Re: Dependency problem when "post" runs command from the rpm

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On Sep 21, 2008, at 1:31 PM, Toralf Lund wrote:

> Jeff Johnson wrote:
>>
>> On Sep 15, 2008, at 11:24 PM, Michael A. Peters wrote:
>>
>>> Toralf Lund wrote:
>>>> I've run into an installation order issue related to the "post"  
>>>> scriptlet in one of my packages. Basically, this scripts executes  
>>>> a (command-line only) program installed by the package, and this  
>>>> program pretty much needs everything required by the package. The  
>>>> problem is, if I install my package along with some of the  
>>>> required software, the requirements are often installed *after*  
>>>> the "main" package [ ... ]
>>>
>>> Perhaps my understanding is wrong - but I believe:
>>>
>>
>>
>> Um, yes, wrong.
>>
>>> [ .. ]
>>
>> The %pre and %post scripts are run immediately before/after a  
>> package is installed,
>> not after all the packages are installed.
> Exactly. This is what's causing me trouble; essentially, I have a  
> command that would be better to run at the end of the entire  
> transaction. But I think I understand why rpm doesn't work that way...

There are %posttrans scriptlets that run at the end of the transaction.

>
>>
>> This is also true for %preun/%postun when a package is erased, the  
>> scripts are run
>> immediately before/after the erasure.
>>
>>> My understanding of this may not be 100%
>>>
>>
>> What is most confusing is that rpm does install before erase. Which  
>> means that %post
>> scriptlet is run before %preun is run, which is perhaps counter- 
>> intuitive, but is exactly
>> what is needed if shared libraries are being upgraded on live  
>> systems. The new librrary
>> must be installed before the old library is removed in ordeer to  
>> minimize the window
>> where the library is not available.
> Quite.
>>
>> [ ... ]
>>
>> And finally that brings the topic to context markers like  
>> Requires(post) etc.
>>
>> Context markers like Requires(post) are intended to break  
>> dependency loops while
>> ordering.
>>
>> A package that "needs" some other package solely while running a  
>> %post scriptlet,
>> not after being installed, can carry a Requires(post) hint to the  
>> ordering within rpm.
> In my case the script and the package itself both need (more or  
> less) the same libs. Logically, they may be seen as independent sets  
> of dependencies, though, I think...
>>
>> The hint excludes dependency loops between install <=> erase  
>> packages.
>>
>> The other major affect of adding an explicit Requires(post) hint is  
>> that those
>> dependencies are not registered in an rpmdb because they were  
>> needed solely
>> for installing, not for using or erasing, a package. There's no  
>> need to keep track
>> of the install context dependencies after the install has been done  
>> because
>> the %post scriptlet is run only during install, never run after  
>> install.
>>
>> hth
> Well. It doesn't help me too much with my original issue. But, like  
> I said elsewhere, I can't seem to reproduce the problem I thought I  
> had, so maybe it doesn't matter. I'm still confused, though.
>
> Question: Can I generally assume the packages are ordered according  
> to "Requires" these days, i.e. that if package A requires something  
> provided by package B, then B is installed before A (when A and B  
> are both part of the same transaction)? I'm fairly sure I couldn't  
> when I started using rpm, so I had to mess about with ""PreReq"  
> instead...

Yes, except for dependency loops, where all dependencies involved
in the loop are ignored for ordering purposes.

Requires: == PreReq: for like 8 years now, but I'm sure you can find
any answer you wish to hear regarding rpm PreReq:

