How to make bootable usb from iso linux

How to Make Bootable USB from ISO using Linux Terminal

There are many USB creator software available to create a bootable Linux USB Drive. Here I will show you how to create a bootable USB flash from ISO file using the Linux terminal.

Table of Contents

Make Bootable USB from ISO using Linux Terminal

Follow the steps to make a bootable USB from iso file using the terminal.

Step1: Check USB Drive

Connect the USB flash drive to your machine and check if it’s connected successfully. Use lsblk command to list all information about the attached block devices.

From the list find your USB drive’s mounted partition. In our case it’s /dev/sdc1. It is mounted by default.

Next, we must unmount the USB flash drive by the following command:

Make sure to change according to your USB drive and check if it has been unmounted again with lsblk command.

You must see the output without mount point in front of sdc1:

Step 2: Download Linux ISO File

Here we will create a Ubuntu bootable flash drive, first go to ubuntu website and download the iso file to your Linux computer. Or you can download iso file from the command line using wget or curl command.

This will download iso file to the current directory.

Step 3: Create Bootable Drive from Terminal

We are going to use dd command to create a bootable USB flash drive.

Where bs is read and write BYTES bytes at a time, if is the input file, of is the output file. The conv=fdatasync bit is important as dd can return before the write operation finishes.

By default the progress of the command will not be displayed, to view the progress you can use pv command:

Note: From 8.24 version of GNU Coreutils, dd command has the option to show the progress.

After the process is finished you can use USB as a bootable drive for ubuntu installation or repair.

Conclusion

If this resource helped you, let us know your care by a Thanks Tweet. Tweet a thanks

Ubuntu Documentation

mkusb

a tool for creating bootable USB drives

Simple. Safe. Reliable.

mkusb is a simple, safe tool to create a bootable drive from an iso image or a compressed image file. The bootable drive is a mass storage device: A USB drive, an internal drive, or an eSATA drive.

The tool provides a safe frontend to select the correct origin file and destination drive, to prevent mistakes that might overwrite the wrong drive. It uses dd under the hood.

Tutorials

See mkusb in action: Here are several quite good recent mkusb walk-through video tutorials.

Quick Start

1. Enable the Universe pocket of the Ubuntu Repositories. Some flavors of Ubuntu already have this enabled. Running this command won’t cause any harm to those flavors.

2. Add the mkusb PPA

If you want the stable version:

or if you want the bleeding edge version:

5. Download or view the detailed mkusb quick start manual pdf that leads users through safely using the software. There is also an alternate link.

WARNING: mkusb will overwrite the entire target device

All existing data on your USB device (or mass storage device) will be lost when you use mkusb to convert the device from storage into bootable media. mkusb clones the ISO 9660 file system with its content from the iso file, overwriting any existing filesystem and data.

To convert the USB (or mass storage device) from bootable back to ordinary storage, you must reformat it (make a new partition table and file system). Once again, all previous data or ‘persistent’ data will be lost.

Advanced usage

When to use (and not use) isohybrid

Cloning an iso file to a mass storage device makes a boot drive, provided it is a hybrid iso file, post-processed with isohybrid. See this link to the isohybrid sub-page

Isohybrid should be run only once, and many iso files are already treated before uploading to the internet. The Ubuntu iso files are already treated with isohybrid. Use isohybrid only, if the USB drive does not boot after installing using mkusb.

This method with dd has a high success rate. It is particularly good for pre-release testing and new releases, when the standard tools like Unetbootin might not be ready (if the configuration of the booting has been changed since the previous release).

Upgrade mkusb

Normally you want to keep and installed system up to date automatically, via a GUI application or the following command lines,

Then all installed packages (from standard repositories and PPAs so also mkusb) will be upgraded.

But a live-only or persistent live system can be damaged by such general updates & upgrades. Instead it is recommended to keep most program packages as they are, and only upgrade packages when really necessary. The following command lines work, when you want to update & upgrade the program packages that belong to mkusb without affecting the other program packages.

Command line syntax

You can use mkusb with an option and with a source file as parameter. You may find it more convenient than to use the graphical interface via [dash or a menu and] a desktop file.

There are more details in

Using mkusb and mkusb-nox from the command line is described in more detail at /advanced

Autoclone

It is possble to autostart the shellscript autoclone in a persistent live drive with Lubuntu and mkusb to install an operating system automatically, which is convenient if you maintain several operatings systems at different places. autoclone is ‘replacing’ the interactive shellscript dus alias mkusb-dus, and calls the executing shellscript dus-live. See the following link,

Software Features

mkusb is a flexible set of tools. You can treat the collection as a single guided application, or you can call subordinate scripts directly, or you can let mkusb choose for you.

mkusb-dus: For Graphical Environments

Most Desktop users will want this version. ‘dus’ is an acronym: Do USB Stuff. It can create LiveUSB with and without persistence.

