Table of Contents
Why You Need a Bootable USB
To install Linux on a real machine or in many virtualized scenarios, you typically start the computer from an installation image stored on a USB drive. A “bootable USB” is a USB stick that contains:
- A Linux installation image (an
.isofile) - A bootloader so your computer can start from it
This chapter focuses on the practical steps to turn an ordinary USB stick into a bootable Linux installer.
What You Need Before You Start
- USB drive
- Capacity: typically 4 GB minimum, but many distributions now require 8 GB or more
- All data on it will be erased.
- Linux ISO file
- Download from the official site of your chosen distribution (e.g. Ubuntu, Fedora, Debian).
- Check that you’re downloading for the right architecture (commonly
x86_64oramd64for modern PCs). - A working computer
- You can create the USB from Windows, macOS, or Linux.
- (Optional but recommended) Checksum file (
.sha256,.sha256sum, or similar) to verify the ISO.
Choosing a Tool to Create the Bootable USB
The common approaches depend on your current operating system:
- On Windows
- Graphical tools:
- Rufus (very popular, lightweight)
- balenaEtcher (simple, cross-platform)
- Ventoy (stores multiple ISOs on one USB)
- Command-line tools (less common for beginners).
- On macOS
- Graphical tools:
- balenaEtcher
- Terminal:
ddand related utilities.- On Linux
- Graphical tools:
- balenaEtcher
- GNOME Disks (often called “Disks”)
- Distribution-specific utilities like “Startup Disk Creator” (Ubuntu)
- Command-line:
ddor specialised tools likeventoy(after installation).
For beginners, a graphical tool (Rufus or balenaEtcher) is usually the easiest.
Verifying the ISO (Basic Overview)
Many distributions publish a checksum (often SHA256) for the ISO. You can quickly verify that the download isn’t corrupted:
- On Linux/macOS (in the directory with the ISO):
sha256sum your-distro.iso- On Windows (PowerShell):
Get-FileHash .\your-distro.iso -Algorithm SHA256Compare the output with the checksum listed on the distribution’s download page. They must match exactly. This step is optional for casual use, but good practice.
Creating a Bootable USB on Windows (Rufus)
Rufus is a single .exe file, no installation required (for the portable version).
- Download Rufus
- From the official website: search for “Rufus USB” and download the latest version.
- Insert your USB drive
- Make sure you’ve backed up any data on it.
- Open Rufus
- Under Device, choose your USB stick.
- Under Boot selection, click SELECT and choose your Linux
.iso. - Partition scheme and target system
- For most modern computers with UEFI:
- Partition scheme:
GPT - Target system:
UEFI (non-CSM) - For older BIOS-only machines:
- Partition scheme:
MBR - Target system:
BIOS (or UEFI-CSM) - If unsure, leaving defaults usually works for most recent PCs.
- File system
- Leave it as the default (
FAT32is common and widely supported). - Write method
- For most standard Linux ISOs, select ISO Image mode (Recommended) if prompted.
- Start the write
- Click START.
- Confirm any warning that the USB will be erased.
- Wait for completion
- When Rufus says READY, safely eject the USB via Windows before unplugging it.
Your USB is now bootable.
Creating a Bootable USB on Windows or macOS (balenaEtcher)
balenaEtcher has a very simple interface and works similarly on all supported OSes.
- Download and install balenaEtcher
- From the official balenaEtcher website.
- Run Etcher
- Click Flash from file and select your Linux
.iso. - Click Select target and choose your USB drive.
- Click Flash!.
- Wait for flashing and validation
- Etcher writes the image and then verifies it.
- When it reports success, you can safely remove the USB (use your OS’s safe eject option).
Creating a Bootable USB on Linux (Graphical Tools)
Using GNOME Disks (often just “Disks”)
This tool is available on many GNOME-based desktops.
- Launch Disks
- Search for “Disks” in your application menu.
