Fix VirtualBox image generation: switch-to-configuration in chroot needs /bin/sh
Update the troubleshooting section for systemd
modules/system/boot/loader/grub/memtest.nix: use 'memtest86plus' instead of 'memtest86'

The 'memtest86' package didn't work on any of my machines. 'memtest86plus', on
the other hand, seems to work just fine. Does anyone know why we keep the
seemingly older version around still?
initrd: Don't enable the root shell by default

Starting an authenticated root shell is a security hole, so don't do
it by default.  The kernel command line parameter
‘initrd.shell_on_fail’ restores the original.  (Of course, this only
improves security if you have a password on GRUB to prevent the kernel
command line from being edited by unauthorized users.)
Give our kernel parameters a common prefix ("boot.*")
Guard against portmap and rpcbind both being enabled
Merge branch 'systemd' of github.com:NixOS/nixos into systemd
Start dhcpcd/wpa_supplicant after systemd-udev-settle

This is necessary to prevent a race.  Udev 197 has a new naming scheme
for network devices, so it will rename (say) eth0 to eno0.  This fails
with "error changing net interface name eth0 to eno1: Device or
resource busy" if another process has opened the interface in the
meantime.
Add/fix systemd unit descriptions