Re: [PATCH] image.bbclass: set file timestamps inside the rootfs and initramfs image

["Moessbauer, Felix" <felix.moessbauer@siemens.com>]

On Mon, 2022-11-07 at 13:55 +0530, venkata.pyla@toshiba-tsip.com wrote:
> From: venkata pyla <venkata.pyla@toshiba-tsip.com>
> 
> As part of reproducible-build work, one of the problem chosen to
> solve
> is the file time stamps inside rootfs and initramfs are not identical
> between two builds.
> 
> With the help of reproducible-builds.org and their suggestions, the
> above problem can be fixed using 'SOURCE_DATE_EPOCH' variable [2].
> 
> In case of rootfs file time-stamps, set all the files and folders
> that
> are newer than 'SOURCE_DATE_EPOCH' and set it to same.

Hi,

is there a particular reason why we don't set all dates exactly to
SOURCE_DATE_EPOCH? Otherwise we might still have reproducibility issues
in case some files are provided by the sstate cache, hence have an
older timestamp. Building w/ or w/o cache should not make a difference.

Felix

> In case of initramfs, regenerate the initramfs image with
> 'SOURCE_DATE_EPOCH' variable set as the mkinitramfs script is already
> taken care of creating reproducible initramfs image when the
> variable is set in the environment[3].
> 
> The SOURCE_DATE_EPOCH variable should be set to the last modification
> of
> the git repository as explained in the documentation[2].
> 
> e.g:
> SOURCE_DATE_EPOCH=$(git log -1 --pretty=%ct)
> 
> To know more about the reproducible builds and its goals please refer
> [1].
> 
> [1] https://reproducible-builds.org/
> [2] https://reproducible-builds.org/docs/source-date-epoch/
> [3] 
> https://manpages.debian.org/bullseye/initramfs-tools-core/mkinitramfs.8.en.html#ENVIRONMENT
> 
> Signed-off-by: venkata pyla <venkata.pyla@toshiba-tsip.com>
> ---
>  meta/classes/image.bbclass | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/meta/classes/image.bbclass b/meta/classes/image.bbclass
> index ccff810..c1bb4fd 100644
> --- a/meta/classes/image.bbclass
> +++ b/meta/classes/image.bbclass
> @@ -431,6 +431,21 @@ do_rootfs_finalize() {
>              "${ROOTFSDIR}/etc/apt/sources.list.d/bootstrap.list"
>  
>          rm -f "${ROOTFSDIR}/etc/apt/sources-list"
> +
> +        # Recreate initramfs inorder to set timestamps to
> SOURCE_DATE_EPOCH
> +        # inorder to make reproducible initramfs
> +        test ! -z "${SOURCE_DATE_EPOCH}" && \
> +           SOURCE_DATE_EPOCH=${SOURCE_DATE_EPOCH} chroot
> "${ROOTFSDIR}" \
> +                  update-initramfs -u -v
> +
> +       # Set timestamp to files inside the rootfs image inorder to
> make
> +       # reproducible rootfs
> +       test ! -z "${SOURCE_DATE_EPOCH}" && \
> +           find ${ROOTFSDIR} -newermt \
> +               "$(date -d@${SOURCE_DATE_EPOCH} '+%Y-%m-%d
> %H:%M:%S')" \
> +               -printf "%y %p\n" \
> +               -exec touch '{}' -h -d@${SOURCE_DATE_EPOCH} ';'
> +
>  EOSUDO
>  }
>  addtask rootfs_finalize before do_rootfs after do_rootfs_postprocess
> -- 
> 2.20.1
> 
>