Details about installation and other aspects of using mkusb via GUI are described at /gui

mkusb-nox: For Servers and Shell Environments

Most user without a GUI will want this. See the NOX Quick Start Manual. It can create LiveUSB with and without persistence.

mkusb-min: The smallest safety belt over dd

However, the slightly larger (20kiB) mkusb-minp version can create LiveUSBs with persistence from iso files of Ubuntu 19.10 and Debian 10 and newer. See the detailed description.

mkusb-bas: When Nothing Else Works

Additional Feature: mkusb-plug

mkusb-plug is a bash shellscript, that wraps a graphical user interface around

xorriso-dd-target to identify the target device via a plug-in test method. This is a very safe way to identify the target device.

mkusb-sedd to create standard cloned live and installer drives and also persistent live drives.

mkusb-tow to create Windows installer drives.

Additional Feature: mkusb-xscl

mkusb-xscl is a bash shellscript, that wraps a graphical user interface around xorriso-dd-target. It can help you manage all the options and save the settings, that work best for you.

Is Thunar cluttering your Desktop?

Installation

mkusb releases

Old: mkusb version 12 uses dus and guidus, the user interface

dus and its graphical front end guidus are easy to use and to maintain.

— v12 Release Notes
— more details about v12
— guidus detailed instructions

New: mkusb version 22 introduces dus-iso2usb

This makes a system that can boot via grub into an iso file both in UEFI mode and BIOS mode (alias CSM alias legacy mode), ‘grub-n-iso’.

Older Releases: mkusb versions 7-11 are deprecated. Find details about improvements and added features at /v7 /v8 /v9 /v10 /v11

If you use mkusb, help test it!

Grab a tarball.
Review the Testing Page to see how to provide feedback and report problems.
Also report workflow issues that could be fixed by a new feature.

Ubuntu

Ubuntu users should use the #Quick Start section at the top of the page. Quick Start has easy, step-by-step instructions. Try it first.

If you encounter problems with the Quick Start instructions:

Ubuntu systems must enable the «Universe» pocket of the Ubuntu repositories in order to install the pv package (18.04 and older) and the wmctrl package. Some flavors of Ubuntu, including Kubuntu, Lubuntu, and Xubuntu already have Universe enabled. Other flavors should use the following command to enable Universe:

Use only versions of Ubuntu that are within their community support window (5 years LTS, 9 months non-LTS). After end of community support there will be no updates, not even security updates. If you waited too long and can no longer install programs from the Ubuntu repositories due to end of life, you can use a web browser to install mkusb-min and use it in a terminal window (or in text mode) to create a live system in a USB drive or memory card. This is more tedious than using the PPA, so don’t wait until end of life.

Debian

Other linux distros

When a linux distro is getting close to end of life, please try to find a new version or another distro with support for a fair interval of time, and that works in the computer. After end of life there will be no updates, not even security updates, so the connection to internet is no longer secure.

If you can run a web browser, you can install mkusb-min and use it in a terminal window (or in text mode) to create a live system in a USB drive or memory card. This works, but is not very convenient, if you are not used to terminal windows and command lines.

You can use mkusb to create a USB boot drive or a memory card with a new operating system to try (and install if it works well).

Windows Installation

Quick method to get a portable linux system

The 9W-DUS_i686.exe application provides a quick method to get a portable linux system with the tool dus (mkusb-dus). It can create persistent live systems in Ubuntu and Debian and systems developed from them. It can also be used for other system tasks and can be a first step from Windows. See this link,

Win32 Disk Imager

Win32 Disk Imager is a cloning tool for Windows to make USB pendrives boot Ubuntu and other linux operating systems.

Description of the method and the tool

Warning about overwriting the target device

mkusb will ‘use the whole device’, actually only the head end (size of the iso file), but the rest of the device is not available. mkusb simply clones the ISO 9660 file system with its content from the iso file. This ISO 9660 file system works from CD/DVD disks, and also from USB drives. After using a USB pendrive like this, you make a new partition table and file system, if you want to use it for another purpose.

Help selecting the correct target device

The crucial task of mkusb was and is to help selecting the correct device and avoid overwriting other devices.

