Password protect Netdata with NGINX / Permission denied while connecting to upstream error

Netdata is great free tool for generating server statistics. By default it’s open for entire world on port 19999 – It is not a good idea to leave this open so everyone can your system statistics.

One way to limit access from where it is accessible is by editing netdata.conf and specify IPS in “allow connections from” variable.

allow connections from = ip's that are allowed to access>

There is no option to password protect it. This can be done with NGINX. You can create reverse proxy, so that nginx will serve content from netdata application. To make netdata accessible on subfolder of your hostname, eg., then create nginx configuration like bellow.

First generate password file for nginx:

htpasswd -c /etc/nginx/.htpasswd "username"

Then create or edit existing nginx configuration to something like this:

upstream netdata {
        keepalive 64;

server {
     listen 443 ssl http2;
     location = /netdata {
         return 301 /netdata/;

    location ~ /netdata/(?.*) {

        auth_basic "Restricted Content";
        auth_basic_user_file /etc/nginx/.htpasswd;

        proxy_redirect off;
        proxy_set_header Host $host;   

        proxy_set_header X-Forwarded-Host $host;
        proxy_set_header X-Forwarded-Server $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_http_version 1.1;
        proxy_pass_request_headers on;
        proxy_set_header Connection "keep-alive";
        proxy_store off;
        proxy_pass http://netdata/$ndpath$is_args$args;

        gzip on;
        gzip_proxied any;
        gzip_types *;

    error_log /var/log/nginx/error.log;
    access_log off;

Also, don’t forget to edit netdata.conf and change some variables. Make netdata accessible only from localhost (nginx):

bind to =
allow connections from = localhost
allow dashboard from = localhost

You should also allow connection to port 19999 only to local traffic (localhost).

Restart nginx and netdata, then try to access like: http(s)://

If you’re getting error like bellow in your nginx error log, than chances are that SELinux is active. Disable selinux or execute this command “setsebool -P httpd_can_network_connect true”.

[crit] 8411#0: *1 connect() to failed (13: Permission denied) while connecting to upstream, client:, server:, request: "GET /netdata/ HTTP/1.1", upstream: "", host: ""




NGINX: rewrite non-www to www for multi domain virtual hosts

If you have NGINX virtual host that has a multi different domains pointing to same document root (multi server_name), and you want to automatically redirect non-www to www, than bellow is simple solution. I also wanted to redirect to https with www.

If you don’t need https redirection, than you can simply use variable $scheme instead of “https:”. 

if ( $host !~ ^www\. ) {
            return 302 https://www.$host$request_uri;

So virtual host should look something like this:

server {

      if ( $host !~ ^www\. ) {
           return 302 https://www.$host$request_uri;
      return 302 https://$host$request_uri;

You should also make this redirect in your https server definition. otherwise request for won’t redirect to www.

server {
      if ( $host !~ ^www\. ) {
              return 302 https://www.$host$request_uri;

      ssl on;
      ssl_certificate /etc/letsencrypt/live/;
      ssl_certificate_key /etc/letsencrypt/live/;

      .... //other nginx configuration ....

Find common/identical lines within two files without DIFF

Here is really simple trick how to search for strings that are the same within two different files.

For presenting purposes I created two files with some text in it. Some text is the same, some not.

File 1:

> $ cat file1.txt 


> $ cat file2.txt 

Here is how to find strings that are the same within both files:

> $ cat file1.txt file2.txt | sort | uniq -c | grep "2 " 
2 test3
2 test4

So, strings test3 and test4 occurring in both files.

Nice way to do HTTP to HTTPS redirection with Apache .htaccess

I had some sites on shared hosting environment for which I had to do http to https redirection with .htaccess file. I did 302 redirection intentionally so that in case of error, browser doesn’t cache redirection. You can aslo make permanent 301 redirect if needed.

This is nice and simple way to do it:

RewriteEngine On
RewriteCond %{HTTPS} off
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=302]

Moodle – mysql/mariadb Antelope to Barracuda installation warning

I tried to install Moodle 3.5.2 on cPanel server and got this warning in installation process:

“Your database has tables using Antelope as the file format. You are recommended to convert the tables to the Barracuda file format. See the documentation Administration via command line for details of a tool for converting InnoDB tables to Barracuda.”

