It's not *always* DNS

Two weeks ago, I had the pleasure to play with Foremans Kerberos integration and iron out a few long standing kinks.

It all started with a user reminding us that Kerberos authentication is broken when Foreman is deployed on CentOS 8, as there is no more mod_auth_kerb available. Given mod_auth_kerb hasn't seen a release since 2013, this is quite understandable. Thankfully, there is a replacement available, mod_auth_gssapi. Even better, it's available in CentOS 7 and 8 and in Debian and Ubuntu too!

So I quickly whipped up a PR to completely replace mod_auth_kerb with mod_auth_gssapi in our installer and successfully tested that it still works in CentOS 7 (even if upgrading from a mod_auth_kerb installation) and CentOS 8.

Yay, the issue at hand seemed fixed. But just writing a post about that would've been boring, huh?

Well, and then I dared to test the same on Debian…

Turns out, our installer was using the wrong path to the Apache configuration and the wrong username Apache runs under while trying to setup Kerberos, so it could not have ever worked. Luckily Ewoud and I were able to fix that too. And yet the installer was still unable to fetch the keytab from my FreeIPA server 😿

Let's dig deeper! To fetch the keytab, the installer does roughly this:

# kinit -k
# ipa-getkeytab -k http.keytab -p HTTP/foreman.example.com

And if one executes that by hand to see the a actual error, you see:

# kinit -k
kinit: Cannot determine realm for host (principal host/foreman@)

Well, yeah, the principal looks kinda weird (no realm) and the interwebs say for "kinit: Cannot determine realm for host":

  • Kerberos cannot determine the realm name for the host. (Well, duh, that's what it said?!)
  • Make sure that there is a default realm name, or that the domain name mappings are set up in the Kerberos configuration file (krb5.conf)

And guess what, all of these are perfectly set by ipa-client-install when joining the realm…

But there must be something, right? Looking at the principal in the error, it's missing both the domain of the host and the realm. I was pretty sure that my DNS and config was right, but what about gethostname(2)?

# hostname
foreman

Bingo! Let's see what happens if we force that to be an FQDN?

# hostname foreman.example.com
# kinit -k

NO ERRORS! NICE!

We're doing science here, right? And I still have the CentOS 8 box I had for the previous round of tests. What happens if we set that to have a shortname? Nothing. It keeps working fine. And what about CentOS 7? VMs are cheap. Well, that breaks like on Debian, if we force the hostname to be short. Interesting.

Is it a version difference between the systems?

  • Debian 10 has krb5 1.17-3+deb10u1
  • CentOS 7 has krb5 1.15.1-50.el7
  • CentOS 8 has krb5 1.18.2-8.el8

So, something changed in 1.18?

Looking at the krb5 1.18 changelog the following entry jumps at one: Expand single-component hostnames in host-based principal names when DNS canonicalization is not used, adding the system's first DNS search path as a suffix.

Given Debian 11 has krb5 1.18.3-5 (well, testing has, so lets pretend bullseye will too), we can retry the experiment there, and it shows that it works with both, short and full hostname. So yeah, it seems krb5 "does the right thing" since 1.18, and before that gethostname(2) must return an FQDN.

I've documented that for our users and can now sleep a bit better. At least, it wasn't DNS, right?!

Btw, freeipa won't be in bulsseye, which makes me a bit sad, as that means that Foreman won't be able to automatically join FreeIPA realms if deployed on Debian 11.

Controlling Somfy roller shutters using an ESP32 and ESPHome

Our house has solar powered, remote controllable roller shutters on the roof windows, built by the German company named HEIM & HAUS. However, when you look closely at the remote control or the shutter motor, you'll see another brand name: SIMU. As the shutters don't have any wiring inside the house, the only way to control them is via the remote interface. So let's go on the Internet and see how one can do that, shall we? ;)

First thing we learn is that SIMU remote stuff is just re-branded Somfy. Great, another name! Looking further we find that Somfy uses some obscure protocol to prevent (replay) attacks (spoiler: it doesn't!) and there are tools for RTL-SDR and Arduino available. That's perfect!

Always sniff with RTL-SDR first!

Given the two re-brandings in the supply chain, I wasn't 100% sure our shutters really use the same protocol. So the first "hack" was to listen and decrypt the communication using RTL-SDR:

$ git clone https://github.com/dimhoff/radio_stuff
$ cd radio_stuff
$ make -C converters am_to_ook
$ make -C decoders decode_somfy
$ rtl_fm -M am -f 433.42M -s 270K | ./am_to_ook -d 10 -t 2000 -  | ./decode_somfy
<press some buttons on the remote>

The output contains the buttons I pressed, but also the id of the remote and the command counter (which is supposed to prevent replay attacks). At this point I could just use the id and the counter to send own commands, but if I'd do that too often, the real remote would stop working, as its counter won't increase and the receiver will drop the commands when the counters differ too much.

But that's good enough for now. I know I'm looking for the right protocol at the right frequency. As the end result should be an ESP32, let's move on!

Acquiring the right hardware

Contrary to an RTL-SDR, one usually does not have a spare ESP32 with 433MHz radio at home, so I went shopping: a NodeMCU-32S clone and a CC1101. The CC1101 is important as most 433MHz chips for Arduino/ESP only work at 433.92MHz, but Somfy uses 433.42MHz and using the wrong frequency would result in really bad reception. The CC1101 is essentially an SDR, as you can tune it to a huge spectrum of frequencies.

