systemd-getty-generator reads console=ttyS0 off the kernel cmdline and
auto-creates serial-getty@ttyS0.service, which BindsTo dev-ttyS0.device.
On hardware without a physical serial port the device node never shows
up, systemd waits its full default 90s timeout, and only then proceeds.
systemd.mask= on the kernel cmdline is a first-class option — masks
the unit before the generator's link even gets activated. Kernel
messages still go to ttyS0 if a port is present; we just don't try
to spawn a login prompt there.
josh
c45349f62c