RE: [PATCH] image.bbclass: fix non-reproducible file time-stamps inside rootfs image

[<Venkata.Pyla@toshiba-tsip.com>]

>-----Original Message-----
>From: isar-users@googlegroups.com <isar-users@googlegroups.com> On Behalf
>Of Jan Kiszka
>Sent: 02 January 2023 21:03
>To: pyla venkata(ＴＳＩＰ TMIEC ODG Porting) <Venkata.Pyla@toshiba-
>tsip.com>; isar-users@googlegroups.com
>Cc: amikan@ilbers.de; henning.schild@siemens.com; hayashi kazuhiro(林 和宏
>□ＳＷＣ◯ＡＣＴ) <kazuhiro3.hayashi@toshiba.co.jp>; dinesh kumar(ＴＳＩＰ
>TMIEC ODG Porting) <dinesh.kumar@toshiba-tsip.com>
>Subject: Re: [PATCH] image.bbclass: fix non-reproducible file time-stamps inside
>rootfs image
>
>On 02.01.23 15:58, venkata.pyla@toshiba-tsip.com wrote:
>> From: venkata pyla <venkata.pyla@toshiba-tsip.com>
>>
>> As part of reproducible-build work, the rootfs images generated on
>> same source should be identical between two builds.
>>
>> In this commit it tries to solve one of the non-reproducible problem
>> i.e. the rootfs file time-stamps generated during build time are not
>> reproducible, it uses one of the solution provided in the debian
>> live-build image project (refer [1]), it fixes by finding all the
>> files/folders that are gernerated newly and set the time-stamp
>> provided by `SOURCE_DATE_EPOCH` environment variable.
>>
>> [1] https://salsa.debian.org/live-team/live-build/-/merge_requests/218
>>
>
>Just out of curiosity: How does Yocto address this?

Yocto also does similar approach as debian live-build but in yocto it set the timestamp `REPRODUCIBLE_TIMESTAMP_ROOTFS` to all the rootfs files
See the reference code https://github.com/yoctoproject/poky/blob/master/meta/classes-recipe/image.bbclass#L673
whereas in debian live-build it assumes the files from the debian packages are reproducible so only the newly changed or created files are set to the timestamp `SOURCE_DATE_EPOCH`

>
>Jan
>
>> Signed-off-by: venkata pyla <venkata.pyla@toshiba-tsip.com>
>> ---
>>  meta/classes/image.bbclass | 9 +++++++++
>>  1 file changed, 9 insertions(+)
>>
>> diff --git a/meta/classes/image.bbclass b/meta/classes/image.bbclass
>> index 813e1f3..f592a12 100644
>> --- a/meta/classes/image.bbclass
>> +++ b/meta/classes/image.bbclass
>> @@ -430,6 +430,15 @@ do_rootfs_finalize() {
>>              "${ROOTFSDIR}/etc/apt/sources.list.d/bootstrap.list"
>>
>>          rm -f "${ROOTFSDIR}/etc/apt/sources-list"
>> +
>> +        # Set same time-stamps to the newly generated file/folders in the
>> +        # rootfs image for the purpose of reproducible builds.
>> +        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
>
>--
>Siemens AG, Technology
>Competence Center Embedded Linux
>
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