Forcearch

Previously you were able to only build for compatible architectures. I.e., you can build i386 package on x86_64 architecture. When you tried to build for incompatible architecture, you get this error:

$ mock -r fedora-28-ppc64le shell
ERROR: Cannot build target ppc64le on arch x86_64, because it is not listed in legal_host_arches ('ppc64le',)

Now, you can build for any architecture using a new option –force-arch ARCH. GH#120 You have to have installed package qemu-user-static, which is a new soft dependence. Try this:

$ sudo dnf install qemu-user-static
$ mock -r fedora-28-ppc64le --forcearch ppc64le shell

and you get the prompt in PPC64LE Fedora. You can do this for any architecture supported by QEMU. You got just INFO in the log stating:

INFO: Unable to build arch ppc64le natively on arch x86_64. Setting forcearch to use software emulation.

Note: Do not confuse --forcearch and --arch which are very different options.

qemu-user-static emulates user space, but cannot emulate kernel space. If your package need some architecture specific kernel calls or e.g., is parsing output of lscpu then this feature is not for you. :(

This has been added to Mock 1.4.11.

Since version 2.0 you do not need to use --forcearch as Mock will detect that you want to use different than your native architecture and use qemu-user-static automatically.