youresuchageek

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Last update 02/01/2013

The Goal:

You have a Raspberry Pi and want to use it as your secure Web reverse proxy gateway to access to your various Internal services through your main fully qualified domain name or IP.

Let's say:

You have a main router or ISP Box
Your Rpi will be in front of the Internet by redirecting http/https por
For this configuration to work from both inside and outside your home network, your domain name (here "myowndomain.com") must be associated with your public IP

ts from your router to your Rpi

You have or not internal servers providing Web sites or services your want to access from your public IP / domain name

We will use:

nginx as the great secure reverse proxy instance
SSL with auto signed or officially signed certificate to secure our web traffic
htpasswd to password protect your shellinbox from being visible and accessible whitout credentials
shellinabox to host a nice Web SSH frontend

Summary of steps:

Step 1: OPTIONAL - Get a fully Qualified Domain Name (FQDN)
Step 2: Manage your SSL certificate
Step 3: Put a Shellinabox in your Pi ^^
Step 4: Install and configure Nginx

Step 1: OPTIONAL - Get a Fully Qualified Domain Name

This is absolutely optional, but you could think about getting a qualified domain name to access to your home network. (a domain costs very few per year, and your can dynamically associate it with your public IP)

In many cases, when you connect from secure places (such as your company site), trying to access to a web site using its public IP will be prohibited by internals web proxies and firewalls.

By using a fqdn to associate your public IP to a real Internal domain name, your site is as official as any Internet company web site :-)

As an alternative to buy your own domain name, you can also use dynamic free domain name services such as no-ip.org, but most of company proxy will also block them.

And finally, this is just clean and beautiful ^^

In this post, i will assume for the example purpose that your domaine name is "myowndomain.com". (still the fqdn is optional)

Step 2: Manage your SSL certificate

Off course, we will want to secure our Web traffic using an SSL certificate, there is 2 ways to achieve this:

1. Generating an "auto-signed" SSL certificate

You can very easily generate an auto-signed SSL certificate, you will have exactly the same security and encrypting level than any official certificate but this certificate won't be officially recognized over the Internet.

That means that when connecting to your site, your Web browser will warn you about the impossibility to guaranty your security connecting to this site, and you have to accept this.

I personally prefer having an official SSL certificate :-)

2. Buy and generate an Officially signed SSL certificate

You can also buy an official SSL certificate for very few, in this case your browser will automatically recognize your certificate as valid and you won't get any warn.

There is some places where you can get a free official SSL certificate for personal use. (look for "startssl")

In both cases, Google is your friend ^^

How to generate an auto signed certificate:

Install OpenSSL:

$ sudo apt-get install openssl

Generate your self signed certificate:

sudo mkdir -p /etc/ssl/localcerts
openssl req -new -x509 -days 3650 -nodes -out /etc/ssl/localcerts/autosigned.crt -keyout /etc/ssl/localcerts/autosigned.key
chmod 600 /etc/ssl/localcerts/*

Note: Respond to OpenSSL questions as you wish, it does not really mind as your certificate is a self-signed anyway

Step 3: Put a shellinabox in your Pi ^^

As explained before, shellinabox is a wonderfull web frontend to SSH, this way you will access to your SSH server without having to deal with an SSH client.

By the past, i wrote an article about an other SSH web frontend "ajaxterm" which is nice too, but in my opinion much more limited and low.

So i recommend to use shellinabox instead.

You will be able to access to your SSH server using standard Web ports even when connecting from places where external SSH traffic is prohibited :-)

To install:

# sudo apt-get install shellinabox

By default, shellinabox uses the port "4200" to listen to, you can let that as it is as your nginx reverse proxy take care about redirecting our request to this internal service.

If you want to manage your shellinabox configuration, take a look at main config files:

/etc/default/shellinabox
/etc/shellinabox/*

Default configuration is ok for us, test your shellinabox by connecting from a browser inside your network: http://<mypiserver>:4200

Note that even if we won't use it, shellinabox comes with embeded SSL auto-signed certificate configuration to redirect http to https and secure your web traffic.

Step 4: Install and configure Nginx

Ok, serious things now, let's install and configure nginx.

Nginx is an extremely powerful Opensource Web server, light secure and fast, that can be used as reverse proxy instance gateway to your internal Web services.

It is more and more used by many companies web site with high load Web Sites, do not hesitate to take a look at official sites:

I used by the past Apache running as a reverse proxy to do this job, but nginx assumes this job with great success, it's very modular and easy to maintain, this is why i recommend your Nginx.

