Dedicated Server: 10 Gbit/s-port available

From now on and by your request, we offer you an internet connection of 10 Gbit/s (for every server) for our dedicated servers Dual Xeon and 10-Core.

With this upgrade, your server will receive an Internet uplink of 10 Gbit/s (=10.000 Mbit/s) instead of the regular port. We use a high-quality network card from Intel in order to provide you with that bandwidth.

This upgrade is especially suited for customers who generate traffic peaks, which exceed the standard connection of 1 Gbit/s.

You can add the 10 Gibt/s-port for 99.99 € /month plus a one-time setup fee in the same amount. New customers can select the upgrade during the order process of the respective dedicated server on Contabo.com.

Do you already have a dedicated server and would like to add this upgrade? No problem at Contabo! Existing customers can order this upgrade at any time. Please contact our customer support department and specify your wish.


Impressions of the cooling system at our data center in Nuremberg

This year, as we have proudly informed you earlier, we won the German Data Center Award for our data center in Nuremberg. An independent jury awarded us first place in category 6: "Increase in energy efficiency through reconstruction in an existing data center"

Today, we show you some impressions from our cooling systems. Day and night, they ensure that thousands of servers receive reliable air-conditioning in our data center in Nuremberg. 🙂


These pictures show you our redundant air-conditioning systems. They are highly efficient and state-of-the-art machines and use external air for cooling - leading to significant savings in energy consumption.

There you can see our double-pumping plant. It transports the cooling water into the data center. Should it ever fail, the second one will take over instantly and ensure that your servers will always receive the best cooling.

By the way, our website provides more information about our data centers.

Posted by: Markus | Tagged as: , , , No Comments

No space left on your HDD/SSD? Find big files and remove them!

It does not matter if you do website hosting, provide a gameserver or use other services, if you have no space left on your HDD/SSD problems will occur. Your websites might not be reachable anymore, your players cannot connect to your gameserver or all other services will not start.

To avoid this it is necessary to find big files on your system and to get rid of them. Today we will show you how to do this.


1. Connect to your server using SSH

2. Execute the following code:

# Change into root folder
cd /

# Find the top 10 files. This may take a while:
find -type f -exec du -Sh {} + | sort -rh | head -n 10

Once finished, a list of the ten largest files will be displayed. Normally these files might be old downloads or big log files. Files that are no longer used can be deleted, of course. Before deleting log files you should check them for errors you can solve so that the issue will be permanently fixed.

3. Using the command below you can remove files

rm <path_to_file>


In Windows you might not find big log files but forgotten downloads. To find them the following freeware is perfect:


Once you downloaded and executed the software you can start scanning a partition. A list of all files will be displayed. Please make sure not to delete Windows system files 😉 .

Posted by: Matthias | Tagged as: , , , , No Comments

Overview of available RAID levels

With this tutorial we will explain certain types of RAID levels to you.
Some of you might have already experienced a loss of data, no matter if it was an SD card holding some vacation photos or a hard disk holding important files. Losing data can be very costly if you try to restore them by some specialist. An expert is needed and the procedure takes a lot of time, the easiest way to avoid those costs is simply to avoid any data loss in the first place.

This overview is not relevant for any VPS, your VPS systems are already running safe on a RAID system monitored by experienced technicians.

Creating backups is still very important, a RAID does not replace any backup!

You can find further instructions within the following tutorial: Data loss and how to avoid it

There are some points which you should think about first, there are several results depending on your requirements.

  1. How important is the performance?
  2. How much data security should be provided by the RAID?
  3. Are system resources available to manage the RAID, such as CPU and RAM

Depending on the results of the above questions and your budget, there are several options available:
A hardware RAID is always more expensive but provides the best performance and security (if combined with a battery backup unit).
A software RAID is the easiest way to go for a RAID, it is able to handle almost any type of RAID and can be set up within a few minutes.

An overview of available RAID levels is shown below:


The RAID 0 provides increased write and read performance, the data will be distributed to at least two disks. Since there is no redundancy all data will be lost in case one disk fails.

  • At least two hard disks are needed
  • No disk redundancy at all
  • Maximum (complete) storage capacity available
  • Improved read and write performance


The RAID 1 provides increased read performance (depending on the software/hardware controller used), all data will be mirrored to a second disk. There is also a RAID 1E available - in that case all data will be mirrored to additional disks too.

