Bifrost uses grub.

The Bifrost kernel uses initramfs to bootstrap the system.

The initramsfs will:
1. lookup the partition labeled 'bifrost'.
2. perform fsck on this partition (if fs is of the ext-family).
3. mount the partition as the root filesystem.
4. mount /proc in the rootfs.
4. exec /sbin/init.

The 'init' program in the initramfs will understand the following kernel commandline options:
rootfstype=NNN
 Mount rootfs as this type of filesystem. Default is 'ext2'.

rootfslabel=NNN
 Give an alternative label of the rootfs. The default is 'bifrost'.

rootdelay=N
 Wait this many seconds before probing for rootfs partition.

root=NNN
 Override autodetection of rootfs partition.

init=NNN
 Run this program instead of /sbin/init.

usbreset
 init will perform usbreset on all usb-ports.

async
 Mount the root filesystems with asynchronous writes enabled.