Oh and we need some cables, a bread board, the usual stuff ;)

The wiring is rather simple:

ESP32 wiring for a CC1101

And the end result isn't too beautiful either, but it works:

ESP32 and CC1101 in a simple case

Acquiring the right software

In my initial research I found an Arduino sketch and was totally prepared to port it to ESP32, but luckily somebody already did that for me! Even better, it's explicitly using the CC1101. Okay, okay, I cheated, I actually ordered the hardware after I found this port and the reference to CC1101. ;)

As I am using ESPHome for my ESPs, the idea was to add a "Cover" that's controlling the shutters to it. Writing some C++, how hard can it be?

Turns out, not that hard. You can see the code in my GitHub repo. It consists of two (relevant) files: somfy_cover.h and somfy.yaml.

somfy_cover.h essentially wraps the communication with the Somfy_Remote_Lib library into an almost boilerplate Custom Cover for ESPHome. There is nothing too fancy in there. The only real difference to the "Custom Cover" example from the documentation is the split into SomfyESPRemote (which inherits from Component) and SomfyESPCover (which inherits from Cover) -- this is taken from the Custom Sensor documentation and allows me to define one "remote" that controls multiple "covers" using the add_cover function. The first two params of the function are the NVS name and key (think database table and row), and the third is the rolling code of the remote (stored in somfy_secrets.h, which is not in Git).

In ESPHome a Cover shall define its properties as CoverTraits. Here we call set_is_assumed_state(true), as we don't know the state of the shutters - they could have been controlled using the other (real) remote - and setting this to true allows issuing open/close commands at all times. We also call set_supports_position(false) as we can't tell the shutters to move to a specific position.

The one additional feature compared to a normal Cover interface is the program function, which allows to call the "program" command so that the shutters can learn a new remote.

somfy.yaml is the ESPHome "configuration", which contains information about the used hardware, WiFi credentials etc. Again, mostly boilerplate. The interesting parts are the loading of the additional libraries and attaching the custom component with multiple covers and the additional PROG switches:

esphome:
  name: somfy
  platform: ESP32
  board: nodemcu-32s
  libraries:
    - SmartRC-CC1101-Driver-Lib@2.5.6
    - Somfy_Remote_Lib@0.4.0
    - EEPROM
  includes:
    - somfy_secrets.h
    - somfy_cover.h


cover:
  - platform: custom
    lambda: |-
      auto somfy_remote = new SomfyESPRemote();
      somfy_remote->add_cover("somfy", "badezimmer", SOMFY_REMOTE_BADEZIMMER);
      somfy_remote->add_cover("somfy", "kinderzimmer", SOMFY_REMOTE_KINDERZIMMER);
      App.register_component(somfy_remote);
      return somfy_remote->covers;

    covers:
      - id: "somfy"
        name: "Somfy Cover"
      - id: "somfy2"
        name: "Somfy Cover2"

switch:
  - platform: template
    name: "PROG"
    turn_on_action:
      - lambda: |-
          ((SomfyESPCover*)id(somfy))->program();
  - platform: template
    name: "PROG2"
    turn_on_action:
      - lambda: |-
          ((SomfyESPCover*)id(somfy2))->program();

The switch to trigger the program mode took me a bit. As the Cover interface of ESPHome does not offer any additional functions besides movement control, I first wrote code to trigger "program" when "stop" was pressed three times in a row, but that felt really cumbersome and also had the side effect that the remote would send more than needed, sometimes confusing the shutters. I then decided to have a separate button (well, switch) for that, but the compiler yelled at me I can't call program on a Cover as it does not have such a function. Turns out, you need to explicitly cast to SomfyESPCover and then it works, even if the code becomes really readable, NOT. Oh and as the switch does not have any code to actually change/report state, it effectively acts as a button that can be pressed.

At this point we can just take an existing remote, press PROG for 5 seconds, see the blinds move shortly up and down a bit and press PROG on our new ESP32 remote and the shutters will learn the new remote.

And thanks to the awesome integration of ESPHome into HomeAssistant, this instantly shows up as a new controllable cover there too.

Future Additional Work

I started writing this post about a year ago… And the initial implementation had some room for improvement…

More than one remote

The initial code only created one remote and one cover element. Sure, we could attach that to all shutters (there are 4 of them), but we really want to be able to control them separately.

Thankfully I managed to read enough ESPHome docs, and learned how to operate std::vector to make the code dynamically accept new shutters.

Using ESP32's NVS

The ESP32 has a non-volatile key-value storage which is much nicer than throwing bits at an emulated EEPROM. The first library I used for that explicitly used EEPROM storage and it would have required quite some hacking to make it work with NVS. Thankfully the library I am using now has a plugable storage interface, and I could just write the NVS backend myself and upstream now supports that. Yay open-source!

Remaining issues

Real state is unknown

As noted above, the ESP does not know the real state of the shutters: a command could have been lost in transmission (the Somfy protocol is send-only, there is no feedback) or the shutters might have been controlled by another remote. At least the second part could be solved by listening all the time and trying to decode commands heard over the air, but I don't think this is worth the time -- worst that can happen is that a closed (opened) shutter receives another close (open) command and that is harmless as they have integrated endstops and know that they should not move further.

Can't program new remotes with ESP only

To program new remotes, one has to press the "PROG" button for 5 seconds. This was not exposed in the old library, but the new one does support "long press", I just would need to add another ugly switch to the config and I currently don't plan to do so, as I do have working remotes for the case I need to learn a new one.

building a simple KVM switch for 30€

Prompted by tweets from Lesley and Dave, I thought about KVM switches again and came up with a rather cheap solution to my individual situation (YMMY, as usual).

