Category Archives: Thoughts

Current distribution of WhatsApp alternatives [Update]

Android_robotMany people are discussing alternatives to WhatsApp right now. Here I just track how many installations the currently discussed, crypto-enabled alternatives have according to the app store.

WhatsApp was already bad before Facebook acquired it. But at least now people woke up and are considering secure alternatives. Yes, this move could have come earlier, but I do welcome the new opportunity: its the first time wide spread encryption actually has a chance in the consumer market. So for most of the people out there the question is more “which alternative should I use” instead of “should I use one”. Right now I do not have the faintest idea which alternative with crypto support will make the break through – but you could say I am well prepare.

Screenshot installed instant messengers
Screenshot installed instant messengers

Well – that’s obviously not a long term solution. Thus, to shed some light on the various alternatives and how they stand right now, here is a quick statistical overview:

Secure Instant Messengers, state updated 2014-03-11
Name WebPage/GooglePlay installed devices Ratings Google +1
ChatSecure Website / Google Play 100 000 – 500 000 1 626 2 620
Kontalk Website / Google Play 10 000 – 50 000 237 265
surespot Website / Google Play 50 000 – 100 000 531 632
Telegram Website / Google Play 10 000 000 – 50 000 000 273 089 97 641
Threema Website / Google Play 500 000 – 1 000 000 9 368 12 594
TextSecure Website / Google Play 100 000 – 500 000 2 478 2 589

The statistics are taken from Google’s Android Play Store. I would love to include iTunes statistics, but it seems they are not provided via the web page. If you know how to gather them please drop me a note and I’ll include them here.

These numbers just help to show how fat an application is spread – it does not say anything about the quality. For example Threema is not Open Source and thus not a real alternative. So, if you want to know more details about the various options, please read appropriate reviews like the one from MissingM.

Postfix Architecture Overview

Postfix LogoPostfix consists of numerous services, commandos and queues. The documentation describes them in detail, but a general overview was missing – so I gave it a try.

The Postfix documentation is very detailed and of high quality. One example is postfix.org/OVERVIEW.html which explains the various services, queues and commandos and how they interact with each other. However, despite the included ASCII diagrams a “big picture” is missing. Since we do have quite some customers using Postfix at credativ my company gave me some time to spend at creating such an overview. Here you go:

Postfix Architecture Overview
Postfix Architecture Overview

The image links to the company website where you can download the PDF, but there is also a Postfix Architecture Overview Github repository including the odg, a pdf and a png.

Of course Postfix is far too complex to highlight all services and all commandos and all ways of communication, so the picture had to be simplified. For example, the process of flushing mails does only cover the deferred and incoming queue and not the processes which actually trigger the flushing. Also, policyd’s are missing, and I would actually like to include where Milter filters can be attached. Maybe I’ll update the graphic in the future. The license will be CC-BY-SA, so if you have ideas to extend the picture further you will be able to send me pull requests. Speaking about ideas, thanks to Patrick Ben Koetter who gave me the idea to create such an image.

[Howto] First Steps With Ansible

Ansible LogoAnsible is a tool to manage systems and their configuration. Without the need for a client installed agent and with the ability to launch programs with command line, it seems to fit between classic configuration management like Puppet on one hand and ssh/dsh on the other.

Background

System/Configuration management is a hot topic right now. At Fosdem2014 there was an entire track dedicated to the topic – and the rooms where constantly overcrowded. There are more and more large server installations out there these days. With virtualization, it again get sensible and possible to have one server for each service. All these often rather similar machines need to be managed and thus central configuration management tools like Puppet or Chef became very popular. They keep all configuration stored in recipes on a central server, and the clients connect to it and pull the recipes regularly to ensure if everything is fine.

But sometimes there are smaller tasks: tasks which only need to be done once or once in a while, but for which a configuration management recipe might be too much. Also, it might happen that you have machines where you cannot easily install a Puppet client, or for example where you have machines which cannot contact your configuration management server via pull due to security concerns. For that situations ssh is often the tool of sysadmin’s choice. There are also cluster or distributed versions available like dsh.

Ansible now fits right in between these two classes of tools: it does provide the possibility to serve recipes from a central server, but does not require the clients to run any other agent but ssh.

Basic configuration, simple commands

First of all Ansible needs to know the hosts its going to serve. They can be managed on the central server in /etc/ansible/hosts or in a file configured in the shell variable ANSIBLE_HOSTS. The hosts can be listed as IP addresses or host names, and can contain additional information like user names, ssh port and so on:

[web-servers]
www.example.net ansible_ssh_port=222
www.example.com ansible_ssh_user=liquidat

[db-servers]
192.168.1.1
blue ansible_ssh_host=192.168.1.50

As soon as the hosts are defined, an Ansible “ping” can be used to see if they all can be reached. This is done from the central server – Ansible is per default a pushing service, not a pulling one.

