Re: [PATCH 0/5] allow creation of users/groups before rootfs creation

["Schaffner, Tobias" <tobias.schaffner@siemens.com>]

On 25.01.23 17:29, Schild, Henning (T CED SES-DE) wrote:
> Am Wed, 25 Jan 2023 14:44:40 +0100
> schrieb Gylstorff Quirin <quirin.gylstorff@siemens.com>:
> 
>> On 1/25/23 14:29, Henning Schild wrote:
>>> Am Wed, 25 Jan 2023 10:01:51 +0100
>>> schrieb "T. Schaffner" <tobias.schaffner@siemens.com>:
>>>    
>>>> From: Tobias Schaffner <tobias.schaffner@siemens.com>
>>>>
>>>> This patch series will allow to specify a `pre` flag for the USER_
>>>> and GROUP_ bitbake variables. If this flag is set to `true` the
>>>> given user or group will be created in the rootfs configuration
>>>> step instead of on rootfs postprocessing. This is helpful when a
>>>> specific id should be used which would otherwise be picked by a
>>>> user or group created by one of the installed packages.
>>>
>>> While i do understand the reason i am not sure how relevant that is.
>>> Why would anything only function with a fixed ID? Whoever provided
>>> that thing should maybe fix it.
>>
>> Specific IDs are necessary for Updating an A/B rootfs system with a
>> persistent partition. In this case you do not want to change any IDs
>> as this can lead to wrong file permissions.
> 
> I see, that is much more understandable. It also goes into the
> reproducible build direction.
> But if that is the case the solution does not seem to be good enough
> because it only considers users/groups created by isar. Not the ones
> created by installing debian packages. Where the order could be
> potentially random. Say you DEBIAN_DEPENDS or IMAGE_PREINSTALL "ftpd
> wwwd" which will craete users "ftp www" where the two deamons do not
> have any dep on each other and apt-get could install them in any order.
> That order might in reality not change too often but it could i.e. when
> you move from debian11 to debian12 or when you bring the third (or
> 10th) user-adding package into your new firmware.

Thanks for the review!

This series is not about reproducible builds. The IDs of the users and
groups that are created by debian packages are expected to change
between _image_ versions. So we expect these IDs to be different after
a swupdate.

For reproducible builds it is important that the ordering of installed
packages and their dependencies stay the same but that is a different
story. I expect the ordering algorithm for a specific set of packages
including dependencies to be deterministic but would have to look into
that in detail.

Still, if somebody had a requirement that a user or group of a package
(e.g. ftp or www) stays the same, one could use this change to create
the user beforehand and pin its id using this change.

> So what you maybe really want is giving isar an /etc/passwd /etc/group
> pair. Every new firmware is build with the given layer code and that
> file-pair from the first release. Where you inject those files between
> bootstrap and install ... hoping that bootstrap will always be the same.
> Maybe one can inject before bootstrap ... or write a postproc function
> that will find all different ids and all files and fix up. Or at least
> start with an assertion in postproc that looks at the old database.

Care that just adding /etc/passwd and /etc/group might not be enough but
you would have to handle the side effects of a useradd/groupadd call
properly (E.g. creating the home if set). And I expect more things to
come up if you have a detailed look.

Take into account that the specific patch that introduces the pre flag
is small, easy to maintain and configure.

> Is the problem of uid/gid depend on install order known in the debian
> community and how do others solve it? Gentoo has moved from such
> dynamic allocation to static some years ago, probably for similar
> reasons.

I am open to discuss this with the reproducible build guys but again
IMHO this discussion belongs into another thread.

> Henning
> 
>>>
>>> So i am willing to say that this is super-niche! And it deserves a
>>> niche-solution in its layer, not a feature in Isar.
>>>
>>> You could hook in a task between bootstrap and image_install. Or you
>>> could rebuild a bootstrap package to have reserved ids. You could
>>> run "the thing" in namespaces ...
>>>
>>> So is that really relevant? Please go into detail.
>>>
>>> Whatever happens i think the python rewrite is cool. But the code
>>> may have been coming/inspired from OE ... in which case it would
>>> not be cool, because it would fork away further.
>>
>>
>> OE uses a complete different implementation than to original:
>> https://git.openembedded.org/openembedded-core/tree/meta/classes/useradd.bbclass
>>
>> see also:
>>
>> https://git.openembedded.org/openembedded-core/tree/meta-skeleton/recipes-skeleton/useradd/useradd-example.bb
>>
>>
>>
>> Quirin
>>>
>>> Henning
>>>    
>>>> A rewrite of the image-account-extension in python was done on the
>>>> way. This allows us to drop a lot of encoding and parsing code that
>>>> was used to transition to shell and therefore made it easier to
>>>> read and maintain.
>>>>
>>>> Using python functions for more complex tasks allows us the usage
>>>> of unittests. A very basic infrastructure for unittesting using
>>>> the build in python unittest and the bb.parse module was added.
>>>> This was used to test the re-implementation of the
>>>> image-account-extension as a first showcase.
>>>>
>>>> Tobias Schaffner (5):
>>>>     simplify image-account-extension
>>>>     allow creation of users/groups before rootfs creation
>>>>     create a minimal python unittest infrastructure
>>>>     add unittests for the image-account-extension
>>>>     set minimal python version in user_manual to 3.5
>>>>
>>>>    doc/user_manual.md                            |   4 +-
>>>>    meta/classes/image-account-extension.bbclass  | 391
>>>> +++++++----------- testsuite/unittests/README.md                 |
>>>> 28 ++ testsuite/unittests/bitbake.py                |  37 ++
>>>>    testsuite/unittests/rootfs.py                 |  45 ++
>>>>    .../unittests/test_image_account_extension.py | 175 ++++++++
>>>>    6 files changed, 434 insertions(+), 246 deletions(-)
>>>>    create mode 100644 testsuite/unittests/README.md
>>>>    create mode 100644 testsuite/unittests/bitbake.py
>>>>    create mode 100644 testsuite/unittests/rootfs.py
>>>>    create mode 100644
>>>> testsuite/unittests/test_image_account_extension.py
>>>>   
>>>    
>>
>>
>>
>>
>