MarsSeed [1] filed a deletion request for linuxcnc-sim [2]: Duplicate of AUR/linuxcnc, and currently has an older pkgver than that one. As per submitter's explanation: " -sim means simulation. LinuxCNC needs special kernel with realtime extensions (RTAI/preempt-rt). This PKGCONFIG hasn't got dependency of an RTAI kernel (it works with the stock kernel), so this is only OK for simulation. The other linuxcnc could have/should have to work with real-time kernel and good for a real CNC machine... " But somewhat contrary to the above statement, the linuxcnc package can also be built and run on vanilla kernels, in simulation mode. Because that PKGBUILD does not mandate any kernel type/variant/version (no linux kernel declared as dependency). There is no meaningful build configuration difference between the two packages (only formatting differences). It's enough to keep one linuxcnc package. [1] https://aur.archlinux.org/account/MarsSeed/ [2] https://aur.archlinux.org/pkgbase/linuxcnc-sim/