To install:

# sudo apt-get install nginx-full

Now let's configure the beast:

First, some configuration in main config file "/etc/nginx/nginx.conf", here is a sample config file:

# /etc/nginx/nginx.conf

user www-data;
worker_processes 4;
pid /var/run/nginx.pid;

events {
 worker_connections 768;
}

http {

 sendfile on;
 tcp_nopush on;
 tcp_nodelay on;
 keepalive_timeout 65;
 types_hash_max_size 2048;

 include /etc/nginx/mime.types;
 default_type application/octet-stream;

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

 gzip on;
 gzip_disable "msie6";

 include /etc/nginx/conf.d/*.conf;
 include /etc/nginx/sites-enabled/*;
}

Please note that as Apache configuration style under Debian/Ubuntu, any configuration file (for site or module) included in conf.d or sites-enabled will be loaded at Nginx start

A good practice is to create a symbolic link from "sites-available" to "sites-enabled".

Let's deactivate the default web site we won't use by removing its symbolic link:

$ sudo rm /etc/nginx/sites-enable/default

Create an htpasswd file that will contain your credentials (adapt <username>)

$ sudo htpasswd -c /etc/nginx/.htpasswd <username>

Now create your main web site configuration file, example:

/etc/nginx/sites-available/main

Here is a sample secured configuration:

access_log off;
add_header Cache-Control public;
server_tokens off;


# HTTP 80
server {
 listen         80;
 server_name _;
 rewrite ^ https://myowndomain.com$request_uri? permanent;
}

# HTTPS 443
server  {

 include    /etc/nginx/proxy.conf;

 listen 443 ssl;
 keepalive_timeout 70;

 server_name myowndomain.com;

 # SSL config
 ssl on;
 ssl_certificate /etc/ssl/localcerts/autosigned.crt;
 ssl_certificate_key /etc/ssl/localcerts/autosigned.key;

 ssl_session_timeout 5m;
 ssl_protocols SSLv3 TLSv1.2;
 ssl_ciphers RC4:HIGH:!aNULL:!MD5;
 ssl_prefer_server_ciphers on;
 ssl_session_cache shared:SSL:10m;

 add_header X-Frame-Options DENY;

 # DDOS protection - Tune Values or deactivate in case of issue
 # limit_conn conn_limit_per_ip 20;
 # limit_req zone=req_limit_per_ip burst=20 nodelay;

 # status for ngxin auditing
 location /nginx-status {
      stub_status on;
      access_log off;
      allow 127.0.0.1;
      deny all;
  }

 location / {
  rewrite ^ https://myowndomain.com/shellinabox/ permanent;
  }

 location /shellinabox/ {
  proxy_pass http://localhost:4200;
                auth_basic            "Access Restricted";
                auth_basic_user_file  "/etc/nginx/.htpasswd";
                access_log /var/log/nginx/shellinabox.access.log;
                error_log /var/log/nginx/shellinabox.error.log;
  }
}

Create the file "/etc/nginx/proxy.conf" with following content:

proxy_redirect          off;
proxy_set_header        Host            $host;
proxy_set_header        X-Real-IP       $remote_addr;
proxy_set_header        X-Forwarded-For $proxy_add_x_forwarded_for;
client_max_body_size    10m;
client_body_buffer_size 128k;
proxy_connect_timeout   90;
proxy_send_timeout      90;
proxy_read_timeout      90;
proxy_buffers           32 4k;

Activate your nginx web site and restart:

sudo ln -s /etc/nginx/sites-enables/main /etc/nginx/sites-available/main
sudo service nginx restart

NOTE:

For this configuration to work from both inside and outside your home network, your domain name (here "myowndomain.com") must be associated with your public IP

Now test accessing to your Web site from both internal and external access :-)

As you understood, you can manage as many internal Web sites as you need through a unique Web instance and virtual hosts. (called location in Nginx)

In the sample config, shellinabox is the default site accessible with your domain name, but you change it and/or add any other internal web sites very easily.

Just add a new location related to your internal Web site you want to be able to access and you're done :-)

Unknown

The Goal:

With Observium associated with Unix agent check_mk the goal will be to monitor any available indicator (CPU, Mem, Traffic interface...) and most of all, specific Raspberry Pi main indicators dynamically allocated when running Overclocked with Turbo mode:

CPU Frequency
CORE Frequency
CORE Voltage
BCM2835 Soc Temperature

Corresponding "vgencmd" commands:

# CPU Frequency
vcgencmd measure_clock arm

# CORE Frequency
vcgencmd measure_clock core

# CORE Voltage
vcgencmd measure_volts core

# SoC Temp
vcgencmd measure_temp

There are also other indicators you may want to monitor, even i don't feed it myself useful.
The present article will take care of these 4 indicators.