As I've written last year, my desk has one monitor, keyboard and mouse and two computers. Since writing that post I got a new (bigger) monitor, but also an USB switch again (a DIGITUS USB 3.0 Sharing Switch) - this time one that doesn't freak out my dock \o/

However, having to switch the used computer in two places (USB and monitor) is rather inconvenient, but also getting an KVM switch that can do 4K@60Hz was out of question.

Luckily, hackers gonna hack, everything, and not only receipt printers (😉). There is a tool called ddcutil that can talk to your monitor and change various settings. And udev can execute commands when (USB) devices connect… You see where this is going?

After installing the package (available both in Debian and Fedora), we can inspect our system with ddcutil detect. You might have to load the i2c_dev module (thanks Philip!) before this works -- it seems to be loaded automatically on my Fedora, but you never know 😅.

$ sudo ddcutil detect
Invalid display
   I2C bus:             /dev/i2c-4
   EDID synopsis:
      Mfg id:           BOE
      Model:
      Serial number:
      Manufacture year: 2017
      EDID version:     1.4
   DDC communication failed
   This is an eDP laptop display. Laptop displays do not support DDC/CI.

Invalid display
   I2C bus:             /dev/i2c-5
   EDID synopsis:
      Mfg id:           AOC
      Model:            U2790B
      Serial number:
      Manufacture year: 2020
      EDID version:     1.4
   DDC communication failed

Display 1
   I2C bus:             /dev/i2c-7
   EDID synopsis:
      Mfg id:           AOC
      Model:            U2790B
      Serial number:
      Manufacture year: 2020
      EDID version:     1.4
   VCP version:         2.2

The first detected display is the built-in one in my laptop, and those don't support DDC anyways. The second one is a ghost (see ddcutil#160) which we can ignore. But the third one is the one we can (and will control). As this is the only valid display ddcutil found, we don't need to specify which display to talk to in the following commands. Otherwise we'd have to add something like --display 1 to them.

A ddcutil capabilities will show us what the monitor is capable of (or what it thinks, I've heard some give rather buggy output here) -- we're mostly interested in the "Input Source" feature (Virtual Control Panel (VCP) code 0x60):

$ sudo ddcutil capabilities

   Feature: 60 (Input Source)
      Values:
         0f: DisplayPort-1
         11: HDMI-1
         12: HDMI-2

Seems mine supports it, and I should be able to switch the inputs by jumping between 0x0f, 0x11 and 0x12. You can see other values defined by the spec in ddcutil vcpinfo 60 --verbose, some monitors are using wrong values for their inputs 🙄. Let's see if ddcutil getvcp agrees that I'm using DisplayPort now:

$ sudo ddcutil getvcp 0x60
VCP code 0x60 (Input Source                  ): DisplayPort-1 (sl=0x0f)

And try switching to HDMI-1 using ddcutil setvcp:

$ sudo ddcutil setvcp 0x60 0x11

Cool, cool. So now we just need a way to trigger input source switching based on some event…

There are three devices connected to my USB switch: my keyboard, my mouse and my Yubikey. I do use the mouse and the Yubikey while the laptop is not docked too, so these are not good indicators that the switch has been turned to the laptop. But the keyboard is!

Let's see what vendor and product IDs it has, so we can write an udev rule for it:

$ lsusb

Bus 005 Device 006: ID 17ef:6047 Lenovo ThinkPad Compact Keyboard with TrackPoint

Okay, so let's call ddcutil setvcp 0x60 0x0f when the USB device 0x17ef:0x6047 is added to the system:

ACTION=="add", SUBSYSTEM=="usb", ATTR{idVendor}=="17ef", ATTR{idProduct}=="6047", RUN+="/usr/bin/ddcutil setvcp 0x60 0x0f"
$ sudo vim /etc/udev/rules.d/99-ddcutil.rules
$ sudo udevadm control --reload

And done! Whenever I connect my keyboard now, it will force my screen to use DisplayPort-1.

On my workstation, I deployed the same rule, but with ddcutil setvcp 0x60 0x11 to switch to HDMI-1 and my cheap not-really-KVM-but-in-the-end-KVM-USB-switch is done, for the price of one USB switch (~30€).

Note: if you want to use ddcutil with a Lenovo Thunderbolt 3 Dock (or any other dock using Displayport Multi-Stream Transport (MST)), you'll need kernel 5.10 or newer, which fixes a bug that prevents ddcutil from talking to the monitor using I²C.

systemd + SELinux = 🔥

Okay, getting a title that will ensure clicks for this post was easy. Now comes the hard part: content!

When you deploy The Foreman, you want a secure setup by default. That's why we ship (and enable) a SELinux policy which allows you to run the involved daemons in confined mode.

We have recently switched our default Ruby application server from Passenger (running via mod_passenger inside Apache httpd) to Puma (running standalone and Apache just being a reverse proxy). While doing so, we initially deployed Puma listening on localhost:3000 and while localhost is pretty safe, a local user could still turn out evil and talk directly to Puma, pretending to be authenticated by Apache (think Kerberos or X.509 cert auth).

Obviously, this is not optimal, so the next task was to switch Puma to listen on an UNIX socket and only allow Apache to talk to said socket.

This doesn't sound overly complicated, and indeed it wasn't. The most time/thought was spent on doing that in a way that doesn't break existing setups and still allows binding to a TCP socket for setups where users explicitly want that.

We also made a change to the SELinux policy to properly label the newly created socket and allow httpd to access it.

The whole change was carefully tested on CentOS 7 and worked like a charm. So we merged it, and it broke. Only on CentOS 8, but broken is broken, right?