- Select the USB drive
- Be careful to choose the correct device.
- Restore Disk Image
- Click the menu button (often three vertical dots) and choose Restore Disk Image….
- Select your Linux
.iso. - Confirm
- Verify the correct USB is selected and start the write.
- Wait and eject
- When finished, safely remove the USB.
Using Ubuntu’s Startup Disk Creator
On Ubuntu and some derivatives:
- Search for Startup Disk Creator in the menu.
- Choose the downloaded
.iso. - Select the target USB drive.
- Click Make Startup Disk.
- Wait for completion and safely remove the USB.
Creating a Bootable USB on Linux or macOS (Command Line with `dd`)
The dd command writes data directly to a device. It is powerful and dangerous if you choose the wrong target disk. Double-check everything.
Step 1: Identify the USB device
On Linux:
lsblk
Look for your USB drive, e.g. /dev/sdb or /dev/sdc. Do not include partition numbers like /dev/sdb1 as the device target.
On macOS:
diskutil list
Find the USB disk, e.g. /dev/disk2.
Step 2: Unmount the USB partitions (if needed)
On Linux:
sudo umount /dev/sdX*
Replace sdX with your device (e.g. sdb).
On macOS:
diskutil unmountDisk /dev/diskN
Replace diskN with your USB disk (e.g. disk2).
Step 3: Write the ISO with `dd`
On Linux:
sudo dd if=path/to/your-distro.iso of=/dev/sdX bs=4M status=progress conv=fsync
On macOS (use rdisk for better speed):
sudo dd if=path/to/your-distro.iso of=/dev/rdiskN bs=4mif= input file (your ISO)of= output file (the entire USB device)bs= block size (e.g.4M)status=progressshows progress (Linux)conv=fsynchelps ensure all data is written
Wait until the command completes and the shell prompt returns.
Step 4: Safely remove the USB
On Linux:
sudo eject /dev/sdXOn macOS:
diskutil eject /dev/diskNUsing Ventoy for Multiple ISOs (Optional)
Ventoy is different from traditional tools: it turns the USB into a special drive where you simply copy ISO files, and it presents a boot menu.
Basic idea:
- Install Ventoy to the USB using the Ventoy tool (available for Windows and Linux).
- After installation, mount the USB and copy multiple
.isofiles onto it. - Boot from the USB; Ventoy shows a menu where you pick which ISO to boot.
This is handy if you test many distributions or need rescue tools, but it’s slightly more advanced than single-ISO tools like Rufus or Etcher.
Recognizing a Successful Bootable USB
After creating the USB, you typically:
- Insert it into the target computer.
- Enter the boot menu or firmware setup (UEFI/BIOS) at startup (often by pressing a key like
F12,F2,Del, orEsc). - Choose the USB as the boot device.
If the USB is correctly prepared and your system is configured to boot from it, you should see the Linux distribution’s boot or installation menu.
If instead you boot into your usual OS or see an error like “No bootable device,” the issue may be:
- USB not set as first boot device / not selected in the boot menu.
- Wrong partition scheme vs. firmware mode (UEFI vs BIOS).
- Incomplete or failed write process.
- Corrupted or wrong ISO file.
Common Pitfalls and Quick Checks
- USB not appearing in tool:
- Try replugging or using another port.
- On Windows, close other software that might use the USB.
- Tool warns about ISO mode vs DD mode (Rufus):
- If unsure, start with ISO mode.
- Use DD mode only if told by the distribution’s documentation.
- After flashing, Windows shows a tiny or unreadable USB:
- This is normal: a bootable Linux USB uses partitions and filesystems Windows may not understand.
- Do not reformat if you plan to use it for installation.
- Very slow writing:
- Old USB 2.0 drives can be slow; patience may be required.
- Using a USB 3.0 port and drive can speed things up.
Once you’ve created a working bootable USB, you’re ready to move on to installing Linux on real hardware or using it for live sessions and troubleshooting.