Because this was production hosting server, I was unable to just globally change mysql settings. To be able to proceed installation, open config.php file of your moodle and change variable dbcollation like this:

dbcollation' => 'utf8_unicode_ci'

Multidomain webroot for Letsencrypt with NGINX

If you have web server on which there is a lot of virtual hosts, you may want to have one webroot directory for Letsencrypt SSL certificates only. So when Letsencrypt will make the requests for SSL registration or renewal, it will look in this directory. In this case I did this on CentOS 7 with NGINX web server.

First, let’s create directory what will be used for letsencrypt purposes. It must be writable by your web server user. You can define different path.

[root@machine ~]# mkdir -p /var/www/le-certs
[root@machine ~]# chown -R wwwuser:wwwgroup /var/www/le-certs

Letsencrypt will need access in “.well-known/acme-challenge”. For NGINX add something like this in your server block for desired virtual host.

location ~ /.well-known/acme-challenge/ {
             root /var/www/le-certs/;

You can also create new file named, for example le-config.conf and add block above in to it. Then you can simply include this line in your virtual hosts. 

server {
             listen :443 ssl http2;
             root /var/www/mywebsite/;

             include le-config.conf;



WordPress returning 404 Error on all subpages

In this case I used NGINX as reverse proxy for ssl offloading in front of Apache. On this WordPress installation I was getting 404 on all subpages. Htaccess syntax was correct as it was nginx configuration. In this case, problem was caused because of missing “AllowOverride” Apache directive which didn’t allow htaccess to be processed. I added “AllowOverride ALL” in apache configuration for this virtual host. Subpages started to work.


<VirtualHost *:8080>
DocumentRoot /var/www/

<Directory "/var/www/">
AllowOverride All

WordPress: Too Many Redirects Issue when NGINX reverse proxy to Apache

I installed NGINX and put it in front of Apache for SSL offloading and caching static content. Traffic is proxied from Nginx to Apache.  When I tried to open site via https, it returned this painful error “Too Many Redirects”.

Try to add this in your wp-config.php – if you have everything else configured correctly, it should work:

$_SERVER['HTTPS'] = 'On';

MySQL/MariaDB – [ERROR] Plugin InnoDB registration as a STORAGE ENGINE failed error

I was migrating server and rsync all databases to new mariadb server. When tried to start mariadb on new server, I was getting this error:

Apr 24 18:30:26 mysqld[9703]: 2018-04-24 18:30:26 140298644924544 [ERROR] Plugin 'InnoDB' init function returned error.
Apr 24 18:30:26 mysqld[9703]: 2018-04-24 18:30:26 140298644924544 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
Apr 24 18:30:26 mysqld[9703]: 2018-04-24 18:30:26 140298644924544 [Note] Plugin 'FEEDBACK' is disabled.
Apr 24 18:30:26 mysqld[9703]: 2018-04-24 18:30:26 140298644924544 [ERROR] Unknown/unsupported storage engine: InnoDB
Apr 24 18:30:26 mysqld[9703]: 2018-04-24 18:30:26 140298644924544 [ERROR] Aborting

Solution is to generate new ib_logfile0 and ib_logfile1 files. Just try steps bellow.

[root@lol ~]# cd /var/lib/mysql
[root@lol mysql]# mv ib_logfile0 ib_logfile0-backup 
[root@lol mysql]# mv ib_logfile1 ib_logfile1-backup
[root@lol mysql]# systemctl start mysql
[root@lol mysql]# mysql
Welcome to the MariaDB monitor.

It should work.

Linux: restore all system permissions of your server

If you ever found your self in situation when you accidentally overwrite all permissions of your system, and everything stops working, then solution bellow may do the trick. This CentOS server was overwritten by wrong permissions through the whole system. Quick solution is to set up right permissions back. If you have backup of server that’s great. Otherwise you’ll have to set up new server with similar installation or do this on some other server with similar installation.

On “new” server, copy permissions of the whole system and save it to a file. You can also exclude dirs that you don’t need also.

find / -not -path "/proc*" -not -path "/dev*" -not -path "/sys*" -not -path "/var/www*" -exec stat -c "chmod %a %n;" {} \; > permissions.txt

On your “broken” server, rewrite all permissions:

cat permissions.txt | bash

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