This is the start of my Thanksgiving story "learn how to debug SELinux issues" ;)

From the logs of our integration test I knew the issue was Apache not being able to talk to that new socket (we archive sos reports as part of the tests, and those clearly had it in the auditd logs). But I also knew we did prepare our policy for that change, so either our preparation was not sufficient or the policy wasn't properly loaded.

The same sos report also contained the output of semanage fcontext --list which stated that all regular files called /run/foreman.sock would get the foreman_var_run_t type assigned. Wait a moment, all regular files?! A socket is not a regular file! Let's quickly make that truly all files. That clearly changed the semanage fcontext --list output, but the socket was still created as var_run_t?!

It was time to actually boot a CentOS 8 VM and try more things out. Interestingly, you actually can't add a rule for /run/something, as /run is an alias (equivalency in SELinux speak) for /var/run:

# semanage fcontext --add -t foreman_var_run_t /run/foreman.sock
ValueError: File spec /run/foreman.sock conflicts with equivalency rule '/run /var/run'; Try adding '/var/run/foreman.sock' instead

I have no idea how the list output in the report got that /run rule, but okay, let's match /var/run/foreman.sock.

Did that solve the issue? Of course not! And you knew it, as I didn't get to the juciest part of the headline yet: systemd!

We use systemd to create the socket, as it is both convenient and useful (no more clients connecting before Rails has finished booting). But why is it wrongly labeling our freshly created socket?! A quick check with touch shows that the policy is correct now, the touched file gets the right type assigned. So it must be something with systemd…

A bit of poking (and good guesswork based on prior experience with a similar issue in Puppet: PUP-2169 and PUP-10548) led to the realization that a systemctl daemon-reexec after adding the file context rule "fixes" the issue. Moving the poking to Google, you quickly end up at systemd issue #9997 which is fixed in v245, but that's in no EL release yet. And indeed, the issue seems fixed on my Fedora 33 with systemd 246, but I still need it to work on CentOS 7 and 8…

Well, maybe that reexec isn't that bad after all? At least the socket is now properly labeled and httpd can connect to it on CentOS 8.

Btw, no idea why the connection worked on CentOS 7, as there the socket was also wrongly labeled, but SELinux didn't deny httpd to open it.

Big shout out to lzap and ewoud for helping me with this beast!

Building documentation for Ansible Collections using antsibull

In my recent post about building and publishing documentation for Ansible Collections, I've mentioned that the Ansible Community is currently in the process of making their build tools available as a separate project called antsibull instead of keeping them in the hacking directory of ansible.git.

I've also said that I couldn't get the documentation to build with antsibull-docs as it wouldn't support collections yet. Thankfully, Felix Fontein, one of the maintainers of antsibull, pointed out that I was wrong and later versions of antsibull actually have partial collections support. So I went ahead and tried it again.

And what should I say? Two bug reports by me and four patches by Felix Fontain later I can use antsibull-docs to generate the Foreman Ansible Modules documentation!

Let's see what's needed instead of the ugly hack in detail.

We obviously don't need to clone ansible.git anymore and install its requirements manually. Instead we can just install antsibull (0.17.0 contains all the above patches). We also need Ansible (or ansible-base) 2.10 or never, which currently only exists as a pre-release. 2.10 is the first version that has an ansible-doc that can list contents of a collection, which antsibull-docs requires to work properly.

The current implementation of collections documentation in antsibull-docs requires the collection to be installed as in "Ansible can find it". We had the same requirement before to find the documentation fragments and can just re-use the installation we do for various other build tasks in build/collection and point at it using the ANSIBLE_COLLECTIONS_PATHS environment variable or the collections_paths setting in ansible.cfg1. After that, it's only a matter of passing --use-current to make it pick up installed collections instead of trying to fetch and parse them itself.

Given the main goal of antisibull-docs collection is to build documentation for multiple collections at once, it defaults to place the generated files into <dest-dir>/collections/<namespace>/<collection>. However, we only build documentation for one collection and thus pass --squash-hierarchy to avoid this longish path and make it generate documentation directly in <dest-dir>. Thanks to Felix for implementing this feature for us!

And that's it! We can generate our documentation with a single line now!

antsibull-docs collection --use-current --squash-hierarchy --dest-dir ./build/plugin_docs theforeman.foreman

The PR to switch to antsibull is open for review and I hope to get merged in soon!

Oh and you know what's cool? The documentation is now also available as a preview on ansible.com!


  1. Yes, the paths version of that setting is deprecated in 2.10, but as we support older Ansible versions, we still use it. 

Building and publishing documentation for Ansible Collections

I had a draft of this article for about two months, but never really managed to polish and finalize it, partially due to some nasty hacks needed down the road. Thankfully, one of my wishes was heard and I had now the chance to revisit the post and try a few things out. Sadly, my wish was granted only partially and the result is still not beautiful, but read yourself ;-)

UPDATE: I've published a follow up post on building documentation for Ansible Collections using antsibull, as my wish was now fully granted.

As part of my day job, I am maintaining the Foreman Ansible Modules - a collection of modules to interact with Foreman and its plugins (most notably Katello). We've been maintaining this collection (as in set of modules) since 2017, so much longer than collections (as in Ansible Collections) existed, but the introduction of Ansible Collections allowed us to provide a much easier and supported way to distribute the modules to our users.

Now users usually want two things: features and documentation. Features are easy, we already have plenty of them. But documentation was a bit cumbersome: we had documentation inside the modules, so you could read it via ansible-doc on the command line if you had the collection installed, but we wanted to provide online readable and versioned documentation too - something the users are used to from the official Ansible documentation.

