting OpenBSD Secure Shell server...
Feb 04 14:10:27 ubu20a sshd[2042]: error: Bind to port 22 on 0.0.0.0 failed: Address already in use.
Feb 04 14:10:27 ubu20a sshd[2042]: error: Bind to port 22 on :: failed: Address already in use.
Feb 04 14:10:27 ubu20a sshd[2042]: fatal: Cannot bind any address.
Feb 04 14:10:27 ubu20a systemd[1]: ssh.service: Main process exited, code=exited, status=255/EXCEPTION
Feb 04 14:10:27 ubu20a systemd[1]: ssh.service: Failed with result 'exit-code'.
Feb 04 14:10:27 ubu20a systemd[1]: Failed to start OpenBSD Secure Shell server.

我在端口 22 上看到的唯一监听是1/init：

$ sudo netstat -tulpen
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       User       Inode      PID/Program name    
tcp        0      0 127.0.0.53:53           0.0.0.0:*               LISTEN      101        34051      556/systemd-resolve 
tcp        0      0 127.0.0.1:631           0.0.0.0:*               LISTEN      0          37066      745/cupsd           
tcp6       0      0 :::22                   :::*                    LISTEN      0          34718      1/init              
udp        0      0 0.0.0.0:5353            0.0.0.0:*                           115        37068      743/avahi-daemon: r 
udp        0      0 0.0.0.0:52172           0.0.0.0:*                           115        37070      743/avahi-daemon: r 
udp        0      0 127.0.0.53:53           0.0.0.0:*                           101        34047      556/systemd-resolve 
udp        0      0 0.0.0.0:631             0.0.0.0:*                           0          39715      822/cups-browsed    
udp6       0      0 :::5353                 :::*                                115        37069      743/avahi-daemon: r 
udp6       0      0 :::39012                :::*                                115        37071      743/avahi-daemon: r 

虽然我可以得到ssh.service以启动备用端口（例如，端口2020）我想明白了，修复（如果可能的话），这本期通过端口22。

注意事项：

• linux sysadmin 不是我的强项，所以如果我遗漏了一些非常明显的东西......继续射击信使
• 如果答案是RTFM一个链接，FMTR将不胜感激
• 我浏览了前十几个建议的“重复”问题，但没有发现任何适用于这个问题的问题

Answer 1

评论有点长...

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我采纳了 @steeldriver 的建议并运行了建议的systemctl调用：

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$ systemctl -all list-sockets\nLISTEN                       UNITS                           ACTIVATES               \n... snip ...\n/run/udev/control            systemd-udevd-control.socket    systemd-udevd.service   \n/run/uuidd/request           uuidd.socket                    uuidd.service           \n[::]:22                      tinysshd.socket                 tinysshd@0.service      \naudit 1                      systemd-journald-audit.socket   systemd-journald.service\nkobject-uevent 1             systemd-udevd-kernel.socket     systemd-udevd.service \n

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有趣的是从底部开始的第三行......称为tinysshd监听端口 22。

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我找不到任何解释tinysshd（即，似乎不是系统所需的服务），因此我删除了tinysshd( sudo apt remove tinysshd) 并能够成功启动ssh服务：

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$ sudo service ssh status\n\xe2\x97\x8f ssh.service - OpenBSD Secure Shell server\n     Loaded: loaded (/lib/systemd/system/ssh.service; enabled; vendor preset: enabled)\n     Active: active (running) since Thu 2021-02-04 15:14:34 CST; 3s ago\n       Docs: man:sshd(8)\n             man:sshd_config(5)\n    Process: 3887 ExecStartPre=/usr/sbin/sshd -t (code=exited, status=0/SUCCESS)\n   Main PID: 3888 (sshd)\n      Tasks: 1 (limit: 7032)\n     Memory: 1.3M\n     CGroup: /system.slice/ssh.service\n             \xe2\x94\x94\xe2\x94\x803888 sshd: /usr/sbin/sshd -D [listener] 0 of 10-100 startups\n\nFeb 04 15:14:34 ubu20a systemd[1]: Starting OpenBSD Secure Shell server...\nFeb 04 15:14:34 ubu20a sshd[3888]: Server listening on 0.0.0.0 port 22.\nFeb 04 15:14:34 ubu20a sshd[3888]: Server listening on :: port 22.\nFeb 04 15:14:34 ubu20a systemd[1]: Started OpenBSD Secure Shell server.\n

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我还可以看到sshd正在监听端口 22：

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$ sudo netstat -tulpen\nActive Internet connections (only servers)\nProto Recv-Q Send-Q Local Address           Foreign Address         State       User       Inode      PID/Program name    \n...snip ...\ntcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      0          66119      3888/sshd: /usr/sbi \ntcp6       0      0 :::22                   :::*                    LISTEN      0          66121      3888/sshd: /usr/sbi \n... snip ...\n

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