Doing the same thing many times

For the first time I was helping to test a new Ubuntu version (Lubuntu 12.04 LTS). After a while I wanted to make it simpler and safer to transfer the code to the USB pendrive.

The standard tools

The standard tools to create USB boot drives are described with more details at the following links,

Tools like Rufus and Unetbootin assume you have a USB drive partitioned with a FAT32 file system and pick the content (file by file) of the iso file and enter it into the FAT32 file system. They must also install a bootloader. This process is much more complicated and prone to problems than cloning an iso file or compressed image file. This is why they might not be ready for a new release (if the configuration of the booting has been changed since the previous release).

dd image of iso file to USB device safely

But I also read somewhere that it should be possible to boot from a direct image of the iso file. So I tried it with dd, the ‘disk destroyer’. And it works, the computer boots from a USB device (pendrive, stick, flash drive, but also disk or SSD) just like it were from a CD drive. Also like a CD, it will be mounted read-only, so it cannot carry persistence.

Since dd is a bit risky, I made a shell-script, so that you get advice from a help text and need not run dd, but with support from the script to avoid writing to any wrong drive. The first time you must select the correct USB device, if more than one are connected. So it is safer and also much more convenient (but nothing is 100% safe).

I cloned ubuntu-12.04-desktop-amd64.iso this way, and the USB pendrive worked in both UEFI and CSM (BIOS) modes (but that version of Ubuntu has passed end of life now, and there are current versions with similar or better compatibility, that boot when cloned to a USB drive).

The block size ‘bs=4096’ is used, when mkusb calls dd under the hood. This was selected after testing different block sizes in different cases, when mkusb was new in April 2012. Software and hardware have been developed during five years, so I made a new test in June 2017, and found no reason to change the block size. There is a detailed description of the new test at this link,

iso-testing mode

In mkusb version 11 and mkusb-nox the next daily build will automatically select the correct USB device (when it is inserted into the computer). So for the next daily builds it is safe and very convenient. This feature was removed in mkusb version 12 alias mkusb-dus.

Shell script

The shell-script mkusb has been updated and improved many times and will be updated again when necessary. It is now convenient to use also for one-off creations of USB boot devices from iso files and compressed image files and also to wipe the drives if necessary after the cloning. The shellscript can monitor the data transfer with pv, and suggests that you install it, if not available.

Persistent live systems

Most of the time it is enough with a live only USB pendrive and only a waste of effort to create a persistent live system. The cloning method of mkusb is very reliable and works with most linux distros. It needs hybrid iso files. But sometimes it is better to have a persistent live system, and beginning with version 10 mkusb can create such systems.

‘mkusb/persistent’ system in one single drive

This is a system that is prepared automatically by mkusb.

See the following sub-page for more details: /persistent

‘Simple persistence’ in two drives

This is a system that uses a cloned read-only boot drive (CD, DVD, USB) and another drive with partitions for persistence.

See the following sub-page for more details: /sp

Expansion and imaging from a compressed image file

mkusb can clone or flash complete installed systems from an image file file.img or a compressed image file file.img.gz or file.img.xz, for example

dd_Ubuntu_16.04-gamma-UEFI-n-BIOS-4-pendrive-12GB.img.xz from http://phillw.net/isos/linux-tools/uefi-n-bios and

dd_Ubuntu_16.04-gamma-UEFI-n-BIOS-12GB.img.xz for solid state and hard disk drives

dd_text_16.04-UEFI-n-BIOS_2016-05-27_4-pendrive-7.8GB.img.xz mini system with a text user interface

dd_text_16.04-UEFI-n-BIOS_2016-05-27_intel-4-pendrive-7.8GB.img.xz mini system with a text user interface for Intel graphics

From mkusb version 10.6.6 there are built in functions, that make it possible to use this method not only with the MSDOS partition table but also the GUID partition table (GPT), where there is a backup table at the very end of the drive. The functions gpt_zap and gpt_fix are built into mkusb.

Check the download with md5sum

Remember to check with md5sum, that the compressed image file was downloaded successfully.

Re-use the pendrive

In order to re-use the pendrive after installing a linux operating system, it is usually enough to format it completely (including MBR) using gparted in linux or Disk Management in Windows. See details in this link.

Wipe the first megabyte or the whole device

Sometimes there are data on a USB drive, that make the operating system or some tool confused. In such cases it often helps to wipe the first megabyte, overwrite it with zeros. But it means that all data on the drive will be lost. See the following sub-page for more details.

