By default the machine should boot in GRUB with no countdown timer, leaving you time to choose which OS you want to boot. If this isn’t the case, put Chimera Linux on a USB drive, boot on it (RAM mode), then:

# mount /dev/sda3 /mnt
# mount /dev/sda2 /mnt/boot
# mount /dev/sda1 /mnt/boot/efi
# chimera-chroot /mnt
  # grub-install /dev/sda
  # update-grub

In case something broke real bad or the SSD is getting upgraded, here is how to reinstall the system:

• Start with Chimera Linux for the initial partition table. Follow its documentation.
• The Haiku installation is straightforward, follow one of the many tutorials or videos online. Note that this will override GRUB. Follow the Troubleshooting section above if you want to recover it at this point.
• 9front: TODO: remember the painpoints. Note that this will override GRUB. Follow the Troubleshooting section above if you want to recover it at this point.
• The default DragonflyBSD installer won’t let you install it on part of the disk. Follow this very manual installation guide to get around that.

• Set GRUB_TIMEOUT to -1 in /etc/default/grub
• Add the following to /etc/grub.d/40_custom:

menuentry "Haiku" {
  set root=(hd0,gpt1)
  chainloader ($root)/EFI/BOOT/HAIKU.EFI
}

menuentry "9front" {
  set root=(hd0,gpt5)
  chainloader ($root)/efi/boot/bootx64.efi
}

menuentry "Dragonfly BSD" {
  set root=(hd0,gpt1)
  chainloader ($root)/EFI/BOOT/DFLY.EFI
}