can pkg_{pre, post}rm functions be run at all for image creation?

can pkg_{pre, post}rm functions be run at all for image creation?

[Robert P. J. Day]

  followup to earlier note, is it true that the pkg_prerm and
pkg_postrm functions cannot be run at all during image creation, but
only on the actual running target? this would seem reasonable as it
doesn't seem to make sense to be running any sort of removal code
during image creation.

  (i'm assuming that it is never the case that any sort of package
removal is done during image creation, and that the creation process
will install *only* those packages that should be part of the final
image, is that correct?)

  however, if the above is correct, then it would make sense that all,
say, pkg_prerm() functions would never be written with respect to the
variable ${D}, which would be relevant only during image creation. but
i can see things like this in sysklogd.inc:

pkg_prerm_${PN} () {
        if test "x$D" = "x"; then
        if test "$1" = "upgrade" -o "$1" = "remove"; then
                /etc/init.d/syslog stop
        fi
        fi
}

so what does that mean?

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================

Re: can pkg_{pre, post}rm functions be run at all for image creation?

[Khem Raj]

On Sat, Aug 2, 2014 at 9:34 AM, Robert P. J. Day <rpjday@crashcourse.ca> wrote:
> say, pkg_prerm() functions would never be written with respect to the
> variable ${D}, which would be relevant only during image creation. but
> i can see things like this in sysklogd.inc:
>
> pkg_prerm_${PN} () {
>         if test "x$D" = "x"; then

note that its not ${D} (bitbake context) but $D which is evaluated in
the context when the script is run.

Re: can pkg_{pre, post}rm functions be run at all for image creation?

[Robert P. J. Day]

On Sat, 2 Aug 2014, Khem Raj wrote:

> On Sat, Aug 2, 2014 at 9:34 AM, Robert P. J. Day <rpjday@crashcourse.ca> wrote:
> > say, pkg_prerm() functions would never be written with respect to the
> > variable ${D}, which would be relevant only during image creation. but
> > i can see things like this in sysklogd.inc:
> >
> > pkg_prerm_${PN} () {
> >         if test "x$D" = "x"; then
>
> note that its not ${D} (bitbake context) but $D which is evaluated
> in the context when the script is run.

  i still don't understand ... what are the possible values of $D
here, and what would they represent?

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================

Re: can pkg_{pre, post}rm functions be run at all for image creation?

[Khem Raj]

On 14-08-02 15:57:00, Robert P. J. Day wrote:
> On Sat, 2 Aug 2014, Khem Raj wrote:
> 
> > On Sat, Aug 2, 2014 at 9:34 AM, Robert P. J. Day <rpjday@crashcourse.ca> wrote:
> > > say, pkg_prerm() functions would never be written with respect to the
> > > variable ${D}, which would be relevant only during image creation. but
> > > i can see things like this in sysklogd.inc:
> > >
> > > pkg_prerm_${PN} () {
> > >         if test "x$D" = "x"; then
> >
> > note that its not ${D} (bitbake context) but $D which is evaluated
> > in the context when the script is run.
> 
>   i still don't understand ... what are the possible values of $D
> here, and what would they represent?

At build time it will not be expanded by bitbake like ${D} is. but
during image creation it will be. But when doing on-device install of
this package $D will be empty. Its a way to differentiate actions during
image creation and on-device install/update/remove

-Khem

Re: can pkg_{pre, post}rm functions be run at all for image creation?

[Robert P. J. Day]

On Sat, 2 Aug 2014, Khem Raj wrote:

> On 14-08-02 15:57:00, Robert P. J. Day wrote:
> > On Sat, 2 Aug 2014, Khem Raj wrote:
> >
> > > On Sat, Aug 2, 2014 at 9:34 AM, Robert P. J. Day <rpjday@crashcourse.ca> wrote:
> > > > say, pkg_prerm() functions would never be written with respect to the
> > > > variable ${D}, which would be relevant only during image creation. but
> > > > i can see things like this in sysklogd.inc:
> > > >
> > > > pkg_prerm_${PN} () {
> > > >         if test "x$D" = "x"; then
> > >
> > > note that its not ${D} (bitbake context) but $D which is evaluated
> > > in the context when the script is run.
> >
> >   i still don't understand ... what are the possible values of $D
> > here, and what would they represent?
>
> At build time it will not be expanded by bitbake like ${D} is. but
> during image creation it will be. But when doing on-device install
> of this package $D will be empty. Its a way to differentiate actions
> during image creation and on-device install/update/remove

  but the yocto dev manual states pretty clearly that pkg_prerm and
pkg_postrm functions are *not* used during image creation. so you're
saying they are? under what circumstances?

