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"Bruce Hill, Jr." 03-12-2012 05:05 PM

virtual/shadow
 
These virtual apps are irritating me, and the fanboi answers in #gentoo
are worse.

What is the purpose of virtual/shadow and why would I want it?

Today's update output:

server ~ # emerge -aDjNquv world
[ebuild N ] virtual/shadow-0

Would you like to merge these packages? [Yes/No] No

Quitting.

--
Happy Penguin Computers >`)
126 Fenco Drive (
Tupelo, MS 38801 ^^
662-269-2706; 662-491-8613
support at happypenguincomputers dot com
http://www.happypenguincomputers.com

Paul Hartman 03-12-2012 05:50 PM

virtual/shadow
 
On Mon, Mar 12, 2012 at 1:05 PM, Bruce Hill, Jr.
<daddy@happypenguincomputers.com> wrote:
> *These virtual apps are irritating me, and the fanboi answers in #gentoo
> are worse.
>
> What is the purpose of virtual/shadow and why would I want it?

Virtual packages are kind of an abstraction layer for compatible
alternative packages. Other packages can depend on the virtual instead
of depending on every combination of possible alternatives, and the
user can install whichever of the alternatives he prefers.

For example, MariaDB is a drop-in replacement for MySQL. From a
dependency standpoint, they are compatible. Instead of any program
depending on MySQL being modified to check for either MySQL or
MariaDB, virtual/mysql was created and it can be satisfied by either
dev-db/mysql or dev-db/mariadb being installed.

In the case of shadow, he new virtual is to allow you to use either
sys-apps/shadow or sys-apps/hardened-shadow. See here:
http://www.gossamer-threads.com/lists/gentoo/dev/249394

If you view the virtual package's ebuild, this line is the key:
RDEPEND="|| ( >=sys-apps/shadow-4.1 sys-apps/hardened-shadow )"


HTH :)

Nikos Chantziaras 03-12-2012 06:19 PM

virtual/shadow
 
On 12/03/12 20:05, Bruce Hill, Jr. wrote:

These virtual apps are irritating me, and the fanboi answers in #gentoo
are worse.

What is the purpose of virtual/shadow and why would I want it?


Paul's answers covers it, but I'll give an explanation that is the
reverse of a fanboi answer.


The reason we need virtuals is because of a shortcoming in portage: lack
of "provides" functionality. RPM packages can tell the package manager
what they provide. For example, RPMs for libav and ffmpeg can both use
"ffmpeg" as their "provides" field. Portage can't do that, so it needs
a new "virtual/ffmpeg" package instead.

"Bruce Hill, Jr." 03-12-2012 06:21 PM

virtual/shadow
 
On March 12, 2012 at 2:50 PM Paul Hartman <paul.hartman+gentoo@gmail.com>
wrote:

> On Mon, Mar 12, 2012 at 1:05 PM, Bruce Hill, Jr.
> <daddy@happypenguincomputers.com> wrote:
> > These virtual apps are irritating me, and the fanboi answers in
#gentoo
> > are worse.
> >
> > What is the purpose of virtual/shadow and why would I want it?
>
> Virtual packages are kind of an abstraction layer for compatible
> alternative packages. Other packages can depend on the virtual instead
> of depending on every combination of possible alternatives, and the
> user can install whichever of the alternatives he prefers.
>
> For example, MariaDB is a drop-in replacement for MySQL. From a
> dependency standpoint, they are compatible. Instead of any program
> depending on MySQL being modified to check for either MySQL or
> MariaDB, virtual/mysql was created and it can be satisfied by either
> dev-db/mysql or dev-db/mariadb being installed.
>
> In the case of shadow, he new virtual is to allow you to use either
> sys-apps/shadow or sys-apps/hardened-shadow. See here:
> http://www.gossamer-threads.com/lists/gentoo/dev/249394
>
> If you view the virtual package's ebuild, this line is the key:
> RDEPEND="|| ( >=sys-apps/shadow-4.1 sys-apps/hardened-shadow )"
>
>
> HTH :)
>


Thanks for the kind explanation. I didn't realize hardened was not a
profile (selinux is) and wondered why anything to do with hardened would
even show up on my system(s).
--
Happy Penguin Computers >`)
126 Fenco Drive (
Tupelo, MS 38801 ^^
662-269-2706; 662-491-8613
support at happypenguincomputers dot com
http://www.happypenguincomputers.com

"Bruce Hill, Jr." 03-12-2012 06:30 PM

virtual/shadow
 
On March 12, 2012 at 3:19 PM Nikos Chantziaras <realnc@gmail.com> wrote:

