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README.md

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+# osbuild
+
+A build system for operating system images, working towards an image build
+pipeline that's more comprehensible, reproducible, and extendable.
+
+## Pipelines
+
+The build process for an image is described by a pipeline. Each
+[*stage*](/stages) in a pipeline is a program that, given some configuration,
+modifies a file system tree. Pipelines are defined as JSON files like this one:
+
+```json
+{
+  "name": "Example Image",
+  "pipeline": [
+    {
+      "name": "io.weldr.dnf",
+      "options": {
+        "packages": [ "@core", "httpd" ]
+      }
+    },
+    {
+      "name": "io.weldr.systemd",
+      "options": {
+        "enabled_services": [ "httpd" ]
+      }
+    },
+    {
+      "name": "io.weldr.qcow2",
+      "options": {
+        "target": "output.qcow2"
+      }
+    }
+  ]
+}
+```
+
+`osbuild` runs each of stages in turn, somewhat isolating them into mount and
+pid namespaces. It injects the `options` object with a `tree` key pointing to
+the file system tree and passes that to the stage via its `stdin`.
+Stages may have side effects: the `io.weldr.qcow2` stage in the above example
+packs the tree into a `qcow2` image.