Encrypted Backup-Server with Debian and Dirvish – LVM in LUKS

If you haven’t heard of Dirvish, it’s about time. It is a very neat, rsync and hardlink based backup solution, just like a pro version of Apple’s TimeMachine.

What I want

My setup is quite specific for my use case: Having used dirvish at work for a while I was still stuck with backup-manager on my own servers, which is quite neat, but it leaves you with differential tarballs of your system which makes it an annoying task finding a specific version of one file somewhere in the past.

Dirvish, running on the backup server, logs into the target system using ssh and syncs the whole filesystem (you can define excludes, of course) to a folder with a timestamp in its name on the backup server. The next time it runs (simple cronjob) it will create a new timestamped folder, sync only changed files and hardlink everything else.
So, in the end we get a kind of snapshot of each time dirvish ran, where we can simply copy files back or even roll back the complete system.

When setting up my new dirvish backup server (replacing the ancient tarball and ftp solution) I wanted it to save data incrementally and store it on en encrypted device. For easiness of use I simply enter the encryption password manually after booting. Therefore only the dirvish partition (“bank”) is on an encrypted device, the rest of the machine is plain.
Caveat: The ssh key for accessing the other machines is on the unencrypted partition, this needs some rework to be done …

System: LVM on LUKS on VD in VM on LVM. For sure!

My Backup server runs in a VM on one of my Xen systems. Actually, the whole dirvish-bank (i.e. the location of all backups) is also synced to another machine at home for real backup.

The VM has got two virtual disks: the system disk, xvda, and (for historic reason) xvdc as storage for dirvish. This disk is completely encrypted using LUKS. I won’t cover encryption in detail here.

Inside this encrypted container I will create a LVM volume group, and backup will be done on volumes inside this group. The reason for this nested LVMs (the virtual disks already live in a LVM on the host) is that I will be able to create different “tiers” of backups if possible: If space on the underlying host gets tight, I will be able to move lower priority hosts on a second volume and don’t risk critical machines not being backuped.

So we basically have:


I did this on a freshly installed Debian Jessie, though it will quite surely work similarly on Ubuntu, SuSE or RedHatish systems. So first install cryptsetup:

Next, let’s encrypt our whole data disk:

You need to answer some questions, especially for a password. Use a good one, but remember that you will have to type it each time you want to mount the volume. We better create a backup of the LUKS-Header and set up a second, even more complex password. Store both at a very save place:

We now have a completely encrypted partition and will make it available through deivcemapper under /dev/mapper/lukslvm:

Let’s create a lvm within our container, the virtual disk hat 210GB:

Finally we create our mount point and an entry in /etc/fstab.

We use noauto to prevent the system stalling on boot because the encrypted container isn’t open already. We also use noatime and dirnoatime to speed up rsync comparison.

Preparing dirvish

Now let’s get the backup running.

First you need to create a key pair for ssh login to the target machines. I won’t cover this here because there are trillions of pages about this. I called the keys id_rsa.dirvish and and put them in /root/.ssh/ and copied the public key to all target machines (ansible is a very good friend!) Do yourself a favour and test if the login works.

Now install dirvish:

Now go to /etc/dirvish and edit the master.conf file.

We here define the bank (like “place where you store precious things”), which of course is our volume in the LUKS vault.

We also have some common excludes and a default expiry.

Debian provides a cronjob with some automatism, we won’t use that but rather create our own cronjob later in this process.

Backing up

Now let’s create our first backup. We will create a backup of the dirvish machine itself. Won’t help against failing disks, but against failing admins breaking stuff.

For each target machine we will create a folder hierarchy, the so called vault, which looks like this:

HOST will of course be the hostname of the target machine. Calling it *-root is just convention for backups of the root-tree. You could call it e.g. HOST-mailspool if you only backup the mail dir of a host.

Which means:

  • client: Hostname (needs to be resolvable!) of the target machine.
  • tree: Folder to backup.
  • xdev: 1 means that it will stay within the filesystem. Take care if you have /var or /home in different volumes (which I tend to have).
  • index: Type of compression of the index file (file list)
  • log: Type of compression of the log file saved within the folder.
  • image-default: Timestamp of the backup folder
  • exclude: Folders to be excluded.

There are a lot more config items, some of them which I use quite often:

  • pre-server: Path to a script on the dirvish server to be run before backup starts.
  • post-server: Path to a script on the dirvish server to be run after backup starts.
  • pre-client: Path to a script on the target machine to be run before backup starts. This is helpful for dumping sql databases before backing up.
  • post-client: Path to a script on the target machine to be run after backup starts.
  • speed-limit: Maximum transfer speed in Mbit/s

When we are finished creating our vault, we need to initialise it. This creates the first complete sync.

Depending on the size of the machine this can take quite a while. When done our vault will look like this:

tree now contains the folder hierarchy synced from the target, while the other files contain meta information.

