pmb/netboot: new feature (MR 2064)

pmbootstrap netboot command exposes the generated vendor-codename.img
rootfs through nbd interface so that device can mount it and boot
postmarketOS without having any storage medium at all.

Co-authored-by: Luca Weiss <luca@z3ntu.xyz>

pmb/chroot/zap.py

@@ -15,7 +15,7 @@ import pmb.parse.apkindex
 
 def zap(args, confirm=True, dry=False, pkgs_local=False, http=False,
         pkgs_local_mismatch=False, pkgs_online_mismatch=False, distfiles=False,
-        rust=False):
+        rust=False, netboot=False):
     """
     Shutdown everything inside the chroots (e.g. distccd, adb), umount
     everything and then safely remove folders from the work-directory.
@@ -29,6 +29,7 @@ def zap(args, confirm=True, dry=False, pkgs_local=False, http=False,
         downloaded from mirrors (e.g. from Alpine)
     :param distfiles: Clear the downloaded files cache
     :param rust: Remove rust related caches
+    :param netboot: Remove images for netboot
 
     NOTE: This function gets called in pmb/config/init.py, with only args.work
     and args.device set!
@@ -65,6 +66,8 @@ def zap(args, confirm=True, dry=False, pkgs_local=False, http=False,
         patterns += ["cache_distfiles"]
     if rust:
         patterns += ["cache_rust"]
+    if netboot:
+        patterns += ["images_netboot"]
 
     # Delete everything matching the patterns
     for pattern in patterns:

pmb/config/__init__.py

@@ -210,6 +210,7 @@ chroot_mount_bind = {
     "$WORK/cache_rust": "/mnt/pmbootstrap-rust",
     "$WORK/config_abuild": "/mnt/pmbootstrap-abuild-config",
     "$WORK/config_apk_keys": "/etc/apk/keys",
+    "$WORK/images_netboot": "/mnt/pmbootstrap-netboot",
     "$WORK/packages/$CHANNEL": "/mnt/pmbootstrap-packages",
 }
 

pmb/helpers/frontend.py

@@ -29,6 +29,7 @@ import pmb.helpers.aportupgrade
 import pmb.helpers.status
 import pmb.install
 import pmb.install.blockdevice
+import pmb.netboot
 import pmb.parse
 import pmb.qemu
 
@@ -140,6 +141,11 @@ def sideload(args):
                           args.packages)
 
 
+def netboot(args):
+    if args.action_netboot == "serve":
+        pmb.netboot.start_nbd_server(args)
+
+
 def chroot(args):
     # Suffix
     suffix = _parse_suffix(args)
@@ -543,7 +549,7 @@ def zap(args):
                    distfiles=args.distfiles, pkgs_local=args.pkgs_local,
                    pkgs_local_mismatch=args.pkgs_local_mismatch,
                    pkgs_online_mismatch=args.pkgs_online_mismatch,
-                   rust=args.rust)
+                   rust=args.rust, netboot=args.netboot)
 
     # Don't write the "Done" message
     pmb.helpers.logging.disable()

pmb/netboot/__init__.py

@@ -0,0 +1,68 @@
+# Copyright 2022 Mark Hargreaves, Luca Weiss
+# SPDX-License-Identifier: GPL-3.0-or-later
+import logging
+import os
+import socket
+import time
+
+import pmb.chroot.root
+import pmb.helpers.run
+
+
+def start_nbd_server(args, ip="172.16.42.2", port=9999):
+    """
+    Start nbd server in chroot_native with pmOS rootfs.
+    :param ip: IP address to serve nbd server for
+    :param port: port of nbd server
+    """
+
+    pmb.chroot.apk.install(args, ['nbd'])
+
+    chroot = f"{args.work}/chroot_native"
+
+    rootfs_path = f"/mnt/pmbootstrap-netboot/{args.device}.img"
+    if not os.path.exists(chroot + rootfs_path) or args.replace:
+        rootfs_path2 = f"/home/pmos/rootfs/{args.device}.img"
+        if not os.path.exists(chroot + rootfs_path2):
+            raise RuntimeError("The rootfs has not been generated yet, please "
+                               "run 'pmbootstrap install' first.")
+        if args.replace and not \
+                pmb.helpers.cli.confirm(args, f"Are you sure you want to "
+                                              f"replace the rootfs for "
+                                              f"{args.device}?"):
+            return
+        pmb.chroot.root(args, ["cp", rootfs_path2, rootfs_path])
+        logging.info(f"NOTE: Copied device image to {args.work}"
+                     f"/images_netboot/. The image will persist \"pmbootstrap "
+                     f"zap\" for your convenience. Use \"pmbootstrap netboot "
+                     f"serve --help\" for more options.")
+
+    logging.info(f"Running nbd server for {args.device} on {ip} port {port}.")
+
+    while True:
+        logging.info("Waiting for postmarketOS device to appear...")
+
+        # Try to bind to the IP ourselves before handing it to nbd-servere
+        # This is purely to improve the UX as nbd-server just quits when it
+        # cannot bind to an IP address.
+        test_socket = socket.socket()
+        while True:
+            try:
+                test_socket.bind((ip, 9998))
+            except OSError as e:
+                if e.errno != 99:  # Cannot assign requested address
+                    raise e
+                # Wait a bit before retrying
+                time.sleep(0.5)
+                continue
+            test_socket.close()
+            break
+
+        logging.info("Found postmarketOS device, serving image...")
+        pmb.chroot.root(
+            args, ["nbd-server", f"{ip}@{port}", rootfs_path, "-d"],
+            check=False, disable_timeout=True)
+        logging.info("nbd-server quit. Connection lost?")
+        # On a reboot nbd-server will quit, but the IP address sticks around
+        # for a bit longer, so wait.
+        time.sleep(5)

pmb/parse/arguments.py

@@ -508,6 +508,19 @@ def arguments_status(subparser):
     return ret
 
 
+def arguments_netboot(subparser):
+    ret = subparser.add_parser("netboot",
+                               help="launch nbd server with pmOS rootfs")
+    sub = ret.add_subparsers(dest="action_netboot")
+    sub.required = True
+
+    start = sub.add_parser("serve", help="start nbd server")
+    start.add_argument("--replace", action="store_true",
+                       help="replace stored netboot image")
+
+    return ret
+
+
 def package_completer(prefix, action, parser=None, parsed_args=None):
     args = parsed_args
     pmb.config.merge_with_args(args)
@@ -646,6 +659,7 @@ def arguments():
     arguments_kconfig(sub)
     arguments_export(sub)
     arguments_sideload(sub)
+    arguments_netboot(sub)
     arguments_flasher(sub)
     arguments_initfs(sub)
     arguments_qemu(sub)
@@ -682,6 +696,8 @@ def arguments():
                      dest="pkgs_local_mismatch",
                      help="also delete locally compiled packages without"
                      " existing aport of same version")
+    zap.add_argument("-n", "--netboot", action="store_true",
+                     help="also delete stored images for netboot")
     zap.add_argument("-o", "--pkgs-online-mismatch", action="store_true",
                      dest="pkgs_online_mismatch",
                      help="also delete outdated packages from online mirrors"