Building HTML from Ansible modules

Ansible modules contain documentation in form of YAML blocks documenting the parameters, examples and return values of the module. The Ansible documentation site is built using Sphinx from reStructuredText. As the modules don't contain reStructuredText, Ansible hashad a tool to generate it from the documentation YAML: build-ansible.py document-plugins. The tool and the accompanying libraries are not part of the Ansible distribution - they just live in the hacking directory. To run them we need a git checkout of Ansible and source hacking/env-setup to set PYTHONPATH and a few other variables correctly for Ansible to run directly from that checkout.

It would be nice if that'd be a feature of ansible-doc, but while it isn't, we need to have a full Ansible git checkout to be able to continue.The tool has been recently split out into an own repository/distribution: antsibull. However it was also a bit redesigned to be easier to use (good!), and my hack to abuse it to build documentation for out-of-tree modules doesn't work anymore (bad!). There is an issue open for collections support, so I hope to be able to switch to antsibull soon.

Anyways, back to the original hack.

As we're using documentation fragments, we need to tell the tool to look for these, because otherwise we'd get errors about not found fragments. We're passing ANSIBLE_COLLECTIONS_PATHS so that the tool can find the correct, namespaced documentation fragments there. We also need to provide --module-dir pointing at the actual modules we want to build documentation for.

ANSIBLEGIT=/path/to/ansible.git
source ${ANSIBLEGIT}/hacking/env-setup
ANSIBLE_COLLECTIONS_PATHS=../build/collections python3 ${ANSIBLEGIT}/hacking/build-ansible.py document-plugins --module-dir ../plugins/modules --template-dir ./_templates --template-dir ${ANSIBLEGIT}/docs/templates --type rst --output-dir ./modules/

Ideally, when antsibull supports collections, this will become antsibull-docs collection … without any need to have an Ansible checkout, sourcing env-setup or pass tons of paths.

Until then we have a Makefile that clones Ansible, runs the above command and then calls Sphinx (which provides a nice Makefile for building) to generate HTML from the reStructuredText.

You can find our slightly modified templates and themes in our git repository in the docs directory.

Publishing HTML documentation for Ansible Modules

Now that we have a way to build the documentation, let's also automate publishing, because nothing is worse than out-of-date documentation!

We're using GitHub and GitHub Actions for that, but you can achieve the same with GitLab, TravisCI or Jenkins.

First, we need a trigger. As we want always up-to-date documentation for the main branch where all the development happens and also documentation for all stable releases that are tagged (we use vX.Y.Z for the tags), we can do something like this:

on:
  push:
    tags:
      - v[0-9]+.[0-9]+.[0-9]+
    branches:
      - master

Now that we have a trigger, we define the job steps that get executed:

    steps:
      - name: Check out the code
        uses: actions/checkout@v2
      - name: Set up Python
        uses: actions/setup-python@v2
        with:
          python-version: "3.7"
      - name: Install dependencies
        run: make doc-setup
      - name: Build docs
        run: make doc

At this point we will have the docs built by make doc in the docs/_build/html directory, but not published anywhere yet.

As we're using GitHub anyways, we can also use GitHub Pages to host the result.

      - uses: actions/checkout@v2
      - name: configure git
        run: |
          git config user.name "${GITHUB_ACTOR}"
          git config user.email "${GITHUB_ACTOR}@bots.github.com"
          git fetch --no-tags --prune --depth=1 origin +refs/heads/*:refs/remotes/origin/*
      - name: Set up Python
        uses: actions/setup-python@v2
        with:
          python-version: "3.7"
      - name: Install dependencies
        run: make doc-setup
      - name: Build docs
        run: make doc
      - name: commit docs
        run: |
          git checkout gh-pages
          rm -rf $(basename ${GITHUB_REF})
          mv docs/_build/html $(basename ${GITHUB_REF})
          dirname */index.html | sort --version-sort | xargs -I@@ -n1 echo '<div><a href="@@/"><p>@@</p></a></div>' >> index.html
          git add $(basename ${GITHUB_REF}) index.html
          git commit -m "update docs for $(basename ${GITHUB_REF})" || true
      - name: push docs
        run: git push origin gh-pages

As this is not exactly self explanatory:

  1. Configure git to have a proper author name and email, as otherwise you get ugly history and maybe even failing commits
  2. Fetch all branch names, as the checkout action by default doesn't do this.
  3. Setup Python, Sphinx, Ansible etc.
  4. Build the documentation as described above.
  5. Switch to the gh-pages branch from the commit that triggered the workflow.
  6. Remove any existing documentation for this tag/branch ($GITHUB_REF contains the name which triggered the workflow) if it exists already.
  7. Move the previously built documentation from the Sphinx output directory to a directory named after the current target.
  8. Generate a simple index of all available documentation versions.
  9. Commit all changes, but don't fail if there is nothing to commit.
  10. Push to the gh-pages branch which will trigger a GitHub Pages deployment.

Pretty sure this won't win any beauty contest for scripting and automation, but it gets the job done and nobody on the team has to remember to update the documentation anymore.

You can see the results on theforeman.org or directly on GitHub.

Scanning with a Brother MFC-L2720DW on Linux without any binary blobs

Back in 2015, I've got a Brother MFC-L2720DW for the casual "I need to print those two pages" and "I need to scan these receipts" at home (and home-office ;)). It's a rather cheap (I paid less than 200€ in 2015) monochrome laser printer, scanner and fax with a (well, two, wired and wireless) network interface. In those five years I've never used the fax or WiFi functions, but printed a scanned a few pages.

Brother offers Linux drivers, but those are binary blobs which I never really liked to run.