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================

Re: can pkg_{pre, post}rm functions be run at all for image creation?

[Paul Eggleton]

On Sunday 03 August 2014 02:56:04 Robert P. J. Day wrote:
> On Sat, 2 Aug 2014, Khem Raj wrote:
> > On 14-08-02 15:57:00, Robert P. J. Day wrote:
> > > On Sat, 2 Aug 2014, Khem Raj wrote:
> > > > On Sat, Aug 2, 2014 at 9:34 AM, Robert P. J. Day 
<rpjday@crashcourse.ca> wrote:
> > > > > say, pkg_prerm() functions would never be written with respect to
> > > > > the
> > > > > variable ${D}, which would be relevant only during image creation.
> > > > > but
> > > > > i can see things like this in sysklogd.inc:
> > > > > 
> > > > > pkg_prerm_${PN} () {
> > > > > 
> > > > >         if test "x$D" = "x"; then
> > > > 
> > > > note that its not ${D} (bitbake context) but $D which is evaluated
> > > > in the context when the script is run.
> > > > 
> > >   i still don't understand ... what are the possible values of $D
> > > 
> > > here, and what would they represent?
> > 
> > At build time it will not be expanded by bitbake like ${D} is. but
> > during image creation it will be. But when doing on-device install
> > of this package $D will be empty. Its a way to differentiate actions
> > during image creation and on-device install/update/remove
> 
>   but the yocto dev manual states pretty clearly that pkg_prerm and
> pkg_postrm functions are *not* used during image creation. so you're
> saying they are? under what circumstances?

They wouldn't normally be. You could in theory issue some package removal 
commands as part of postprocessing on the image but I can't see much use for 
that given we have things like PACKAGE_EXCLUDE now.

Khem was simply correcting your reference to ${D}. I can only imagine the 
example you gave is just belt-and-braces to make sure it could never be run 
outside the context of the real target.

Cheers,
Paul

-- 

Paul Eggleton
Intel Open Source Technology Centre

Re: can pkg_{pre, post}rm functions be run at all for image creation?

[Robert P. J. Day]

On Mon, 4 Aug 2014, Paul Eggleton wrote:

> On Sunday 03 August 2014 02:56:04 Robert P. J. Day wrote:
> > On Sat, 2 Aug 2014, Khem Raj wrote:
> > > On 14-08-02 15:57:00, Robert P. J. Day wrote:
> > > > On Sat, 2 Aug 2014, Khem Raj wrote:
> > > > > On Sat, Aug 2, 2014 at 9:34 AM, Robert P. J. Day
> <rpjday@crashcourse.ca> wrote:
> > > > > > say, pkg_prerm() functions would never be written with respect to
> > > > > > the
> > > > > > variable ${D}, which would be relevant only during image creation.
> > > > > > but
> > > > > > i can see things like this in sysklogd.inc:
> > > > > >
> > > > > > pkg_prerm_${PN} () {
> > > > > >
> > > > > >         if test "x$D" = "x"; then
> > > > >
> > > > > note that its not ${D} (bitbake context) but $D which is evaluated
> > > > > in the context when the script is run.
> > > > >
> > > >   i still don't understand ... what are the possible values of $D
> > > >
> > > > here, and what would they represent?
> > >
> > > At build time it will not be expanded by bitbake like ${D} is. but
> > > during image creation it will be. But when doing on-device install
> > > of this package $D will be empty. Its a way to differentiate actions
> > > during image creation and on-device install/update/remove
> >
> >   but the yocto dev manual states pretty clearly that pkg_prerm and
> > pkg_postrm functions are *not* used during image creation. so you're
> > saying they are? under what circumstances?
>
> They wouldn't normally be. You could in theory issue some package
> removal commands as part of postprocessing on the image but I can't
> see much use for that given we have things like PACKAGE_EXCLUDE now.