Wipe the whole device

To wipe-whole-device with mkusb is a very special task, that is not recommended except in very special situations. Other tools are better to wipe an entire HDD or SSD for example hdparm or DBAN.

Windows USB install drive

There is a new Windows installer via mkusb-plug that works well in 64-bit versions of Ubuntu with Windows versions 7, 8, 10, and 11. This method is also ported to mkusb-dus (version 12.5.7) using the same tool mkusb-tow.

The following [old] method works well both with 32-bit and 64-bit versions of Ubuntu, also older versions. This method is tested and works with Windows versions 7, 8, and early editions of 10. With 64-bit versions of Windows, the target drive will be able to boot and install in BIOS mode as well as in UEFI mode.

Reliable to extract via a tarfile

Sometimes in Ubuntu based 32-bit systems, it was not possible to extract the content from the Windows iso file directly to a USB pendrive. The files were not copied correctly (with any of the standard copying tools: cp, rsync, dd) in Ubuntu 16.04.1 LTS (the current Ubuntu version, when this feature was added to mkusb-nox). But it works in a reliable way to extract to a tarfile, and then extract from the tarfile to the USB pendrive.

Problem with the 4 GiB max file size in FAT32

Several (but not all) Windows 10 iso files released in October 2018, Win10_1809Oct_Language_x64.iso contain a version of the file install.wim with size > 4 GiB. It means that the previous method does not work because the FAT32 file system cannot manage it.

New method works with current versions of Windows

use mkusb-plug with the tool mkusb-tow. This works in both BIOS and UEFI mode also with secure boot.

use mkusb-dus with the same tool mkusb-tow. See this link.

use woeusb according to this link. This works in both BIOS and UEFI mode but not with secure boot.

do it yourself with detailed help at help.ubuntu.com/community/Installation/iso2usb/diy/windows-installer-for-big-files. This works in both BIOS and UEFI mode also with secure boot. It is actually the same method that is automated in mkusb-plug.

mkusb-nox

mkusb-nox 11.1.2: added feature: make USB install drive for Windows.

dus with guidus alias mkusb version 12

The two step extraction method is ported from mkusb-nox to dus, and lets you use a graphical interface for the user dialogue.

The output into the console window is similar to that from mkusb-nox.

See the following screenshot and text dump, guidus-console_making_windows-boot-drive.png:

See also this text dump with the whole output, which can be seen if you scroll the text in the console window:

References

Screendumps were made with the previous and current versions of mkusb. There are (text) screendumps from previous versions, including the latest non-menu version 7, in the corresponding version of the quick start manual.

Screendumps that illustrate how to use mkusb:

Artwork subwiki page, a place for icons and misc stuff.

Win32 Disk Imager is a corresponding tool for Windows to make USB pendrives boot Ubuntu and other linux operating systems.

mkusb (последним исправлял пользователь nio-wiklund 2022-07-18 13:59:55)

The material on this wiki is available under a free license, see Copyright / License for details
You can contribute to this wiki, see Wiki Guide for details

3 Ways to Create Bootable Ubuntu USB Startup Disk

Creating a bootable USB drive is one of the most preferred ways of testing and installing a Linux operating system on a PC. This is so because most modern PCs don’t come with a DVD drive anymore. Further, USB drives are easily portable and less delicate than a CD / DVD.

Many graphical tools abound that can help you create a bootable USB drive. One of the most widely used tools is Rufus, a simple yet very effective tool. Sadly, it’s only available for Windows systems.

Thankfully, Ubuntu ships with its own tool called Startup Disk Creator. The tool is easy to use and allows you to create a bootable Ubuntu USB disk in no time.

With a bootable Ubuntu USB drive you can perform the following operations:

With that in mind, let’s see how you can create a bootable Ubuntu USB startup disk.

Requirements

For this exercise, ensure that you have the following prerequisites before you get started:

In this guide, we will explore three methods that you can use to create a bootable Ubuntu USB startup disk.

On this page:

Let’s shift gears and see how you can create a startup Ubuntu.

Creating Ubuntu USB Startup Disk Using Graphic Tool

The Startup disk creator is Ubuntu’s native tool that comes preinstalled in every modern Ubuntu release. It allows a user to create a Live USB drive from an ISO image is a simple yet fast and effective way.

To launch Startup Disk creator, click on ‘Activities’ at the top left corner of your desktop and search for the tool in the application manager as shown. Next, click on the ‘Startup Disk Creator’ option to launch it.

Launch Startup Disk Creator

Once launched, you will get a window as shown. The upper section displays the path of the ISO image, the version of the ISO file and its size. If all options are okay, proceed and hit the ‘Make Startup Disk’ option to commence the process of creating the bootable USB drive.