$ ansible all -m ping
www.example.net | success >> {
    "changed": false, 
    "ping": "pong"
}
...

As seen above, Ansible was called with flag “m” which means module – the module “ping” just contacts the servers and checks if everything is ok. In this case the servers answer was successfully. Also, as you see the output is formatted in JSON style which is helpful in case the results need to be parsed anywhere.

In case you want to call arbitrary commands the flag “a” is needed:

$ ansible all -a "whoami" --sudo -K
sudo password: 
www.example.net | success | rc=0 >>
root
...

The “a” flag provides arguments to the invocated modules. In case no module is given, the argument of the flag is executed on the machine directly. The flag “sudo” does call the argument with sudo rights, “K” asks for the sudo password. Btw., note that this requires all servers to use the same sudo password, so to run Ansible you should think about configuring sudo with NOPASSWD.

More modules

There are dozens of modules provided with Ansible. For example, the file module can change permissions and ownership of a file or delete files and directories. The service module can check the state of services:

$ ansible www.example.com -m service -a "name=sshd state=restarted" --sudo -K
sudo password: 
www.example.com | success >> {
    "changed": true, 
    "name": "sshd", 
    "state": "started"
}

There are modules to send e-mails, copy files, install software via various package managers, for the management of cloud resources, to manage different databases, and so on. For example, the copy module can be used to copy files – and shows that files are only transferred if they are not already there:

$ ansible www.example.com -m copy -a "src=/home/liquidat/tmp/test.yml dest=/home/liquidat/text.yaml"
www.example.com | success >> {
    "changed": <strong>true</strong>, 
    "dest": "/home/liquidat/text.yaml", 
    "gid": 500, 
    "group": "liquidat", 
    "md5sum": "504e549603f616826707d60be0d9cd40", 
...

$ ansible www.example.com -m copy -a "src=/home/liquidat/tmp/test.yml dest=/home/liquidat/text.yaml"
www.example.com | success >> {
    "changed": <strong>false</strong>, 
...
}

In the second attempt the “changed” status is on “false”, indicating that the file was not actually changed since it was already there.

Playbooks

However, Ansible can be used for more than a distributed shell on steroids: configuration management and system orchestration. Both is realized in Ansible via so called Playbooks. In such Yaml files all the necessary tasks are stored which either ensure a given configuration or set up a specific system. In the end the Playbooks just list the Ansible commandos and modules which could also be called via command line. However, Playbooks also offer a dependency/notification system where given tasks are only executed if other tasks did change anything. Playbooks are called with a specific command line: ansible-playbook $PLAYBOOK.yml

For example, imagine a setup where you copy a file, and if that file was copied (so not there before or changed in the meantime) you need to restart sshd:

---
- hosts: www.example.com
  remote_user: liquidat
  tasks:
      - name: copy file
        copy: src=~/tmp/test.txt dest=~/test.txt
        notify:
            - restart sshd
  handlers:
      - name: restart sshd
        service: name=sshd state=restarted
        sudo: yes

As you see the host and user is configured in the beginning. There could be also host groups if needed. It is followed by the actual task – copying the file. All tasks of a Playbook are usually executed. This given task definition does have a notifier: if the task is executed with a “change” state of “true”, than a “handler” is notified. A handler is a task which is only executed if its called for. In this case, sshd is restarted after we copied over a file.

And the output is clear as well:

$ ansible-playbook tmp/test.yml -K
sudo password: 

PLAY [www.example.com] ********************************************************* 

GATHERING FACTS *************************************************************** 
ok: [www.example.com]

TASK: [copy file] ************************************************************* 
changed: [www.example.com]

NOTIFIED: [restart sshd] ****************************************************** 
changed: [www.example.com]

PLAY RECAP ******************************************************************** 
www.example.com             : ok=3    changed=2    unreachable=0    failed=0

The above example is a simple Playbook – but Playbooks offer many more functions: templates, variables based on various sources like the machine facts, conditions and even looping the same set of tasks over different sets of variables. For example, if we take the copy task but loop over a set of file names, each which should have a different name on the target system:

- name: copy files
  copy: src=~/tmp/{{ item.src_name }} dest=~/{{ item.dest_name }}                               
  with_items:                                                                                   
    - { src_name: file1.txt, dest_name: dest-file1.txt }                                      
    - { src_name: file2.txt, dest_name: dest-file2.txt }  

Also, Playbooks can include other Playbooks so you can have a set of ready-made Playbooks at your hand and combine them as you like. As you see Ansible is incredible powerful and does provide the ability to write Playbooks for very complex management tasks and system setups.

