add nixos/discord webhook post (#272)

* add nixos/discord webhook post

Signed-off-by: Christine Dodrill <me@christine.website>

* oops

Signed-off-by: Christine Dodrill <me@christine.website>

blog/nixos-discord-webhook-2020-11-30.markdown

@@ -0,0 +1,146 @@
+---
+title: Discord Webhooks via NixOS and Systemd Timers
+date: 2020-11-30
+series: howto
+tags:
+  - nixos
+  - discord
+  - systemd
+---
+
+# Discord Webhooks via NixOS and Systemd Timers
+
+Recently I needed to set up a Discord message on a cronjob as a part of
+moderating a guild I've been in for years. I've done this before using
+[cronjobs](/blog/howto-automate-discord-webhook-cron-2018-03-29), however this
+time we will be using [NixOS](https://nixos.org/) and [systemd
+timers](https://wiki.archlinux.org/index.php/Systemd/Timers). Here's what you
+will need to follow along:
+
+- A machine running NixOS
+- A [Discord](https://discord.com/) account
+- A
+  [webhook](https://support.discord.com/hc/en-us/articles/228383668-Intro-to-Webhooks)
+  configured for a channel
+- A message you want to send to Discord
+  
+[If you don't have moderation permissions in any guilds, make your own for
+testing! You will need the "Manage Webhooks" permission to create a
+webhook.](conversation://Mara/hacker)
+
+## Setting Up Timers
+
+systemd timers are like cronjobs, except they trigger systemd services instead
+of shell commands. For this example, let's create a daily webhook reminder to
+check on your Animal Crossing island at 9 am.
+
+Let's create the systemd service at the end of the machine's
+`configuration.nix`:
+
+```nix
+systemd.services.acnh-island-check-reminder = {
+  serviceConfig.Type = "oneshot";
+  script = ''
+    MESSAGE="It's time to check on your island! Check those stonks!"
+    WEBHOOK="${builtins.readFile /home/cadey/prefix/secrets/acnh-webhook-secret}"
+    USERNAME="Domo"
+    
+    ${pkgs.curl}/bin/curl \
+      -X POST \
+      -F "content=$MESSAGE" \
+      -F "username=$USERNAME" \
+      "$WEBHOOK"
+  '';
+};
+```
+
+[This service is a <a href="https://stackoverflow.com/a/39050387">oneshot</a>
+unit, meaning systemd will launch this once and not expect it to always stay
+running.](conversation://Mara/hacker)
+
+Now let's create a timer for this service. We need to do the following:
+
+- Associate the timer with that service
+- Assign a schedule to the timer
+
+Add this to the end of your `configuration.nix`:
+
+```nix
+systemd.timers.acnh-island-check-reminder = {
+  wantedBy = [ "timers.target" ];
+  partOf = [ "acnh-island-check-reminder.service" ];
+  timerConfig.OnCalendar = "TODO(Xe): this";
+};
+```
+
+Before we mentioned that we want to trigger this reminder every morning at 9 am.
+systemd timers specify their calendar config in the following format:
+
+```
+DayOfWeek Year-Month-Day Hour:Minute:Second
+```
+
+So for something that triggers every day at 9 AM, it would look like this:
+
+```
+*-*-* 8:00:00
+```
+
+[You can ignore the day of the week if it's not
+relevant!](conversation://Mara/hacker)
+
+So our final timer definition would look like this:
+
+```nix
+systemd.timers.acnh-island-check-reminder = {
+  wantedBy = [ "timers.target" ];
+  partOf = [ "acnh-island-check-reminder.service" ];
+  timerConfig.OnCalendar = "*-*-* 8:00:00";
+};
+```
+
+## Deployment and Testing
+
+Now we can deploy this with `nixos-rebuild`:
+
+```console
+$ sudo nixos-rebuild switch
+```
+
+You should see a line that says something like this in the `nixos-rebuild`
+output:
+
+```
+starting the following units: acnh-island-check-reminder.timer
+```
+
+Let's test the service out using `systemctl`:
+
+```console
+$ sudo systemctl start acnh-island-check-reminder.service
+```
+
+And you should then see a message on Discord. If you don't see a message, check
+the logs using `journalctl`:
+
+```console
+$ journalctl -u acnh-island-check-reminder.service
+```
+
+If you see an error that looks like this:
+
+```
+curl: (26) Failed to open/read local data from file/application
+```
+
+This usually means that you tried to do a role or user mention at the beginning
+of the message and curl tried to interpret that as a file input. Add a word like
+"hey" at the beginning of the line to disable this behavior. See
+[here](https://stackoverflow.com/questions/6408904/send-request-to-curl-with-post-data-sourced-from-a-file)
+for more information.
+
+---
+
+Also happy December! My site has the [snow
+CSS](https://christine.website/blog/let-it-snow-2018-12-17) loaded for the
+month. Enjoy!

nix/sources.json

@@ -17,10 +17,10 @@
         "homepage": "",
         "owner": "nmattia",
         "repo": "naersk",
-        "rev": "ce273fa593dcc94a629d0d869f07d96d2b337e37",
+        "rev": "8d562105f960c487cfc013c0e666c1951b03d392",
-        "sha256": "1hx47l7gfim0cs9fn8r91wwl0641wi2fdq67ygb4ydx7msb8sm6h",
+        "sha256": "16a1k5wamp67sqc341rlbmppm2xldfl207k9yhksgcvd4rw3iy20",
         "type": "tarball",
-        "url": "https://github.com/nmattia/naersk/archive/ce273fa593dcc94a629d0d869f07d96d2b337e37.tar.gz",
+        "url": "https://github.com/nmattia/naersk/archive/8d562105f960c487cfc013c0e666c1951b03d392.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "niv": {