The printer part works just fine with a "Generic PCL 6/PCL XL" driver in CUPS or even "driverless" via AirPrint on Linux. You can also feed it plain PostScript, but I found it rather slow compared to PCL. On recent Androids it works using the built in printer service or Mopria Printer Service for older ones - I used to joke "why would you need a printer on your phone?!", but found it quite useful after a few tries.

However, for the scanner part I had to use Brother's brscan4 driver on Linux and their iPrint&Scan app on Android - Mopria Scan wouldn't support it.

Until, last Friday, I've seen a NEW package being uploaded to Debian: sane-airscan. And yes, monitoring the Debian NEW queue via Twitter is totally legit!

sane-airscan is an implementation of Apple's AirScan (eSCL) and Microsoft's WSD/WS-Scan protocols for SANE. I've never heard of those before - only about AirPrint, but thankfully this does not mean nobody has reverse-engineered them and created something that works beautifully on Linux. As of today there are no packages in the official Fedora repositories and the Debian ones are still in NEW, however the upstream documentation refers to an openSUSE OBS repository that works like a charm in the meantime (on Fedora 32).

The only drawback I've seen so far: the scanner only works in "Color" mode and there is no way to scan in "Grayscale", making scanning a tad slower. This has been reported upstream and might or might not be fixable, as it seems the device does not announce any mode besides "Color".

Interestingly, SANE has an eSCL backend on its own since 1.0.29, but it's disabled in Fedora in favor of sane-airscan even though the later isn't available in Fedora yet. However, it might not even need separate packaging, as SANE upstream is planning to integrate it into sane-backends directly.

Using Ansible Molecule to test roles in monorepos

Ansible Molecule is a toolkit for testing Ansible roles. It allows for easy execution and verification of your roles and also manages the environment (container, VM, etc) in which those are executed.

In the Foreman project we have a collection of Ansible roles to setup Foreman instances called forklift. The roles vary from configuring Libvirt and Vagrant for our CI to deploying full fledged Foreman and Katello setups with Proxies and everything. The repository also contains a dynamic Vagrant file that can generate Foreman and Katello installations on all supported Debian, Ubuntu and CentOS platforms using the previously mentioned roles. This feature is super helpful when you need to debug something specific to an OS/version combination.

Up until recently, all those roles didn't have any tests. We would run ansible-lint on them, but that was it.

As I am planning to do some heavier work on some of the roles to enhance our upgrade testing, I decided to add some tests first. Using Molecule, of course.

Adding Molecule to an existing role is easy: molecule init scenario -r my-role-name will add all the necessary files/examples for you. It's left as an exercise to the reader how to actually test the role properly as this is not what this post is about.

Executing the tests with Molecule is also easy: molecule test. And there are also examples how to integrate the test execution with the common CI systems.

But what happens if you have more than one role in the repository? Molecule has support for monorepos, however that is rather limited: it will detect the role path correctly, so roles can depend on other roles from the same repository, but it won't find and execute tests for roles if you run it from the repository root. There is an undocumented way to set MOLECULE_GLOB so that Molecule would detect test scenarios in different paths, but I couldn't get it to work nicely for executing tests of multiple roles and upstream currently does not plan to implement this. Well, bash to the rescue!

for roledir in roles/*/molecule; do
    pushd $(dirname $roledir)
    molecule test
    popd
done

Add that to your CI and be happy! The CI will execute all available tests and you can still execute those for the role you're hacking on by just calling molecule test as you're used to.

However, we can do even better.

When you initialize a role with Molecule or add Molecule to an existing role, there are quite a lot of files added in the molecule directory plus an yamllint configuration in the role root. If you have many roles, you will notice that especially the molecule.yml and .yamllint files look very similar for each role.

It would be much nicer if we could keep those in a shared place.

Molecule supports a "base config": a configuration file that gets merged with the molecule.yml of your project. By default, that's ~/.config/molecule/config.yml, but Molecule will actually look for a .config/molecule/config.yml in two places: the root of the VCS repository and your HOME. And guess what? The one in the repository wins (that's not yet well documented). So by adding a .config/molecule/config.yml to the repository, we can place all shared configuration there and don't have to duplicate it in every role.

And that .yamllint file? We can also move that to the repository root and add the following to Molecule's (now shared) configuration:

lint: yamllint --config-file ${MOLECULE_PROJECT_DIRECTORY}/../../.yamllint --format parsable .

This will define the lint action as calling yamllint with the configuration stored in the repository root instead of the project directory, assuming you store your roles as roles/<rolename>/ in the repository.

And that's it. We now have a central place for our Molecule and yamllint configurations and only need to place role-specific data into the role directory.

Automatically renaming the default git branch to "devel"

It seems GitHub is planning to rename the default brach for newly created repositories from "master" to "main". It's incredible how much positive PR you can get with a one line configuration change, while still working together with the ICE.

However, this post is not about bashing GitHub.

Changing the default branch for newly created repositories is good. And you also should do that for the ones you create with git init locally. But what about all the repositories out there? GitHub surely won't force-rename those branches, but we can!

Ian will do this as he touches the individual repositories, but I tend to forget things unless I do them immediately…

Oh, so this is another "automate everything with an API" post? Yes, yes it is!

And yes, I am going to use GitHub here, but something similar should be implementable on any git hosting platform that has an API.

Of course, if you have SSH access to the repositories, you can also just edit HEAD in an for loop in bash, but that would be boring ;-)

I'm going with devel btw, as I'm already used to develop in the Foreman project and devel in Ansible.

acquire credentials

My GitHub account is 2FA enabled, so I can't just use my username and password in a basic HTTP API client. So the first step is to acquire a personal access token, that can be used instead. Of course I could also have implemented OAuth2 in my lousy script, but ain't nobody have time for that.