Create Bootable Ubuntu USB Disk

Thereafter, you will get a pop-up notification asking you whether to proceed with the creation or abort. Click on the ‘Yes’ option to initialize the creation of the bootable drive. Provide your password to authenticate and start the process.

Initialize USB Bootable Drive Creation

The Startup Disk Creator tool will begin writing the disk image onto the USB drive. This should only a few minutes to be completed.

Writing Disk Image to USB Drive

Once complete, you will get the notification pop-up below indicating that all went well. To try out Ubuntu, click on the ‘Test Disk’ button. If you want to go ahead and start using the bootable drive, simply click ‘Quit’.

USB Disk Creation Complete

Creating Ubuntu USB Startup Disk Using DDrescue Command

The ddrescue tool is a popular data recovery tool that you can use to recover data from failed storage devices such as hard drives, pen drives, etc. Additionally, you can use the ddrescue tool to convert an ISO image to a startup USB drive.

To install ddrescue on Ubuntu / Debian systems execute the command.

NOTE: Repositories refer to it as gddrescue. However when invoking it on the terminal use ddrescue.

Next, we need to verify the block device volume of the USB drive. To achieve this, use the lsblk command as shown below:

Verify USB Block Device Volume

Now use the syntax below to create a bootable USB stick.

For example to create a Ubuntu 20.04 startup disk we executed the command below.

The process takes a few minutes and your bootable USB drive will be ready in no time.

Create Bootable USB Disk Using ddrescue Command

Creating Ubuntu USB Startup Disk Using dd Command

Another simple and easy to use command-line tool you can use to create a startup disk is the dd command. To use the tool, plug in your USB drive and identify the device volume using the lsblk command.

Next, unmount the USB drive using the command below:

Once the USB drive is unmounted, run the following command:

Where Ubuntu-20.04-beta-desktop-amd64.iso is the ISO file and bs=4M is an optional argument to help accelerate the process of creating the bootable drive.

Create Bootable USB Disk Using dd Command

You can now eject your Live USB drive and plug it to any PC and either try out or install Ubuntu.

This brings us to the end of this topic. We hope you found this guide useful and that you can now comfortably create a bootable USB startup disk using all the methods explained herein.

If You Appreciate What We Do Here On TecMint, You Should Consider:

TecMint is the fastest growing and most trusted community site for any kind of Linux Articles, Guides and Books on the web. Millions of people visit TecMint! to search or browse the thousands of published articles available FREELY to all.

If you like what you are reading, please consider buying us a coffee ( or 2 ) as a token of appreciation.

We are thankful for your never ending support.

A Bash Script to Create a Bootable USB from ISO in Linux

Bootiso is a powerful Bash script to easily and securely create a bootable USB device from one ISO file. It helps you create a bootable USB from an ISO with a single command from the terminal. It is a well tailored script that carefully organized and validated using shellcheck.

It has to be run with root authority, and if external programs it requires are not available on your system, it will ask you to install them and exits. Bootiso checks that the selected ISO has the correct mime-type, otherwise it exits. To prevent system damages, it ensures that the selected device is connected only via USB.

Before formating and partitioning your USB device, it prompts you to accept execution of the actions to prevent any data loss. Importantly, it manages any failure from an internal command appropriately exits. In addition, it performs a cleanup of any temporary files on exit by employing the trap utility.

Install Bootiso Script in Linux

The easy way to install bootiso from sources is to clone the git repository and set execute permission as shown.

Next, move the script to a bin path (for example

/bin/ or /usr/local/bin/) to run it like any other Linux commands on your system.

Once installed, the syntax for running bootiso is to provide the ISO as first argument.

Next, to make the device ( /dev/sdb ) as a bootable device, simply provide the ISO as the first argument. Note that if there is only one USB device attached to the system (as in the case above), the script will automatically select it, otherwise, it will ask you to select from an auto-generated list of all attached USB drives.

Create Bootable USB in Linux Terminal

For more information on other bootiso capabilities and options, see the help message.

That’s It! Bootiso is a powerful Bash script to easily and securely create a bootable USB device from one ISO file, with a single command on the terminal. Use the comment form below to share your thoughts about it or ask questions.

If You Appreciate What We Do Here On TecMint, You Should Consider:

TecMint is the fastest growing and most trusted community site for any kind of Linux Articles, Guides and Books on the web. Millions of people visit TecMint! to search or browse the thousands of published articles available FREELY to all.

