Re: [RFC PATCH 2/2] recipes-core: Add recipe for base-files

[Henning Schild <henning.schild@siemens.com>]

Am Thu, 25 Feb 2021 01:06:16 -0800 (PST)
schrieb "vijaikumar....@gmail.com" <vijaikumar.kanagarajan@gmail.com>:

> On Thursday, February 25, 2021 at 1:56:02 PM UTC+5:30 Jan Kiszka
> wrote:
> 
> > On 25.02.21 06:08, vijaikumar....@gmail.com wrote:   
> > > 
> > > 
> > > On Thursday, February 25, 2021 at 9:27:51 AM UTC+5:30 
> > > vijaikumar....@gmail.com wrote: 
> > > 
> > > On Wed, Feb 24, 2021 at 5:43 PM Henning Schild 
> > > <henning...@siemens.com> wrote:   
> > > > 
> > > > Am Tue, 23 Feb 2021 14:08:29 +0530 
> > > > schrieb vijai kumar <vijaikumar....@gmail.com>: 
> > > >   
> > > > > On Sat, Feb 20, 2021 at 1:59 PM Henning Schild 
> > > > > <henning...@siemens.com> wrote:   
> > > > > > 
> > > > > > Am Sat, 20 Feb 2021 01:27:19 +0530 
> > > > > > schrieb Vijai Kumar K <Vijaikumar_...@mentor.com>: 
> > > > > >   
> > > > > > > /etc/os-release is a symlink to /usr/lib/os-release and   
> > > belongs to   
> > > > > > > the base-files package. 
> > > > > > > 
> > > > > > > ISAR has been modifying the /etc/os-release during   
> > > postprocessing   
> > > > > > > to inject custom data onto it. 
> > > > > > > 
> > > > > > > Since this file belongs to base-files, an
> > > > > > > update/reinstall   
> > > of the   
> > > > > > > package would overwrite the file with the one provided by 
> > > > > > > base-files.   
> > > > > > 
> > > > > > To some degree such an update would be right to do so. The
> > > > > >  
> > > BUILD_ID   
> > > > > > will for sure be invalidated, other custom fields might
> > > > > > still be valid though. 
> > > > > >   
> > > > > > > Instead of modifying the contents of /etc/os-release
> > > > > > > during post-processing, provide a modified base-files
> > > > > > > recipe in ISAR which provides the similar changes in
> > > > > > > os-release.   
> > > > > > 
> > > > > > I am beginning to wonder if we have to write certain bits
> > > > > > to   
> > > other   
> > > > > > files. Bits that need to go into /etc/os-release could be   
> > > appended   
> > > > > > with a hook 
> > > > > > See isar-disable-apt-cache, or we use the divert that
> > > > > > Silvano proposed.   
> > > > > 
> > > > > I have not used hooks before, but looks like it might help in
> > > > > our case. 
> > > > >   
> > > > > >   
> > > > > > > Signed-off-by: Vijai Kumar K <Vijaikumar_...@mentor.com> 
> > > > > > > --- 
> > > > > > > .../recipes-core/images/isar-image-base.bb   
> > > <http://isar-image-base.bb> | 2 +   
> > > > > > > meta/classes/image-postproc-extension.bbclass | 40   
> > > --------------   
> > > > > > > meta/classes/image.bbclass | 20 ------- 
> > > > > > > meta/recipes-core/base-files/base-files.bb   
> > > <http://base-files.bb> | 6 ++   
> > > > > > > meta/recipes-core/base-files/base-files.inc | 55 
> > > > > > > +++++++++++++++++++ 5 files changed, 63 insertions(+), 60 
> > > > > > > deletions(-) create mode 100644 
> > > > > > > meta/recipes-core/base-files/base-files.bb   
> > > <http://base-files.bb> create mode 100644   
> > > > > > > meta/recipes-core/base-files/base-files.inc 
> > > > > > > 
> > > > > > > diff --git   
> > > a/meta-isar/recipes-core/images/isar-image-base.bb 
> > > <http://isar-image-base.bb>   
