boot - Missing Operating System on USB drive - Ask Ubuntu

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• how install ubuntu usb key? (without using startup disk creator) 17 answers

i'm trying install minimal ubuntu installation on usb drive (complete install, not live boot). after installation, however, when try boot usb, "missing operating system".

i think there might problem grub, don't know how fix it. i've done install usb before messed main grub file, don't want that.

this output of fdisk -l pertaining usb drive:

disk /dev/sdc: 4027 mb, 4027580416 bytes 124 heads, 62 sectors/track, 1023 cylinders, total 7866368 sectors units = sectors of 1 * 512 = 512 bytes sector size (logical/physical): 512 bytes / 512 bytes i/o size (minimum/optimal): 512 bytes / 512 bytes disk identifier: 0x73a571aa  device boot      start         end      blocks   id  system /dev/sdc1            2048     7616511     3807232   83  linux /dev/sdc2         7618558     7864319      122881    5  extended /dev/sdc5         7618560     7864319      122880   82  linux swap / solaris 

also, boot partition may not labeled bootable, based on output. please help!

update

i followed terrance's suggestion, /dev/sdc1 labeled boot partition. however, drive still won't boot.

i not asking how install ubuntu usb drive, i'm asking fixing usb i've installed ubuntu to.

update

terrance's updated answer solved me. note, working on usb had create /boot/extlinux/syslinux.cfg file containing:

prompt 0 timeout 50 default arch  label arch         linux ../vmlinuz-4.4.0-45-generic         append root=uuid=[the usb uuid]         initrd ../initrd.img-4.4.0-45-generic 

you can set boot flag on first partition of usb drive typing in following terminal window:

sudo parted /dev/sdc set 1 boot on 

also try installing extlinux , syslinux-common putting boot files on usb drive. terminal, type in:

sudo apt install extlinux syslinux-common 

after installed, have usb drive in , type in:

sudo mkdir -p /mnt/usb/boot/extlinux sudo extlinux --install /mnt/usb/boot/extlinux 

or whatever mount point usb drive /media/username/1001-baab/boot/extlinux

then should install mbr code usb drive following command: don't worry, not overwrite usb drive.

dd if=/usr/lib/extlinux/mbr.bin of=/dev/sdc bs=440 count=1 

make sure /dev/sdc usb drive.

more info can found here: http://shallowsky.com/linux/extlinux.html

from manpage extlinux:

name        extlinux  -  install  syslinux bootloader on ext2/ext3/ext4/btrfs        filesystem 

hope helps!