Install Nginx Fresh install nginx service start fails

not related but Apache .htaccess doesn't work in Nginx so lines you added for don't work

Code (Text):

  auth_basic "Private";
  auth_basic_user_file /usr/local/nginx/conf/conf.d/-snip-.net.HtPasswd;

see for Nginx method https://community.centminmod.com/threads/how-to-properly-password-protect-a-directory-or-file.579/

You can debug custom changes to nginx config you make using nginx debug test config command

Code (Text):

nginx -t

but that journalctl log shows settings and stuff that are no longer supported i.e. spdy

Code (Text):

Dec 21 04:41:42 ns5445.ip.ip.ip.ip.net nginx[19465]: nginx: [emerg] invalid parameter "spdy" in /usr/local/nginx/conf/conf.d/mytestsite.net.ssl.conf:16
Dec 21 04:41:42 ns5445.ip.ip.ip.ip.net nginx[19465]: nginx: configuration file /usr/local/nginx/conf/nginx.conf test failed
Dec 21 04:41:42 ns5445.ip.ip.ip.ip.net systemd[1]: nginx.service: control process exited, code=exited status=1

and missing include files

Code (Text):

Dec 21 04:41:38 ns5445.ip.ip.ip.ip.net nginx[19422]: nginx: [emerg] open() "/usr/local/nginx/conf/autoprotect/mytestsite.net/autoprotect-mytestsite.net.conf" failed (2: No such file or directory) in /usr/local/nginx/conf/conf.d/mytestsite.net.conf:34
Dec 21 04:41:38 ns5445.ip.ip.ip.ip.net nginx[19422]: nginx: configuration file /usr/local/nginx/conf/nginx.conf test failed
Dec 21 04:41:38 ns5445.ip.ip.ip.ip.net systemd[1]: nginx.service: control process exited, code=exited status=1

downgrading Nginx via centmin.sh menu option 4 probably fixed the spdy one as the routine as a check for invalid spdy directive and removes it. But no idea why downgrade would fix missing /usr/local/nginx/conf/autoprotect/mytestsite.net/autoprotect-mytestsite.net.conf include file as you should get the same error regardless of nginx version if that include file is referenced in your nginx vhost config but is missing

If you have messed with your Nginx vhost include files after initial install and ran centmin.sh menu option 4, then the nginx upgrade/downgrade routine automatically makes a backup of your previous Nginx vhost config files at /usr/local/nginxbackup/ that you can reference to see the differences

Code (Text):

ls -lah /usr/local/nginxbackup/
total 36K
drwxr-xr-x.   4 root root 4.0K Apr  4  2017 .
drwxr-xr-x.  28 root root 4.0K Dec  3 04:38 ..
drwxr-xr-x. 278 root root  16K Jan 22  2018 confbackup
drwxr-xr-x.   2 root root  12K Jan 23  2018 nginxdirbackup

example command to list last 5 backups

Code (Text):

ls -lAhrt  /usr/local/nginxbackup/confbackup/ | tail -5
drwxr-xr-x.  9 root root  32K Jan 22  2018 conf_220118-104938
drwxr-xr-x.  9 root root  32K Jan 22  2018 conf_220118-105452
drwxr-xr-x.  9 root root  32K Jan 22  2018 conf_220118-110103
drwxr-xr-x.  9 root root  32K Jan 22  2018 conf_220118-110317
drwxr-xr-x.  9 root root  32K Jan 22  2018 conf_220118-111629

listing of backup config.d directory Nginx vhosts that you can inspect and compare

Code (Text):

ls -lAhrt  /usr/local/nginxbackup/confbackup/conf_220118-111629/conf.d/

-rw-r--r-- 1 root root 3.3K Jan 22  2018 domain1.com.ssl.conf
-rw-r--r-- 1 root root 2.0K Jan 22  2018 domain1.com.conf
-rw-r--r-- 1 root root 1.1K Jan 22  2018 demodomain.com.conf
-rw-r--r-- 1 root root 3.2K Jan 22  2018 virtual.conf

example comparing domain1.com.ssl.conf backed up copy with live copy

Code (Text):

diff -u /usr/local/nginxbackup/confbackup/conf_220118-111629/conf.d/domain1.com.ssl.conf /usr/local/nginx/conf/conf.d/domain1.com.ssl.conf

output

Code (Text):

diff -u /usr/local/nginxbackup/confbackup/conf_220118-111629/conf.d/domain1.com.ssl.conf /usr/local/nginx/conf/conf.d/domain1.com.ssl.conf 
--- /usr/local/nginxbackup/confbackup/conf_220118-111629/conf.d/domain1.com.ssl.conf    2018-01-22 11:04:52.069971411 +0000
+++ /usr/local/nginx/conf/conf.d/domain1.com.ssl.conf   2021-12-20 12:21:21.051930884 +0000
@@ -20,8 +20,8 @@
   ssl_certificate_key  /usr/local/nginx/conf/ssl/domain1.com/domain1.com.key;
   include /usr/local/nginx/conf/ssl_include.conf;

-  http2_max_field_size 16k;
-  http2_max_header_size 32k;
+  #http2_max_field_size 16k;
+  #http2_max_header_size 32k;
   # mozilla recommended
   ssl_ciphers EECDH+CHACHA20:EECDH+CHACHA20-draft:EECDH+ECDSA+AESGCM:EECDH+aRSA+AESGCM:EECDH+ECDSA+SHA256:EECDH+ECDSA+SHA384:EECDH+aRSA+SHA256:EECDH+aRSA+SHA384:EECDH+AES128:!aNULL:!eNULL:!LOW:!3DES:!MD5:!EXP:!PSK:!SRP:!DSS:!RC4:!EDH-DSS-DES-CBC3-SHA:!EDH-RSA-DES-CBC3-SHA:!KRB5-DES-CBC3-SHA:!CAMELLIA;
   ssl_prefer_server_ciphers   on;

 

did you manually create that nginx vhost config file or use centmin.sh menu option 2 or nv command to create it? If you manually copied it over, then that could explain the issue as your old nginx vhost might be quite old.

If the line relates to the listen directive on port 443, you can change it
from

Code (Text):

listen 443 ssl spdy;

to

Code (Text):

listen 443 ssl http2;

and restart nginx server

 

That is strange. Thanks for the heads up will investigate