NixOS Installation Guide/Manual USB Creation

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Using syslinux.cfg

If you have trouble booting from a USB drive or sdcard with Unetbootin (I just got a blinking cursor instead of a bootloader on an Asus eee 1000) the procedure described on http://knoppix.net/wiki/Bootable_USB_Key should work. After preparing the sdcard with mkdiskimage and syslinux you can mount it and copy all the content from the NixOS iso: 

$ mount -o loop ~/Downloads/nixos-graphical-0.1pre27337-i686-linux.iso /media/iso
$ rsync -av --progress /media/iso/ /media/sd-card/

The syslinux.cfg needs to be created manually, but the details can easily be derived from the grub.cfg on the NixOS install cd.

I specified the root device by UUID, to get the UUID: 

blkid /dev/mmcblk0p1

The relevant section from the live cd: /media/sd-card/boot/grub/grub.cfg 

menuentry "NixOS Installer / Rescue" {
  linux /boot/bzImage init=/nix/store/r7xhnzymi1ll49r4glf1dwr5y1alx0bl-system/init root=LABEL=NIXOS_INSTALL_CD_0.1pre27337 splash=verbose vga=0x317
  initrd /boot/initrd
}

can be used in the syslinux config file: /media/sd-card/syslinux.cfg (you should just need to update the init path and the root UUID / LABEL or device path) 

DEFAULT linux
LABEL linux
  SAY Now booting the kernel from SYSLINUX...
  KERNEL /boot/bzImage
  APPEND init=/nix/store/r7xhnzymi1ll49r4glf1dwr5y1alx0bl-system/init root=UUID=509C-63E2 ro initrd=/boot/initrd splash=verbose

Note: in place of using mkdiskimage, you can simply format your SDCard as a fat32 system and install syslinux on it: 

mkdosfs -F32 /dev/mmcblk0p1
syslinux -s /dev/mmcblk0p1

Using grub

  1. Download the ISO image from https://nixos.org/download/#nixos-iso.
  2. Prepare your USB stick. If it isn't yet partitioned to your liking, create a bootable partition on /dev/sdb1: 
    fdisk /dev/sdb

    And format it with: 

    mkdosfs /dev/sdb1

    Add ext2 partitions if you like. If you want both 32-bit and 64-bit NixOS, you need at least two partitions. You can directly use the entire disk without partition if that's what you like. Once you have your VFAT (dosfs) block device, you should give it a label, within a 11-character limit, e.g.: 

    dosfslabel /dev/sdb1 NIXBOOT
  3. Mount the bootable USB partition with: 
    mkdir -p /media/NIXBOOT
mount /dev/sdb1 /media/NIXBOOT
  4. Mount the ISO image with: 
    mkdir -p /media/iso
mount -o loop ~/Downloads/nixos-graphical-0.2pre4463_5e88e9b-c877f45-x86_64-linux.iso /media/iso
  5. Copy the contents of the NixOS ISO (/media/iso) to your USB stick (/media/NIXBOOT) with: 
    rsync -av --progress /media/iso/ /media/NIXBOOT/
  6. Install a complete and recent GRUB to the USB stick with: 
    grub-install /dev/sdb --root-directory=/media/NIXBOOT/
  7. Edit the file /media/NIXBOOT/boot/grub/grub.cfg. Start from an existing grub.cfg, say from your hard drive or from another working bootable USB stick (e.g., from GRML.org). Then, merge in the entry for NixOS from /media/iso/boot/grub/grub.cfg, modifying the LABEL to be that of your VFAT partition: 
    menuentry "NixOS Installer / Rescue" {
  linux /boot/bzImage init=/nix/store/p94ckcksmhj90cr868cpcajrqgzwy57w-nixos-0.2pre4463_5e88e9b-c877f45/init root=LABEL=NIXBOOT
  initrd /boot/initrd
}
  8. To share your USB stick with other distributions (e.g., GRML, or both 32- and 64- bit NixOS), you can move NixOS's bzImage and initrd to different location (e.g., /boot/nix32/ and /boot/nix64/), and you appropriately edit the entries in your grub.cfg. If you have both nix32 and nix64, only one can have its nix-store.squashfs in the root of any given partition. That's where you can use a second partition, for the second one. For instance, copy the contents of your 64-bit NixOS to the first partition, with label NIX64, and copy the nix-store.squashfs of your 32-bit NixOS to the second partition with label NIX32 (and create an empty nix/store). Copy the 32-bit kernel and initrd to /boot/nix32/ on the bootable partition, and edit the grub.cfg of the bootable partition accordingly.
  9. There you go: you have a bootable NixOS USB drive, possibly allowing you to boot NixOS 64-bit, NixOS 32-bit, GRML 64-bit, GRML 32-bit, FreeBSD, FreeDOS, boot-sector-tetris, etc. Just you convince your BIOS to let you boot off it.
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