  • At least two hard disks are needed
  • n-1 disks can fail
  • 1/n of storage available (n = number of disks, with two disks = > 1/2 of total storage)
  • Improved read performance


The RAID 5 provides increased write and read performance, the data is written to at least two disks, an additional disk is always used for storing parity data. The parity data has to be calculated for every write - so for very write intensive applications the RAID 5 requires a lot of performance due to the necessary calculations.

  • At least three hard disks are needed
  • One disk can fail
  • n-1/n of storage available (n = number of disks, with three disks = > 2/3 of total storage)
  • Improved read and write performance
  • Requires a lot of CPU time


The RAID 6 provides increased read performance, the data is written to at least two disks, two additional disks are always used for storing parity data. The parity data has to be calculated for every write - so for very write intensive applications the RAID 6 requires a lot of performance due to the necessary calculations. As there are two parity bits saved on the disks, the needed CPU time is very high.

  • At least four hard disks are needed
  • Two disks can fail simultaneously
  • n-2/n of storage available (n = number of disks, with two disks = > 2/4 (half) of total storage)
  • Improved read performance
  • Requires the most CPU time


A RAID 01 is a combination of two or more volume groups. Each volume group is configured to have a RAID 0, those volume groups are mirrored in a RAID 1. With a total number of four disks one entire volume group can fail with both disks and no data will be lost.

  • At least four hard disks are needed
  • Two disks can fail simultaneously if they belong to the same logical volume group
  • Half of total storage capacity is available
  • Improved read and write performance


A RAID 10 is a combination of two or more volume groups. Each volume group is configured to have a RAID 1, those volume groups are striped in a RAID 0. With a total number of four disks, two disks can fail simultaneously and no data will be lost - the failed disks must not belong to the same volume group.

  • At least four hard disks are needed
  • Two disks can fail simultaneously if they do not belong to the same logical volume group
  • Half of total storage capacity is available
  • Improved read and write performance


The difference between RAID 01 and RAID 10 is only visible with six or more disks, if you have six disks a RAID 10 will provide a higher calculated security rate. We do recommend using a RAID 10 instead of using a RAID 01 even if you do only have four disks. Some RAID controllers do not even support a RAID 01 anymore. RAID 5 and RAID 6 require the highest CPU time since a checksum has to be calculated on every writing process to the disk. Only a few enterprise RAID controllers do support RAID 5 and RAID 6, due to the need of calculating checksums the writing speed might suffer which might then cause problems when using write intensive applications.

For our dedicated servers it is always possible to order additional hard disks or RAID controllers, current prices can be found on our web site. If you need a special configuration, please contact our support team any day between 8 am and 11 pm (German timezone, UTC+2).

Posted by: Gianni-Donato | Tagged as: , , , , , 2 Comments

Available now: Fedora 26 and Suse Leap 42.3

As of today, we offer you the brand new Fedora 26, it replaces the previous version 25. Additionally, Suse Leap was updated as well and the latest version 42.3 is available at Contabo!

Both operating systems can be combined with the Software RAID 1 and Webmin. In addition, Fedora 26 can be installed via VNC as well.

Being an existing customer, you can easily upgrade to the new versions through your customer control panel.

We always offer you a large selection of Linux distributions (as well as Windows Server 2012 and 2016). Just click on "Customize & Order" below your desired (virtual) server model in order to get a detailed overview and select the operating system of your choice!

Please note: You can find further information and a product overview on our website!

Posted by: Markus | Tagged as: , , , , , No Comments

Analysing log files in Windows and Linux

Everyone knows the scenario, you want to analyze an issue of your server or local computer but where to find all those log files?

In the following tutorial we are going to analyze specific log files in Linux and logs in the Windows Event Viewer. An additional chapter will go through the log analysis via Systemd.

Linux log files

Unfortunately, it is quite different from distribution to distribution, which information can be extracted from specific log files. In the following we will analyze the log file structure of Debian 8 and CentOS 7.2. The first location to look for log files should always be /var/log/. Depending on their configuration, Apache, Nginx or similar applications write log files to this folder too. System log specifications and locations can be found in the file /etc/rsyslog.conf.

Debian 8:

  • /var/log/auth.log

Logs of successful and failed authentications to your system can be found in this log file. It is also logged when a user invokes commands via sudo.