  oooooh ... that's still kind of weaselly terminology. :-) i'm not
*trying* to be annoyingly pedantic, but this is just the kind of thing
that students tend to ask about, which is why i want to nail the
details.

  the current docs state that pkg_*rm routines are *not* run during
image creation, and i'm going to accept that. that means that if a
pkg_*rm routine *is* written with reference to ${D}, as long as that's
run on the target, it won't make a difference. so the references to
${D} in that context don't *hurt*, they're just unnecessary. and
potentially confusing, which is why i'm trying to clarify this. (every
pkg_*rm routine i've seen, *if* it tests the value of ${D}, bailed if
it was set, which makes sense if they should never, ever be invoked at
image creation time.)

  WRT stuff run at rootfs postprocessing time, sure, you could always
run a package removal command, but clarify this for me -- once you're
into rootfs postprocessing, you're running in a "pseudo" environment
such that you are *effectively* running inside that rootfs, no? so in
that case, all filename references would be full names WRT to the root
filesystem -- no references to ${D}. is that correct? or am i just
confused?

> Khem was simply correcting your reference to ${D}. I can only
> imagine the example you gave is just belt-and-braces to make sure it
> could never be run outside the context of the real target.

  fair enough. as it is, it's simply overkill. gotcha.

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================

Re: can pkg_{pre, post}rm functions be run at all for image creation?

[Paul Eggleton]

On Monday 04 August 2014 09:42:35 Robert P. J. Day wrote:
> On Mon, 4 Aug 2014, Paul Eggleton wrote:
> > On Sunday 03 August 2014 02:56:04 Robert P. J. Day wrote:
> > > On Sat, 2 Aug 2014, Khem Raj wrote:
> > > > On 14-08-02 15:57:00, Robert P. J. Day wrote:
> > > > > On Sat, 2 Aug 2014, Khem Raj wrote:
> > > > > > On Sat, Aug 2, 2014 at 9:34 AM, Robert P. J. Day
> > 
> > <rpjday@crashcourse.ca> wrote:
> > > > > > > say, pkg_prerm() functions would never be written with respect
> > > > > > > to
> > > > > > > the
> > > > > > > variable ${D}, which would be relevant only during image
> > > > > > > creation.
> > > > > > > but
> > > > > > > i can see things like this in sysklogd.inc:
> > > > > > > 
> > > > > > > pkg_prerm_${PN} () {
> > > > > > > 
> > > > > > >         if test "x$D" = "x"; then
> > > > > > 
> > > > > > note that its not ${D} (bitbake context) but $D which is evaluated
> > > > > > in the context when the script is run.
> > > > > > 
> > > > >   i still don't understand ... what are the possible values of $D
> > > > > 
> > > > > here, and what would they represent?
> > > > 
> > > > At build time it will not be expanded by bitbake like ${D} is. but
> > > > during image creation it will be. But when doing on-device install
> > > > of this package $D will be empty. Its a way to differentiate actions
> > > > during image creation and on-device install/update/remove
> > > > 
> > >   but the yocto dev manual states pretty clearly that pkg_prerm and
> > > 
> > > pkg_postrm functions are *not* used during image creation. so you're
> > > saying they are? under what circumstances?
> > 
> > They wouldn't normally be. You could in theory issue some package
> > removal commands as part of postprocessing on the image but I can't
> > see much use for that given we have things like PACKAGE_EXCLUDE now.
> 
>   oooooh ... that's still kind of weaselly terminology. :-) i'm not
> *trying* to be annoyingly pedantic, but this is just the kind of thing
> that students tend to ask about, which is why i want to nail the
> details.

Is this pointless right now? Yes. Does it hurt? No.

>   the current docs state that pkg_*rm routines are *not* run during
> image creation, and i'm going to accept that. that means that if a
> pkg_*rm routine *is* written with reference to ${D}, as long as that's
> run on the target, it won't make a difference. so the references to
> ${D} in that context don't *hurt*, they're just unnecessary. and
> potentially confusing, which is why i'm trying to clarify this. (every
> pkg_*rm routine i've seen, *if* it tests the value of ${D}, bailed if
> it was set, which makes sense if they should never, ever be invoked at
> image creation time.)

