Unable to start nginx on a Plesk server: PID file /run/nginx.pid not readable (yet?) after start.

Symptoms

• The nginx service fails to start with the following error message:

  # service nginx status
  ● nginx.service - Startup script for nginx service
  Loaded: loaded (/usr/lib/systemd/system/nginx.service; enabled; vendor preset: disabled)
  Active: failed (Result: timeout) since Wed 2018-02-14 14:33:44 UTC; 9s ago
  
  Feb 14 14:32:14 multiserver-test1 systemd[1]: Starting Startup script for nginx service...
  Feb 14 14:32:14 multiserver-test1 nginx[30160]: nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
  Feb 14 14:32:14 multiserver-test1 nginx[30160]: nginx: configuration file /etc/nginx/nginx.conf test is successful
  Feb 14 14:32:14 multiserver-test1 systemd[1]: PID file /run/nginx.pid not readable (yet?) after start.
  Feb 14 14:33:44 multiserver-test1 systemd[1]: nginx.service start operation timed out. Terminating.
  Feb 14 14:33:44 multiserver-test1 systemd[1]: Failed to start Startup script for nginx service.
  Feb 14 14:33:44 multiserver-test1 systemd[1]: Unit nginx.service entered failed state.
  Feb 14 14:33:44 multiserver-test1 systemd[1]: nginx.service failed.

• The directory /var/run is not a symbolic link to the directory /run:

  # ls -ld /var/run
  drwxr-xr-x 12 root root 4096 Feb 14 14:33 /var/run

• The directory /run exists on the server:

  # ls -ld /run
  drwxr-xr-x 31 root root 920 Feb 19 10:01 /run

• The pid setting is commented out in nginx configuration files:

  # grep -ir pid /etc/nginx
  /etc/nginx/nginx.conf.default:#pid /var/run/nginx.pid;
  /etc/nginx/nginx.conf:#pid /var/run/nginx.pid;

Cause

The directory /var/run is not a symbolic link to the directory /var:

# ls -ld /var/run
drwxr-xr-x 12 root root 4096 Feb 14 14:28 /var/run

Resolution

1. Connect to the Plesk server via SSH.

2. Rename the original directory:

   # mv /var/run /var/run_orig

3. Create a symbolic link to /run:

   # ln -s ../run /var/run
   # ls -ld /var/run
   lrwxrwxrwx 1 root root 6 Feb 14 14:47 /var/run -> ../run

4. Reboot the server for the changes to take affect.

5. Verify that nginx is running:

   # service nginx status