Comment 39 for bug 1615021

Just a note that the udev rules change from comment 6 seems to be necessary to reliably get an image booted under QEMU to bring up a getty on the serial console. What seems to happen without it is that udevd spends all its time running copies of 'readlink', and it doesn't get around to telling systemd about the presence of ttyAMA0 until after systemd's 1m30 timeout has expired and it gives up, reporting "Timed out waiting for device dev-ttyAMA0.device". (This happens most of the time on an emulated QEMU CPU and at least occasionally on one running with single-vcpu KVM, probably dependent on speed of the host hardware.)