Tag: Walk through

"Catch and Release" by "Trish Hamme" on Flickr

Releasing files for multiple operating systems with Github Actions in 2021

JonTheNiceGuy Leave a comment

Hi! Long time, no see!

I’ve been working on my Decision Records open source project for a few months now, and I’ve finally settled on the cross-platform language Rust to create my script. As a result, I’ve got a build process which lets me build for Windows, Mac OS and Linux. I’m currently building a single, unsigned binary for each platform, and I wanted to make it so that Github Actions would build and release these three files for me. Most of the guidance which is currently out there points to some unmaintained actions, originally released by GitHub… but now they point to a 3rd party “release” action as their recommended alternative, so I thought I’d explain how I’m using it to release on several platforms at once.

Although I can go into detail about the release file I’m using for Rust-Decision-Records, I’m instead going to provide a much more simplistic view, based on my (finally working) initial test run.

GitHub Actions

GitHub have a built-in Continuous Integration, Continuous Deployment/Delivery (CI/CD) system, called GitHub Actions. You can have several activities it performs, and these are executed by way of instructions in .github/workflows/<somefile>.yml. I’ll be using .github/workflows/build.yml in this example. If you have multiple GitHub Action files you wanted to invoke (perhaps around issue management, unit testing and so on), these can be stored in separate .yml files.

The build.yml actions file will perform several tasks, separated out into two separate activities, a “Create Release” stage, and a “Build Release” stage. The Build stage will use a “Matrix” to execute builds on the three platforms at the same time – Linux AMD64, Windows and Mac OS.

The actual build steps? In this case, it’ll just be writing a single-line text file, stating the release it’s using.

So, let’s get started.

Create Release

A GitHub Release is typically linked to a specific “tagged” commit. To trigger the release feature, every time a commit is tagged with a string starting “v” (like v1.0.0), this will trigger the release process. So, let’s add those lines to the top of the file:

name: Create Release

on:
  push:
    tags:
      - 'v*'

You could just as easily use the filter pattern ‘v[0-9]+.[0-9]+.[0-9]+’ if you wanted to use proper Semantic Versioning, but this is a simple demo, right? 😉

Next we need the actual action we want to start with. This is at the same level as the “on” and “name” tags in that YML file, like this:

jobs:
  create_release:
    name: Create Release
    runs-on: ubuntu-latest
    steps:
      - name: Create Release
        id: create_release
        uses: softprops/action-gh-release@v1
        with:
          name: ${{ github.ref_name }}
          draft: false
          prerelease: false
          generate_release_notes: false

So, this is the actual “create release” job. I don’t think it matters what OS it runs on, but ubuntu-latest is the one I’ve seen used most often.

In this, you instruct it to create a simple release, using the text in the annotated tag you pushed as the release notes.

This is using a third-party release action, softprops/action-gh-release, which has not been vetted by me, but is explicitly linked from GitHub’s own action.

If you check the release at this point, (that is, without any other code working) you’d get just the source code as a zip and a .tgz file. BUT WE WANT MORE! So let’s build this mutha!

Build Release

Like with the create_release job, we have a few fields of instructions before we get to the actual actions it’ll take. Let’s have a look at them first. These instructions are at the same level as the jobs:\n create_release: line in the previous block, and I’ll have the entire file listed below.

  build_release:
    name: Build Release
    needs: create_release
    strategy:
      matrix:
        os: [ubuntu-latest, macos-latest, windows-latest]
        include:
          - os: ubuntu-latest
            release_suffix: ubuntu
          - os: macos-latest
            release_suffix: mac
          - os: windows-latest
            release_suffix: windows
    runs-on: ${{ matrix.os }}

So this section gives this job an ID (build_release) and a name (Build Release), so far, so exactly the same as the previous block. Next we say “You need to have finished the previous action (create_release) before proceeding” with the needs: create_release line.

But the real sting here is the strategy:\n matrix: block. This says “run these activities with several runners” (in this case, an unspecified Ubuntu, Mac OS and Windows release (each just “latest”). The include block asks the runners to add some template variables to the tasks we’re about to run – specifically release_suffix.

The last line in this snippet asks the runner to interpret the templated value matrix.os as the OS to use for this run.

Let’s move on to the build steps.

    steps:
      - name: Checkout code
        uses: actions/checkout@v2

      - name: Run Linux Build
        if: matrix.os == 'ubuntu-latest'
        run: echo "Ubuntu Latest" > release_ubuntu
      
      - name: Run Mac Build
        if: matrix.os == 'macos-latest'
        run: echo "MacOS Latest" > release_mac

      - name: Run Windows Build
        if: matrix.os == 'windows-latest'
        run: echo "Windows Latest" > release_windows

This checks out the source code on each runner, and then has a conditional build statement, based on the OS you’re using for each runner.

It should be fairly simple to see how you could build this out to be much more complex.

The final step in the matrix activity is to add the “built” file to the release. For this we use the softprops release action again.

      - name: Release
        uses: softprops/action-gh-release@v1
        with:
          tag_name: ${{ needs.create_release.outputs.tag-name }}
          files: release_${{ matrix.release_suffix }}

The finished file

So how does this all look when it’s done, this most simple CI/CD build script?

name: Create Release

on:
  push:
    tags:
      - 'v*'

jobs:
  create_release:
    name: Create Release
    runs-on: ubuntu-latest
    steps:
      - name: Create Release
        id: create_release
        uses: softprops/action-gh-release@v1
        with:
          name: ${{ github.ref_name }}
          draft: false
          prerelease: false
          generate_release_notes: false

  build_release:
    name: Build Release
    needs: create_release
    strategy:
      matrix:
        os: [ubuntu-latest, macos-latest, windows-latest]
        include:
          - os: ubuntu-latest
            release_suffix: ubuntu
          - os: macos-latest
            release_suffix: mac
          - os: windows-latest
            release_suffix: windows
    runs-on: ${{ matrix.os }}
    steps:
      - name: Checkout code
        uses: actions/checkout@v2

      - name: Run Linux Build
        if: matrix.os == 'ubuntu-latest'
        run: echo "Ubuntu Latest" > release_ubuntu
      
      - name: Run Mac Build
        if: matrix.os == 'macos-latest'
        run: echo "MacOS Latest" > release_mac

      - name: Run Windows Build
        if: matrix.os == 'windows-latest'
        run: echo "Windows Latest" > release_windows

      - name: Release
        uses: softprops/action-gh-release@v1
        with:
          tag_name: ${{ needs.create_release.outputs.tag-name }}
          files: release_${{ matrix.release_suffix }}

I hope this helps you!

My Sources and Inspirations

Featured image is “Catch and Release” by “Trish Hamme” on Flickr and is released under a CC-BY license.

"Milestone, Otley" by "Tim Green" on Flickr

Changing the default routing metric with Netplan, NetworkManager and ifupdown

JonTheNiceGuy Leave a comment

In the past few months I’ve been working on a project, and I’ve been doing the bulk of that work using Vagrant.

