I created a bootable flash drive by

dd /path/to/ubuntu.iso /dev/sdb

Now after finishing installation of Ubuntu using the flash drive, what command can modify the flash drive , so that it can be used again for storing my personal files transferred to and from Ubuntu and Windows machines? Which file system is recommended for using the flash drive across OSes?



In the following steps I am assuming as an example that you want to restore an 8GB USB flash drive to usable condition after writing the Ubuntu iso to it using dd, although of course the exact size of the USB flash drive is not important. The results of these steps are reproducible. I reformatted 2 USB flash drives with the following steps after writing Ubuntu ISOs to them with dd. As a side remark, it's kind of annoying to use dd instead of a GUI program like Startup Disk Creator, but dd is the only program I have found that works for writing the Ubuntu Minimal CD to a bootable USB flash drive.

  1. Remove all of your USB devices except for the 8GB USB flash drive that you want to reformat, so you won't get confused about the device name of the USB flash drive later on.

  2. List all the partitions.

     sudo fdisk -l

    Search the results of the command for output that looks like this:

     Disk /dev/sdc: 7864 MB, 7864320000 bytes
     30 heads, 33 sectors/track, 15515 cylinders, total 15360000 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: 0x00016288
        Device Boot      Start         End      Blocks   Id  System
     /dev/sdc1   *        2048    15359999     7678976    b  W95 FAT32

    If you see something like 7864 MB (8GB) in the output (see the example output above), then that is your 8GB USB flash drive. In this example it is called /dev/sdc. Now open the Disks application from the Dash and check again to make sure that the device name of your 8GB pendrive is the same as what you got from running the command: sudo fdisk -l.

  3. Create a partition table on the disk of type msdos, sometimes known as Master Boot Record (MBR).

     sudo parted /dev/sdc mklabel msdos

    In this example I used /dev/sdc for the name of the device which is what was found in the results of step 2. I can't stress strongly enough how important it is to verify the device name before running this step!

    Warning: If you type the wrong device name you may overwrite your operating system or another one of your partitions containing important personal files!!! So be careful and check the device name a second time. Open the Disks application and check the device name of your 8GB USB flash drive in Disks. It should be the same device name!!! Now check again! You don't want to accidentally type the wrong device name!

  4. Add an empty "primary" partition, which will hold a FAT filesystem later.

     sudo parted -a none /dev/sdc mkpart primary fat32 0 8192 

    Once again in this example I used /dev/sdc for the name of the device which is what was found in the results of step 2. The command specifies the start point (from 0 MB) to the end point (8192 MB). If the 8GB USB flash drive does not have the full 8192 MB space, parted will adjust it automatically. If the terminal returns a message that the start point can't start at 0 MB and you have to use some other small number close to 0 MB, type Y to accept this. Note the command is creating a single, primary partition on the whole disk.

    This newly created partition will have the ID /dev/sdc1. That is because the device name in this example is /dev/sdc and the 1 at the end is because it is the first partition on that device.

  5. Create a FAT filesystem on the /dev/sdc1 partition by formatting the partition.

     mkfs.vfat -n "8GB-USB" /dev/sdc1

    /dev/sdc1 is the partition ID from step 4. "8GB-USB" is the partition label, which can be your own choice of label, just enclose the label inside two double quote characters.

You now have a ready-to-use reformatted USB flash drive with an 8GB FAT partition.

| improve this answer | |
  • Thanks. I was wondering if you have some good suggestion on unix.stackexchange.com/questions/445443/…? – Tim May 23 '18 at 0:16
  • I found an answer at Ask Ubuntu by sudodus that I liked and commented for him to rewrite it and post it as an answer to your question. Here is a teaser: askubuntu.com/questions/768970/… sudodus is the developer who created mkusb. – karel May 23 '18 at 0:27
  • The reason why I like sudodus's answer is most Linux live USB applications format the USB as a Read-only filesystem that can't be written to not even by a root user, however mkusb can also create a usbdata partition for storing data and sharing data with computers running Windows. – karel May 23 '18 at 0:44

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.