> On 12/03/12 20:05, Bruce Hill, Jr. wrote:
> > These virtual apps are irritating me, and the fanboi answers in
#gentoo
> > are worse.
> >
> > What is the purpose of virtual/shadow and why would I want it?
>
> Paul's answers covers it, but I'll give an explanation that is the
> reverse of a fanboi answer.
>
> The reason we need virtuals is because of a shortcoming in portage: lack
> of "provides" functionality. RPM packages can tell the package manager
> what they provide. For example, RPMs for libav and ffmpeg can both use
> "ffmpeg" as their "provides" field. Portage can't do that, so it needs
> a new "virtual/ffmpeg" package instead.
>
>


My only experience building software was making scripts to work on my own
computer(s), which didn't require checking deps for everybody and his
brother's possible setups; so frequently portage offends me with it's dep
checking and installing.

Thanks for the patience, guys. My mind has not morphed to The Gentoo Way
(R) yet and frequently bucks up against this type of pkg mgr.
--
Happy Penguin Computers >`)
126 Fenco Drive (
Tupelo, MS 38801 ^^
662-269-2706; 662-491-8613
support at happypenguincomputers dot com
http://www.happypenguincomputers.com

Alan McKinnon 03-12-2012 07:29 PM

virtual/shadow
 
On Mon, 12 Mar 2012 21:19:12 +0200
Nikos Chantziaras <realnc@gmail.com> wrote:

> On 12/03/12 20:05, Bruce Hill, Jr. wrote:
> > These virtual apps are irritating me, and the fanboi answers in
> > #gentoo are worse.
> >
> > What is the purpose of virtual/shadow and why would I want it?
>
> Paul's answers covers it, but I'll give an explanation that is the
> reverse of a fanboi answer.
>
> The reason we need virtuals is because of a shortcoming in portage:
> lack of "provides" functionality. RPM packages can tell the package
> manager what they provide. For example, RPMs for libav and ffmpeg
> can both use "ffmpeg" as their "provides" field. Portage can't do
> that, so it needs a new "virtual/ffmpeg" package instead.
>
>

Anyone care to offer an opinion on what it will take to get PROVIDES
support in portage?



--
Alan McKinnnon
alan.mckinnon@gmail.com

Q 03-12-2012 09:34 PM

virtual/shadow
 
On Mon, 12 Mar 2012 22:29:10 +0200
Alan McKinnon <alan.mckinnon@gmail.com> wrote:

> Anyone care to offer an opinion on what it will take to get PROVIDES
> support in portage?

IMO, it would take virtuals causing so many headachy breakages that
some devs started keeping up a steady drumbeat on irc and mailing
lists. When the number of virtual packages gets close to a thousand,
I'd guess that might happen. Then there would be years of discussion
and GLEP proposals, and by EAPI 207 it should be done.

;)

Nikos Chantziaras 03-12-2012 10:54 PM

virtual/shadow
 
On 13/03/12 00:34, Q wrote:

On Mon, 12 Mar 2012 22:29:10 +0200
Alan McKinnon<alan.mckinnon@gmail.com> wrote:


Anyone care to offer an opinion on what it will take to get PROVIDES
support in portage?


IMO, it would take virtuals causing so many headachy breakages that
some devs started keeping up a steady drumbeat on irc and mailing
lists. When the number of virtual packages gets close to a thousand,
I'd guess that might happen. Then there would be years of discussion
and GLEP proposals, and by EAPI 207 it should be done.


The problem isn't the amount of virtuals. This doesn't affect the users
much. It's the inability for people to offer replacement packages in
overlays.

Neil Bothwick 03-12-2012 11:23 PM

virtual/shadow
 
On Tue, 13 Mar 2012 01:54:30 +0200, Nikos Chantziaras wrote:

> >> Anyone care to offer an opinion on what it will take to get PROVIDES
> >> support in portage?
> >
> > IMO, it would take virtuals causing so many headachy breakages that
> > some devs started keeping up a steady drumbeat on irc and mailing
> > lists. When the number of virtual packages gets close to a thousand,
> > I'd guess that might happen. Then there would be years of discussion
> > and GLEP proposals, and by EAPI 207 it should be done.
>
> The problem isn't the amount of virtuals. This doesn't affect the
> users much. It's the inability for people to offer replacement
> packages in overlays.

They could include a modified virtual in the overlay, but your point is
valid; including the information in the ebuilds is more flexible.


--
Neil Bothwick

Light travels faster than sound. This is why some people appear bright
until you hear them speak.


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