Partition – How to Use a Partitioned Live USB

live-usblivecdpartition

I have a USB device and i'm trying to create it in a way that it has 2 partitions: one for a live linux disc and the other for document storage.

I created the partitions using gparted and and set a boot flag to the one I want to use as the live disc. Now, I have a usb like this:

Disk /dev/sdc: 14.6 GiB, 15623782400 bytes, 30515200 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
Disklabel type: dos
Disk identifier: 0xc3072e18

Device     Boot   Start      End  Sectors  Size Id Type
/dev/sdc1       8439808 30515199 22075392 10.5G 83 Linux
/dev/sdc2  *      51200  8439807  8388608    4G  b W95 FAT32

I then used dd to flash an Ubuntu iso to /dev/sdc2

sudo dd if=/dev/shm/ubuntu-17.04-desktop-amd64.iso of=/dev/sdc2 bs=4M

When the disc is flashed onto the usb drive, I try to boot from my laptop and it shows "Operating system not found". When i try to use qemu/kvm, it shows a kernel panic like this:

How would I be able to do this properly?

Best Answer

You received the Operating system not found error because by writing the ISO to a disk partition rather than the disk as a whole, you inadvertently did not write a boot loader to the disk's MBR gap. And... apparently the PC doesn't care about the boot flag.

I see two possible solutions, but I must say, I'm really just pulling this out of my [censored].

Partition the disk after `dd`'ing the ISO

The best part of this solution is that you'll know whether it's feasible real quick.

dd the ISO to the entire USB disk
Check the USB disk for partitions using a partitioning tool. If you see partitions, you can probably add one for your encrypted volume.

Add a bootloader to chainload into the partition.

The idea here is to add a boot loader to the USB disk's MBR gap, and have it chainload whatever boot loader is in the partition. Chainloading basically delegates the boot loader's functionality to another bootloader. I'll direct to you Gentoo's documentation on the topic, considering it's quite thorough.

Other

If the above fail, you can try building your own Ubuntu ISO, adjusting how it boots.

Related Solutions

Debian – How to Move Root (/) to a New Partition

I'd suggest using LVM. To switch over, something like this:

Create a physical volume (pvcreate) on your existing /dev/sda2 (Windows partition)
Create a volume group consisting of just /dev/sda2 (vgcreate)
Create a logical volume to hold your / and /home (any reason you're splitting them? You don't need to.) (lvcreate)
mkfs the two new logical volumes (device: /dev/mapper/vgname-lvname)
If you're not already booted from a rescue disc, boot from one (you could use the Debian install disc, just switch to a terminal at the appropriate point, or alternatively a Ubuntu disc)
mount the new logical volumes (or just one, if you decide not to split). If you mount both, make sure to mount home inside the new root (e.g., as /new-root/ and /new-root/home) Mount your old rootfs somewhere, too.
use tar to copy the files over. Something like ( cd /old-root && tar --one-file-system -c . ) | ( cd /new-root && tar vx )
chroot into your new root filesystem, and:
1. change /etc/fstab to give the proper root filesystem
2. mount /proc and /sys and /boot (inside the chroot)
3. update-initramfs -u
4. update-grub
5. if you're paranoid, look at the generated /boot/grub/grub.cfg to check that it picked up the new rootfs.
6. exit the chroot
Finally, unmount the filesystems you mounted (starting with /new-root/{proc,sys,boot}), and reboot.
Confirm you've booted to the new root filesystem. E.g., check /proc/mounts. Confirm your data is present. (You do have backups too, right?) VERY IMPORTANT.
This is the point of no return. The next steps destroy your old partitions.
You can now pvcreate your old partitions, then add them to your volume group (vgextend)
You can now resize your / and /home logical volumes using lvextend followed by resize2fs (or whichever tool for your filesystem). This can be done online, with your system running.

Once you're on LVM, any future disk changes are much easier. You can use the LVM commands to do pretty much any disk change, with the system running even.

(Note: I haven't done this for a bit, I may have missed a step or two, but I'm pretty sure I haven't missed anything catastrophic. And of course, your original install & data is still around until after you've confirmed you're booted onto the new rootfs)

DD Command – How to Clone a Partition from Disk Image

# losetup --find --show --partscan --read-only 2013-02-09-wheezy-raspbian.img
/dev/loop7
# dd if=/dev/loop7p2 of=/dev/narnia bs=1M

If --partscan doesn't work, you can also use one of:

# partx -a /dev/loop7
# kpartx /dev/loop7

or similar partition mapping solutions.

You should probably mount it first just to see if it's the right thing or what.

Of course you can also read the fdisk output and give dd the skip=131072 or whatever directly, i.e. make it skip that many blocks of input so it starts reading at where the partition is located; but it's nicer to see actual partitions with a loop device.