Fix #363: Omit /home/user when calculating system image size (#389)

* The system image size is now calculated as: root size - home size.
* New function in `pmb/helpers/other.py`: `folder_size()`, with a
  testcase.
* Instead of copying everything to the system image folder, and
  deleting the home folder afterwards, do not copy the home folder
  in the first place.
* Added `pmbootstrap -s` to skip generating the initramfs for faster
  debugging.
* Set the default value in the "are you sure, that your partition has
  at least..." to "y", so we can run `yes '' | pmbootstrap install`
  to make it run through the whole installation process.
* Increase full size to 120%, boot partition gets 15 MB free space now

pmb/install/install.py

@@ -26,65 +26,78 @@ import pmb.chroot.other
 import pmb.chroot.initfs
 import pmb.config
 import pmb.helpers.run
+import pmb.helpers.other
 import pmb.install.blockdevice
 import pmb.install
 
 
 def mount_device_rootfs(args):
     # Mount the device rootfs
-    logging.info("(native) copy rootfs_" + args.device + " to" +
-                 " /mnt/install/")
     mountpoint = "/mnt/rootfs_" + args.device
     pmb.helpers.mount.bind(args, args.work + "/chroot_rootfs_" + args.device,
                            args.work + "/chroot_native" + mountpoint)
     return mountpoint
 
 
-def get_chroot_size(args):
+def get_subpartitions_size(args):
+    """
+    Calculate the size of the whole image and boot subpartition.
+
+    :returns: (full, boot) the size of the full image and boot
+              partition as integer in bytes
+    """
+    # Calculate required sizes first
+    chroot = args.work + "/chroot_rootfs_" + args.device
+    root = pmb.helpers.other.folder_size(args, chroot)
+    boot = pmb.helpers.other.folder_size(args, chroot + "/boot")
+    home = pmb.helpers.other.folder_size(args, chroot + "/home")
+
+    # The home folder gets omitted when copying the rootfs to
+    # /dev/installp2
+    full = root - home
+
+    # Add some free space, see also:
+    # https://github.com/postmarketOS/pmbootstrap/pull/336
+    full *= 1.20
+    boot += 15 * 1024 * 1024
+    return (full, boot)
+
+
+def copy_files_from_chroot(args):
+    """
+    Copy all files from the rootfs chroot to /mnt/install, except
+    for the home folder (because /home will contain some empty
+    mountpoint folders).
+    """
     # Mount the device rootfs
+    logging.info("(native) copy rootfs_" + args.device + " to" +
+                 " /mnt/install/")
     mountpoint = mount_device_rootfs(args)
+    mountpoint_outside = args.work + "/chroot_native" + mountpoint
 
-    # Run the du command
-    result = pmb.chroot.root(args, ["sh", "-c", "du -cm . | grep total$ | cut -f1"],
-                             working_dir=mountpoint, return_stdout=True)
-    return result
-
-
-def get_chroot_boot_size(args):
-    # Mount the device rootfs
-    mountpoint = mount_device_rootfs(args)
-
-    # Run the du command
-    result = pmb.chroot.root(args, ["sh", "-c", "du -cm ./boot | grep total$ | cut -f1"],
-                             working_dir=mountpoint, return_stdout=True)
-    return result
-
-
-def copy_files(args):
-    # Mount the device rootfs
-    mountpoint = mount_device_rootfs(args)
-
-    # Get all folders inside the device rootfs
+    # Get all folders inside the device rootfs (except for home)
     folders = []
-    for path in glob.glob(args.work + "/chroot_native" + mountpoint + "/*"):
+    for path in glob.glob(mountpoint_outside + "/*"):
+        if path.endswith("/home"):
+            continue
         folders += [os.path.basename(path)]
 
     # Run the copy command
     pmb.chroot.root(args, ["cp", "-a"] + folders + ["/mnt/install/"],
                     working_dir=mountpoint)
 
-# copy over keys and delete unneded mount folders
 
-
-def fix_mount_folders(args):
-    # copy over keys
-    rootfs = args.work + "/chroot_native/mnt/install/"
+def copy_files_other(args):
+    """
+    Copy over keys, create /home/user.
+    """
+    # Copy over keys
+    rootfs = args.work + "/chroot_native/mnt/install"
     for key in glob.glob(args.work + "/config_apk_keys/*.pub"):
         pmb.helpers.run.root(args, ["cp", key, rootfs + "/etc/apk/keys/"])
 
-    # delete everything (-> empty mount folders) in /home/user
-    pmb.helpers.run.root(args, ["rm", "-r", rootfs + "/home/user"])
-    pmb.helpers.run.root(args, ["mkdir", rootfs + "/home/user"])
+    # Create /home/user
+    pmb.helpers.run.root(args, ["mkdir", "-p", rootfs + "/home/user"])
     pmb.helpers.run.root(args, ["chown", pmb.config.chroot_uid_user,
                                 rootfs + "/home/user"])
 
@@ -153,27 +166,24 @@ def install(args):
     for flavor in pmb.chroot.other.kernel_flavors_installed(args, suffix):
         pmb.chroot.initfs.build(args, flavor, suffix)
 
-    size_image = str(int(float(get_chroot_size(args)) * 1.15)) + "M"
-    size_boot = str(int(get_chroot_boot_size(args)) + 5) + "M"
-
     # Set the user password
     set_user_password(args)
 
     # Partition and fill image/sdcard
     logging.info("*** (3/5) PREPARE INSTALL BLOCKDEVICE ***")
     pmb.chroot.shutdown(args, True)
+    (size_image, size_boot) = get_subpartitions_size(args)
     pmb.install.blockdevice.create(args, size_image)
     pmb.install.partition(args, size_boot)
     pmb.install.format(args)
 
     # Just copy all the files
     logging.info("*** (4/5) FILL INSTALL BLOCKDEVICE ***")
-    copy_files(args)
-    fix_mount_folders(args)
+    copy_files_from_chroot(args)
+    copy_files_other(args)
 
     # If user has a ssh pubkey, offer to copy it to device
     copy_ssh_key(args)
-
     pmb.chroot.shutdown(args, True)
 
     # Convert system image to sparse using img2simg