Yes, but when we are talking about preinst/postinst/prerm/postrm, as mentioned 
before it is $D *not* ${D}. If you use ${D} instead there, you will have 
problems.

>   WRT stuff run at rootfs postprocessing time, sure, you could always
> run a package removal command, but clarify this for me -- once you're
> into rootfs postprocessing, you're running in a "pseudo" environment
> such that you are *effectively* running inside that rootfs, no? so in
> that case, all filename references would be full names WRT to the root
> filesystem -- no references to ${D}. is that correct? or am i just
> confused?

You are a bit confused yes. do_rootfs may be running under pseudo, but it is 
not chrooted such that / is the root of the image being constructed; hence why 
you need to use $D in order to be looking in the right place in both contexts 
(during constructing the rootfs on the build machine where $D is set, and on 
the target where $D is not set).

Cheers,
Paul

-- 

Paul Eggleton
Intel Open Source Technology Centre

Re: can pkg_{pre, post}rm functions be run at all for image creation?

[Richard Purdie]

On Mon, 2014-08-04 at 09:42 -0400, Robert P. J. Day wrote:
>   oooooh ... that's still kind of weaselly terminology. :-) i'm not
> *trying* to be annoyingly pedantic, but this is just the kind of thing
> that students tend to ask about, which is why i want to nail the
> details.
> 
>   the current docs state that pkg_*rm routines are *not* run during
> image creation, and i'm going to accept that. that means that if a
> pkg_*rm routine *is* written with reference to ${D}, as long as that's
> run on the target, it won't make a difference. so the references to
> ${D} in that context don't *hurt*, they're just unnecessary. and
> potentially confusing, which is why i'm trying to clarify this. (every
> pkg_*rm routine i've seen, *if* it tests the value of ${D}, bailed if
> it was set, which makes sense if they should never, ever be invoked at
> image creation time.)

In the interests of being pedantic since I know you value correctness,
they test $D. If they used ${D}, it would get expanded by bitbake at
build time which is not what you want.

>   WRT stuff run at rootfs postprocessing time, sure, you could always
> run a package removal command, but clarify this for me -- once you're
> into rootfs postprocessing, you're running in a "pseudo" environment
> such that you are *effectively* running inside that rootfs, no? so in
> that case, all filename references would be full names WRT to the root
> filesystem -- no references to ${D}. is that correct? or am i just
> confused?

Pseudo environment means you can perform operations as root, its not a
chroot. You could be in a pseudo chroot of course but our image
generation isn't.

Cheers,

Richard

Re: can pkg_{pre, post}rm functions be run at all for image creation?

[Robert P. J. Day]

On Mon, 4 Aug 2014, Richard Purdie wrote:

> On Mon, 2014-08-04 at 09:42 -0400, Robert P. J. Day wrote:
> >   oooooh ... that's still kind of weaselly terminology. :-) i'm not
> > *trying* to be annoyingly pedantic, but this is just the kind of thing
> > that students tend to ask about, which is why i want to nail the
> > details.
> >
> >   the current docs state that pkg_*rm routines are *not* run during
> > image creation, and i'm going to accept that. that means that if a
> > pkg_*rm routine *is* written with reference to ${D}, as long as that's
> > run on the target, it won't make a difference. so the references to
> > ${D} in that context don't *hurt*, they're just unnecessary. and
> > potentially confusing, which is why i'm trying to clarify this. (every
> > pkg_*rm routine i've seen, *if* it tests the value of ${D}, bailed if
> > it was set, which makes sense if they should never, ever be invoked at
> > image creation time.)
>
> In the interests of being pedantic since I know you value correctness,
> they test $D. If they used ${D}, it would get expanded by bitbake at
> build time which is not what you want.
>
> >   WRT stuff run at rootfs postprocessing time, sure, you could always
> > run a package removal command, but clarify this for me -- once you're
> > into rootfs postprocessing, you're running in a "pseudo" environment
> > such that you are *effectively* running inside that rootfs, no? so in
> > that case, all filename references would be full names WRT to the root
> > filesystem -- no references to ${D}. is that correct? or am i just
> > confused?
>
> Pseudo environment means you can perform operations as root, its not a
> chroot. You could be in a pseudo chroot of course but our image
> generation isn't.

  ok, i think i've got it, thanks, both of you.

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================