The last step is creating a cronjob now. Simply add a line to /etc/crontab for each vault. Make sure to use different running times:

Ok, there’s one more step: Create any kind of monitoring facility, e.g. use post-server to send the summary and the log by mail, or parse these files and react on the results or use your existing monitoring solution…


Bridged Xen on Debian Wheezy on a Hetzner Server

Xen (not XeServer, btw!) seems to have taken a bak-seat recently, RedHat/CentOS/Fedora concentrating on KVM and Debian silently neglecting it.

This is reflected in documentation, there is a lot of outdated stuff around, especially about bridged setups. Same occurs to packages, at least in Debian Wheezy (NB: I also tried on testing, same results with fairly newer packages).

My aim was a virtual host which is directly connected to the internet without any external firewall running different virtual machines which ARE thoroughly firewalled. In order to archive this, I am running the quite decent Sophos UTM (formerly Astaro) as a VM, this is the only virtual machine with direct access to the external network interface. It’s other interface just like all other VMs are connected to an internal bridge without any link to the rest of the world. This is why routing isn’t an option.

This article focusses on the Xen server and the bridging setup, maybe I will write another one later about Sophos UTM etc.



I am running this setup on some servers at Hetzner, though this should be working at most other hosters (some tend to drop the switch connection when they sense a pseudo ARP-spoofing, take care!), I am in no way affiliated to Hetzner.

My setup needs a secondary IP address (the main IP address is used for management of the host, I am assuming the following setup:

External Host-IP:

Secondary IP, used on UTM: At least at Hetzner, this IP address needs to have it’s own MAC address assigned, this can be done in their Robot tool.

Setting up the host

I want to have my host running directly on the (Software-)RAID, I personally don’t really like running the OS on LVM. But I also want to have my VMs live in an LVM realm in order to easily take snapshots, clone etc.

This means that Hetzner’s default setup isn’t very helpful. But they have an answer file based installation using the rescue system. Therefore: boot into the rescue system and run install image.

Note: Preserve the temporary password for the rescue system, you will need it for the freshly installed system!

This lets you define your custom install file and then installs everything within a few minutes. I chose Debian Wheezy Minimal. The only two settings I changed were the hostname (I am using dome in this example) and the partition setup:


I chose 50GB for my root filesystem and 12GB swap.

After saving the file and starting the installation, I had to wait for about five minutes and was presented with a brand new Debian system.


After the first boot I changed the root password and added my own SSH key.

Note: This document doesn’t cover hardening your server, which you really should do!

First thing to do is updating all package sources:

I tend to install emacs23-nox as soon as possible, YMMV.

It is quite handy to add your domain, if you are using one, to /etc/resolv.conf and to /etc/hosts.

Next is changing the network setup, so edit /etc/network/interfaces :

So we transformed our (only) network card eth0 into a bridge called virbr0 and added a secondary bridge, virbr1.

Set up Xen

First install the xen system (4.1 on Wheezy) and the xen-tools which are quite helpful setting up VMs.

This will install xen and all the necessary tools.

In order to boot into a xen enabled hypervisor, we need to adapt GRUB:

Before we reboot we also adapt the boot command line in /etc/default/grub :

This basically limits resources on Dom0.

Now update grub and reboot:

After reboot we can check if Xen is up and running.

Looks fine.

Now we need to set up the network, which is quite straight forward:

Edit the file /etc/xen/xend-config.sxp  and comment out everything about networking, routing and vif except this line:

You  may also fine tune your Xen setup by changing the following lines:

The first thing we changed tells Xen to run a script called vif-bridge  located in /etc/xen/scripts/  as soon as a virtual machine is being created. The script basically checks if the bridge exists and connects the VMs virtual network card to the bridge.

Now we need to adapt this file to our naming convention, so let’s replace the occurrences of xenbr  to virbr  in the file /etc/xen/scripts/vif-bridge :

Now restart xend (for some reason the service is called xen  on Debian.

Getting the first VM up and running

Using xen-create-image  from the xen-tools makes it a piece of cake installing our first VM:

You can safely ignore the warning about vif-bridge.

Now there’s a little bug in the xen-tools:

So edit /etc/xen/test.cfg and remove the m from 512m:

Now let’s run it:

We can now connect a console to the vm and see why’s going on (you can also create it with the -c parameter above …).

Hint: CTRL + 5 gets you to of the console again.


HowTo: VPN between FritzBox and Sophos UTM (was: Astaro UTM) with DynDNS

After searching ans trying quite a lot, I finally managed to connect my Sophos UTM 9 (which is very nice and free for hime users!) to my FritzBox. Especially the fact that I don’t have a fixed IP address at home makes this a bit tricky.


The UTM is running as a virtual machine on my root server. It has got one public IP (RED, which is bridged (bridge0) to the network card of the host, and one private IP (GREEN) on a secondary bridge (bridge1) in my Xen environment.



