Re: [gentoo-dev] BUILDROOT concept (was Re: [gentoo-dev] ROOT variable)

[Paul Smith]

%% david@×××××××××.com writes:

  >> Mm.  But of course, this will only work if your embedded system just
  >> happens to be the same architecture as your build system... which I
  >> think is not a good restriction to make.

  d> I still don't see how `ROOT=/tmp/foo emerge blah` doesn't solve
  d> your problem.

Maybe I'm misreading the code, but from what I can see, when you set
ROOT it only changes where RDEPEND packages are searched for.

It does _NOT_ change where DEPEND packages are searched for: they're
still searched for on the native system not in the ROOT system.  If the
native system and the root system are very different, that doesn't seem
like it can work properly.

  >> I don't see how this solves the problem.  First, the point is to
  >> allow multiple "build" images, which this does not do, since it
  >> still uses the local host for all DEPEND information.  I don't want
  >> to have to update (or downgrade!)  my local host's installation of
  >> packages just to build a ROOT with a different setup!  Second, the
  >> ROOT is not a real Portage system here: all the Portage database
  >> information, etc. is on the local system.  Third, this still won't
  >> work if the ROOT target is to be run on different hardware than the
  >> build system.  Etc.

  d> I don't understand what you mean by 'portage database information'.
  d> Maybe you could explain more, becuase I don't see any problems here
  d> either.

If you look at the code in emerge (this is from the latest Portage CVS)
you'll see things like this:

	if myroot=="/":
		mydep["/"]=edepend["DEPEND"]+" "+edepend["RDEPEND"]
		if not self.select_dep("/",mydep["/"],myparent=mp,myuse=myuse):
			return 0
	else:
		mydep["/"]=edepend["DEPEND"]
		mydep[myroot]=edepend["RDEPEND"]
		if not self.select_dep("/",mydep["/"],myparent=mp,myuse=myuse):
			return 0
		elif not self.select_dep(myroot,mydep[myroot],myparent=mp,myuse=myuse):
			return 0

IIUC, this shows that if ROOT is not the default (is not "/") then
emerge will check the native system for the DEPEND requirements and
check the ROOT image only for the RDEPEND requirements.

Also, you'll see many instances of code like this:

	mylogfile=open("/var/log/emerge.log", "a")

which is obviously going to be updating the emerge.log file on the
native system, not in the ROOT image.  And this:

	profilever=os.path.basename(os.path.normpath(os.readlink("/etc/make.profile")))

which shows Portage checking the profile on the native system, not the
one in the ROOT system.  I do see that the ebuild cache is kept in ROOT,
so that's good (originally I thought it wasn't there).  But there is
this suspicious looking bit in portage.py, although it might be a bug:

	worldlist=grabfile("/var/cache/edb/world")

I would think that this should be using the world file in the ROOT, not
the native system.


More generally, what I want to be able to do is build for a target
(ROOT) a specific set of packages and versions _without_ having to
modify my physical system in any way.  I don't want the build of the
ROOT to have any relationship to what I have installed on my physical
system.  If I want ROOT to have a version of a package that doesn't work
with a newer version of GTK or whatever, I don't want to have to
downgrade the version on my physical system in order to build that
ROOT.  Maybe I want to create a ROOT system with a KDE desktop but don't
want KDE installed on my build system.  Etc.

Right now the construction of the ROOT is accomplished by a combination
of stuff on the physical system and stuff in the ROOT image.

-- 
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 Paul D. Smith <psmith@××××××××××××××.com>   HASMAT--HA Software Mthds & Tools
 "Please remain calm...I may be mad, but I am a professional." --Mad Scientist
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   These are my opinions---Nortel Networks takes no responsibility for them.

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