[[!meta title="Bootless: barebones tutorial"]]

This tutorial helps you to build a Grub USB stick to boot your operating systems.

Create basic folder structure
-----------------------------

    mkdir -p   /tmp/bootless/{grub,custom}
    ln    -s . /tmp/bootless/boot
    wget https://git.fluxo.info/bootless/plain/templates/grub.cfg   -O /tmp/bootless/grub/grub.cfg
    wget https://git.fluxo.info/bootless/plain/templates/custom.cfg -O /tmp/bootless/grub/custom.cfg

Edit the config files
---------------------

Please check and customize the downloaded configuration above. The defaults allows you to load into Grub
and boot your OS using the grub shell.

Example: Full Disk Encryption
-----------------------------

Here is an example of a Full Disk Encryption with an entry loaded into `custom.cfg`:

    menuentry 'darkstar full disk encryption' {
      # Loads luks and lvm modules so you can access kernel
      # and initrd from inside your encrypted OS!
      insmod luks
      insmod lvm

      # This opens the encrypted volume /dev/mapper/darkstar-root
      # and sets it as the root in the grub shell.
      cryptomount lvm/darkstar-root
      set         root=(crypto0)

      # This loads the kernel and initramfs
      echo        "Loading ${volume}..."
      linux       /boot/vmlinuz-3.16.0-4-amd64 root=/dev/mapper/root cryptopts=target=root,source=/dev/mapper/darkstar-root ro quiet
      echo        'Loading initial ramdisk ...'
      initrd      /boot/initrd.img-3.16.0-4-amd64
    }

Example: boot with images loaded into the USB stick
---------------------------------------------------

You may also place custom images into the USB stick -- with the drawback to have to keep them up-to-date:

    cp -r /boot /tmp/bootless/custom/debian

    menuentry 'darkstar: preloaded images' {
      # This loads the kernel and initramfs using images preloaded into the USB stick.
      echo        "Loading ${volume}..."
      linux       /boot/custom/debian/vmlinuz-3.16.0-4-amd64 root=/dev/mapper/root cryptopts=target=root,source=/dev/mapper/darkstar-root ro quiet
      echo        'Loading initial ramdisk ...'
      initrd      /boot/custom/debian/initrd.img-3.16.0-4-amd64
    }

Example: builtin bootless functions
-----------------------------------

The supplied configuration provides two functions, `bootfde` and `bootimg` that simplify the two previous examples into:

    menuentry 'darkstar: full disk encryption' {
      bootfde darkstar-root
    }

    menuentry 'darkstar: preloaded images' {
      bootimg darkstar-root
    }

Create a bootable image
-----------------------

    grub-mkrescue -o output.img /tmp/bootless

Record the image into the USB stick
-----------------------------------

*WARNING!* This will irrevocably replace the contents of your USB stick.

Pay attention to get the right device. If your USB stick is attached to
your computer and reachable through `/dev/sdb`, you just have to run

    sudo dd if=output.img of=/dev/sdb