merge develop into production

• Add flo to prod: ssh key + root access (!292 (merged))
• Add flo's ssh key to the staging grid root user authorized_keys (!291 (merged))
• Configure journald to discard logs before they're older than 30 days (!285 (merged))
• Fix docs code blocks (!289 (merged))
• nixpkgs update 2022-04-13 (!287 (merged))
• Add update-nixpkgs / diff-closures documentation (!288 (merged))

docs/dev/README.rst

@@ -45,22 +45,27 @@ Updatings Pins
 Nixpkgs
 ```````
 
-To update the version of NixOS we deploy with, run:
-
-.. code: shell
+To update the version of NixOS we deploy with, run::
 
    nix-shell --run 'update-nixpkgs'
 
-That will update ``nixpkgs-2015.json`` to the latest release on the nixos-21.05 channel.
+That will update ``nixpkgs.json`` to the latest release on the nixos release channel.
 
 To update the channel, the script will need to be updated,
 along with the filenames that have the channel in them.
 
+To create a text summary of what an update changes - to put in Merge Requests, for example - run::
+
+    nix-build -A morph -o result-before
+    update-nixpkgs
+    nix-build -A morph -o result-after
+    nix-shell -p nixUnstable
+    nix --extra-experimental-features nix-command store diff-closures ./result-before/ ./result-after/
+
+
 Gitlab Repositories
 ```````````````````
-To update the version of packages we import from gitlab, run:
-
-.. code: shell
+To update the version of packages we import from gitlab, run::
 
    nix-shell --command 'update-gitlab-repo nixos/pkgs/<package>/repo.json'