Hey Robert, may I make a suggestion? Rather than ask someone to explain the
implementation of pkg_postinst to you, why don’t you read the
implementation and ask questions about specific code where it’s unclear
what or why.

Alex

On Fri 17. Dec 2021 at 16.35, Robert P. J. Day <rpjday@crashcourse.ca>
wrote:

>
>   i know i once asked about this (probably on oe-core list), but i was
> reading this section in the dev manual,
>
>
> http://docs.yoctoproject.org/dev-manual/common-tasks.html#post-installation-scripts
>
> and i think it needs work, or i just have no idea how to read it
> properly, so let me ask some really dumb, basic questions.
>
>   first, IIRC, once upon a time, such a script had the option of being
> run at image install time, or on-target install time (depending on i
> think whether the script exited with 0 or 1 or something like that).
> those days are gone, and the new design is to use one of:
>
>   pkg_postinst
>   pkg_postinst_ontarget
>
> fair enough, but in the old days, such a script might check the value
> of ${D} to see if it was running in the image context, or on-target
> context, and obviously run differently. given the current setup with
> those two distinct routines, is there any purpose in such a script
> *ever* checking the value of ${D} anymore? that is, is it safe to
> assume that the first version above is run in image context, and the
> second in on-target context? or is there still some obscure reason to
> need to check?
>
>   i ask as i see this in base-passwd_3.5.29.bb:
>
>     pkg_postinst:${PN}-update () {
>     #!/bin/sh
>     if [ -n "$D" ]; then
>             exit 0
>     fi
>     ${sbindir}/update-passwd
>     }
>
>   how does one interpret that? or is just a holdover from the old
> days? certainly that section in the docs is not going to help a reader
> understand the (still) numerous references to ${D} in some of those
> scripts.
>
> rday
>
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