By default and convention, all Vagrant machines, set up using Virtualbox have a “NAT” interface defined as the first network interface, but I like to configure a second interface as a “Bridged” interface which gives the host a “Real” IP address on the network as this means that any security appliances I have on my network can see what device is causing what traffic, and I can quickly identify which hosts are misbehaving.

By default, Virtualbox uses the network 10.0.2.0/24 for the NAT interface, and runs a DHCP server for that interface. In the past, I’ve removed the default route which uses 10.0.2.2 (the IP address of the NAT interface on the host device), but with Ubuntu 20.04, this route keeps being re-injected, so I had to come up with a solution.

Fixing Netplan

Ubuntu, in at least 20.04, but (according to Wikipedia) probably since 17.10, has used Netplan to define network interfaces, superseding the earlier ifupdown package (which uses /etc/network/interfaces and /etc/network/interface.d/* files to define the network). Netplan is a kind of meta-script which, instructs systemd or NetworkManager to reconfigure the network interfaces, and so making the configuration changes here seemed most sensible.

Vagrant configures the file /etc/netplan/50-cloud-init.yml with a network configuration to support this DHCP interface, and then applies it. To fix it, we need to rewrite this file completely.

#!/bin/bash

# Find details about the interface
ifname="$(grep -A1 ethernets "/etc/netplan/50-cloud-init.yaml" | tail -n1 | sed -Ee 's/[ ]*//' | cut -d: -f1)"
match="$(grep macaddress "/etc/netplan/50-cloud-init.yaml" | sed -Ee 's/[ ]*//' | cut -d\  -f2)"

# Configure the netplan file
{
  echo "network:"
  echo "  ethernets:"
  echo "    ${ifname}:"
  echo "      dhcp4: true"
  echo "      dhcp4-overrides:"
  echo "        route-metric: 250"
  echo "      match:"
  echo "        macaddress: ${match}"
  echo "      set-name: ${ifname}"
  echo "  version: 2"
} >/etc/netplan/50-cloud-init.yaml

# Apply the config
netplan apply

When I then came to a box running Fedora, I had a similar issue, except now I don’t have NetPlan to work with? How do I resolve this one?!

Actually, this is a four line script!

#!/bin/bash

# Get the name of the interface which has the IP address 10.0.2.2
netname="$(ip route | grep 10.0.2.2 | head -n 1 | sed -Ee 's/^(.*dev )(.*)$/\2/;s/proto [A-Za-z0-9]+//;s/metric [0-9]+//;s/[ \t]+$//')"

# Ask NetworkManager for a list of all the active connections, look for the string "eth0" and then just get the connection name.
nm="$(nmcli connection show --active | grep "${netname}" | sed -Ee 's/^(.*)([ \t][-0-9a-f]{36})(.*)$/\1/;s/[\t ]+$//g')"
# Set the network to have a metric of 250
nmcli connection modify "$nm" ipv4.route-metric 250
# And then re-apply the network config
nmcli connection up "$nm"

The last major interface management tool I’ve experienced on standard server Linux is “ifupdown” – /etc/network/interfaces. This is mostly used on Debian. How do we fix that one? Well, that’s a bit more tricky!

#!/bin/bash

# Get the name of the interface with the IP address 10.0.2.2
netname="$(ip route | grep 10.0.2.2 | head -n 1 | sed -Ee 's/^(.*dev )(.*)$/\2/;s/proto [A-Za-z0-9]+//;s/metric [0-9]+//;s/[ \t]+$//')"

# Create a new /etc/network/interfaces file which just looks in "interfaces.d"
echo "source /etc/network/interfaces.d/*" > /etc/network/interfaces

# Create the loopback interface file
{
  echo "auto lo"
  echo "iface lo inet loopback"
} > "/etc/network/interfaces.d/lo"
# Bounce the interface
ifdown lo ; ifup lo

# Create the first "real" interface file
{
  echo "allow-hotplug ${netname}"
  echo "iface ${netname} inet dhcp"
  echo "  metric 1000"
} > "/etc/network/interfaces.d/${netname}"
# Bounce the interface
ifdown "${netname}" ; ifup "${netname}"

# Loop through the rest of the interfaces
ip link | grep UP | grep -v lo | grep -v "${netname}" | cut -d: -f2 | sed -Ee 's/[ \t]+([A-Za-z0-9.]+)[ \t]*/\1/' | while IFS= read -r int
do
  # Create the interface file for this interface, assuming DHCP
  {
    echo "allow-hotplug ${int}"
    echo "iface ${int} inet dhcp"
  } > "/etc/network/interfaces.d/${int}"
  # Bounce the interface
  ifdown "${int}" ; ifup "${int}"
done

Looking for one consistent script which does this all?

#!/bin/bash
# This script ensures that the metric of the first "NAT" interface is set to 1000,
# while resetting the rest of the interfaces to "whatever" the DHCP server offers.

function netname() {
  ip route | grep 10.0.2.2 | head -n 1 | sed -Ee 's/^(.*dev )(.*)$/\2/;s/proto [A-Za-z0-9]+//;s/metric [0-9]+//;s/[ \t]+$//'
}

if command -v netplan
then
  ################################################
  # NETPLAN
  ################################################

  # Find details about the interface
  ifname="$(grep -A1 ethernets "/etc/netplan/50-cloud-init.yaml" | tail -n1 | sed -Ee 's/[ ]*//' | cut -d: -f1)"
  match="$(grep macaddress "/etc/netplan/50-cloud-init.yaml" | sed -Ee 's/[ ]*//' | cut -d\  -f2)"

  # Configure the netplan file
  {
    echo "network:"
    echo "  ethernets:"
    echo "    ${ifname}:"
    echo "      dhcp4: true"
    echo "      dhcp4-overrides:"
    echo "        route-metric: 1000"
    echo "      match:"
    echo "        macaddress: ${match}"
    echo "      set-name: ${ifname}"
    echo "  version: 2"
  } >/etc/netplan/50-cloud-init.yaml

  # Apply the config
  netplan apply
elif command -v nmcli
then
  ################################################
  # NETWORKMANAGER
  ################################################

  # Ask NetworkManager for a list of all the active connections, look for the string "eth0" and then just get the connection name.
  nm="$(nmcli connection show --active | grep "$(netname)" | sed -Ee 's/^(.*)([ \t][-0-9a-f]{36})(.*)$/\1/;s/[\t ]+$//g')"
  # Set the network to have a metric of 250
  nmcli connection modify "$nm" ipv4.route-metric 1000
  nmcli connection modify "$nm" ipv6.route-metric 1000
  # And then re-apply the network config
  nmcli connection up "$nm"
elif command -v ifup
then
  ################################################
  # IFUPDOWN
  ################################################

  # Get the name of the interface with the IP address 10.0.2.2
  netname="$(netname)"
  # Create a new /etc/network/interfaces file which just looks in "interfaces.d"
  echo "source /etc/network/interfaces.d/*" > /etc/network/interfaces
  # Create the loopback interface file
  {
    echo "auto lo"
    echo "iface lo inet loopback"
  } > "/etc/network/interfaces.d/lo"
  # Bounce the interface
  ifdown lo ; ifup lo
  # Create the first "real" interface file
  {
    echo "allow-hotplug ${netname}"
    echo "iface ${netname} inet dhcp"
    echo "  metric 1000"
  } > "/etc/network/interfaces.d/${netname}"
  # Bounce the interface
  ifdown "${netname}" ; ifup "${netname}"
  # Loop through the rest of the interfaces
  ip link | grep UP | grep -v lo | grep -v "${netname}" | cut -d: -f2 | sed -Ee 's/[ \t]+([A-Za-z0-9.]+)[ \t]*/\1/' | while IFS= read -r int
  do
    # Create the interface file for this interface, assuming DHCP
    {
      echo "allow-hotplug ${int}"
      echo "iface ${int} inet dhcp"
    } > "/etc/network/interfaces.d/${int}"
    # Bounce the interface
    ifdown "${int}" ; ifup "${int}"
  done
fi

Featured image is “Milestone, Otley” by “Tim Green” on Flickr and is released under a CC-BY license.

