[OE-core] [PATCH v3 07/11] image_types.bbclass: improve cpio image reproducibility

[Bystricky, Juro]

> 
> Is it useful to keep the option using cpio from the host? Why not
> always use cpio-native?
> 

I guess it is a judgement call which tools to build and which tools to use from the host. Not building tools which are guaranteed to be on the host saves build time. Also, the need for cpio-native with the reproducible options it is going to be fairly rare.

> >    do_image_cpio[depends] += "cpio-replacement-
> native:do_populate_sysroot"
> >    EXTRANATIVEPATH += "cpio-native"
> >
> > 2. Provide a way to pass custom arguments to cpio. This is done via
> >    a new variable IMAGE_CMD_CPIO. For binary reproducible cpio archives
> >    one needs to set (in local.conf)
> >
> >    IMAGE_CMD_CPIO = "cpio --ignore-devno --reproducible "
> >
> > 3. A symlink is created as part of the image. Here we make sure it gets
> the
> >    timestamps (mtime) based on the timestamp of the symlink target,
> rather than
> >    the timestamp corresponding to the build time.
> >
> > Signed-off-by: Juro Bystricky <juro.bystricky at intel.com>
> > ---
> >  meta/classes/image_types.bbclass | 14 ++++++++++++--
> >  1 file changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/meta/classes/image_types.bbclass
> b/meta/classes/image_types.bbclass
> > index e0368c7..50d0c07 100644
> > --- a/meta/classes/image_types.bbclass
> > +++ b/meta/classes/image_types.bbclass
> > @@ -122,9 +122,17 @@ IMAGE_CMD_TAR ?= "tar"
> >  # ignore return code 1 "file changed as we read it" as other tasks(e.g.
> do_image_wic) may be hardlinking rootfs
> >  IMAGE_CMD_tar = "${IMAGE_CMD_TAR} -cf
> ${IMGDEPLOYDIR}/${IMAGE_NAME}${IMAGE_NAME_SUFFIX}.tar -C ${IMAGE_ROOTFS} .
> || [ $? -eq 1 ]"
> >
> > +# By default, cpio from the host is used, which can be quite old. If
> > +# you need special parameters (like --ignore-devno --reproducible) which
> are only
> > +# supported by GNU cpio upstream >= 2.12, then override that default:
> > +# IMAGE_CMD_CPIO = "cpio --ignore-devno"
> > +# do_image_cpio[depends] += "cpio-replacement-
> native:do_populate_sysroot"
> > +# EXTRANATIVEPATH += "cpio-native"
> > +
> > +IMAGE_CMD_CPIO ?= "cpio"
> >  do_image_cpio[cleandirs] += "${WORKDIR}/cpio_append"
> >  IMAGE_CMD_cpio () {
> > -       (cd ${IMAGE_ROOTFS} && find . | cpio -o -H newc
> >${IMGDEPLOYDIR}/${IMAGE_NAME}${IMAGE_NAME_SUFFIX}.cpio)
> > +       (cd ${IMAGE_ROOTFS} && find . | ${IMAGE_CMD_CPIO} -o -H newc -v
> >${IMGDEPLOYDIR}/${IMAGE_NAME}${IMAGE_NAME_SUFFIX}.cpio)
> >         # We only need the /init symlink if we're building the real
> >         # image. The -dbg image doesn't need it! By being clever
> >         # about this we also avoid 'touch' below failing, as it
> > @@ -134,10 +142,12 @@ IMAGE_CMD_cpio () {
> >                 if [ ! -L ${IMAGE_ROOTFS}/init ] && [ ! -e
> ${IMAGE_ROOTFS}/init ]; then
> >                         if [ -L ${IMAGE_ROOTFS}/sbin/init ] || [ -e
> ${IMAGE_ROOTFS}/sbin/init ]; then
> >                                 ln -sf /sbin/init
> ${WORKDIR}/cpio_append/init
> > +                               # improve reproducibility: set the link
> mtime to be the same as the target
> > +                               touch -h -r ${IMAGE_ROOTFS}/sbin/init
> ${WORKDIR}/cpio_append/init
> >                         else
> >                                 touch ${WORKDIR}/cpio_append/init
> >                         fi
> > -                       (cd  ${WORKDIR}/cpio_append && echo ./init | cpio
> -oA -H newc -F ${IMGDEPLOYDIR}/${IMAGE_NAME}${IMAGE_NAME_SUFFIX}.cpio)
> > +                       (cd  ${WORKDIR}/cpio_append && echo ./init |
> ${IMAGE_CMD_CPIO} -oA -H newc -F
> ${IMGDEPLOYDIR}/${IMAGE_NAME}${IMAGE_NAME_SUFFIX}.cpio)
> >                 fi
> >         fi
> >  }
> > --
> > 2.7.4
> >
> > --
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