Using LXD to Test SaltStack

What, why, and how?

I recently setup a new company MacBook and discovered that the default shell was ZSH, so I thought it was about time I followed the advice from my colleagues and try out its magic. I got stuck in and proceeded to perfect my environment. Initially with oh-my-zsh and then with Pyenv.

After doing that and discovering Nirvana I thought it would be cool to do the same for my Linode instance.

That was just a process of repeating what I'd done on the Mac and it got me thinking about setting it up on SaltStack in case I ever had to do it again.

Furthermore, as I already had LXD installed and running on the Linode instance, I thought I could test it out there.

LXD

As it turned out my LXD implementation was... agricultural to put it charitably. When I had first set it up I had simply used the loopback ZFS storage pool and this turned out to be too small and while researching how to increase its size I came to realise that creating the pool on a dedicated device would be a better approach. So, I headed over to Linode and created a new volume and attached it to my trusty Ubuntu 20.04 instance.

Then I had to figure out how to make LXD use that device. After much searching through the LXD documentation which pretty much rivals the pre-fire Library of Alexandria in volume and complexity, it turned out to be quite easy.

Furthermore, migrating the existing LXD containers to the new volume turned out to be just as easy.

Create the volume

Find the newly attached volume:

In the Linode console I had named the new volume zfspool, so I searched for its local mapping per the LXD docs.

ls -l /dev/disk/by-id/
lrwxrwxrwx 1 root  9 May 23 13:23 scsi-0Linode_Volume_zfspool -> ../../sdc

Then came creating the "zpool". I did this using the native ZFS tool, however, it turned out to be not-an-easy-thing to figure out how to "bind" it to LXD. So, I eventually deleted it after much head-scratching:

# cool
sudo zpool create zfs_lxd /dev/sdc
# erg...
sudo zpool destroy zfs_lxd

Thereafter, I created and the new zpool using the lxc commmand:

lxc storage create lxd_zfs_pool zfs source=/dev/sdc zfs.pool_name=zfs_pool

To confirm that I had done it properly, I checked the storage list:

lxc storage list
+--------------+--------+--------------------------------------------+-------------+---------+
|     NAME     | DRIVER |                   SOURCE                   | DESCRIPTION | USED BY |
+--------------+--------+--------------------------------------------+-------------+---------+
| default      | zfs    | /var/snap/lxd/common/lxd/disks/default.img |             | 5       |
+--------------+--------+--------------------------------------------+-------------+---------+
| lxd_zfs_pool | zfs    | zfs_pool                                   |             | 2       |
+--------------+--------+--------------------------------------------+-------------+---------+

Using lxc storage list --debug shows a lot more output which includes information on which storage pools the various items are kept. By default, there were two items: images and profiles (containers?)

Move the containers

Then came moving the existing containers which were stored one the loopback pool onto the new dedicated device pool. This involved stopping each container and then moving it to a temp container on the new pool. The -s switch allowed for new storage to be specified. Thereafter, the moved container was given its old name back. The process was:

lxc stop <container>
lxc move <container> <container>-temp -s lxd_zfs_pool
lxc move <container>-temp <container>
lxc start <container>

My containers were already stopped so I did the migration with this one-liner:

for c in nginx timescaledb ubuntu-docker; \
   do lxc move ${c} ${c}-temp -s lxd_zfs_pool && \
   lxc move ${c}-temp ${c}; \
done

I then confirmed that the containers had been migrated:

lxd storage list --debug
<lots of lines>
[
   {
      "config": {
         "size": "5GB",
         "source": "/var/snap/lxd/common/lxd/disks/default.img",
         "zfs.pool_name": "default"
      },
      "description": "",
      "name": "default",
      "driver": "zfs",
      "used_by": [
         "/1.0/images/52c9bf12cbd3b06d591c5f56f8d9a185aca4a9a7da4d6e9f26f0ba44f68867b7"
      ],
      "status": "Created",
      "locations": [
         "none"
      ]
   },
   {
      "config": {
         "source": "zfs_pool",
         "volatile.initial_source": "/dev/sdc",
         "zfs.pool_name": "zfs_pool"
      },
      "description": "",
      "name": "lxd_zfs_pool",
      "driver": "zfs",
      "used_by": [
         "/1.0/images/52c9bf12cbd3b06d591c5f56f8d9a185aca4a9a7da4d6e9f26f0ba44f68867b7",
         "/1.0/instances/mariadb",
         "/1.0/instances/nginx",
         "/1.0/instances/timescaledb",
         "/1.0/instances/ubuntu-docker",
         "/1.0/profiles/default"
      ],
      "status": "Created",
      "locations": [
         "none"
      ]
   }
]

Thereafter, to ensure that further containers are created in the correct pool, I made the dedicated device the default:

lxc profile device set default root pool=lxd_zfs_pool

Set Up SaltStack

With LXD in good order, I went ahead with the SaltStack setup. For the moment, one master and one minion.