"Picture in Picture" by "Mats" on Flickr

Hints and Tips when using Vagrant on Windows

JonTheNiceGuy Leave a comment

I’ve been using HashiCorp’s Vagrant with Oracle’s VirtualBox for several years (probably since 2013, if my blog posts are anything to go by), and I’ve always been pretty comfortable with how it works.

This said, when using a Windows machine running Microsoft’s Hyper-V (built into Windows since Windows 7/2018) VirtualBox is unable (by default) to run 64 bit virtual machines (thanks to Hyper-V “stealing” the VT-x/AMD-V bit from the BIOS/EFI).

Around last year or maybe even the year before, Microsoft introduced a “Hypervisior Platform” add-on, which lets VirtualBox run 64 bit machines on a Hyper-V host (more on this later). HOWEVER, it is much slower than in native mode, and can often freeze on booting…

Meanwhile, Vagrant, (a configuration file that acts as a wrapper around various hypervisors, using VirtualBox by default) boots machines in a “headless” mode by default, so you can’t see the freezing.

I’m trying to use an Ubuntu 18.04 virtual machine for various builds I’m creating, and found that I’d get a few issues on boot, so let’s get these sorted out.

VirtualBox can’t start 64bit virtual machines when Hyper-V is installed.

You need to confirm that certain Windows features are enabled, including “Hyper-V” and “Windows Hypervisor Platform”. Confirm you’re running at least Windows 10 version 1803 which is the first release with the “Windows Hypervisor Platform”.

GUI mode

Run winver to bring up this box. Confirm the version number is greater than 1803. Mine is 1909.

A screenshot of the “winver” command, highlighting the version number, which in this case shows 1909, but needs to show at least 1803.

Right click on the start menu, and select “Apps and Features”. Click on “Programs and Features”.

The settings panel found by right clicking the “Start Menu” and selecting “Apps and Features”. Note the desired next step – “Programs and Features” is highlighted.

In the “Programs and Features” window, click on “Turn Windows Features on or off”. Note the shield icon here indicates that administrative access is required, and you may be required to authenticate to the machine to progress past this stage.

A fragment of the “Programs and Features” window, with the “Turn Windows features on or off” link highlighted.

Next, ensure that the following “Windows Features” are enabled; “Hyper-V”, “Virtual Machine Platform” and “Windows Hypervisor Platform”. Click on “OK” to install these features, if they’re not already installed.

A screen capture of the “Turn Windows features on or off” dialogue box, with certain features obscured and others highlighted.

Note that once you’ve pressed “OK”, you’ll likely need to reboot your machine, if any of these features were not already installed.

CLI mode

Right click on the start menu, and start an Administrative Powershell session.

Run the command Get-ComputerInfo | select WindowsVersion. You should get a response which looks like this:

WindowsVersion
--------------
1909

Note that the version number needs to be greater than 1803.

Next, find the names of the features you need to install. These features have region specific names, so outside EN-GB, these names may not match your requirements!

Run the command Get-WindowsOptionalFeature -online | select FeatureName,State and you’re looking for the following lines (this has been cropped to just what you need):

FeatureName                                     State
-----------                                     -----
HypervisorPlatform                            Enabled
VirtualMachinePlatform                        Enabled
Microsoft-Hyper-V-All                         Enabled

If any of these three features are not enabled, run Enable-WindowsOptionalFeature -online -FeatureName x where “x” is the name of the feature, listed in the above text block, you want to install. For example: Enable-WindowsOptionalFeature -online -FeatureName HypervisorPlatform,VirtualMachinePlatform,Microsoft-Hyper-V-All. If you run this when they’re already enabled, it should return RestartNeeded : False, but otherwise you’re likely to need to reboot.

After the reboot

After you’ve rebooted, and you start a 64 bit virtual machine in VirtualBox, you’ll see this icon in the bottom corner.

A screen grab of the VirtualBox Status Bar, highlighting the “Slow Mode” icon representing the CPU

Booting the Virtual Machine with Vagrant fails because it takes too long to boot

This was historically a big issue with Vagrant and VirtualBox, particularly with Windows Vagrant boxes, but prior to the Hyper-V/VirtualBox solution, it’d been largely fixed (or at least, I wasn’t seeing it!) There is a “standard” timeout for booting a Virtual Machine, I think at approximately 5 minutes, but I might be wrong. To make this “issue” stop occurring, add this config.vm.boot_timeout = 0 line to your Vagrantfile, like this:

Vagrant.configure("2") do |config|
  config.vm.boot_timeout = 0
end

This says to Vagrant, don’t worry how long it takes to boot, just keep waiting until it does. Yes, it will be slower, but it should get there in the end!

Booting the Virtual Maching with Vagrant does not fail, but it never authenticates with your Private Key.

Your VM may sit at this block for quite a while:

==> default: Waiting for machine to boot. This may take a few minutes...
    default: SSH address: 127.0.0.1:2222
    default: SSH username: vagrant
    default: SSH auth method: private key

If this occurs, you may find that your virtual machine has hung during the boot process… but weirdly, a simple work-around to this is to ensure that the VirtualBox GUI is open, and that you’ve got a block like this (config.vm.provider / vb.gui=true / end) in your Vagrantfile:

Vagrant.configure("2") do |config|
  config.vm.provider "virtualbox" do |vb|
    vb.gui = true
  end
end

This forces VirtualBox to open a window with your Virtual Machine’s console on it (much like having a monitor attached to real hardware). You don’t need to interact with it, but any random hangs or halts on your virtual machine may be solved just by bringing this window, or the VirtualBox Machines GUI, to the foreground.

Sometimes you may see, when this happens, a coredump or section of kernel debugging code on the console. Don’t worry about this!

Vagrant refuses to SSH to your virtual machine when using the vagrant ssh command.

Provisioning works like a treat, and you can SSH into the virtual machine from any other environment, but, when you run vagrant ssh, you get an error about keys not being permitted or usable. This is fixable by adding a single line, either to your system or user -wide environment variables, or by adding a line to your Vagrantfile.