Take a look here: http://www.elinux.org/RPI_vcgencmd_usage

Global list of indicators available through "vgencmd":

vcgencmd measure_clock arm
vcgencmd measure_clock core
vcgencmd measure_clock h264
vcgencmd measure_clock isp
vcgencmd measure_clock v3d
vcgencmd measure_clock uart
vcgencmd measure_clock pwm
vcgencmd measure_clock emmc
vcgencmd measure_clock pixel
vcgencmd measure_clock vec
vcgencmd measure_clock hdmi
vcgencmd measure_clock dpi
vcgencmd measure_volts core
vcgencmd measure_volts sdram_c
vcgencmd measure_volts sdram_i
vcgencmd measure_volts sdram_p

Installing Observium is out of the scope of this article, Observium installations documentations and well known and easy to read, see above.

Main sources:

I recommend to install Observium and Mysql into a central server which will request our Rpi to generate graphs and so on.

We will use an additional agent called "check_mk" to request the Rpi, system load generated by snmp and Unix agent are very limited which is very great, the Rpi is a small power device and you don't want monitoring to generate high system load!

One time you have Observium up and running, follow this guide to integrate any Raspberry Pi you want to monitor :-)

Summary of steps:

Step 1: Install and configure snmpd
Step 2: Install check_mk agent (Unix Agent)
Step 3: Add the custom Raspberry agent script
Step 4: Observium custom application configuration
Step 5: Configure your Rpi in Observium, the easy part!

Memorandum

Step 1: Install and configure snmpd

First thing, we will begin by installing the snmpd daemon, to do so:

$ sudo apt-get install snmpd snmp-mibs-downloader

Let's configure some little things:

Edit "/etc/default/snmpd" and:

set: export MIBS=UCD-SNMP-MIB

Replace the line "SNMPDOPTS=" with the following values to prevent snmpd to log each connection (default behavior):

SNMPDOPTS='-LS 0-4 d -Lf /dev/null -u snmp -g snmp -I -smux -p /var/run/snmpd.pid'

Edit "/etc/snmp/snmpd.conf" and:

Comment with "#" the default line "agentaddress udp:127.0.0.1:161" which only allows connections from the localhost itself

Comment out the line "agentaddress udp:161,udp6:[::1]:161" to allow remote connections

Comment out the line "rocommunity secret <LANSUBNET>" (adapt <LANSUBNET> to the CIDR value of your LAN subnet, example: 192.168.0/24"

Note: "secret" will the name of the snmp community, only accessible through your local network)

Configure "sysLocation" and "sysContact"

Look for the section "EXTENDING THE AGENT" and add the following line:

extend .1.3.6.1.4.1.2021.7890.1 distro /usr/bin/distro

Install the "distro" script coming from observium (to recognize the remote OS)

$ sudo wget http://www.observium.org/svn/observer/trunk/scripts/distro -O /usr/bin/distro
$ sudo chmod 755 /usr/bin/distro

Finally restart snmpd daemon:

$ sudo service snmpd restart

Step 2: Install check_mk agent (Unix agent)

We will used the great Unix agent "check_mk" called Unix agent by Observium.

If you want more information about this very cool tool, check its main Web site:
http://mathias-kettner.de/checkmk_monitoring_system.html

Install Xinetd requirement:

$ sudo apt-get install xinetd

Download and install check_mk:

$ wget http://mathias-kettner.com/download/check-mk-agent_1.2.0p3-2_all.deb
$ sudo dpkg -i check-mk-agent_1.2.0p3-2_all.deb

Verify that the package installation generated the xinetd configuration file called "

/etc/xinetd.d/check_mk".

