If you use auto.conf to configure a build, e.g. set the final MACHINE value, this will not be seen when trying to install the extensible SDK because only local.conf gets copied.
Fix merged to master: http://git.yoctoproject.org/cgit/cgit.cgi/poky/commit/?id=39f6472605fb40c01e0bbfe52702a1b3beb55690
Verified on http://downloads.yoctoproject.org/releases/yocto/milestones/yocto-2.1_M2/toolchain/x86_64/ :~/poky_sdk/conf$ cat auto.conf # WARNING: this configuration has been automatically generated and in # most cases should not be edited. If you need more flexibility than # this configuration provides, it is strongly suggested that you set # up a proper instance of the full build system and use that instead. INHERIT += "report-error" DISTRO = "poky" PACKAGE_CLASSES = "package_rpm package_deb package_ipk" SDKMACHINE ?= "x86_64" IMAGE_FSTYPES_append = " tar.gz" BB_TASK_NICE_LEVEL = "5" BB_TASK_NICE_LEVEL_task-testimage = "0" BB_TASK_IONICE_LEVEL = "2.7" BB_TASK_IONICE_LEVEL_task-testimage = "2.1" MACHINE = "qemuarm64" PREMIRRORS = "" BB_GENERATE_MIRROR_TARBALLS = "1" ADTREPO = "http://adtrepo.yoctoproject.org//2.0+snapshot"