[PATCH v2] wic: add option to specify the diskid

[PATCH v2] wic: add option to specify the diskid

[Steffen Greber]

This adds a feature to specify the disk ID when creating a disk with
the wic tool. This is useful when using the DOS partition scheme and
booting with root=PARTUUID=<partuuid>. In DOS partitions, the partition
ID is <diskid>-<partition-number>, so it makes sense to let the user
define the disk ID.

You can specify it in the kickstart file using the --diskid argument
to the bootloader command. The value can be given in decimal or
hexadecimal format (e.g. 3735928559 or 0xdeadbeef). If omitted, the
previous behaviour does not change.

Signed-off-by: Steffen Greber <sgreber@lilafast.org>

Add WIC tests and support setting GPT diskid

Add unit tests for wic.py to cover previous patch review.
Also extend implementation to allow defining the diskid for GPT partitions.

CC: Ross Burton <Ross.Burton@arm.com>
Signed-off-by: Steffen Greber <sgreber@lilafast.org>
---
changes in v2:
- add diskid support for gpt tabels
- add wic tests as requested by the reviewer
---
 meta/lib/oeqa/selftest/cases/wic.py      | 36 ++++++++++++++++++++++++
 scripts/lib/wic/ksparser.py              | 20 +++++++++++++
 scripts/lib/wic/plugins/imager/direct.py | 20 +++++++------
 3 files changed, 68 insertions(+), 8 deletions(-)

diff --git a/meta/lib/oeqa/selftest/cases/wic.py b/meta/lib/oeqa/selftest/cases/wic.py
index bb4ac23ebf..d7a9b14658 100644
--- a/meta/lib/oeqa/selftest/cases/wic.py
+++ b/meta/lib/oeqa/selftest/cases/wic.py
@@ -1905,6 +1905,42 @@ INITRAMFS_IMAGE = "core-image-initramfs-boot"
             self.assertIn("Source parameter 'fill' only works with the '--fixed-size' option, exiting.", result.output)
             self.assertNotEqual(0, result.status)
 
+    def test_diskid_on_msdos_partition(self):
+        """Test diksid on msdos partions"""
+        img = 'core-image-minimal'
+        diskid = "0xdeadbbef"
+        with NamedTemporaryFile("w", suffix=".wks") as wks:
+            wks.writelines(['bootloader --ptable msdos --diskid %s\n' % diskid,
+                            'part /boot --size=100M --active --fstype=ext4 --label boot\n'
+                            'part /     --source rootfs      --fstype=ext4 --label root\n'])
+            wks.flush()
+            cmd = "wic create %s -e %s -o %s" % (wks.name, img, self.resultdir)
+            runCmd(cmd)
+            wksname = os.path.splitext(os.path.basename(wks.name))[0]
+            out = glob(os.path.join(self.resultdir, "%s-*direct" % wksname))
+            self.assertEqual(1, len(out))
+            sysroot = get_bb_var('RECIPE_SYSROOT_NATIVE', 'wic-tools')
+            result = runCmd("%s/usr/sbin/sfdisk -l %s | grep 'Disk identifier:'" % (sysroot, out[0]))
+            self.assertEqual("Disk identifier: %s" % diskid.lower(), result.output)
+
+    def test_diskid_on_gpt_partition(self):
+        """Test diksid on gpt partions"""
+        img = 'core-image-minimal'
+        diskid = "deadbeef-cafe-babe-f00d-cec2ea4eface"
+        with NamedTemporaryFile("w", suffix=".wks") as wks:
+            wks.writelines(['bootloader --ptable gpt --diskid %s\n' % diskid,
+                            'part /boot --size=100M --active --fstype=ext4 --label boot\n'
+                            'part /     --source rootfs      --fstype=ext4 --label root\n'])
+            wks.flush()
+            cmd = "wic create %s -e %s -o %s" % (wks.name, img, self.resultdir)
+            runCmd(cmd)
+            wksname = os.path.splitext(os.path.basename(wks.name))[0]
+            out = glob(os.path.join(self.resultdir, "%s-*direct" % wksname))
+            self.assertEqual(1, len(out))
+            sysroot = get_bb_var('RECIPE_SYSROOT_NATIVE', 'wic-tools')
+            result = runCmd("%s/usr/sbin/sfdisk -l %s | grep 'Disk identifier:'" % (sysroot, out[0]))
+            self.assertEqual("Disk identifier: %s" % diskid.upper(), result.output)
+
 class ModifyTests(WicTestCase):
     def test_wic_ls(self):
         """Test listing image content using 'wic ls'"""
diff --git a/scripts/lib/wic/ksparser.py b/scripts/lib/wic/ksparser.py
index a762d3b6cf..4ccd70dc55 100644
--- a/scripts/lib/wic/ksparser.py
+++ b/scripts/lib/wic/ksparser.py
@@ -16,6 +16,7 @@ import os
 import shlex
 import logging
 import re
+import uuid
 
 from argparse import ArgumentParser, ArgumentError, ArgumentTypeError
 
@@ -196,6 +197,7 @@ class KickStart():
         bootloader.add_argument('--configfile')
         bootloader.add_argument('--ptable', choices=('msdos', 'gpt', 'gpt-hybrid'),
                                 default='msdos')
+        bootloader.add_argument('--diskid')
         bootloader.add_argument('--timeout', type=int)
         bootloader.add_argument('--source')
 
