About ===== Nixsap is a set of modules built on top of [NixOS](https://nixos.org/)/[Nixpkgs](https://nixos.org/nixpkgs/). Nixsap provides NixOS modules in the `nixsap` "namespace", e. g. `nixsap.apps.mariadb` or `nixsap.system.users`, and adds or overrides some packages in Nixpkgs. From vanila Nixpkgs, Nixsap relies only on basic services like systemd, ssh, ntpd and package set (extending and overriding it). Features ======== Plug & Play ----------- Each module under the [modules](./modules) directory is automatically available. When creating a new machine just use imports = [ ]; Each package `foo` under the [./pkgs](./pkgs) is automatically available as `pkgs.foo`. For example: pkgs/writeXML.nix => pkgs.writeXML pkgs/rdsdump/default.nix => pkgs.rdsdump You can use this techniques in your own projects. You can take out any modules or packages and put them into your project with your modifications without maintaning a fork of Nixsap. When taking modules you have to change the `nixsap` namespace to something different to avoid conflicts. Package Overlay --------------- Nixsap modules use a package overlay located in [./pkgs/default.nix](./pkgs/default.nix). It is also possible to build and install packages from this overlay independently, for example: ``` nix-build -E '(import { overlays = [ (import ./pkgs/default.nix) ]; })' -A icinga2 ``` Automatic unix user id ----------------------- To create daemon users just add their names into the list `nixsap.system.users.daemons`. List `nixsap.system.users.normal` does the same for users with login shell, and `nixsap.system.groups` for unix groups. Users and groups will automatically get their ids based on their names in a deterministic manner. See examples in the [applications directory](./modules/apps) and implementation in [modules/system/users.nix](modules/system/users.nix). This feature is used throughout `nixsap.apps`. Examples: # id icinga uid=1240920351(icinga) gid=100(users) groups=21(proc),100(users) # id pashev uid=1141737888(pashev) gid=100(users) groups=100(users),21(proc),62(systemd-journal),1061782283(sysops) # id jenkins-dumpoo uid=1201814562(jenkins-dumpoo) gid=1201814562(jenkins-dumpoo) groups=96(keys),1201814562(jenkins-dumpoo) # id mariadb uid=1213117043(mariadb) gid=1213117043(mariadb) groups=96(keys),1213117043(mariadb) Keyrings -------- [Keyrings](modules/deployment/keyrings.nix) provide a means of deploying secret files with sensitive content. It's inspired by [NixOps](https://nixos.org/nixops/) and relies on it as on reference implementation. Most applications from `nixsap.apps` recognize keys from their parameters or extract them from configuration files and automatically build their keyrings. Multi-instance applications --------------------------- For most [applications](./modules/apps) it is possible to run multiple instances of them on the same machine. Each instance may have its own home directory and user. For example `jenkins-foo` with home directory `/jenkins/foo` and user `jenkins-foo`. Not all applications allow that purely for historical reasons, and this will be fixed eventually. Design ====== Static analysis --------------- There are a handful of tools used thoughout the applications to ensure correctness at build time: `writeBashScript`, `writeXML`, `writePHPFile`. `writeBashScript` uses [shellcheck](https://www.shellcheck.net/). `writeXML` runs [xmllint](http://xmlsoft.org/xmllint.html). `writePHPFile` relies on PHP's built-in syntax checker. The objective it to do static analysis and linting for every single file _at build time_. What is wanted: configuration files for Nginx, Icinga; MySQL and PostgreSQL scripts, etc. Parametrization --------------- Everything that _can_ be used at build time should have a parameter (integer, string, path, etc.). Examples are TCP port, data directory, UNIX user. TCP port can be used for configuring firewall or HTTP proxy, data directory can be used for setting up mount points, UNIX user can be included into extra groups, etc. When we have it all parametrized we do not repeat ourselves. Parametrization also helps modularity. I. e. you can define default set of values and override only some of them in specific setups. Some applications accept only discrete set of options, in that case we should parametrize them all. Examples are memcached, php-fpm and sproxy2. Parametrization should give access to all application features. Ideally, parameters should exactly match to the application options, including their names and meanings. Examples are MariaDB and PostgreSQL. This makes documentation unnecessary, because each parameter is documented somewhere else. Almost every parameter, if it's not required by application (i. e. has a built-in default value), should have value `null` by default. If such parameter is not set, it is not passed to the application. This is twofold: more transparency because we use _application's_ defaults (not ours), and it is safer to use different versions of application, when particular options may be added or removed. Even though, if the value of parameter is required at build time, the parameter should have default value, preferably application's default. Example is MariaDB's TCP port. We need it to configure firewall, thus we define it to be 3306 by default. If application default value is known to be insecure, we should set our own, _secure_, default value. Recommendations =============== * [nixpkgs](https://nixos.org/nixpkgs/) >= 18.03 License ======= This project is under the MIT license (see [LICENSE](LICENSE)), unless stated otherwise in individual files.