The environment variable is VAGRANT_PREFER_SYSTEM_BIN, and by setting this to 0, it will use bundled versions of ssh or rsync instead of using any versions provided by Windows.

You can add a line like this ENV['VAGRANT_PREFER_SYSTEM_BIN']="0" to your Vagrantfile, outside of the block Vagrant.configure…end, like this:

ENV['VAGRANT_PREFER_SYSTEM_BIN']="0"
Vagrant.configure("2") do |config|
end

Sources

Featured image is “Picture in Picture” by “Mats” on Flickr and is released under a CC-BY-SA license.

"2015_12_06_Visé_135942" by "Norbert Schnitzler" on Flickr

Idea for Reusable “Custom Data” templates across multiple modules with Terraform

JonTheNiceGuy 1 Comment

A few posts ago I wrote about building Windows virtual machines with Terraform, and a couple of days ago, “YoureInHell” on Twitter reached out and asked what advice I’d give about having several different terraform modules use the same basic build of custom data.

They’re trying to avoid putting the same template file into several repos (I suspect so that one team can manage the “custom-data”, “user-data” or “cloud-init” files, and another can manage the deployment terraform files), and asked if I had any suggestions.

I had three ideas.

Using a New Module

This was my initial thought; create a new module called something like “Standard Build File”, and this build file contains just the following terraform file, and a template file called “build.tmpl”.

variable "someKey" {
  default = "someVar"
}

variable "hostName" {
  default = "hostName"
}

variable "unsetVar" {}

output "template" {
  value = templatefile("build.tmpl",
    {
      someKey  = var.someKey
      hostName = var.hostName
      unsetVar = var.unsetVar
    }
  )
}

Now, in your calling module, you can do:

module "buildTemplate" {
  source   = "git::https://git.example.net/buildTemplate.git?ref=latestLive"
  # See https://www.terraform.io/docs/language/modules/sources.html
  #   for more details on how to specify the source of this module
  unsetVar = "Set To This String"
}

output "RenderedTemplate" {
  value = module.buildTemplate.template
}

And that means that you can use the module.buildTemplate.template anywhere you’d normally specify your templateFile, and get a consistent, yet customizable template (and note, because I specified a particular tag, you can use that to move to the “current latest” or “the version we released into live on YYYY-MM-DD” by using a tag, or a commit ref.)

Now, the downside to this is that you’ve now got a whole separate module for creating your instances that needs to be maintained. What are our other options?

Git Submodules for your template

I use Git Submodules a LOT for my code. It’s a bit easy to get into a state with them, particularly if you’re not great at keeping on top of them, but… if you are OK with them, you’d create a repo, again, let’s use “https://git.example.net/buildTemplate.git” as our git repo, and put your template in there. In your terraform git repo, you’d run this command: git submodule add https://git.example.net/buildTemplate.git and this would add a directory to your repo called “buildTemplate” that you can use your templatefile function in Terraform against (like this: templatefile("buildTemplate/build.tmpl", {someVar="var"})).

Now, this means that you’ve effectively got two git repos in one tree, and if any changes occur in your submodule repo, you’d need to do git checkout main ; git pull to get the latest updates from your main branch, and when you check it out initially on another machine, you’ll need to do git clone https://git.example.net/terraform --recurse-submodules to get the submodules populated at the same time.

A benefit to this is that because it’s “inline” with the rest of your tree, if you need to make any changes to this template, it’s clearly where it’s supposed to be in your tree, you just need to remember about the submodule when it comes to making PRs and suchforth.

How about that third idea?

Keep it simple, stupid 😁

Why bother with submodules, or modules from a git repo? Terraform can be quite easy to over complicate… so why not create all your terraform files in something like this structure:

project\build.tmpl
project\web_servers\main.tf
project\logic_servers\main.tf
project\database_servers\main.tf

And then in each of your terraform files (web_servers, logic_servers and database_servers) just reference the file in your project root, like this: templatefile("../build.tmpl", {someVar="var"})

The downside to this is that you can’t as easily farm off the control of that build script to another team, and they’d be making (change|pull|merge) requests against the same repo as you… but then again, isn’t that the idea for functional teams? 😃

Featured image is “2015_12_06_Visé_135942” by “Norbert Schnitzler” on Flickr and is released under a CC-BY-SA license.

"Router" by "Ryan Hodnett" on Flickr

Post-Config of a RaspberryPi Zero W as an OTG-USB Gadget that routes

JonTheNiceGuy Leave a comment

In my last post in this series I mentioned that I’d got my Raspberry Pi Zero W to act as a USB Ethernet adaptor via libComposite, and that I was using DNSMasq to provide a DHCP service to the host computer (the one you plug the Pi into). In this part, I’m going to extend what local services I could provide on this device, and start to use this as a router.

Here’s what you missed last time… When you plug the RPi in (to receive power on the data line), it powers up the RPi Zero, and uses a kernel module called “libComposite” to turn the USB interface into an Ethernet adaptor. Because of how Windows and non-Windows devices handle network interfaces, we use two features of libComposite to create an ECM/CDC interface and a RNDIS interface, called usb0 and usb1, and whichever one of these two is natively supported in the OS, that’s which interface comes up. As a result, we can then use DNSMasq to “advertise” a DHCP address for each interface, and use that to advertise services on, like an SSH server.

By making this device into a router, we can use it to access the network, without using the in-built network adaptor (which might be useful if your in-built WiFi adaptors isn’t detected under Linux or Windows without a driver), or to protect your computer from malware (by adding a second firewall that doesn’t share the same network stack as it’s host), or perhaps to ensure that your traffic is sent over a VPN tunnel.

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"raspberry pie" by "stu_spivack" on Flickr

Post-Config of a RaspberryPi Zero W as an OTG-USB Gadget for off-device computing

JonTheNiceGuy 2 Comments

History

A few months ago, I was working on a personal project that needed a separate, offline linux environment. I tried various different schemes to run what I was doing in the confines of my laptop and I couldn’t make what I was working on actually achieve my goals. So… I bought a Raspberry Pi Zero W and a “Solderless Zero Dongle“, with the intention of running Docker containers on it… unfortunately, while Docker runs on a Pi Zero, it’s really hard to find base images for the ARMv6/armhf platform that the Pi Zero W… so I put it back in the drawer, and left it there.

Roll forwards a month or so, and I was doing some experiments with Nebula, and only had an old Chromebook to test it on… except, I couldn’t install the Nebula client for Linux on there, and the Android client wouldn’t give me some features I wanted… so I broke out that old Pi Zero W again…

Now, while the tests with Nebula I was working towards will be documented later, I found that a lot of the documentation about using a Raspberry Pi Zero as a USB gadget were rough and unexplained. So, this post breaks down much of the content of what I found, what I tried, and what did and didn’t work.

Late Edit 2021-06-04: I spotted some typos around providing specific DHCP options for interfaces, based on work I’m doing elsewhere with this script. I’ve updated these values accordingly. I’ve also created a specific branch for this revision.

