build-livefs-lxd: helper to run build-livefs inside an LXD VM

Creates (or reuses) a per-suite LXD VM, mounts the livecd-rootfs
checkout into it, waits for the VM to be ready, installs dependencies,
and runs build-livefs inside the VM — keeping the host clean.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

live-build/build-livefs-lxd

@@ -0,0 +1,126 @@
+#!/usr/bin/env python3
+
+import pathlib
+import subprocess
+import time
+
+import click
+
+
+@click.command(
+    context_settings={"ignore_unknown_options": True, "allow_extra_args": True}
+)
+@click.option("--suite", required=True, help="Ubuntu suite/series (e.g. noble)")
+@click.option(
+    "--vm-name",
+    default=None,
+    help="LXD VM name (default: livefs-builder-{suite})",
+)
+@click.argument("extra_args", nargs=-1, type=click.UNPROCESSED)
+def main(suite, vm_name, extra_args):
+    livecd_rootfs_root = pathlib.Path(__file__).resolve().parent.parent
+    vm_name = vm_name or f"livefs-builder-{suite}"
+    host_conf = (
+        pathlib.Path.home() / ".config" / "livecd-rootfs" / "build-livefs.conf"
+    )
+
+    result = subprocess.run(["lxc", "info", vm_name], capture_output=True)
+    if result.returncode != 0:
+        subprocess.run(
+            [
+                "lxc", "launch", f"ubuntu-daily:{suite}", vm_name, "--vm",
+                "--config", "limits.cpu=4",
+                "--config", "limits.memory=8GiB",
+                "--device", "root,size=100GiB",
+            ],
+            check=True,
+        )
+
+    device_info = subprocess.run(
+        ["lxc", "config", "device", "show", vm_name],
+        capture_output=True,
+        text=True,
+        check=True,
+    ).stdout
+    if "livecd-rootfs" not in device_info:
+        subprocess.run(
+            [
+                "lxc",
+                "config",
+                "device",
+                "add",
+                vm_name,
+                "livecd-rootfs",
+                "disk",
+                f"source={livecd_rootfs_root}",
+                "path=/srv/livecd-rootfs",
+            ],
+            check=True,
+        )
+
+    info = subprocess.run(
+        ["lxc", "info", vm_name], capture_output=True, text=True, check=True
+    ).stdout
+    if "Status: STOPPED" in info:
+        subprocess.run(["lxc", "start", vm_name], check=True)
+
+    for _ in range(30):
+        result = subprocess.run(
+            ["lxc", "exec", vm_name, "--", "true"], capture_output=True
+        )
+        if result.returncode == 0:
+            break
+        time.sleep(2)
+    else:
+        raise click.ClickException(f"VM {vm_name!r} did not become ready in time")
+
+    subprocess.run(
+        ["lxc", "exec", vm_name, "--", "cloud-init", "status", "--wait"], check=True
+    )
+
+    subprocess.run(
+        ["lxc", "exec", vm_name, "--", "apt-get", "install", "-y", "livecd-rootfs"],
+        check=True,
+    )
+
+    if host_conf.exists():
+        subprocess.run(
+            [
+                "lxc",
+                "exec",
+                vm_name,
+                "--",
+                "mkdir",
+                "-p",
+                "/root/.config/livecd-rootfs",
+            ],
+            check=True,
+        )
+        subprocess.run(
+            [
+                "lxc",
+                "file",
+                "push",
+                str(host_conf),
+                f"{vm_name}/root/.config/livecd-rootfs/build-livefs.conf",
+            ],
+            check=True,
+        )
+
+    subprocess.run(
+        [
+            "lxc",
+            "exec",
+            vm_name,
+            "--",
+            "/srv/livecd-rootfs/live-build/build-livefs",
+            "--suite",
+            suite,
+            *extra_args,
+        ],
+        check=True,
+    )
+
+
+if __name__ == "__main__":
+    main()