stages: add org.osbuild.ostree.fillvar

Pre-populate /var directory for a given deployment.

stages/org.osbuild.ostree.fillvar

@@ -0,0 +1,124 @@
+#!/usr/bin/python3
+"""
+Pre-populate /var directory for a given stateroot.
+"""
+
+
+import contextlib
+import os
+import sys
+import subprocess
+
+import osbuild.api
+from osbuild.util import ostree
+
+
+SCHEMA = """
+"additionalProperties": false,
+"required": ["deployment"],
+"properties": {
+  "deployment": {
+    "additionalProperties": false,
+    "required": ["osname", "ref"],
+    "properties": {
+      "osname": {
+        "description": "Name of the stateroot to be used in the deployment",
+        "type": "string"
+      },
+      "ref": {
+        "description": "OStree ref to create and use for deployment",
+        "type": "string"
+      },
+      "serial": {
+        "description": "The deployment serial (usually '0')",
+        "type": "number",
+        "default": 0
+      }
+    }
+  }
+}
+"""
+
+
+class MountGuard(contextlib.AbstractContextManager):
+    def __init__(self):
+        self.mounts = []
+
+    def mount(self, source, target, bind=True, ro=False, mode="0755"):
+        options = []
+        if bind:
+            options += ["bind"]
+        if ro:
+            options += ["ro"]
+        if mode:
+            options += [mode]
+
+        args = ["--make-private"]
+        if options:
+            args += ["-o", ",".join(options)]
+
+        subprocess.run(["mount"] + args + [source, target], check=True)
+        self.mounts += [{"source": source, "target": target}]
+
+        subprocess.run(["mount"] + args + [source, target], check=True)
+
+    def unmount(self):
+
+        while self.mounts:
+            mount = self.mounts.pop()  # FILO: get the last mount
+            target = mount["target"]
+            subprocess.run(["umount", "--lazy", target],
+                           check=True)
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self.unmount()
+
+
+def populate_var(sysroot):
+    # Like anaconda[1] and Fedora CoreOS dracut[2]
+    # [1] pyanaconda/payload/rpmostreepayload.py
+    # [2] ignition-ostree-populate-var.sh
+
+    for target in ('lib', 'log'):
+        os.makedirs(f"{sysroot}/var/{target}", exist_ok=True)
+
+    for target in ('home', 'roothome', 'lib/rpm', 'opt', 'srv',
+                   'usrlocal', 'mnt', 'media', 'spool', 'spool/mail'):
+
+        if os.path.exists(f"{sysroot}/var/{target}"):
+            continue
+
+        res = subprocess.run(["systemd-tmpfiles", "--create", "--boot",
+                              "--root=" + sysroot,
+                              "--prefix=/var/" + target],
+                             encoding="utf-8",
+                             stdout=sys.stderr,
+                             check=False)
+
+        # According to systemd-tmpfiles(8), the return values are:
+        #  0 → success
+        # 65 → so some lines had to be ignored, but no other errors
+        # 73 → configuration ok, but could not be created
+        #  1 → other error
+        if res.returncode not in [0, 65]:
+            raise RuntimeError(f"Failed to provision /var/{target}")
+
+
+def main(tree, options):
+    dep = options["deployment"]
+    osname = dep["osname"]
+    ref = dep["ref"]
+    serial = dep.get("serial", 0)
+
+    deployment = ostree.deployment_path(tree, osname, ref, serial)
+
+    with MountGuard() as mgr:
+        mgr.mount(f"{deployment}/var", f"{deployment}/var")
+        populate_var(deployment)
+
+
+if __name__ == '__main__':
+    stage_args = osbuild.api.arguments()
+    r = main(stage_args["tree"],
+             stage_args["options"])
+    sys.exit(r)