Late Edit 2021-06-06: I’ve noticed this document doesn’t cover IPv6 at all right now. I started to perform some tweaks to cover IPv6, but as my ISP has decided not to bother with IPv6, and won’t support Hurricane Electric‘s Tunnelbroker system, I can’t test any of it, without building out an IPv6 test environment… maybe soon, eh?

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"Blueprints" by "Cameron Degelia" on Flickr

Using Architectural Decision Records (ADR) with adr-tools

JonTheNiceGuy Leave a comment

Introducing Architectural Decision Records

Over the last week, I discovered a new tool for my arsenal called Architectural Decision Records (ADR). They were first written about in 2011, in a post called “Documenting Architecture Decisions“, where the author, Michael Nygard, advocates for short documents explaining each decision that influences the architecture of an environment.

I found this via a Github repository, created by the team at gov.uk, which includes their ADR library, and references the tool they use to manage these documents – adr-tools.

Late edit 2021-01-25: I also found a post which suggests that Spotify uses ADR.

Late edit 2021-08-11: I wrote a post about using other tooling.

Late edit 2021-12-14: I released (v0.0.1) my own rust-based application for making Decision Records. Yes, Decision Records – not Architecture Decision Records… because I think you should be able to apply the same logic to all decisions, not just architectural ones.

Installing adr-tools on Linux

Currently adr-tools are easier to install under OSX rather than Linux or Windows Subsystem for Linux (WSL) (I’m working on this – bear with me! 😃 ).

The current installation notes suggest for Linux (which would also work on WSL) is to download the latest release tar.gz or zip file and unpack it into your path somewhere. This isn’t exactly the best way to deploy anything on Linux, but… I guess it works right now?

For me, I downloaded the file, and unpacked the whole tar.gz file (as root) into /usr/local/bin/, giving me a directory of /usr/local/bin/adr-tools-3.0.0/. There’s a subdirectory in here, called src which contains a large number of files – mostly starting _adr or adr- and two additional files, init.md and template.md.

Rather than putting all of these files into /usr/local/bin directly, instead I leave them in the adr-tools-3.0.0 directory, and create a symbolic link (symlink) to the /usr/local/bin directory with this command:

cd /usr/local/bin
ln -s adr-tools-3.0.0/src/* .

This gives me all those files in one place, so I can refer to them later.

An aside – why link everything in that src directory? (Feel free to skip this block!)

Now, why, you might ask, do all of these unrelated files need to be in the same place? Well…. the author of the script has put this in at the top of almost all the files:

#!/bin/bash
set -e
eval "$($(dirname $0)/adr-config)"

And then in that script, it says:

#!/bin/bash
basedir=$(cd -L $(dirname $0) > /dev/null 2>&1 && pwd -L)
echo "adr_bin_dir=$basedir"
echo "adr_template_dir=$basedir"

There are, technically, good reasons for this! This is designed to be run in, what in the Windows world, you might call as a “Portable Script”. So, you bung adr-tools into some directory somewhere, and then just call adr somecommand and it knows that all the files are where they need to be. The (somewhat) down side to this is that if you just want to call adr somecommand rather than path/to/my/adr somecommand then all those files need to be there

I’m currently looking to see if I can improve this somewhat, so that it’s not quite so complex to install, but for now, that’s what you need.

Anyway…

Using adr-tools to document your decisions

I’ll start documenting a fictional hosted web service project, and note down some of the decisions which have been made.

Initializing your ADR directory

Start by running adr init. You may want to specify a directory where you want to put these records, so instead use: adr init path/to/adr, like this:

Initializing the ADR in “documentation/architecture-decisions” with adr init documentation/architecture-decisions

You’ll notice that when I run this command, it creates a new entry, called 0001-record-architecture-decisions.md. Let’s open this up, and see what’s in here.

The VSCode record for the choice to use ADR. It is a markdown file, with the standard types of data recorded.

In here we have the record ID (1.), the title of the record Record architecture decisions, the date the choice was made Date: 2021-01-19, a status of Accepted, the context on why we made this choice, the decision, and the consequences of making this decision. Make changes, if needed, and save it. Let’s move on.

Creating our first own record

This all is quite straightforward thus far. Let’s create our next record.

Issuing the command adr new <sometitle> you create the next ADR record.

Let’s open up that record.

The template for the ADR record for “Use AWS”.

Like the first record, we have a title, a status, a context, decision and consequences. Let’s define these.

A “finished” brief ADR record.

This document shouldn’t be very long! It just describes why a choice was made and what that entails.

Changing decisions – completely replacing (superseding) a decision

Of course, over time, decisions will be replaced due to various decisions elsewhere.

You can ask adr to supersede a previous record, using the “-s” flag, and the record number.

Let’s look at how that works on the second ADR record.

After the command adr new -s 2 Use Azure, the ADR record number 2 has a new status, “Superceded by” and the superseded linked document. Yes, “Superceded” is a typo. There is an open PR for it

So, under the “Status”, where is previously said “Approved”, it now says “Superceded by [3. Use Azure](0003-use-azure.md)“. This is a markdown statement which indicates where the superseded document is located. As I mentioned in the comment below the above image, there is an open Pull Request to fix this on the adr-tools, so hopefully that typo won’t last long!

We’ve got our new ADR too – let’s take a look at that one?

Our new ADR shows that it “supercedes” the previous record. Which is good! Typo aside :)

Other references

Of course, you don’t always completely overrule a decision. Sometimes your decision is influenced by, or has a dependency on something else, like this one.

We know which provider we’re using at long last, now let’s pick a region. Use the -l flag to “link” between the referenced and new ADR. The context for the -l flag is “<number>:<text for link to number>:<text for link in targetted document>”.

The command here is:

adr new -l '3:Dependency:Influences' Use Region UK South and UK West

I’m just going to crop from the “Status” block on both the referenced ADR (3) and the ADR which references it (4):

Status block in ADR 0003 which is referenced by ADR 0004
Status block in the new ADR 0004 which references ADR 0003

And of course, you can also use the same switch to mark documents as partially obsoleted, like this:

adr new -l '4:Partially obsoletes:Partially obsoleted by' Use West Europe region instead of UK West region
Status block in ADR 0004 indicating it’s partially obsoleted. Probably worth updating the status properly to show it’s not just “Accepted”.

If you forget to add the referencing in, you can also use the adr link command, like this:

adr link 3 Influences 5 Dependency

To be clear, that command adds a (complete) line to ADR 0003 saying “Influences [5. ADR Title](link)” and a separate (complete) line to ADR 0005 saying “Dependency [3. ADR Title](link)“.

What else can we do?

There are four other “things” that it’s worth doing at this point.

  1. Note that you can change the template per-ADR directory.

Create a directory called “templates” in the ADR directory, and put a file in there called “template.md“. Tweak this as you need. Ensure you have AT LEAST the line ## Status and # NUMBER. TITLE as these are required by the script.

A much abbreviated template file, containing just “Number”, “Title”, “Date”, “Status”, and a new dummy heading called “Stuff”.
And the result of running adr new Some Text once you’ve created that template.

