[PATCH v2 1/2] ref-manual: add overlayfs-etc class

[PATCH v2 1/2] ref-manual: add overlayfs-etc class

[Vyacheslav Yurkov]

Signed-off-by: Vyacheslav Yurkov <uvv.mail@gmail.com>
---
 documentation/ref-manual/classes.rst | 45 ++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/documentation/ref-manual/classes.rst b/documentation/ref-manual/classes.rst
index 2c191f407..b9baa0004 100644
--- a/documentation/ref-manual/classes.rst
+++ b/documentation/ref-manual/classes.rst
@@ -1769,6 +1769,51 @@ to the unit the following::
 .. note::
 
    The class does not support the ``/etc`` directory itself, because ``systemd`` depends on it.
+   In order to get ``/etc`` in overlayfs see :ref:`overlayfs-etc <ref-classes-overlayfs-etc>` 
+
+.. _ref-classes-overlayfs-etc:
+
+``overlayfs-etc.bbclass``
+=========================
+
+In order to have the ``/etc`` directory in overlayfs a special handling at early 
+boot stage is required. The idea is to supply a custom init script that mounts
+``/etc`` before launching the actual init program, because the latter already
+requires ``/etc`` to be mounted
+
+Example usage in image recipe::
+
+   IMAGE_FEATURES += "overlayfs-etc"
+
+.. note::
+
+   This class must not be inherited directly. Use :term:`IMAGE_FEATURES` or :term:`EXTRA_IMAGE_FEATURES`
+
+Your machine configuration should define at least the device, mount point, and file system type
+you are going to use for ``overlayfs``::
+
+  OVERLAYFS_ETC_MOUNT_POINT = "/data"
+  OVERLAYFS_ETC_DEVICE = "/dev/mmcblk0p2"
+  OVERLAYFS_ETC_FSTYPE ?= "ext4"
+
+To control more mount options you should consider setting mount options
+(``defaults`` is used by default)::
+
+  OVERLAYFS_ETC_MOUNT_OPTIONS = "wsync"
+
+The class provides two options for ``/sbin/init`` generation:
+
+* The default option is to rename the original ``/sbin/init`` to ``/sbin/init.orig`` 
+  and place generated init under original name, i.e. ``/sbin/init``. It has an advantage
+  that you won't need to change any kernel parameters in order to make it work,
+  but it poses a restriction that package-management can't be used, because updating
+  init manager would remove the generated script
+* If you wish to keep original init as is, you can set::
+
+   OVERLAYFS_ETC_USE_ORIG_INIT_NAME = "0"
+
+  Then the generated init will be named ``/sbin/preinit`` and you would need to extend your
+  kernel parameters manually in your bootloader configuration.
 
 .. _ref-classes-own-mirrors:
 
-- 
2.28.0

[PATCH v2 2/2] ref-manual: document overlayfs-etc image feature

[Vyacheslav Yurkov]

Signed-off-by: Vyacheslav Yurkov <uvv.mail@gmail.com>
---
 documentation/ref-manual/features.rst | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/documentation/ref-manual/features.rst b/documentation/ref-manual/features.rst
index ded653221..57fe0cc3c 100644
--- a/documentation/ref-manual/features.rst
+++ b/documentation/ref-manual/features.rst
@@ -219,6 +219,10 @@ Here are the image features available for all images:
 -  *empty-root-password:* Sets the root password to an empty string,
    which allows logins with a blank password.
 
+-  *overlayfs-etc:* Configures the ``/etc`` directory to be in ``overlayfs``.
+   This allows to store device specific information elsewhere, especially
+   if root filesystem is configured to be read-only.
+
 -  *package-management:* Installs package management tools and preserves
    the package manager database.
 
-- 
2.28.0

Re: [docs] [PATCH v2 2/2] ref-manual: document overlayfs-etc image feature

[Michael Opdenacker]

Hi Slava,

Many thanks for the updates!

On 12/16/21 12:22 PM, Vyacheslav Yurkov wrote:
> Signed-off-by: Vyacheslav Yurkov <uvv.mail@gmail.com>
> ---
>  documentation/ref-manual/features.rst | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/documentation/ref-manual/features.rst b/documentation/ref-manual/features.rst
> index ded653221..57fe0cc3c 100644
> --- a/documentation/ref-manual/features.rst
> +++ b/documentation/ref-manual/features.rst
> @@ -219,6 +219,10 @@ Here are the image features available for all images:
>  -  *empty-root-password:* Sets the root password to an empty string,
>     which allows logins with a blank password.
>  
> +-  *overlayfs-etc:* Configures the ``/etc`` directory to be in ``overlayfs``.
> +   This allows to store device specific information elsewhere, especially
> +   if root filesystem is configured to be read-only.
> +
>  -  *package-management:* Installs package management tools and preserves
>     the package manager database.


For both patches: Reviewed-by: Michael Opdenacker
<michael.opdenacker@bootlin.com>
There were a few remaining punctuation and missing article issues (that
I probably failed to report), but I was happy to fix them!

Merged in "master-next".

Thanks again.
Michael.
-- 

Michael Opdenacker, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

Re: [docs] [PATCH v2 2/2] ref-manual: document overlayfs-etc image feature

[Vyacheslav Yurkov]

Hi Michael,
Thanks for the review and updates.

I assume it might be easier to send an update patch separately if 
needed. Or you can do fix-ups in master-next? :)

Cheers,
Slava

On 16.12.2021 17:52, Michael Opdenacker wrote:
> Hi Slava,
>
> Many thanks for the updates!
>
> On 12/16/21 12:22 PM, Vyacheslav Yurkov wrote:
>
> For both patches: Reviewed-by: Michael Opdenacker
> <michael.opdenacker@bootlin.com>
> There were a few remaining punctuation and missing article issues (that
> I probably failed to report), but I was happy to fix them!
>
> Merged in "master-next".
>
> Thanks again.
> Michael.

Re: [docs] [PATCH v2 2/2] ref-manual: document overlayfs-etc image feature

[Michael Opdenacker]

Hi Slava

On 12/17/21 7:07 AM, Vyacheslav Yurkov wrote:
> Hi Michael,
> Thanks for the review and updates.
>
> I assume it might be easier to send an update patch separately if
> needed. Or you can do fix-ups in master-next? :)


I can make fixups in master-next indeed. This way, we just have one commit.
Cheers
Michael.

-- 
Michael Opdenacker, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com