  • /var/log/messages

This file contains log entries of general system information, amongst others, you will also find the system upstart logs.

  • /var/log/dmesg or dmesg

The kernel ring buffer can be read with dmesg. You will find information about the system upstart, runtime kernel module messages and many further messages according to the hard and software of your system. By default, dmesg shows the full ring buffer. However, the output can be customized by adding specific parameters. A thorough documentation can be found on the manual page (man dmesg).

  • /var/log/syslog

This is one of the most important log files in general. Every Linux process is free to log to the syslog by implementing the syslog interface. It also logs the system upstart and executed cron-jobs.

CentOS 7.2:

As the log file structure is quite similar to the one of Debian 8, we will just mention the differences.

  • /var/log/secure

This log file is the equivalent to /var/log/auth.log in Debian systems. All kind of authentications are logged here.

  • /var/log/messages

There is no separation of /var/log/messages and /var/log/syslog in CentOS, all system logs of processes which implement the syslog interface can be found here.

  • /var/log/cron

Cron specific log files are not part of the syslog as in Debian. They can be found in the above mentioned file.


Log analysis via Systemd

Systemd is basically the standard Init system of nearly all major Linux distributions today. Since at least April 2015, when Debian and Ubuntu switched to Systemd, every Linux administrator or user has been in touch with Systemd. As Systemd is a complex system, we will only take a look into the log analysis functionality provided. Every process in Systemd is identified as a unit. All active units can be shown via the following command:

systemctl list-units

When appending the parameter --all, this command also shows all inactive units.

Logs being created by Systemd are managed in the so called Journal. These logs can be accessed via the journalctl binary. If journalctl is called without any parameter, it will print out the whole Journal. However, it is also possible to output the log entries of specific units only. In the following example, we are going to analyze the log files of the Apache web server.

journalctl -u httpd

It is also possible to restrict the output with the parameters --since and --until.

journalctl -u httpd --since "2016-11-01 20:00:00" --until "2016-11-03 20:00:00"

The above command will output the Apache log entries between 2016-11-01 20:00:00 and 2016-11-03 20:00:00. It is also possible to use keywords like "today" or "yesterday".

You can also output the log files of more than one unit at the same time. In the following example we will output all Apache and Nginx log entries which have been logged since yesterday.

journalctl -u httpd -u nginx --since yesterday

If the parameter -f is used, all desired log entries are shown in real time.

The above was only a slight view into the possibilities of journalctl, there are several other useful features which are described on the manual page (man journalctl).


Log analysis via Windows Event Viewer

Windows Event Viewer Overview

In the above picture in the left navigation you can see the entry "Windows Logs". The following entries are most important.

  • Application

This entry will show the events of locally installed applications.

  • Security

Here you can see successful and failed login attempts.

  • System

This entry logs operating system internal events and errors.

Via the entry "Custom Views" -> "Server Roles" -> "Remote Desktop Services" you can see RDP related events and errors.

Potential hardware issues can be identified via "Application and Service Logs" -> "Hardware Events".

Useful for error analysis can also be the overview which can be seen via "Overview and Summary" -> "Summary of Administrative Events", it provides a summarized overview of the system status in general.


VPS: 100 Mbit/s – No limit, no throttling

Not long ago, the following rule regarding the internet connection of our VPS was in effect: 100 Mbit/s-port, when a certain traffic limit was exceeded, the port was limited to 10 Mbit/s.

As of now, we have removed this limitation to less than 100 Mbit/s for you and consequently, for all of our customers.

The same rule that applies to our dedicated servers is now also in effect for all of our VPS:
100 Mbit/s are available at all times – without any limitation, without port throttling, no matter how much traffic you generate.

This new rule is active for all new and existing customers at Contabo and you do not have to take any further action in order to benefit from this. Simply put, we have permanently removed the limitation for all of our customers.

Posted by: Markus | Tagged as: , , 3 Comments

Now available : Configuring the latest available PHP Version on your Webspace package

Today we performed some great update on our Webspace hosts, you are now able to choose between the following PHP Versions for your Website:

  • PHP 5.6 (oldstable)
  • PHP 7.0 (stable)
  • PHP 7.1 (testing)

To configure your desired PHP Version just login to your cPanel interface and navigate to "Software" -> "Multi PHP Manager".

