debian 10: nginx fails to install after system upgrade

 >PROBLEM

Scenario:

After performing an upgrade using:

apt update

apt upgrade

nginx returns installing issues and fails to start, returning an error message like this:

Aug 04 13:28:47 myserver.com systemd[1]: Failed to start A high performance web server and a reverse proxy server.

dpkg: error processing package nginx-full (--configure):

 installed nginx-full package post-installation script subprocess returned error exit status 1

dpkg: dependency problems prevent configuration of nginx:

 nginx depends on nginx-full (<< 1.14.2-2+deb10u4.1~) | nginx-light (<< 1.14.2-2+deb10u4.1~) | nginx-extras (<< 1.14.2-2+deb10u4.1~); however:

  Package nginx-full is not configured yet.

  Package nginx-light is not installed.

  Package nginx-extras is not installed.

>SOLUTION

1. Check the installed packages:

  dpkg -l nginx*

Returns:

||/ Name           Version          Architecture Description

+++-==============-================-============-=========================================================

iU  nginx          1.14.2-2+deb10u4 all          small, powerful, scalable web/proxy server

ii  nginx-common   1.14.2-2+deb10u4 all          small, powerful, scalable web/proxy server - common files

un  nginx-doc      <none>           <none>       (no description available)

un  nginx-extras   <none>           <none>       (no description available)

iF  nginx-full     1.14.2-2+deb10u4 amd64        nginx web/proxy server (standard version)

un  nginx-light    <none>           <none>       (no description available)

root@again4u:/opt# dpkg remove nginx-1.14.2

2. Purge the packages:

  apt purge nginx-common nginx-full

3. Testing the removal:

  dpkg -l nginx*

root@again4u:/opt# dpkg -l nginx*

dpkg-query: no packages found matching nginx*

Shall return "no packages found..."

4. Deactivate the firewall, temporarily.

5. Reinstall nginx.

  apt install -f nginx

  

6. If reinstallation fails returning the same previous issue, uninstall nginx again, repeating the steps above and reboot the server.

If using a remote server, use the provider's interface to reboot it.

Deactivate the firewall, temporarily, and install nginx again:

  apt install -f nginx

7. Test the installation.

  systemctl status nginx

If successful, return something like this:

● nginx.service - A high performance web server and a reverse proxy server

   Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)

   Active: active (running) since Wed 2021-08-04 13:54:48 EDT; 22min ago

     Docs: man:nginx(8)

 Main PID: 723 (nginx)

    Tasks: 3 (limit: 4915)

   Memory: 16.3M

   CGroup: /system.slice/nginx.service

           ├─723 nginx: master process /usr/sbin/nginx -g daemon on; master_process on;

           ├─726 nginx: worker process

           └─727 nginx: worker process

8. Start the firewall.

>ENV

debian 10