The token will require the "repo" permission to be able to change repositories.

And we'll need some boilerplate code (I'm using Python3 and requests, but anything else will work too):

#!/usr/bin/env python3

import requests

BASE='https://api.github.com'
USER='evgeni'
TOKEN='abcdef'

headers = {'User-Agent': '@{}'.format(USER)}
auth = (USER, TOKEN)

session = requests.Session()
session.auth = auth
session.headers.update(headers)
session.verify = True

This will store our username, token, and create a requests.Session so that we don't have to pass the same data all the time.

get a list of repositories to change

I want to change all my own repos that are not archived, not forks, and actually have the default branch set to master, YMMV.

As we're authenticated, we can just list the repositories of the currently authenticated user, and limit them to "owner" only.

GitHub uses pagination for their API, so we'll have to loop until we get to the end of the repository list.

repos_to_change = []

url = '{}/user/repos?type=owner'.format(BASE)
while url:
    r = session.get(url)
    if r.ok:
        repos = r.json()
        for repo in repos:
            if not repo['archived'] and not repo['fork'] and repo['default_branch'] == 'master':
                repos_to_change.append(repo['name'])
        if 'next' in r.links:
            url = r.links['next']['url']
        else:
            url = None
    else:
        url = None

create a new devel branch and mark it as default

Now that we know which repos to change, we need to fetch the SHA of the current master, create a new devel branch pointing at the same commit and then set that new branch as the default branch.

for repo in repos_to_change:
    master_data = session.get('{}/repos/evgeni/{}/git/ref/heads/master'.format(BASE, repo)).json()
    data = {'ref': 'refs/heads/devel', 'sha': master_data['object']['sha']}
    session.post('{}/repos/{}/{}/git/refs'.format(BASE, USER, repo), json=data)
    default_branch_data = {'default_branch': 'devel'}
    session.patch('{}/repos/{}/{}'.format(BASE, USER, repo), json=default_branch_data)
    session.delete('{}/repos/{}/{}/git/refs/heads/{}'.format(BASE, USER, repo, 'master'))

I've also opted in to actually delete the old master, as I think that's the safest way to let the users know that it's gone. Letting it rot in the repository would mean people can still pull and won't notice that there are no changes anymore as the default branch moved to devel.

So…

announcement

I've updated all my (those in the evgeni namespace) non-archived repositories to have devel instead of master as the default branch.

Have fun updating!

code

#!/usr/bin/env python3

import requests

BASE='https://api.github.com'
USER='evgeni'
TOKEN='abcd'

headers = {'User-Agent': '@{}'.format(USER)}
auth = (USER, TOKEN)

session = requests.Session()
session.auth = auth
session.headers.update(headers)
session.verify = True

repos_to_change = []

url = '{}/user/repos?type=owner'.format(BASE)
while url:
    r = session.get(url)
    if r.ok:
        repos = r.json()
        for repo in repos:
            if not repo['archived'] and not repo['fork'] and repo['default_branch'] == 'master':
                repos_to_change.append(repo['name'])
        if 'next' in r.links:
            url = r.links['next']['url']
        else:
            url = None
    else:
        url = None

for repo in repos_to_change:
    master_data = session.get('{}/repos/evgeni/{}/git/ref/heads/master'.format(BASE, repo)).json()
    data = {'ref': 'refs/heads/devel', 'sha': master_data['object']['sha']}
    session.post('{}/repos/{}/{}/git/refs'.format(BASE, USER, repo), json=data)
    default_branch_data = {'default_branch': 'devel'}
    session.patch('{}/repos/{}/{}'.format(BASE, USER, repo), json=default_branch_data)
    session.delete('{}/repos/{}/{}/git/refs/heads/{}'.format(BASE, USER, repo, 'master'))

mass-migrating modules inside an Ansible Collection

In the Foreman project, we've been maintaining a collection of Ansible modules to manage Foreman installations since 2017. That is, 2 years before Ansible had the concept of collections at all.

For that you had to set library (and later module_utils and doc_fragment_plugins) in ansible.cfg and effectively inject our modules, their helpers and documentation fragments into the main Ansible namespace. Not the cleanest solution, but it worked quiet well for us.

When Ansible started introducing Collections, we quickly joined, as the idea of namespaced, easily distributable and usable content units was great and exactly matched what we had in mind.

However, collections are only usable in Ansible 2.8, or actually 2.9 as 2.8 can consume them, but tooling around building and installing them is lacking. Because of that we've been keeping our modules usable outside of a collection.

Until recently, when we decided it's time to move on, drop that compatibility (which costed a few headaches over the time) and release a shiny 1.0.0.

One of the changes we wanted for 1.0.0 is renaming a few modules. Historically we had the module names prefixed with foreman_ and katello_, depending whether they were designed to work with Foreman (and plugins) or Katello (which is technically a Foreman plugin, but has a way more complicated deployment and currently can't be easily added to an existing Foreman setup). This made sense as long as we were injecting into the main Ansible namespace, but with collections the names be became theforeman.foreman.foreman_ <something> and while we all love Foreman, that was a bit too much. So we wanted to drop that prefix. And while at it, also change some other names (like ptable, which became partition_table) to be more readable.

But how? There is no tooling that would rename all files accordingly, adjust examples and tests. Well, bash to the rescue! I'm usually not a big fan of bash scripts, but renaming files, searching and replacing strings? That perfectly fits!

