wic: Add --embed-rootfs argument

This option adds the content of a rootfs on a specific location on the
rootfs.

It is very useful for making a partition that contains the rootfs for a
host and a target Eg:

/ -> Roofs for the host
/export/ -> Rootfs for the target (which will netboot)

Although today we support making a partition for "/export" this might
not be compatible with some upgrade systems, or we might be limited by
the number of partitions.

With this patch we can use something like:

part / --source rootfs --embed-rootfs target-image /export --embed-rootfs target-image2 /export2

on the .wks file.

(From OE-Core rev: efdcf94801f6abe8e4099e324d9a3deccd8d4384)

Signed-off-by: Ricardo Ribalda Delgado <ricardo@ribalda.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/wic/help.py

@@ -980,6 +980,14 @@ DESCRIPTION
                          copies. This option only has an effect with the rootfs
                          source plugin.
 
+         --embed-rootfs: This option is specific to wic. It embeds a rootfs into
+                         the given path to the resulting image. The option
+                         contains two fields, the roofs and the path, separated
+                         by a space. The rootfs follows the same logic as the
+                         rootfs-dir argument. Multiple options can be provided
+                         in order to embed multiple rootfs. This option only has
+                         an effect with the rootfs source plugin.
+
          --extra-space: This option is specific to wic. It adds extra
                         space after the space filled by the content
                         of the partition. The final size can go

scripts/lib/wic/ksparser.py

@@ -138,6 +138,7 @@ class KickStart():
         part.add_argument('--align', type=int)
         part.add_argument('--exclude-path', nargs='+')
         part.add_argument('--include-path', nargs='+')
+        part.add_argument('--embed-rootfs', nargs=2, action='append')
         part.add_argument("--extra-space", type=sizetype)
         part.add_argument('--fsoptions', dest='fsopts')
         part.add_argument('--fstype', default='vfat',

scripts/lib/wic/partition.py

@@ -31,6 +31,7 @@ class Partition():
         self.extra_space = args.extra_space
         self.exclude_path = args.exclude_path
         self.include_path = args.include_path
+        self.embed_rootfs = args.embed_rootfs
         self.fsopts = args.fsopts
         self.fstype = args.fstype
         self.label = args.label

scripts/lib/wic/plugins/source/rootfs.py

@@ -17,6 +17,7 @@ import shutil
 import sys
 
 from oe.path import copyhardlinktree, copytree
+from pathlib import Path
 
 from wic import WicError
 from wic.pluginbase import SourcePlugin
@@ -80,7 +81,7 @@ class RootfsPlugin(SourcePlugin):
 
         new_rootfs = None
         # Handle excluded paths.
-        if part.exclude_path or part.include_path:
+        if part.exclude_path or part.include_path or part.embed_rootfs:
             # We need a new rootfs directory we can delete files from. Copy to
             # workdir.
             new_rootfs = os.path.realpath(os.path.join(cr_workdir, "rootfs%d" % part.lineno))
@@ -100,6 +101,25 @@ class RootfsPlugin(SourcePlugin):
             for path in part.include_path or []:
                 copyhardlinktree(path, new_rootfs)
 
+            for embed in part.embed_rootfs or []:
+                [embed_rootfs, path] = embed
+                #we need to remove the initial / for os.path.join to work
+                if os.path.isabs(path):
+                    path = path[1:]
+                if embed_rootfs in krootfs_dir:
+                    embed_rootfs = krootfs_dir[embed_rootfs]
+                embed_rootfs = cls.__get_rootfs_dir(embed_rootfs)
+                tar_file = os.path.realpath(os.path.join(cr_workdir, "aux.tar"))
+                tar_cmd = "%s tar cpf %s -C %s ." % (cls.__get_pseudo(native_sysroot,
+                                                     embed_rootfs), tar_file, embed_rootfs)
+                exec_native_cmd(tar_cmd, native_sysroot)
+                untar_cmd = "%s tar xf %s -C %s ." % (cls.__get_pseudo(native_sysroot, new_rootfs),
+                                                      tar_file, os.path.join(new_rootfs, path))
+                Path(os.path.join(new_rootfs, path)).mkdir(parents=True, exist_ok=True)
+                exec_native_cmd(untar_cmd, native_sysroot,
+                                cls.__get_pseudo(native_sysroot, new_rootfs))
+                os.remove(tar_file)
+
             for orig_path in part.exclude_path or []:
                 path = orig_path
                 if os.path.isabs(path):