Linux – dd command to create bootable iso image of hard disk

If you are working from within a Linux system (or have access to one), then you can use the 'dd' command to make an ISO from your USB device.

Example: $ dd if=/dev/sdb of=~/usb_image.iso

the 'if' argument designates the input source/file, and the 'of' argument designates the output location name.

Along the same lines, if you have a directory inside your file system that you want to create an ISO out of its contents, then you can use the 'mksiofs' command.

Example: $ mkisofs -o ~/image.iso /source/directory

The the path after the -o parameter is the path where the ISO will be created and the last argument is the path of the source directory.

Ok after some research I've figured out a solution, and I'll go through it step by step. Problem was two-fold.

1. Plug in the USB flash drive and determine the device it's mounted on with the command:

   sudo fdisk -l
   

   This time around it was /dev/sdc1 for me, so I'll use that as my example.

2. Umount the device

   umount /dev/sdc1
   

3. Not sure if necessary but I formatted the drive in FAT32, just in case

   sudo mkdosfs -n 'USB-Drive-Name' -I /dev/sdc -F 32
   

4. Now my ISO was using isolinux not syslinux. I knew it worked with CDs so I figured out that I needed to call the isohybrid command, which allows for an ISO to be recognized by the BIOS from a hard drive.

    isohybrid filename.iso
   

   You can find out more about this command here, but this was the cause of the message "Missing Operating System" The first problem was fixed, but now it said "isolinux.bin was missing or corrupt"

5. The next step is to copy the iso. My second problem lay here, where I was copying to the partition, sdc1, not the device, sdc.

   sudo dd if=filename.iso of=/dev/sdc bs=4k
   

   This seems to work just fine, but the forum where I got the last fix, it was recommended to do the following before unplugging the device:

   sync
   sudo eject /dev/sdc