请原谅来自 Stack Overflow 的交叉帖子，但我意识到这可能是更好的询问位置。
我最近在 AWS 上重建了我的服务器，从 Amazon Linux 升级到 Amazon Linux 2，就像 Linux 1 似乎是 CentOS 的一个分支，现在是 CentOS 7。我的虚拟主机配置与之前的构建保持相同，而所有其他 conf 文件都是较新的默认文件。（仅供参考，不确定它是否有任何影响）。
自从重建我不能再做systemctl restart httpd。我得到错误The Apache HTTP Server httpd pid (NNNN) already running。
我做了很多谷歌搜索，发现很多人都有这个错误，但结果总是与他们所做的不同。我想不出我所做的任何“不同”。
我了解到，我看到的“已经在运行”的 PID 由 root 拥有，是“主进程”，而 apache 拥有的所有其他 PID 都是“工作进程”。CentOS httpd 作为 root 和 apache 用户运行
root 4461 1 0 07:18 ? 00:00:00 /usr/sbin/httpd -k restart
apache 4467 4461 0 07:18 ? 00:00:09 /usr/sbin/httpd -k restart
apache 4468 4461 0 07:18 ? 00:00:08 /usr/sbin/httpd -k restart
apache 4471 4461 0 07:18 ? 00:00:08 /usr/sbin/httpd -k restart
apache 4477 4461 0 07:18 ? 00:00:08 /usr/sbin/httpd -k restart
apache 4498 4461 0 07:18 ? 00:00:07 /usr/sbin/httpd -k restart
apache 5236 4461 0 07:19 ? 00:00:08 /usr/sbin/httpd -k restart
apache 5248 4461 0 07:19 ? 00:00:09 /usr/sbin/httpd -k restart
apache 5987 4461 0 07:20 ? 00:00:09 /usr/sbin/httpd -k restart
apache 5993 4461 0 07:20 ? 00:00:08 /usr/sbin/httpd -k restart
apache 5994 4461 0 07:20 ? 00:00:09 /usr/sbin/httpd -k restart
# systemctl restart httpd;systemctl status httpd;
Job for httpd.service failed. See "systemctl status httpd.service" and "journalctl -xe" for details.
● httpd.service - The Apache HTTP Server
Loaded: loaded (/usr/lib/systemd/system/httpd.service; disabled; vendor preset: disabled)
Active: failed (Result: protocol) since Thu 2021-12-23 19:56:05 UTC; 4ms ago
Docs: man:httpd.service(8)
Process: 31799 ExecStart=/usr/sbin/httpd $OPTIONS -DFOREGROUND (code=exited, status=0/SUCCESS)
Main PID: 31799 (code=exited, status=0/SUCCESS)
Status: "Reading configuration..."
Dec 23 19:56:04 ip-10-5-11-55.ec2.internal systemd[1]: Starting The Apache HTTP Server...
Dec 23 19:56:05 ip-10-5-11-55.ec2.internal httpd[31799]: httpd (pid 4461) already running
Dec 23 19:56:05 ip-10-5-11-55.ec2.internal systemd[1]: Failed to start The Apache HTTP Server.
Dec 23 19:56:05 ip-10-5-11-55.ec2.internal systemd[1]: Unit httpd.service entered failed state.
Dec 23 19:56:05 ip-10-5-11-55.ec2.internal systemd[1]: httpd.service failed.
Apache 错误日志中没有异常：
[Thu Dec 23 07:18:58.777745 2021] [suexec:notice] [pid 4460] AH01232: suEXEC mechanism enabled (wrapper: /usr/sbin/suexec)
[Thu Dec 23 07:18:58.802753 2021] [lbmethod_heartbeat:notice] [pid 4461] AH02282: No slotmem from mod_heartmonitor
[Thu Dec 23 07:18:58.802850 2021] [http2:warn] [pid 4461] AH10034: The mpm module (prefork.c) is not supported by mod_http2. The mpm determines how things are processed in your server. HTTP/2 has more
[Thu Dec 23 07:18:58.847386 2021] [mpm_prefork:notice] [pid 4461] AH00163: Apache/2.4.51 () PHP/7.4.21 configured -- resuming normal operations
[Thu Dec 23 07:18:58.847414 2021] [core:notice] [pid 4461] AH00094: Command line: '/usr/sbin/httpd'
如果我杀死这个“主”PID，那么我可以重新启动没问题。
# kill 4461
# systemctl restart httpd;systemctl status httpd;
● httpd.service - The Apache HTTP Server
Loaded: loaded (/usr/lib/systemd/system/httpd.service; disabled; vendor preset: disabled)
Active: active (running) since Thu 2021-12-23 20:01:31 UTC; 6ms ago
Docs: man:httpd.service(8)
Main PID: 3091 (httpd)
Status: "Configuration loaded."
CGroup: /system.slice/httpd.service
└─3091 /usr/sbin/httpd -DFOREGROUND
Dec 23 20:01:31 ip-10-5-11-55.ec2.internal systemd[1]: Starting The Apache HTTP Server...
Dec 23 20:01:31 ip-10-5-11-55.ec2.internal systemd[1]: Started The Apache HTTP Server.
# ps -Af | grep httpd
root 3145 1 1 20:01 ? 00:00:00 /usr/sbin/httpd -DFOREGROUND
apache 3147 3145 0 20:01 ? 00:00:00 /usr/sbin/httpd -DFOREGROUND
apache 3153 3145 0 20:01 ? 00:00:00 /usr/sbin/httpd -DFOREGROUND
apache 3171 3145 0 20:01 ? 00:00:00 /usr/sbin/httpd -DFOREGROUND
apache 3177 3145 0 20:01 ? 00:00:00 /usr/sbin/httpd -DFOREGROUND
apache 3183 3145 0 20:01 ? 00:00:00 /usr/sbin/httpd -DFOREGROUND
大多数人的建议是“杀死进程”，Apache 无法启动，已经运行但没有处理 pid 文件？但我需要这个在无人看管的情况下工作。我还能看什么？