As you can see, it’s possible to add all sorts of content in this template as a result. Bear in mind, before your template turns into something like this, that it’s supposed to be a short document explaining why each decision was made, not a funding proposal, or a complex epic of your user stories!

Be careful not to let your template run away with you!
  1. Note that you can automatically open an editor, by setting the EDITOR (where the process is expected to finish before returning control, like using nano, emacs or vim, for example) or VISUAL (where the process is expected to “fork”, like for example, gedit or vscode) environment variable, and then running adr new A Title, like this:
  1. We can create “Table of Contents” files, using the adr generate toc command, like this:
Generating the table of contents, for injecting into other files.

This can be included into your various other markdown files. There are switches, so you can set the link path, but your best bet is to find that using adr help generate toc.

  1. We can also generate graphviz files of the link maps between elements of the various ADRs, like this: adr generate graph | dot -Tjpg > graph.jpg

If you omit the “| dot -Tjpg > graph.jpg” part, then you’ll see the graphviz output, which looks like this: (I’ve removed the documents 6 and 7).

digraph {
  node [shape=plaintext];
  subgraph {
    _1 [label="1. Record architecture decisions"; URL="0001-record-architecture-decisions.html"];
    _2 [label="2. Use AWS"; URL="0002-use-aws.html"];
    _1 -> _2 [style="dotted", weight=1];
    _3 [label="3. Use Azure"; URL="0003-use-azure.html"];
    _2 -> _3 [style="dotted", weight=1];
    _4 [label="4. Use Region UK South and UK West"; URL="0004-use-region-uk-south-and-uk-west.html"];
    _3 -> _4 [style="dotted", weight=1];
    _5 [label="5. Use West Europe region instead of UK West region"; URL="0005-use-west-europe-region-instead-of-uk-west-region.html"];
    _4 -> _5 [style="dotted", weight=1];
  }
  _3 -> _2 [label="Supercedes", weight=0]
  _3 -> _5 [label="Influences", weight=0]
  _4 -> _3 [label="Dependency", weight=0]
  _5 -> _4 [label="Partially obsoletes", weight=0]
  _5 -> _3 [label="Dependency", weight=0]
}

To make the graphviz part work, you’ll need to install graphviz, which is just an apt get away.

Any caveats?

adr-tools is not actively maintained. I’ve contacted the author, about seeing if I can help out with the maintenance, but… we’ll see, and given some fairly high profile malware takeovers of projects like this sort of thing on Github, Docker, NPM, and more… I can see why there might be some reluctance to consider it! Also, I’m an unknown entity, I’ve just dropped in on the project and offered to help, with no previous exposure to the lead dev or the project… so, we’ll see. Worst case, I’ll fork it!

Working with this also requires an understanding of markdown files, and why these might be a useful document format for records like this. There was a PR submitted to support multiple file formats (like asciidoc and rst) but these were not approved by the author.

There is no current intention to support languages other than English. The tool is hard-coded to look for strings like “status” and “superceded” which is hard. Part of the reason I raised the PRs I did was to let me fix some of these sorts of issues. Again, we’ll see what happens.

Lastly, it can be overwhelming to see a lot of documents in one place, particularly if they’re as granular as the documents I produced in this demo. If the project supported categories, or could be broken down into components (like doc/adr/networking and doc/adr/server_builds and doc/adr/applications) then this might help, but it’s not on the roadmap right now!

Late edit 2021-01-25: If you don’t think these templates have enough context or content, there are lots of others listed on Joel Parker Henderson’s repo of examples and templates. If you want a python based viewer of ADR records, take a look at adr-viewer.

Featured image is “Blueprints” by “Cameron Degelia” on Flickr and is released under a CC-BY license.

"Raven" by "Jim Bahn" on Flickr

Sending SSH login notifications to Matrix via Huginn using Webhooks

JonTheNiceGuy Leave a comment

On the Self Hosted Podcast’s Discord Server, someone posted a link to the following blog post, which I read and found really interesting…: https://blog.hay-kot.dev/ssh-notifications-in-home-assistant/

You see, the key part of that post wasn’t that they were posting to Home Assistant when they were logging in, but instead that they were triggering a webhook on login. And I can do stuff with Webhooks.

What’s a webhook?

A webhook is a callable URL, either with a “secret” embedded in the URL or some authentication header that lets you trigger an action of some sort. I first came across these with Github, but they’re pretty common now. Services will offer these as a way to get an action in one service to do something in another. A fairly common webhook for those getting started with these sorts of things is where creating a pull request (PR) on a Github repository will trigger a message on something like Slack to say the PR is there.

Well, that’s all well and good, but what does Matrix or Huginn have to do with things?

Matrix is a decentralized, end to end encrypted, eventually consistent database system, that just happens to be used extensively as a chat network. In particular, it’s used by Open Source projects, like KDE and Mozilla, and by Government bodies, like the whole French goverment (lead by DINSIC) the German Bundeswehr (Unified Armed Forces) department.

Matrix has a reference client, Element, that was previously called “Riot”, and in 2018 I produced a YouTube video showing how to bridge various alternative messaging systems into Matrix.

Huginn describes itself as:

Huginn is a system for building agents that perform automated tasks for you online. They can read the web, watch for events, and take actions on your behalf. Huginn’s Agents create and consume events, propagating them along a directed graph. Think of it as a hackable version of IFTTT or Zapier on your own server. You always know who has your data. You do.

Huginn Readme

With Huginn, I can create “agents”, including a “receive webhook agent” that will take the content I send, and tweak it to do something else. In the past I used IFTTT to do some fun things, like making this blog work, but now I use Huginn to post Tweets when I post to this blog.

So that I knew that Huginn was posting my twitter posts, I created a Matrix room called “Huginn Alerts” and used the Matrix account I created for the video I mentioned before to send me messages that it had made the posts I wanted. I followed the guidance from this page to do it: https://drwho.virtadpt.net/archive/2020-02-12/integrating-huginn-with-a-matrix-server/

Enough already. Just show me what you did.

In Element.io

  1. Get an access token for the Matrix account you want to post with.

Log into the web interface at https://app.element.io and go to your settings

Click where it says your handle, then click on where it says “All Settings”.

Then click on “Help & About” and scroll to the bottom of that page, where it says “Advanced”

Get to the “Advanced” part of the settings, under “Help & About” to get your access token.

Click where it says “Access Token: <click to reveal>” (strangely, I’m not posting that 😉)

  1. Click on the room, then click on it’s name at the top to open the settings, then click on “Advanced” to get the “Internal room ID”
Gettng the Room ID. Note, it starts with an exclamation mark (!) and ends :<servername>.

In Huginn

  1. Go to the “Credentials” tab, and click on “New Credential”. Give the credential a name (perhaps “Matrix Bot Access Token”), leave it as text and put your access token in here.
  1. Create a Credential for the Room ID. Like before, name it something sensible and put the ID you found earlier.
  1. Create a “Post Agent” by going to Agents and selecting “New agent”. This will show just the “Type” box. You can type in this box to put “Post Agent” and then find it. That will then provide you with the rest of these boxes. Provide a name, and tick the box marked “Propagate immediately”. I’ll cover the content of the “Options” box after this screenshot.