To configure the PHP.INI and add additional configuration just open the "MultiPHP INI Editor".

Click here for an overview of our webspace offers.

Posted by: Gianni-Donato | Tagged as: , , , , No Comments

New OS: Debian 9 available now!

Just released a few days ago, already available at Contabo: Debian 9, codename Stretch. You can order the operating system with your new VPS or dedicated server. Existing customers can upgrade to Debian 9 through their customer control panel.

You can combine Debian 9 with Webmin, Lamp, Webmin+LAMP and the Software Raid 1.

In its latest version, the developers have replaced MySQL with MariaDB, and a new Kernel version 4.9 is available as well.

Apart from Debian 9, we offer you a large number of Linux distributions, as well as Windows Server 2012 and 2016. Simply click on "Customize & Order" on our VPS and dedicated servers overview sites and select the operating system that matches your requirements - further details can be found on our website!

Posted by: Markus | Tagged as: , , , , 2 Comments

The SSL certificate

Some of you might wonder in which situations an SSL certificate should be used. This tutorial will help you to find an answer whether or not you should upgrade your website or anything else by adding encryption.

The most important parts of a certificate are the public key and the private key.
The following image shows you what is happening when a client tries to establish an encrypted connection to some webserver.



First the client contacts the server and offers available encryption types, the server and the client come to an agreement on which type to use.
The web server sends the public key to the client so the client will be able to encrypt its requests. The webserver got his private key to decrypt all encrypted client requests. With the private key you are able to decrypt all client requests which were encrypted with the public key, that is why you should never hand out your private key to any third party.

To show you the advantage of using encryption, we created an HTML page containing a simple form which can be found on many websites. In the textfields we entered a username and password.

The username we chose: test@contabo.de

The password we entered: "unencryptedpassword"

To show the difference between encrypted messages and not encrypted messages, we captured some packets using a networking-tool.

Without any encryption we could easily extract the username and password used, we could also see which sites we visit.


With encryption enabled we could not find neither username nor password.
It just shows a packet containing some encrypted data, without the private key we cannot determine which data was actually sent.

If you are running a website, an email server or just an FTP server, it is always up to you to offer encryption or not. Offering encryption to your customers is the best way to act professionally.

There are many types of encryption, this post just handles certificates. Usually encryption algorithms have not changed for years, if you are going to optimize your server you will of course have to think about encryption types, etc.


The real meaning of those connection warnings:

If you are running a web interface (cPanel, Plesk, Webmin etc.) you probably encountered a warning as follows:


"The connection is not private", usually you should rethink if you really want to proceed. There is the possibility that some server got hijacked and you are redirected to the wrong website. In this case the warning pops up because the certificate is not valid for the domain we entered. On a web interface you will get a similar warning when using a so called "self signed certificate". Your browser got a list of authorities which it will trust, signed certificates by one of those authorities will not show any warning.

It can be really unwanted if that warning is showing to all of your customers, sometimes this warning is misinterpreted and the website will be left.

There is only one way to remove this warning, you need to get a certificate signed by some official authority.

Some official authorities, such as "Lets Encrypt", will sign your certificate for free, this is a nice option but not really recommended on a production environment. Usually the domain validated certificate or wildcard  certificate is being used for production environment, those certificates usually are valid for 365 days (1 year).

There are some differences between single domain, multi domain and wildcard certificates. Usually you would want a certificate for "yourdomain.tld" or "www.yourdomain.tld". A single domain certificate will be valid only for one of those domains, a multi domain certificate alias UCC (Unified Communications Certificate) is valid for all domains included within that certificate. In case you want "www.yourdomain.tld", "yourdomain.tld" and "subdomain.yourdomain.tld" within a single certificate, a UCC should fit your needs.

There is also some extended validation available, some bigger companies take advantage of this (e.g. PayPal pp_ev). At this point I want to mention that the private key and certificate will always remain the same, there is no encryption change, the certificate will just get signed.

Right after you got your certificate signed by some official authority, everyone will be able to access your encrypted website without any warning.


Encryption is important, all services (email server, FTP server, web server, etc.) running on your server should offer a way to establish an encrypted connection. There is no need of installing a signed certificate on each service, for most services self-signed certificates are fine.


Posted by: Gianni-Donato | Tagged as: , , , , 4 Comments