it's hard to explain it in short topic. okay, assume you're building a separate system via ROOT=/some/dir emerge something as we know portage respects two types of dependencies RDEPs - runtime dependencies and DEPs - compilation time dependencies. if you use ROOT=/some/dir DEPs don't get installed there, which slims down the system. now imagine this situation ---------------------------------------- yOSHi / # ROOT=/home/system emerge -pv mozilla-firefox These are the packages that would be merged, in order: Calculating dependencies... done! [ebuild N ] x11-apps/xdpyinfo-1.0.1 USE="-debug" 0 kB [ebuild N ] www-client/mozilla-launcher-1.51 0 kB [ebuild N ] dev-libs/libIDL-0.8.6 USE="-debug -static" 0 kB [ebuild N ] dev-libs/nspr-4.6.2 USE="ipv6" 0 kB [ebuild N ] app-arch/zip-2.31-r1 USE="crypt" 0 kB [ebuild N ] dev-libs/nss-3.11.1-r1 0 kB [ebuild N ] app-arch/unzip-5.52-r1 0 kB [ebuild N ] x11-apps/xdpyinfo-1.0.1 to /home/system/ USE="-debug" 0 kB [ebuild N ] www-client/mozilla-launcher-1.51 to /home/system/ 0 kB [ebuild N ] dev-libs/libIDL-0.8.6 to /home/system/ USE="-debug -static" 0 kB [ebuild N ] dev-libs/nspr-4.6.2 to /home/system/ USE="ipv6" 0 kB [ebuild N ] app-arch/zip-2.31-r1 to /home/system/ USE="crypt" 0 kB [ebuild N ] dev-libs/nss-3.11.1-r1 to /home/system/ 0 kB [ebuild N ] sys-devel/binutils-config-1.8-r7 to /home/system/ 0 kB [ebuild N ] sys-devel/binutils-2.16.1-r2 to /home/system/ USE="nls -multislot -multitarget -test -vanilla" 0 kB [ebuild N ] app-arch/unzip-5.52-r1 to /home/system/ 0 kB [ebuild N ] www-client/mozilla-firefox-1.5.0.4 to /home/system/ USE="ipv6 -debug -gnome -java -mozdevelop -xinerama -xprint" 0 kB ----------------------------------------------------- as you can see some libraries get installed into main system AND into system in ROOT variable. so, in order to prevent certain packages being built twice (with exactly the same cflags etc) , i tried: FEATURES="buildpkg" ROOT=/home/system emerge -k mozilla-firefox so that portage would build binary packages and then reuse them in the second compile. but portage does not notice the packages it created until you interrupt the merge and rerun the command again. that's where portage notices that some binary packages are available and uses them, skipping their compilation. there could be some kind of environment check after each package when portage builds a string of packages.
*** This bug has been marked as a duplicate of 1343 ***
