Creating bootable USB Drives with Etcher

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Marcel Derweduwen, 123RF

Marcel Derweduwen, 123RF

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Etcher is an easy-to use graphical tool for making a bootable USB from an ISO file.

As a rule, distributions can be downloaded from the Internet as ISO files. If you are not using the file in a virtual machine, you will have to put it on a bootable data storage device. Previously, CD/DVD burners took on the task of putting an ISO image on a fresh medium. Nowadays, USB drives and SD cards have become the medium of choice.

This change has occurred for a number of reasons. For one thing, most handheld computers like notebooks and compact ultra books no longer come with an optical drive. With the introduction of USB 2.0 specifications, the USB interface allows for enough speed to start an entire operating system within an acceptable amount of time. Currently, USB 3.0 lets high performance sticks achieve transfer rates of over 200MBps. These rates far surpass those for optical drives.

Under Linux, there are several, well-established tools that can easily create a bootable USB drive. Even so, the old adage "the devil is in the details" is definitely applicable here. Many ISO files do not start by themselves from a USB. At the very least, you will have to carefully prepare the drive before loading the image.


ISO files are based on the ISO 9660 filesystem standard [1] that was released in 1986. This is a standard that was specially created for optical data storage devices. In order to start an operating system image from an optical data storage device, the device has to have a boot sector according to the El Torito standard, which allows live operation without installing the system. However, ISO files with an El Torito boot sector are not suitable for booting from a USB drive.

The ISO 9660 standard allows for the system area at the beginning of the filesystem to integrate multiple boot sectors in a single image. This makes it possible for a given volume boot record (VBR) to start the operating system from a flash drive. SD cards can be used as an alternative. These cards are also suitable for use as VBR-enabled boot media. ISO images that integrate different boot sectors are known as hybrid images.

Another problem arises with the filesystems on memory sticks. Current devices insist on the use of a FAT32 filesystem. This means that ext3/4 and NTFS do not work for creating bootable USB drives. Therefore, you don't have to modify the filesystem on a newly purchased drive since practically all of them now come with FAT32 by default. Older memory sticks and first generation SD cards mostly come with FAT16, which is also suitable for creating a start medium.


The command-line tool dd [2] is typically used under Linux for sending ISO files to a USB drive. This is a reliable and stable tool. It requires input from the source (if ) and the target (of ). You will need to pay special attention when inputting the target drive. If the path or drive is not correct, then you may end up overwriting the local hard drive.

Several graphical tools that are distribution-specific like USB ImageWriter [3] under Linux Mint, ImageWriter [4] under openSUSE, or the ROSA ImageWriter [5] from ROSA Linux serve as front ends for dd . This simplifies the operation of this tool.

Reformatting the drive is frequently omitted, or reformatting is launched by externally connected tools. However, such tools exclusively write hybrid images to a USB drive since they produce a copy of the ISO image byte by byte. For this, you will most probably need a USB drive that has likewise been prepared with the suitable filesystem.

UNetbootin [6] is the only current tool that can also transfer non-hybrid images to a USB drive correctly. It is able to do this by making complex modifications to the image file. However, the tool often fails when dealing with current ISO images without an entry for a VBR boot sector.

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