- No service depends on `keys.target` anymore which is a systemd target that indicates if all [NixOps keys](https://nixos.org/nixops/manual/#idm140737322342384) were successfully uploaded. Instead, `<key-name>-key.service` should be used to define a dependency of a key in a service. The full issue behind the `keys.target` dependency is described at [NixOS/nixpkgs\#67265](https://github.com/NixOS/nixpkgs/issues/67265).

  The following services are affected by this:

  - [`services.dovecot2`](options.html#opt-services.dovecot2.enable)

  - [`services.nsd`](options.html#opt-services.nsd.enable)

  - [`services.softether`](options.html#opt-services.softether.enable)

  - [`services.strongswan`](options.html#opt-services.strongswan.enable)

  - [`services.strongswan-swanctl`](options.html#opt-services.strongswan-swanctl.enable)

  - [`services.httpd`](options.html#opt-services.httpd.enable)

- The `security.acme.directory` option has been replaced by a read-only `security.acme.certs.<cert>.directory` option for each certificate you define. This will be a subdirectory of `/var/lib/acme`. You can use this read-only option to figure out where the certificates are stored for a specific certificate. For example, the `services.nginx.virtualhosts.<name>.enableACME` option will use this directory option to find the certs for the virtual host.

  `security.acme.preDelay` and `security.acme.activationDelay` options have been removed. To execute a service before certificates are provisioned or renewed add a `RequiredBy=acme-${cert}.service` to any service.

  Furthermore, the acme module will not automatically add a dependency on `lighttpd.service` anymore. If you are using certificates provided by letsencrypt for lighttpd, then you should depend on the certificate service `acme-${cert}.service>` manually.

  For nginx, the dependencies are still automatically managed when `services.nginx.virtualhosts.<name>.enableACME` is enabled just like before. What changed is that nginx now directly depends on the specific certificates that it needs, instead of depending on the catch-all `acme-certificates.target`. This target unit was also removed from the codebase. This will mean nginx will no longer depend on certificates it isn't explicitly managing and fixes a bug with certificate renewal ordering racing with nginx restarting which could lead to nginx getting in a broken state as described at [NixOS/nixpkgs\#60180](https://github.com/NixOS/nixpkgs/issues/60180).

- The old deprecated `emacs` package sets have been dropped. What used to be called `emacsPackagesNg` is now called `emacsPackages`.

- `services.xserver.desktopManager.xterm` is now disabled by default if `stateVersion` is 19.09 or higher. Previously the xterm desktopManager was enabled when xserver was enabled, but it isn't useful for all people so it didn't make sense to have any desktopManager enabled default.

- The WeeChat plugin `pkgs.weechatScripts.weechat-xmpp` has been removed as it doesn't receive any updates from upstream and depends on outdated Python2-based modules.

- Old unsupported versions (`logstash5`, `kibana5`, `filebeat5`, `heartbeat5`, `metricbeat5`, `packetbeat5`) of the ELK-stack and Elastic beats have been removed.

- For NixOS 19.03, both Prometheus 1 and 2 were available to allow for a seamless transition from version 1 to 2 with existing setups. Because Prometheus 1 is no longer developed, it was removed. Prometheus 2 is now configured with `services.prometheus`.

- Citrix Receiver (`citrix_receiver`) has been dropped in favor of Citrix Workspace (`citrix_workspace`).

- The `services.gitlab` module has had its literal secret options (`services.gitlab.smtp.password`, `services.gitlab.databasePassword`, `services.gitlab.initialRootPassword`, `services.gitlab.secrets.secret`, `services.gitlab.secrets.db`, `services.gitlab.secrets.otp` and `services.gitlab.secrets.jws`) replaced by file-based versions (`services.gitlab.smtp.passwordFile`, `services.gitlab.databasePasswordFile`, `services.gitlab.initialRootPasswordFile`, `services.gitlab.secrets.secretFile`, `services.gitlab.secrets.dbFile`, `services.gitlab.secrets.otpFile` and `services.gitlab.secrets.jwsFile`). This was done so that secrets aren't stored in the world-readable nix store, but means that for each option you'll have to create a file with the same exact string, add "File" to the end of the option name, and change the definition to a string pointing to the corresponding file; e.g. `services.gitlab.databasePassword = "supersecurepassword"` becomes `services.gitlab.databasePasswordFile = "/path/to/secret_file"` where the file `secret_file` contains the string `supersecurepassword`.