73 de Jeff
>

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<html><body style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; =
-webkit-line-break: after-white-space; "><br><div><div>On Sep 21, 2008, =
at 1:31 PM, Toralf Lund wrote:</div><br =
class=3D"Apple-interchange-newline"><blockquote type=3D"cite"><div>Jeff =
Johnson wrote:<br><blockquote type=3D"cite"><br></blockquote><blockquote =
type=3D"cite">On Sep 15, 2008, at 11:24 PM, Michael A. Peters =
wrote:<br></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite"><blockquote =
type=3D"cite">Toralf Lund =
wrote:<br></blockquote></blockquote><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite">I've run into an installation =
order issue related to the "post" scriptlet in one of my packages. =
Basically, this scripts executes a (command-line only) program installed =
by the package, and this program pretty much needs everything required =
by the package. The problem is, if I install my package along with some =
of the required software, the requirements are often installed *after* =
the "main" package [ ... =
]<br></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite">Perhaps my understanding is =
wrong - but I believe:<br></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite">Um, yes, =
wrong.<br></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite"><blockquote =
type=3D"cite">[ .. ]<br></blockquote></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite">The %pre and =
%post scripts are run immediately before/after a package is =
installed,<br></blockquote><blockquote type=3D"cite">not after all the =
packages are installed.<br></blockquote>Exactly. This is what's causing =
me trouble; essentially, I have a command that would be better to run at =
the end of the entire transaction. But I think I understand why rpm =
doesn't work that way...</div></blockquote><div><br></div>There are =
%posttrans scriptlets that run at the end of the =
transaction.</div><div><br><blockquote type=3D"cite"><div><br><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite">This is also =
true for %preun/%postun when a package is erased, the scripts are =
run<br></blockquote><blockquote type=3D"cite">immediately before/after =
the erasure.<br></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite"><blockquote =
type=3D"cite">My understanding of this may not be =
100%<br></blockquote></blockquote><blockquote type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite">What is most =
confusing is that rpm does install before erase. Which means that =
%post<br></blockquote><blockquote type=3D"cite">scriptlet is run before =
%preun is run, which is perhaps counter-intuitive, but is =
exactly<br></blockquote><blockquote type=3D"cite">what is needed if =
shared libraries are being upgraded on live systems. The new =
librrary<br></blockquote><blockquote type=3D"cite">must be installed =
before the old library is removed in ordeer to minimize the =
window<br></blockquote><blockquote type=3D"cite">where the library is =
not available.<br></blockquote>Quite.<br><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite">[ ... =
]<br></blockquote><blockquote type=3D"cite"><br></blockquote><blockquote =
type=3D"cite">And finally that brings the topic to context markers like =
Requires(post) etc.<br></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite">Context markers =
like Requires(post) are intended to break dependency loops =
while<br></blockquote><blockquote =
type=3D"cite">ordering.<br></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite">A package that =
"needs" some other package solely while running a %post =
scriptlet,<br></blockquote><blockquote type=3D"cite">not after being =
installed, can carry a Requires(post) hint to the ordering within =
rpm.<br></blockquote>In my case the script and the package itself both =
need (more or less) the same libs. Logically, they may be seen as =
independent sets of dependencies, though, I think...<br><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite">The hint =
excludes dependency loops between install &lt;=3D&gt; erase =
packages.<br></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite">The other major =
affect of adding an explicit Requires(post) hint is that =
those<br></blockquote><blockquote type=3D"cite">dependencies are not =
registered in an rpmdb because they were needed =
solely<br></blockquote><blockquote type=3D"cite">for installing, not for =
using or erasing, a package. There's no need to keep =
track<br></blockquote><blockquote type=3D"cite">of the install context =
dependencies after the install has been done =
because<br></blockquote><blockquote type=3D"cite">the %post scriptlet is =
run only during install, never run after =
install.<br></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote =
type=3D"cite">hth<br></blockquote>Well. It doesn't help me too much with =
my original issue. But, like I said elsewhere, I can't seem to reproduce =
the problem I thought I had, so maybe it doesn't matter. I'm still =
confused, though.<br><br>Question: Can I generally assume the packages =
are ordered according to "Requires" these days, i.e. that if package A =
requires something provided by package B, then B is installed before A =
(when A and B are both part of the same transaction)? I'm fairly sure I =
couldn't when I started using rpm, so I had to mess about with ""PreReq" =
instead...</div></blockquote><div><br></div>Yes, except for dependency =
loops, where all dependencies involved</div><div>in the loop are ignored =
for ordering purposes.</div><div><br></div><div>Requires: =3D=3D PreReq: =
for like 8 years now, but I'm sure you can find</div><div>any answer you =
wish to hear regarding rpm PreReq:</div><div><br></div><div>73 de =
Jeff</div><div><blockquote type=3D"cite"><div><font =
class=3D"Apple-style-span" color=3D"#000000"><font =
class=3D"Apple-style-span" =
color=3D"#144FAE"><br></font></font></div></blockquote></div></body></html=
>=

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