Category: Internet

My webspace provider offers a simple ssh access to upload and download files. One cannot install any software there and has a limited set of commands. I wanted to check the free space on that server because it often runs out of free space and then new uploads fail.

The script on the server

The server does not have a “quota” command and “df” is about the whole filesystem, not just about my webspace. So I used “du -ms .” to check how much data is saved in my webspace. I have creates a small shell script “checkfreespace.sh” and saved it on the server:

#!/bin/bash
export USEDSPACE=`du -ms . | sed "s/[^0-9]*//g"`;
if [ "$USEDSPACE" -lt "9000" ] ; then echo "OK - $USEDSPACE MB used" ; exit 0; else echo "CRITICAL - $USEDSPACE MB used"; exit 2; fi

It checks if less than 9000MB are used and returns “OK” with exit code 0. Otherwise it returns “CRITICAL” with exit code 2. These are keywords that are used by Nagios.

SSH configuration

Then it is necessary to make it possible to login using public key authentication (so that Nagios does not need a password).

1. Use “chsh nagios” to set the shell of nagios to “/bin/bash”.
2. Use “su – nagios” to switch to the home directory of nagios.
3. Create a key pair if necessary e.g. using

   ssh-keygen -t rsa -b 4096 -C your@email.com

   in the .ssh directory of the nagios user and change the owner to the nagios user if necessary.

4. Append the contents of the file .ssh/id_rsa.pub to the file .ssh/authorized_keys on the server.
5. Use “chsh nagios” to set the shell of nagios back to “/bin/false”.

Nagios configuration

Finally you have to configure Nagios. Add this to the commands.cfg file:

define command{
	command_name	check_my_free_space
	command_line	/usr/lib/nagios/plugins/check_by_ssh -H ssh.yourserver.com -l yourusername -C "bash checkfreespace.sh" -t 30
	}

Afterward you have to use this new command in your services file, e.g. add this:

define service {
        service_description             Free webspace;
        check_command                   check_my_free_space
        use                             generic-service;
        host_name  android.calengoo.com;
        notification_interval           0 ; set > 0 if you want to be renotified
        normal_check_interval           60
}

Let’s encrypt offers free SSL certificates that can also be used with Jetty. The following steps show how to get an install such a certificate:

1. Installation
   To install the letsencrypt client on a Linux system, just enter these commands:

   $ git clone https://github.com/letsencrypt/letsencrypt
   $ cd letsencrypt
   $ ./letsencrypt-auto --help

2. Request the certificate
   To request the certificate run this command:

   ./letsencrypt-auto certonly -d yourdomain.com --webroot -w /var/www/

   To verify the address of your server letsencrypt needs to know the directory of your http server. In this example an Apache is used with the directory /var/www/ (and Jetty runs only on the https port).

3. Convert the certificate into a format Jetty can use

   openssl pkcs12 -export -in /etc/letsencrypt/live/yourdomain.com/fullchain.pem -inkey /etc/letsencrypt/live/yourdomain.com/privkey.pem -out fullchain_and_key.p12 -name jetty
   keytool -importkeystore -destkeystore keystore_le -srckeystore fullchain_and_key.p12 -alias jetty
   keytool -import -destkeystore keystore_le -file /etc/letsencrypt/live/yourdomain.com/chain.pem -alias root

4. Install the certificate in Jetty
   Just reference the keystore_le file that you have created in the etc/jetty-ssl.xml file:

   /
   /
   

5. Stop and restart Jetty

If you are looking for a simple and free way to add a table to your Stacks page, you can use one of these, just unzip them and copy them into ~/Library/Application Support/RapidWeaver/Stacks before starting RapidWeaver:

There are two variants:

With custom Stack Elements in each cell:

Download FreeTableStack.stack

With text in each cell:

Download FreeTableTextStack.stack

Settings:

Both Stacks Element allow you to configure the columns and rows of your table and you can specify the colors for the header cells and the lines:

If you would like to add an own style, just open the .stacks file and edit the styles.css file.