First of all we need a way map the old name to the new name. In most cases it's just "drop the prefix", for the others you can have some if/elif/fi:

prefixless_name=$(echo ${old_name}| sed -E 's/^(foreman|katello)_//')
if [[ ${old_name} == 'foreman_environment' ]]; then
  new_name='puppet_environment'
elif [[ ${old_name} == 'katello_sync' ]]; then
  new_name='repository_sync'
elif [[ ${old_name} == 'katello_upload' ]]; then
  new_name='content_upload'
elif [[ ${old_name} == 'foreman_ptable' ]]; then
  new_name='partition_table'
elif [[ ${old_name} == 'foreman_search_facts' ]]; then
  new_name='resource_info'
elif [[ ${old_name} == 'katello_manifest' ]]; then
  new_name='subscription_manifest'
elif [[ ${old_name} == 'foreman_model' ]]; then
  new_name='hardware_model'
else
  new_name=${prefixless_name}
fi

That defined, we need to actually have a ${old_name}. Well, that's a for loop over the modules, right?

for module in ${BASE}/foreman_*py ${BASE}/katello_*py; do
  old_name=$(basename ${module} .py)done

While we're looping over files, let's rename them and all the files that are associated with the module:

# rename the module
git mv ${BASE}/${old_name}.py ${BASE}/${new_name}.py

# rename the tests and test fixtures
git mv ${TESTS}/${old_name}.yml ${TESTS}/${new_name}.yml
git mv tests/fixtures/apidoc/${old_name}.json tests/fixtures/apidoc/${new_name}.json
for testfile in ${TESTS}/fixtures/${old_name}-*.yml; do
  git mv ${testfile} $(echo ${testfile}| sed "s/${old_name}/${new_name}/")
done

Now comes the really tricky part: search and replace. Let's see where we need to replace first:

  1. in the module file
    1. module key of the DOCUMENTATION stanza (e.g. module: foreman_example)
    2. all examples (e.g. foreman_example: …)
  2. in all test playbooks (e.g. foreman_example: …)
  3. in pytest's conftest.py and other files related to test execution
  4. in documentation
sed -E -i "/^(\s+${old_name}|module):/ s/${old_name}/${new_name}/g" ${BASE}/*.py

sed -E -i "/^(\s+${old_name}|module):/ s/${old_name}/${new_name}/g" tests/test_playbooks/tasks/*.yml tests/test_playbooks/*.yml

sed -E -i "/'${old_name}'/ s/${old_name}/${new_name}/" tests/conftest.py tests/test_crud.py

sed -E -i "/`${old_name}`/ s/${old_name}/${new_name}/g' README.md docs/*.md

You've probably noticed I used ${BASE} and ${TESTS} and never defined them… Lazy me.

But here is the full script, defining the variables and looping over all the modules.

#!/bin/bash

BASE=plugins/modules
TESTS=tests/test_playbooks
RUNTIME=meta/runtime.yml

echo "plugin_routing:" > ${RUNTIME}
echo "  modules:" >> ${RUNTIME}

for module in ${BASE}/foreman_*py ${BASE}/katello_*py; do
  old_name=$(basename ${module} .py)
  prefixless_name=$(echo ${old_name}| sed -E 's/^(foreman|katello)_//')
  if [[ ${old_name} == 'foreman_environment' ]]; then
    new_name='puppet_environment'
  elif [[ ${old_name} == 'katello_sync' ]]; then
    new_name='repository_sync'
  elif [[ ${old_name} == 'katello_upload' ]]; then
    new_name='content_upload'
  elif [[ ${old_name} == 'foreman_ptable' ]]; then
    new_name='partition_table'
  elif [[ ${old_name} == 'foreman_search_facts' ]]; then
    new_name='resource_info'
  elif [[ ${old_name} == 'katello_manifest' ]]; then
    new_name='subscription_manifest'
  elif [[ ${old_name} == 'foreman_model' ]]; then
    new_name='hardware_model'
  else
    new_name=${prefixless_name}
  fi

  echo "renaming ${old_name} to ${new_name}"

  git mv ${BASE}/${old_name}.py ${BASE}/${new_name}.py

  git mv ${TESTS}/${old_name}.yml ${TESTS}/${new_name}.yml
  git mv tests/fixtures/apidoc/${old_name}.json tests/fixtures/apidoc/${new_name}.json
  for testfile in ${TESTS}/fixtures/${old_name}-*.yml; do
    git mv ${testfile} $(echo ${testfile}| sed "s/${old_name}/${new_name}/")
  done

  sed -E -i "/^(\s+${old_name}|module):/ s/${old_name}/${new_name}/g" ${BASE}/*.py

  sed -E -i "/^(\s+${old_name}|module):/ s/${old_name}/${new_name}/g" tests/test_playbooks/tasks/*.yml tests/test_playbooks/*.yml

  sed -E -i "/'${old_name}'/ s/${old_name}/${new_name}/" tests/conftest.py tests/test_crud.py

  sed -E -i "/`${old_name}`/ s/${old_name}/${new_name}/g' README.md docs/*.md

  echo "    ${old_name}:" >> ${RUNTIME}
  echo "      redirect: ${new_name}" >> ${RUNTIME}

  git commit -m "rename ${old_name} to ${new_name}" ${BASE} tests/ README.md docs/ ${RUNTIME}
done

As a bonus, the script will also generate a meta/runtime.yml which can be used by Ansible 2.10+ to automatically use the new module names if the playbook contains the old ones.

Oh, and yes, this is probably not the nicest script you'll read this year. Maybe not even today. But it got the job nicely done and I don't intend to need it again anyways.