> > > > > > > b/meta-isar/recipes-core/images/isar-image-base.bb   
> > > <http://isar-image-base.bb> index   
> > > > > > > b381d85..4aa7e66 100644 --- 
> > > > > > > a/meta-isar/recipes-core/images/isar-image-base.bb   
> > > <http://isar-image-base.bb> +++   
> > > > > > > b/meta-isar/recipes-core/images/isar-image-base.bb   
> > > <http://isar-image-base.bb> @@ -11,3 +11,5   
> > > > > > > @@ LIC_FILES_CHKSUM = 
> > > > > > >   
> > > "file://${LAYERDIR_core}/licenses/COPYING.GPLv2;md5=751419260 PV
> > > =   
> > > > > > > "1.0" inherit image 
> > > > > > > + 
> > > > > > > +IMAGE_INSTALL += "base-files" 
> > > > > > > diff --git
> > > > > > > a/meta/classes/image-postproc-extension.bbclass
> > > > > > > b/meta/classes/image-postproc-extension.bbclass index
> > > > > > > 3f00c21..22c6a95 100644 ---
> > > > > > > a/meta/classes/image-postproc-extension.bbclass +++
> > > > > > > b/meta/classes/image-postproc-extension.bbclass @@ -1,38
> > > > > > >  
> > > +1,6 @@   
> > > > > > > # This software is a part of ISAR. 
> > > > > > > # Copyright (C) Siemens AG, 2019 
> > > > > > > 
> > > > > > > -update_etc_os_release() { 
> > > > > > > - OS_RELEASE_BUILD_ID="" 
> > > > > > > - OS_RELEASE_VARIANT="" 
> > > > > > > - OS_RELEASE_VARIANT_VERSION="" 
> > > > > > > - while true; do 
> > > > > > > - case "$1" in 
> > > > > > > - --build-id) OS_RELEASE_BUILD_ID=$2; shift ;; 
> > > > > > > - --variant) OS_RELEASE_VARIANT=$2; shift ;; 
> > > > > > > - --version) OS_RELEASE_VARIANT_VERSION=$2; shift ;; 
> > > > > > > - -*) bbfatal "$0: invalid option specified: $1" ;; 
> > > > > > > - *) break ;; 
> > > > > > > - esac 
> > > > > > > - shift 
> > > > > > > - done 
> > > > > > > - 
> > > > > > > - if [ -n "${OS_RELEASE_BUILD_ID}" ]; then 
> > > > > > > - sudo sed -i '/^BUILD_ID=.*/d' 
> > > > > > > '${IMAGE_ROOTFS}/etc/os-release' 
> > > > > > > - echo "BUILD_ID=\"${OS_RELEASE_BUILD_ID}\"" | \ 
> > > > > > > - sudo tee -a '${IMAGE_ROOTFS}/etc/os-release' 
> > > > > > > - fi 
> > > > > > > - if [ -n "${OS_RELEASE_VARIANT}" ]; then 
> > > > > > > - sudo sed -i '/^VARIANT=.*/d' 
> > > > > > > '${IMAGE_ROOTFS}/etc/os-release' 
> > > > > > > - echo "VARIANT=\"${OS_RELEASE_VARIANT}\"" | \ 
> > > > > > > - sudo tee -a '${IMAGE_ROOTFS}/etc/os-release' 
> > > > > > > - fi 
> > > > > > > - if [ -n "${OS_RELEASE_VARIANT_VERSION}" ]; then 
> > > > > > > - sudo sed -i '/^ISAR_IMAGE_VERSION=.*/d' 
> > > > > > > '${IMAGE_ROOTFS}/etc/os-release' 
> > > > > > > - echo "VARIANT_VERSION=\"${PV}\"" | \ 
> > > > > > > - sudo tee -a '${IMAGE_ROOTFS}/etc/os-release' 
> > > > > > > - fi 
> > > > > > > -}   
> > > > > > 
> > > > > > This is in the image for a good reason, it can not be part
> > > > > > of a package, otherwise it would already be and we might
> > > > > > not have that evil postprocess feature. 
> > > > > > 
> > > > > > Try a run, append a package to IMAGE_PREINSTALL, build
> > > > > > again 
> > > > > > 
> > > > > > I kind of bet that BUILD_ID will be wrong and not show your
> > > > > > new commit or "dirty"   
> > > > > 
> > > > > Yes, It is wrong. 
> > > > > 
> > > > > Since we definitely know that we are bringing in a variable 
> > > > > that changes everytime when there is a change to the source   
> > > code, we   
> > > > > could very well do do_prepare_build[nostamp]="1". 
> > > > > 
> > > > > That with some changes should solve this problem.   