Outlook

Ansible is a tempting solution for configuration management since it does combine direct access with configuration management. If you have your large server data center already configured in an ansible-hosts file, you can it use for both system configuration as well as performing direct tasks. This is a big advantage compared to for example Puppet setups. Also, you can write Playbooks which you only need once in a while, store them at some place – and use them for orchestration purposes. Something which is not easily available with Puppet, but very simple with Ansible. Additionally, Ansible can be used either pushing or pulling, there are tools for both, which makes it much more flexible compared to other solutions out there.

And since you can use Ansible right from the start even without writing complex recipes before the learning curve is not that steep – and the adoption of Ansible is much quicker. There are already customers who use Ansible together with Puppet since Ansible is so much easier and much quicker to learn.

So in the end I can only recommend Ansible to anyone who is dealing with configuration management. It is a certainly helpful tool and even if you don’t start using it it might be interesting to know how other approaches to system and configuration management do look like.

First look at cockpit, a web based server management interface [Update]

TuxOnly recently the Cockpit project was launched, aiming at providing a web based management interface for various servers. It already leaves an interesting impression for simple management tasks – and the design is actually well done.

I just recently came across the only three month old Cockpit project. The mission statement is clear:

Cockpit is a server manager that makes it easy to administer your GNU/Linux servers via a web browser.

The web page also states three aims: beginners friendly interface, multi server management – and that there should be no interference in mixed usage of web interface and shell. Especially the last point caught my attention: many other web based solutions introduce their own magic, thus making it sometimes tricky to co-administrate the system manually via the shell. The listed objectives also make clear that cockpit does not try to replace tools that go much deeper into the configuration of servers, like Webmin, which for example offers modules to configure Apache servers in a quite detailed manner. Cockpit tries to simply administrate the server, not the applications. I must admit that I would always do such a application configuration manually anyway…

The installation of Cockpit is a bit bumpy: besides the requirement of tools like systemd which limits the usage to only very recent distributions (excluding Ubuntu, I guess) there are no packages yet, some manual steps are required. A post at unshut.me highlights the necessary steps for Fedora which I followed: in includes installing dependencies, setting firewall rules, etc. – and in the end it just works. But please note, in case you wanna give it a try: it is not ready for production. Not at all. Use virtual machines!

What I did see after the installation was actually rather appealing: a clean, yet modern web interface offering the most important and simple tasks a sysadmin might need in a daily routine: quickly showing the current health state, providing logs, starting and stopping services, creating new users, switching between servers, etc. And: there is even a working rescue console!

And where ever you click you see quickly what the foundation for Cockpit is: systemd. The logviewer shows systemd journal logs, services are displayed as seen and managed by systemd, and so on. That is the reason why one goal – no interference between shell and web interface – can be rather easily reached: the web interface communicates with systemd, just like a administrator on such a machine would do.  <Update> Speaking about: if you want to get an idea of *how* Cockpit communicates with its components, have a look at their transport graphic. </Update> Systemd by the way also explains why Cockpit currently is developed on Fedora: it ships with fully activated systemd.

But back to Cockpit itself: Some people might note that running a web server on a machine which is not meant to provide web pages is a security issue. And they are right. Each additional service on a server is a potential threat. But also keep in mind that many simple server installations already have an additional web server for example to show Munin statistics. So as always you have to carefully balance the pros of usable system management with the cons of an additional service and a web reachable system console…

To summarize: The interface is slick and easy to use, for simple server setups it could come in handy as a server management tool for example for beginners and accessible from the internal network only. A downside currently is the already mentioned limit to the distributions: as far as I got it, only Fedora 18 and 20 are supported yet. But the project has just begun, and will most certainly pick up more support in the near future, as long as the foundations (systemd) are properly supported in the distribution of your choice. And in the meantime Cockpit might be an extra bonus for people testing the coming Fedora Server. ;-)

Last but not least, in case you wonder how server management looks like with systemd, Cockpit can give you a first impression: it uses systemd and almost nothing else for exactly that.

Wall-Skills.com Advent calender launched – one 1-pager each day

Simple Workflow diagramIt happened: we launched the wall-skills.com Advent calendar, featuring one 1-pager every day to hang up on your office walls. Daily learning and improving your skills just got easier.

As announced a couple of weeks ago Wall-Skills.com launched its Advent calendar today. For the ext 24 days we will release one new 1-pager each day featuring information worth reading and learning about agile software development, IT project management and sometimes even self improvement tips for office workers.

Get the 1-pagers, hang them upon your office and toilet walls, and share knowledge which you think should be shared among your colleagues and team members. Subscribe to the RSS feed and make sure you don’t miss any Advent calendar post.

Today’s feature is about the Agile principles:
Agile-Principles_Wall-Skills

I’d like to thanks to Corinna from finding-marbles.com for her awesome dedication to the project, her design and work – and also for coming up with the idea to transform my 1-pagers into an actual project.

If you have interesting Ideas you’d like to share with the Wall-Skills community, let us know. The Advent calendar is almost filled by now, but there we plan to release more 1-pagers in the weeks after.