@@ -296,6 +298,24 @@ class KickStart():
                             if append_var:
                                 self.bootloader.append = ' '.join(filter(None, \
                                                          (self.bootloader.append, append_var)))
+                            if parsed.diskid:
+                                if parsed.ptable == "msdos":
+                                    try:
+                                        self.bootloader.diskid = int(parsed.diskid, 0)
+                                    except ValueError:
+                                        err = "with --ptbale msdos only 32bit integers " \
+                                              "are allowed for --diskid. %s could not " \
+                                              "be parsed" % self.ptable
+                                        raise KickStartError(err)
+                                else:
+                                    try:
+                                        self.bootloader.diskid = uuid.UUID(parsed.diskid)
+                                    except ValueError:
+                                        err = "with --ptable %s only valid uuids are " \
+                                              "allowed for --diskid. %s could not be " \
+                                              "parsed" % (parsed.ptable, parsed.diskid)
+                                        raise KickStartError(err)
+
                         else:
                             err = "%s:%d: more than one bootloader specified" \
                                       % (confpath, lineno)
diff --git a/scripts/lib/wic/plugins/imager/direct.py b/scripts/lib/wic/plugins/imager/direct.py
index 6e1f1c8cba..ad922cfbf1 100644
--- a/scripts/lib/wic/plugins/imager/direct.py
+++ b/scripts/lib/wic/plugins/imager/direct.py
@@ -76,7 +76,7 @@ class DirectPlugin(ImagerPlugin):
                 break
 
         image_path = self._full_path(self.workdir, self.parts[0].disk, "direct")
-        self._image = PartitionedImage(image_path, self.ptable_format,
+        self._image = PartitionedImage(image_path, self.ptable_format, self.ks.bootloader.diskid,
                                        self.parts, self.native_sysroot,
                                        options.extra_space)
 
@@ -302,7 +302,7 @@ class PartitionedImage():
     Partitioned image in a file.
     """
 
-    def __init__(self, path, ptable_format, partitions, native_sysroot=None, extra_space=0):
+    def __init__(self, path, ptable_format, disk_id, partitions, native_sysroot=None, extra_space=0):
         self.path = path  # Path to the image file
         self.numpart = 0  # Number of allocated partitions
         self.realpart = 0 # Number of partitions in the partition table
@@ -315,7 +315,16 @@ class PartitionedImage():
                           # all partitions (in bytes)
         self.ptable_format = ptable_format  # Partition table format
         # Disk system identifier
-        if os.getenv('SOURCE_DATE_EPOCH'):
+        if disk_id and ptable_format in ('gpt', 'gpt-hybrid'):
+            self.disk_guid = disk_id
+        elif os.getenv('SOURCE_DATE_EPOCH'):
+            self.disk_guid = uuid.UUID(int=int(os.getenv('SOURCE_DATE_EPOCH')))
+        else:
+            self.disk_guid = uuid.uuid4()
+
+        if disk_id and ptable_format == 'msdos':
+            self.identifier = disk_id
+        elif os.getenv('SOURCE_DATE_EPOCH'):
             self.identifier = random.Random(int(os.getenv('SOURCE_DATE_EPOCH'))).randint(1, 0xffffffff)
         else:
             self.identifier = random.SystemRandom().randint(1, 0xffffffff)
@@ -543,11 +552,6 @@ class PartitionedImage():
 
     def _write_disk_guid(self):
         if self.ptable_format in ('gpt', 'gpt-hybrid'):
-            if os.getenv('SOURCE_DATE_EPOCH'):
-                self.disk_guid = uuid.UUID(int=int(os.getenv('SOURCE_DATE_EPOCH')))
-            else:
-                self.disk_guid = uuid.uuid4()
-
             logger.debug("Set disk guid %s", self.disk_guid)
             sfdisk_cmd = "sfdisk --sector-size %s --disk-id %s %s" % \
                         (self.sector_size, self.path, self.disk_guid)

Re: [OE-core] [PATCH v2] wic: add option to specify the diskid

[Mathieu Dubois-Briand]

On Mon Oct 27, 2025 at 3:46 PM CET, Steffen Greber wrote:
> This adds a feature to specify the disk ID when creating a disk with
> the wic tool. This is useful when using the DOS partition scheme and
> booting with root=PARTUUID=<partuuid>. In DOS partitions, the partition
> ID is <diskid>-<partition-number>, so it makes sense to let the user
> define the disk ID.
>
> You can specify it in the kickstart file using the --diskid argument
> to the bootloader command. The value can be given in decimal or
> hexadecimal format (e.g. 3735928559 or 0xdeadbeef). If omitted, the
> previous behaviour does not change.
>
> Signed-off-by: Steffen Greber <sgreber@lilafast.org>
>
> Add WIC tests and support setting GPT diskid
>
> Add unit tests for wic.py to cover previous patch review.
> Also extend implementation to allow defining the diskid for GPT partitions.
>
> CC: Ross Burton <Ross.Burton@arm.com>
> Signed-off-by: Steffen Greber <sgreber@lilafast.org>
> ---

Hi Steffen,

Thanks for the v2, but it looks like the v1 was merged. Can you rebase
on master and make a separate patch for tests and GPT partitions
handling?

Thanks,
Mathieu

-- 
Mathieu Dubois-Briand, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

Re: [PATCH v2] wic: add option to specify the diskid

[Steffen Greber]

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Sure, I can do. Btw I am asking myself if I should also add some documentation? Or will this be done by someone else?

regards

Steffen

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Re: [OE-core] [PATCH v2] wic: add option to specify the diskid

[Alexander Kanavin]

On Mon, 27 Oct 2025 at 18:58, Steffen Greber via
lists.openembedded.org <sgreber=lilafast.org@lists.openembedded.org>
wrote:
> Sure, I can do. Btw I am asking myself if I should also add some documentation? Or will this be done by someone else?

It's better if you can send a patch for the docs as well.

Alex