In the “Options” block is a button marked “Toggle View”. Select this which turns it from the above JSON pretty editor, into this text field (note your text is likely to be different):

My content of that box is as follows:

{
  "post_url": "https://matrix.org/_matrix/client/r0/rooms/{% credential Personal_Matrix_Notification_Channel %}/send/m.room.message?access_token={% credential Matrix_Bot_Access_Credential %}",
  "expected_receive_period_in_days": "365",
  "content_type": "json",
  "method": "post",
  "payload": {
    "msgtype": "m.text",
    "body": "{{ text }}"
  },
  "emit_events": "true",
  "no_merge": "false",
  "output_mode": "clean"
}

Note that the “post_url” value contains two “credential” values, like this:

{% credential Personal_Matrix_Notification_Channel %} (this is the Room ID we found earlier) and {% credential Matrix_Bot_Access_Credential %} (this is the Access Token we found earlier).

If you’ve used different names for these values (which are perfectly valid!) then just change these two. The part where it says “{{ text }}” leave there, because we’ll be using that in a later section. Click “Save” (the blue button at the bottom).

  1. Create a Webhook Agent. Go to Agents and then “New Agent”. Select “Webhook Agent” from the “Type” field. Give it a name, like “SSH Logged In Notification Agent”. Set “Keep Events” to a reasonable number of days, like 5. In “Receivers” find the Notification agent you created (“Send Matrix Message to Notification Room” was the name I used). Then, in the screenshot, I’ve pressed the “Toggle View” button on the “Options” section, as this is, to me a little clearer.

The content of the “options” box is:

{
  "secret": "supersecretstring",
  "expected_receive_period_in_days": 365,
  "payload_path": ".",
  "response": ""
}

Change the “secret” from “supersecretstring” to something a bit more useful and secure.

The “Expected Receive Period in Days” basically means, if you’ve not had an event cross this item in X number of days, does Huginn think this agent is broken? And the payload path of “.” basically means “pass everything to the next agent”.

Once you’ve completed this step, press “Save” which will take you back to your agents, and then go into the agent again. This will show you a page like this:

Copy that URL, because you’ll need it later…

On the server you are logging the SSH to

As root, create a file called /etc/ssh/sshrc. This file will be your script that will run every time someone logs in. It must have the file permissions 0644 (u+rw,g+r,o+r), which means that there is a slight risk that the Webhook secret is exposed.

The content of that file is as follows:

#!/bin/sh
ip="$(echo "$SSH_CONNECTION" | cut -d " " -f 1)"
curl --silent\
     --header "Content-Type: application/json"\
     --request POST\
     --data '{
       "At": "'"$(date -Is)"'",
       "Connection": "'"$SSH_CONNECTION"'",
       "User": "'"$USER"'",
       "Host": "'"$(hostname)"'",
       "Src": "'"$ip"'",
       "text": "'"$USER@$(hostname) logged in from $ip at $(date +%H:%M:%S)"'"
     }'\
     https://my.huginn.website/some/path/web_requests/taskid/secret

The heading line (#!/bin/sh) is more there for shellcheck, as, according to the SSH man page this is executed by /bin/sh either way.

The bulk of these values (At, Connection, User, Host or Src) are not actually used by Huginn, but might be useful for later… the key one is text, which if you recall from the “Send Matrix Message to Notification Room” Huginn agent, we put {{ text }} into the “options” block – that’s this block here!

So what happens when we log in over SSH?

SSH asks the shell in the user’s context to execute /etc/ssh/sshrc before it hands over to the user’s login session. This script calls curl and hands some POST data to the url.

Huginn receives this POST via the “SSH Logged In Notification Agent”, and files it.

Huginn then hands that off to the “Send Matrix Message to Notification Room”:

Huginn makes a POST to the Matrix.org server, and Matrix sends the finished message to all the attached clients.

Featured image is “Raven” by “Jim Bahn” on Flickr and is released under a CC-BY license.

"The Guitar Template" by "Neil Williamson" on Flickr

Testing (and failing inline) for data types in Ansible

JonTheNiceGuy 1 Comment

I tend to write long and overly complicated set_fact statements in Ansible, ALL THE DAMN TIME. I write stuff like this:

rulebase: |
  {
    {% for var in vars | dict2items %}
      {% if var.key | regex_search(regex_rulebase_match) | type_debug != "NoneType"
        and (
          var.value | type_debug == "dict" 
          or var.value | type_debug == "AnsibleMapping"
        ) %}
        {% for item in var.value | dict2items %}
          {% if item.key | regex_search(regex_rulebase_match) | type_debug != "NoneType"
            and (
              item.value | type_debug == "dict" 
              or item.value | type_debug == "AnsibleMapping"
            ) %}
            "{{ var.key | regex_replace(regex_rulebase_match, '\2') }}{{ item.key | regex_replace(regex_rulebase_match, '\2') }}": {
              {# This block is used for rulegroup level options #}
              {% for key in ['log_from_start', 'log', 'status', 'nat', 'natpool', 'schedule', 'ips_enable', 'ssl_ssh_profile', 'ips_sensor'] %}
                {% if var.value[key] is defined and rule.value[key] is not defined %}
                  {% if var.value[key] | type_debug in ['string', 'AnsibleUnicode'] %}
                    "{{ key }}": "{{ var.value[key] }}",
                  {% else %}
                    "{{ key }}": {{ var.value[key] }},
                  {% endif %}
                {% endif %}
              {% endfor %}
              {% for rule in item.value | dict2items %}
                {% if rule.key in ['sources', 'destinations', 'services', 'src_internet_service', 'dst_internet_service'] and rule.value | type_debug not in ['list', 'AnsibleSequence'] %}
                  "{{ rule.key }}": ["{{ rule.value }}"],
                {% elif rule.value | type_debug in ['string', 'AnsibleUnicode'] %}
                  "{{ rule.key }}": "{{ rule.value }}",
                {% else %}
                  "{{ rule.key }}": {{ rule.value }},
                {% endif %}
              {% endfor %}
            },
          {% endif %}
        {% endfor %}
      {% endif %}
    {% endfor %}
  }

Now, if you’re writing set_fact or vars like this a lot, what you tend to end up with is the dreaded dict2items requires a dictionary, got instead. which basically means “Hah! You wrote a giant blob of what you thought was JSON, but didn’t render right, so we cast it to a string for you!”

The way I usually write my playbooks, I’ll do something with this set_fact at line, let’s say, 10, and then use it at line, let’s say, 500… So, I don’t know what the bloomin’ thing looks like then!

So, how to get around that? Well, you could do a type check. In fact, I wrote a bloomin’ big blog post explaining just how to do that!

