nixos/ec2: don't populate nonexistent metadata files

[illustris]

Description of changes

Relevant issue: #212614

curl http://169.254.169.254/1.0/user-data returns an HTML 404 response page. This gets written to /etc/ec2-metadata/user-data by the fetch-ec2-metadata.service, and eventually picked up by amazon-init.service. This service overwrites /etc/nixos/configuration.nix with this 404 page.

adding --fail to the curl call will prevent files from being created in /etc/ec2-metadata if the response is not 200.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 23.05 Release Notes (or backporting 22.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

[illustris]

tested on an EC2 instance:

Feb 26 17:53:41 systemd[1]: Starting fetch-ec2-metadata.service...
Feb 26 17:53:41 fetch-ec2-metadata-start[17721]: (attempt 1/3) getting an EC2 instance metadata service v2 token...
Feb 26 17:53:41 fetch-ec2-metadata-start[17721]: (attempt 1/10) validating the EC2 instance metadata service v2 token...
Feb 26 17:53:41 fetch-ec2-metadata-start[17721]: getting EC2 instance metadata...
Feb 26 17:53:41 fetch-ec2-metadata-start[17734]: curl: (22) The requested URL returned error: 404
Feb 26 17:53:41 systemd[1]: fetch-ec2-metadata.service: Deactivated successfully.
Feb 26 17:53:41 systemd[1]: Finished fetch-ec2-metadata.service.
Feb 26 17:53:41 systemd[1]: fetch-ec2-metadata.service: Consumed 60ms CPU time, received 3.7K IP traffic, sent 2.6K IP traffic.

$ ls -lah /etc/ec2-metadata/
total 20K
drwxr-xr-x  2 root root 4.0K Feb 26 17:53 .
drwxr-xr-x 31 root root 4.0K Feb 26 17:53 ..
-rw-r--r--  1 root root    9 Feb 26 17:53 ami-manifest-path
-rw-r--r--  1 root root   44 Feb 26 17:53 hostname
-rw-r--r--  1 root root  388 Feb 26 17:53 public-keys-0-openssh-key

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/prs-ready-for-review/3032/1890

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/prs-ready-for-review/3032/1932

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/prs-ready-for-review/3032/1933

[yrichardcrak]

Hmm was going to play around with nixos on ec2 today but am running into this issue. Will wait for the merge and try again :)

Thank you!

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/prs-already-reviewed/2617/868