> > > > 
> > > > It will mean that every change will trigger a full reinstall of
> > > > the image, many changes do that, but it sounds bad. 
> > > > 
> > > > And the false-sharing between images and multiconfigs still
> > > > remains. 
> > > > 
> > > > Try two images in one layer with differing DESCRIPTIONS and see
> > > > what happens. That would be the simple case without even
> > > > thinking mc   
> > > 
> > > So basically os-release varies based on the image built. With a 
> > > single package 
> > > like this, it is no longer possible. At anypoint we could have
> > > only one version 
> > > of the package. 
> > > 
> > > 
> > > Basically we just considered each image to be a "derivative" .
> > > Which I don't suppose 
> > > is the case, at least with upstream ISAR. 
> > >   
> > > 
> > > 
> > > Then, again, it makes me wonder if os-release is an apt place for
> > > such information. 
> > > We lose updatability with the other approach. We definitely leave
> > > one file (/etc/os-release or /usr/lib/os-release) 
> > > outdated on a dist upgrade.  
> > >   
> >
> > So far, we did not consider os-release in package-based update
> > scenarios (likely because all our updates were partition based -
> > which doesn't mean package-based will not come one day as well). If
> > we include package-based updates, os-release should be updated by a
> > package as well. 
> >
> > Our os-release modification (ISAR_RELEASE_CMD) is bound to an
> > image. An image is not a package, but we could make it depend on an
> > image-specific package carrying or generating that os-release data.
> > That package should definitely NOT be base-files. We need to divert
> > that file and keep it under our control. Obviously, if the user
> > decides to do a an upgrade of the Debian version on the device
> > without pulling a new image version package, things will really
> > divert - but that is no reasonable use case IMHO. 
> >  
> 
> I am not quite sure if I get all that. We are now talking about a new
> file in a
> new package that depends on image recipe and have it diverted? So that
> package would not be in the final image. But incase you need to
> upgrade you would
> make sure that the package is pulled by making it depend on a
> specific base-files
> package. When base-files upgrades the package would be upgraded to?

My suggestion is to not package that, just like we used to. We just put
our stuff in a file via the image postinst. We write a package
to "reserve" that file name against collision, that file will be empty
in the package, but the hook and its script will live there.

Say we had a package isar-base-files that would contain
/etc/isar-release and /etc/apt/...hook.conf -> /usr/bin/merger.sh

merger.sh: trigger on every base-files update
  for key in isar-release and key starts with "OS_":
    if key in os-release:
      update
    else
      append

Now we might write DESCRIPTION to /etc/os-release and isar-release and
BUILD_ID just to os-release ... because the latter is invalidated with
any sort of live update.
And yes you can use that to give Debian another name and that will
survive updates ... because branding is very important!

Henning

> Thanks,
> Vijai Kumar K
> 
> 
> > Jan 
> >
> > -- 
> > Siemens AG, T RDA IOT 
> > Corporate Competence Center Embedded Linux 
> >  
>