However, that gets unwieldy really quickly, and what I actually wanted to do was to throw the breaks on as soon as I’d created an invalid data type. So, to do that, I created a collection of functions which helped me with my current project, and they look a bit like this one, called “is_a_string.yml“:

- name: Type Check - is_a_string
  assert:
    quiet: yes
    that:
    - vars[this_key] is not boolean
    - vars[this_key] is not number
    - vars[this_key] | int | string != vars[this_key] | string
    - vars[this_key] | float | string != vars[this_key] | string
    - vars[this_key] is string
    - vars[this_key] is not mapping
    - vars[this_key] is iterable
    success_msg: "{{ this_key }} is a string"
    fail_msg: |-
      {{ this_key }} should be a string, and is instead
      {%- if vars[this_key] is not defined %} undefined
      {%- else %} {{ vars[this_key] is boolean | ternary(
        'a boolean',
        (vars[this_key] | int | string == vars[this_key] | string) | ternary(
          'an integer',
          (vars[this_key] | float | string == vars[this_key] | string) | ternary(
            'a float',
            vars[this_key] is string | ternary(
              'a string',
              vars[this_key] is mapping | ternary(
                'a dict',
                vars[this_key] is iterable | ternary(
                  'a list',
                  'unknown (' ~ vars[this_key] | type_debug ~ ')'
                )
              )
            )
          )
        )
      )}}{% endif %} - {{ vars[this_key] | default('unset') }}

To trigger this, I do the following:

- hosts: localhost
  gather_facts: false
  vars:
    SomeString: abc123
    SomeDict: {'somekey': 'somevalue'}
    SomeList: ['somevalue']
    SomeInteger: 12
    SomeFloat: 12.0
    SomeBoolean: false
  tasks:
  - name: Type Check - SomeString
    vars:
      this_key: SomeString
    include_tasks: tasks/type_check/is_a_string.yml
  - name: Type Check - SomeDict
    vars:
      this_key: SomeDict
    include_tasks: tasks/type_check/is_a_dict.yml
  - name: Type Check - SomeList
    vars:
      this_key: SomeList
    include_tasks: tasks/type_check/is_a_list.yml
  - name: Type Check - SomeInteger
    vars:
      this_key: SomeInteger
    include_tasks: tasks/type_check/is_an_integer.yml
  - name: Type Check - SomeFloat
    vars:
      this_key: SomeFloat
    include_tasks: tasks/type_check/is_a_float.yml
  - name: Type Check - SomeBoolean
    vars:
      this_key: SomeBoolean
    include_tasks: tasks/type_check/is_a_boolean.yml

I hope this helps you, bold traveller with complex jinja2 templating requirements!

(Oh, and if you get “template error while templating string: no test named 'boolean'“, you’re probably running Ansible which you installed using apt from Ubuntu Universe, version 2.9.6+dfsg-1 [or, at least I was!] – to fix this, use pip to install a more recent version – preferably using virtualenv first!)

Featured image is “The Guitar Template” by “Neil Williamson” on Flickr and is released under a CC-BY-SA license.

"Main console" by "Steve Parker" on Flickr

Running services (like SSH, nginx, etc) on Windows Subsystem for Linux (WSL1) on boot

JonTheNiceGuy Leave a comment

I recently got a new laptop, and for various reasons, I’m going to be primarily running Windows on that laptop. However, I still like having a working SSH server, running in the context of my Windows Subsystem for Linux (WSL) environment.

Initially, trying to run service ssh start failed with an error, because you need to re-execute the ssh configuration steps which are missed in a WSL environment. To fix that, run sudo apt install --reinstall openssh-server.

Once you know your service runs OK, you start digging around to find out how to start it on boot, and you’ll see lots of people saying things like “Just run a shell script that starts your first service, and then another shell script for the next service.”

Well, the frustration for me is that Linux already has this capability – the current popular version is called SystemD, but a slightly older variant is still knocking around in modern linux distributions, and it’s called SystemV Init, often referred to as just “sysv” or “init.d”.

The way that those services work is that you have an “init” file in /etc/init.d and then those files have a symbolic link into a “runlevel” directory, for example /etc/rc3.d. Each symbolic link is named S##service or K##service, where the ## represents the order in which it’s to be launched. The SSH Daemon, for example, that I want to run is created in there as /etc/rc3.d/S01ssh.

So, how do I make this work in the grander scheme of WSL? I can’t use SystemD, where I could say systemctl enable --now ssh, instead I need to add a (yes, I know) shell script, which looks in my desired runlevel directory. Runlevel 3 is the level at which network services have started, hence using that one. If I was trying to set up a graphical desktop, I’d instead be looking to use Runlevel 5, but the X Windows system isn’t ported to Windows like that yet… Anyway.

Because the rc#.d directory already has this structure for ordering and naming services to load, I can just step over this directory looking for files which match or do not match the naming convention, and I do that with this script:

#! /bin/bash
function run_rc() {
  base="$(basename "$1")"
  if [[ ${base:0:1} == "S" ]]
  then
    "$1" start
  else
    "$1" stop
  fi
}

if [ "$1" != "" ] && [ -e "$1" ]
then
  run_rc "$1"
else
  rc=3
  if [ "$1" != "" ] && [ -e "/etc/rc${$1}.d/" ]
  then
    rc="$1"
  fi
  for digit1 in {0..9}
  do
    for digit2 in {0..9}
    do
      find "/etc/rc${rc}.d/" -name "[SK]${digit1}${digit2}*" -exec "$0" '{}' \; 2>/dev/null
    done
  done
fi

I’ve put this script in /opt/wsl_init.sh

This does a bit of trickery, but basically runs the bottom block first. It loops over the digits 0 to 9 twice (giving you 00, 01, 02 and so on up to 99) and looks in /etc/rc3.d for any file containing the filename starting S or K and then with the two digits you’ve looped to by that point. Finally, it runs itself again, passing the name of the file it just found, and this is where the top block comes in.

In the top block we look at the “basename” – the part of the path supplied, without any prefixed directories attached, and then extract just the first character (that’s the ${base:0:1} part) to see whether it’s an “S” or anything else. If it’s an S (which everything there is likely to be), it executes the task like this: /etc/rc3.d/S01ssh start and this works because it’s how that script is designed! You can run one of the following instances of this command: service ssh start, /etc/init.d/ssh start or /etc/rc3.d/S01ssh start. There are other options, notably “stop” or “status”, but these aren’t really useful here.

Now, how do we make Windows execute this on boot? I’m using NSSM, the “Non-sucking service manager” to add a line to the Windows System services. I placed the NSSM executable in C:\Program Files\nssm\nssm.exe, and then from a command line, ran C:\Program Files\nssm\nssm.exe install WSL_Init.

I configured it with the Application Path: C:\Windows\System32\wsl.exe and the Arguments: -d ubuntu -e sudo /opt/wsl_init.sh. Note that this only works because I’ve also got Sudo setup to execute this command without prompting for a password.

Here I invoke C:\Windows\System32\wsl.exe -d ubuntu -e sudo /opt/wsl_init.sh
I define the name of the service, as Services will see it, and also the description of the service.
I put in MY username and My Windows Password here, otherwise I’m not running WSL in my user context, but another one.

And then I rebooted. SSH was running as I needed it.

Featured image is “Main console” by “Steve Parker” on Flickr and is released under a CC-BY license.