If not (it seems this part fails under Rpi), create the file with the following content:

# +------------------------------------------------------------------+
# |             ____ _               _        __  __ _  __           |
# |            / ___| |__   ___  ___| | __   |  \/  | |/ /           |
# |           | |   | '_ \ / _ \/ __| |/ /   | |\/| | ' /            |
# |           | |___| | | |  __/ (__|   <    | |  | | . \            |
# |            \____|_| |_|\___|\___|_|\_\___|_|  |_|_|\_\           |
# |                                                                  |
# | Copyright Mathias Kettner 2012             mk@mathias-kettner.de |
# +------------------------------------------------------------------+
#
# This file is part of Check_MK.
# The official homepage is at http://mathias-kettner.de/check_mk.
#
# check_mk is free software;  you can redistribute it and/or modify it
# under the  terms of the  GNU General Public License  as published by
# the Free Software Foundation in version 2.  check_mk is  distributed
# in the hope that it will be useful, but WITHOUT ANY WARRANTY;  with-
# out even the implied warranty of  MERCHANTABILITY  or  FITNESS FOR A
# PARTICULAR PURPOSE. See the  GNU General Public License for more de-
# ails.  You should have  received  a copy of the  GNU  General Public
# License along with GNU Make; see the file  COPYING.  If  not,  write
# to the Free Software Foundation, Inc., 51 Franklin St,  Fifth Floor,
# Boston, MA 02110-1301 USA.

service check_mk
{
 type           = UNLISTED
 port           = 6556
 socket_type    = stream
 protocol       = tcp
 wait           = no
 user           = root
 server         = /usr/bin/check_mk_agent

 # If you use fully redundant monitoring and poll the client
 # from more then one monitoring servers in parallel you might
 # want to use the agent cache wrapper:
 #server         = /usr/bin/check_mk_caching_agent

 # configure the IP address(es) of your Nagios server here:
 #only_from      = 127.0.0.1 10.0.20.1 10.0.20.2

 # Don't be too verbose. Don't log every check. This might be
 # commented out for debugging. If this option is commented out
 # the default options will be used for this service.
 log_on_success =

 disable        = no
}

Restart xinetd:

$ sudo service xinetd restart

Finally, ensure your Observium machine willbe authorized to access to the Rpi check_mk service running on port TCP/6556.

Step 3: Add the custom Raspberry agent script

Create a new file "/usr/lib/check_mk_agent/local/raspberry":

#!/bin/bash
#set -x
echo "<<<app-raspberry>>>"
# CPU Frequency
expr `vcgencmd measure_clock arm|cut -f 2 -d "="` / 1000000
# CORE Frequency
expr `vcgencmd measure_clock core|cut -f 2 -d "="` / 1000000
# CORE Voltage
vcgencmd measure_volts core|cut -f 2 -d "="|cut -f 1 -d "V"
# SoC Temp
vcgencmd measure_temp|cut -f 2 -d "="| cut -f 1 -d "'"

Add execution right:

$ sudo chmod a+rx /usr/lib/check_mk_agent/local/raspberry

This script will be called by Observium at each poller time.

Step 4: Observium custom application configuration

Ok now a bigger part, we need to configure Observium to add our custom application has any other.
By this way, we could run this with as many Rpi as you want ;-)

To do so, we need to create and/or modify different configuration files.

Go into your Observium root directory, usually "/opt/observium"

1. "./includes/polling/unix-agent.inc.php" (modify)

Look for the section containing:

      if ($section == "apache") { $sa = "app"; $sb = "apache"; }

And add new one just under :

      if ($section == "raspberry") { $sa = "app"; $sb = "raspberry"; }

2. "./includes/polling/applications/raspberry.inc.php" (create)

Create with following content:

<?php

if (!empty($agent_data['app']['raspberry']))
{
  $raspberry = $agent_data['app']['raspberry'];
}

$raspberry_rrd  = $config['rrd_dir'] . "/" . $device['hostname'] . "/app-raspberry-".$app['app_id'].".rrd";

echo(" raspberry statistics\n");

list($cpufreq, $corefreq, $corevoltage, $soctemp) = explode("\n", $raspberry);
if (!is_file($raspberry_rrd))
{
  rrdtool_create ($raspberry_rrd, "--step 300 \
        DS:cpufreq:GAUGE:600:0:125000000000 \
        DS:corefreq:GAUGE:600:0:125000000000 \
        DS:corevoltage:GAUGE:600:0:125000000000 \
        DS:soctemp:GAUGE:600:0:125000000000 ".$config['rrd_rra']);
}

print "cpufreq: $cpufreq corefreq: $corefreq corevoltage: $corevoltage soctemp: $soctemp";
rrdtool_update($raspberry_rrd, "N:$cpufreq:$corefreq:$corevoltage:$soctemp");

// Unset the variables we set here

unset($raspberry);
unset($raspberry_rrd);
unset($cpufreq);
unset($corefreq);
unset($corevoltage);
unset($soctemp);

?>

3. "./html/includes/graphs/application/raspberry_soctemp.inc.php" (create)