Configuration FritzBox:

My first try was simply using the Add new VPN connections form in the FritzBox. This won’t work, because as soon as you need to rely on a dynamic hostname (as opposed to a fixed IP) the FritzBox forces aggressive mode for IKE, which will fail with the following message:

So I had to create a config file manually, actually I adapted it from a few occurrences in the web:

UTM settings

First, create a policy in UTM:


Now create a gateway which points to the FritzBox:


Make sure that the VPN ID type is set to FQDN and that it matches your dynamic hostname. (usually the same as the gateway). Create a remote network, in this case, I called it Fidicinstrasse (this is where the Fritzbox lives).

Finally, create a connection:


That’s all, wait a few seconds and the connection should come up automatically.






HowTo: Create a simple Tag Cloud for existing HTML content using JS with jQuery

Everybody loves tag clouds. Hopefully, otherwise I spent an hour for nothing creating one for

There are a lot of plugins for jQuery, or external libs etc. for creating tab clouds, most times with fancy AJAX calls, JSON processing and a neat database backend. We only need plain jQuery and for some sexyness the jquery.timer plugin. Please notice that this plugin needs jQuery.plugin to work.

I just wanted to have something which uses my existing HTML list while just extending that with a few tags. My website consists of one single HTML page optically diverted by jQuery tabs and accordions, therefore my main content isn’t visible when the tag cloud is available. So I will just pick some invisible content and display it in an empty space in my page. Another approach could be to just hide everything NOT sporting the chosen tag.

I created a small fiddle at as an example.

So, this is what I got:

I would like to display each group of <dt></dt><dd></dd> when their tags are highlighted. Therefore we need some Tags. I decided to use the name attribute, as it is deprecated though still usable in HTML5 without breaking anything. You could of course also use e.g. class or anything self defined.

Tags are separated by blanks as we really only want single worded tags in this case. You can easily change the separator in order to use tags including spaces, though you would need to display the tags with a border and recreate the selector…

We also need some space for the tags and the highlighted content to be displayed.

Cloud will contain the tag cloud while cloudcontent will be used to display the chosen content.

So, let’s create some dynamics.

We will create a function consisting of three parts. The variable tags will hold an associative array { "tag" => number_of_occurrences }  with all tags.

The first part gathers all tags and fills our associative array with each tag and the number of occurrences.

Here we iterate over all <dt>s, check if they have a name attribute and if so get it’s value and split it into an array.

We now iterate over this array. If the value (i.e. the tag) already exists in our tags list, it increments the number of occurrences of this tag, otherwise it will create a new item with the name of the tag and a number of one.

This is our tags array:

The next part appends all tags to the cloud div

I created different CSS classes with different shades of grey and font sizes. These are applied to a span surrounding each tag, making the higher number be larger and darker. In order to keep it nice, I limited it to 8 levels.

Now we need to create some dynamics when hovering the tags.

As we applied the class cloudelement to all tags, we can simply bind the mouseover() event to them.

We first clear the cloud content div and then append a definition list, then we select all <dt>s where the tag exists in the name attribute and iterate over these. We simply append new <dt></dt><dd></dd>s to our new dl consisting of the <dt>s we have found, the <h3> above it and the following <dd>.

Finally we start a timer which will remove the shown items after five seconds.

The timer will be initialized like this:

So, when time ran out, the callback function will be executed which fades out the complete cloudcontent div, clears it when fading finished and shows it again (empty now) to be prepared to display the next content.

Put the timer initialization together with a call to the tagcloud()  function in the classical $(function() .





HowTo install Ubooquity on QNAP

Ubooquity is a very nice little server which scans your eBooks and Comics and displays them in a tablet friendly way.

It is Java-based and runs fine on your Desktop, but if you’re running a (QNAP-)NAS which already stores all your books, why not have them served nicely.




I did this on A QNAP TS-421 (ARM-CPU) Running OS version 4.x, though this should work the same way (except the Java installation on x86 see link below) on any other QNAP NAS.

I am assuming that you already have IPKG installed and are able to log in via ssh and already have some experience with the (Linux-)shell.

Install coreutils, procps and Java

The start script for the daemon requires the nohup and pgrep command which unfortunately aren’t shipped with the basic installation.

So simply do a

Install Java

Follow the instructions on in order to install Java. In brief:

Install Ubooquity

Download the jar from and put it on your QNAP NAS. I created a Folder Ubooquity in Public/ where everything from Ubooquity lives, so it is in /share/Public/Ubooquity/ now.

Do a test run on the shell:

Now you should be able to connect to the admin server on http://<qnapaddress>:2202/admin

Set a password for administration and play with the Web ui.

Install as a service

As soon as you close the shell from above, Ubooquity quits itself. Not very cool. So we need to install it as a daemon, a service starting on system start and then running all time.

Ubooquity provides a nice startup script called at Get it and put it next to Ubooquity.jar. As pgrep on QNAP doesn’t support the -c (count) option, we need to change one line:

Replace all occurrences of the line


QNAP provides a quite easy way to register an application as a service. Simply edit the file /etc/config/qpkg.conf and add the following block.

You may have to adapt the paths to your installation.

Now you can start Ubooquity in the App Center just like any other app.