The containers

lxc launch ubuntu:20.04 salt-minion-test
lxc launch ubuntu:20.04 salt-master

I used Salt Bootstrap to do exactly that on the Salt master and minion.

By this stage I had already worked on some very basic SaltStack states and pillars which you can see, on GitHub.

From my repo on my Linode instance, I copied the master and minion configs to where they needed to be:

lxc file push configs/master salt-master/etc/salt/
lxc file push configs/minion salt-minion-test/etc/salt/
lxc exec salt-minion-test systemctl restart salt-minion

I also needed to have the master accept the minion's key using salt-key -A. Note to self: Just turn autoaccept on - it's safe enough to do on a closed network.

SaltStack Code

For the moment, I just want to ensure that the target minion has:

  • A user for me
  • ZSH installed
  • ZSH is the default shell for me
  • Pyenv is installed in my home directory

The GitHub repo contains the necessary to make it all work. I still have to add some documentation to the repo and, of course, continually add further states and pillars. Furthermore, it would be cool to test out other SaltStack components such as syndic and vault for storing secret data - I have already used GPG for this purpose at work, so it would be good to test something new.

I cannot go into each SaltStack file, but I'll go over some of them here.

In, the configs directory, you'll find the master and minion configs referenced above. In pillars, there's the general directory which will be specific to the "general" environment referenced in the minion and master configs. The purpose of environments in SaltStack is to easily separate production and development pillars from each other. This makes it easier to write the states, as one doesn't need to include if env=prod do this else do that logic in the various state files.

The pyenv pillar file - pyenv.sls contains values specific to the "general" environment (or profile in anotherr sense.)

# vim: sts=2 ts=2 sw=2 et ai
pyenv:
  enabled: True
  user: ryant
  shell: /bin/zsh
  shellrc: .zshrc
  shell_profile: .zprofile
  python:
    version: 3.9.5

It's corresponding defaults.yaml file in states is pretty much the same thing, but, potentially for another environmenti, the pillar file might differ.

The state defaults.yaml can be overridden by the pillar pyenv.sls file using the mapping file in the state directory.

# vim: sts=2 ts=2 sw=2 et ai
{% import_yaml 'pyenv/defaults.yaml' as defaults %}

{% set pyenv = salt['pillar.get']('pyenv', default=defaults.pyenv, merge=True) %}

The init.sls file, can be equated to Python's __init__.py and can be used to include other state files.

init.sls:

# vim: sts=2 ts=2 sw=2 et ai
{% from "pyenv/map.jinja" import pyenv with context %}
include:
{% if pyenv.shellrc == '.zshrc' %}
  - pyenv.install_zsh
{% endif %}
  - pyenv.install_pyenv
  - pyenv.configure_python

You'll notived that this .sls file (and all others) can be processed using jinja markup. In this case the install_zsh.sls file will be included if the shellrc file defined in defaults.yaml and potentially overridden by pyenv.sls is .zshrc.

install_pyenv.sls:

# vim: sts=2 ts=2 sw=2 et ai
{% from "pyenv/map.jinja" import pyenv with context %}

dependencies:
  pkg.latest:
    - pkgs:
      - make
      - build-essential
      - libssl-dev
      - zlib1g-dev
      - libbz2-dev
      - libreadline-dev
      - libsqlite3-dev
      - wget
      - curl
      - llvm
      - libncursesw5-dev
      - xz-utils
      - tk-dev
      - libxml2-dev
      - libxmlsec1-dev
      - libffi-dev
      - liblzma-dev

git_directory:
  file.absent:
    - name: /home/{{ pyenv.user }}/.pyenv

clone_pyenv_repo:
  cmd.run:
    - name: git clone https://github.com/pyenv/pyenv.git /home/{{ pyenv.user }}/.pyenv
    - runas: {{ pyenv.user }}

install_pyenv:
  cmd.run:
    - name: src/configure && make -C src
    - cwd: /home/{{ pyenv.user }}/.pyenv
    - runas: {{ pyenv.user }}

configure_shellrc:
  file.append:
    - name: /home/{{ pyenv.user }}/{{ pyenv.shellrc }}
    - runas: {{ pyenv.user }}
    - text:
      - export PYENV_ROOT="$HOME/.pyenv"
      - export PATH="$PYENV_ROOT/bin:$PATH"
      - eval "$(pyenv init --path)"
      - eval "$(pyenv init -)"

configure_shell_profile:
  file.append:
    - name: /home/{{ pyenv.user }}/{{ pyenv.shell_profile }}
    - runas: {{ pyenv.user }}
    - text:
      - export PYENV_ROOT="$HOME/.pyenv"
      - export PATH="$PYENV_ROOT/bin:$PATH"
      - eval "$(pyenv init --path)"

This, in combination with the other .sls files worked. No doubt there is room for improvment, but I'll make those as I add further states to the repo. Further candidates are my neovim setup, timescaledb, etc.

I hope this helps at least one person. ;)


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