If you like what you are reading, please consider buying us a coffee ( or 2 ) as a token of appreciation.

We are thankful for your never ending support.

Ubuntu Documentation

Outline

Get the correct Ubuntu installation file, ‘the iso file’, via this link or Ubuntu flavour via this link. Download the iso file into your running computer (for example into the directory Downloads in the internal drive, not into the USB flash drive that you want to make into a USB boot drive).

See also: Installation/FromUSBStickQuick for beginners starting from Windows.

Introduction

Ubuntu can be installed from a USB flash drive. This may be necessary for most new portable computers without DVD drives and is handy for others because a USB flash drive is so convenient. Also, you can configure Ubuntu on the USB flash drive to save changes you make, unlike a read-only CD/DVD disk.

Booting from a USB flash drive created with usb-creator alias Startup Disk Creator and mkusb will behave just as if you had booted from the install CD. It will show the language selection and then the install menu, from which you can install Ubuntu onto the computer’s hard drive or launch the LiveCD environment. Other utilities, e.g. UNetbootin, may create slightly different boot drives or if on UEFI might not work at all with Debian iso files due to a bug

Note: This article uses the term «USB flash drive» alongside USB stick, USB drive, USB device, USB pendrive and thumb drive.

Prerequisites

To create a USB installation device, you will need:

a 4 GB USB flash device/drive/stick. If the iso file is smaller than 2 GB, it is possible to use a 2 GB USB device, at least with some of the methods. Files on this USB device will be erased, so backup the files you want to keep before making the device bootable. Some of the tools require that this USB device is properly formatted and mounted while other tools will overwrite whatever is on the target device. Please follow the instructions for each tool.

an Ubuntu flavour ISO file downloaded from an official web page, ubuntu.com/download or http://releases.ubuntu.com, stored in your running computer (for example in the directory Downloads in the internal drive, not in the USB flash drive that you want to make into a USB boot drive).

Check with md5sum (or another checksum tool) that the download was good. In Linux there is the tool ‘md5sum’. In Windows you can do it with Rufus: click on the circle with a tick mark (more about Rufus here.)

Dummy headlines

After a major remake of this help page the following headlines are kept here because they may be linked to from other web sites. Several other headlines further down in the page are also kept for this reason.

Notes about speed

Notes about size

Notes about bootability

The flash hardware

There is a detailed description at the sub-page /pre

Creating a bootable Ubuntu USB flash drive from Windows

There are various methods available for Windows to create a bootable Ubuntu USB flash drive.

NEVER try to use one of your hard disk drives or partitions in this process unless you really know what you are doing, as data will get erased.

Rufus

Rufus is the tool in Windows that is recommended officially by Ubuntu. A tutorial is available from here.

balenaEtcher

Pendrivelinux’s Universal USB Installer

UNetbootin

Win32 Disk Imager

There is a detailed description at /fromWindows including Rufus, balena Etcher, Universal USB Installer, Unetbootin and Win32 Disk Imager.

Creating a bootable Ubuntu USB flash drive from Ubuntu

Install and run Startup Disk Creator alias usb-creator

You must enter a password because this is a risky operation. Use the password of the current user ID (the same as for login and running tasks with 'sudo'. Password is not required when installing from a ‘live’ system (booted from a DVD disk or another USB flash drive).

The Startup Disk Creator clones the iso file, which means that you need neither erase nor format the target drive. It will be completely overwritten anyway by the cloning process. The Startup Disk Creator looks like this in Ubuntu 18.04 LTS:

Notes

NEVER try to use one of your hard disk drives or SSDs or partitions in this process unless you really know what you are doing, as data will get erased.

There are bugs that affect the Ubuntu Startup Disk Creator, when you run it in old Ubuntu versions in BIOS mode and try to create USB boot drives with other versions. In the Ubuntu Startup Disk Creator version 0.3.2 in Ubuntu 16.04 LTS, these bugs are no longer a problem, so you can install any version of the Ubuntu flavours from 16.04 LTS and newer versions.

UNetbootin

There is a detailed description at /fromUbuntu including the Startup Disk Creator, UNetbootin and mkusb.

Creating a bootable Ubuntu USB flash drive from Mac OSX

Test if running in UEFI mode

You may want to test if your Ubuntu flavour is running in [U]EFI mode. An installed system and a live system too is using the directory /sys/firmware/efi, so you can run the following command line,

The following command line is more robust and also easier to understand, so you may prefer it (if you copy & paste and are not bothered by typing a long command line),