Ubuntu Installation Failed? Find the Stage Before Trying Again

When an Ubuntu installation fails, the most useful question isn’t “Which fix should I try?” It’s “At what stage did it fail?” A USB that won’t boot, a crash during partitioning, and a system that won’t start after installation are different problems. Repeating the install without narrowing down the failure often just repeats the same mistake.

First, identify the failure point

Match what you saw to the stage where it happened:

• The USB doesn’t appear or boot: check the ISO, USB creation, and firmware boot mode.
• The installer opens, then crashes or freezes: look for the underlying installer error.
• Disk setup fails: check the target drive, available space, and existing partitions.
• The install completes, but Ubuntu won’t boot: investigate the bootloader and firmware rather than assuming the installation files are missing.
• Package downloads fail: troubleshoot the live environment’s network, or skip downloads during installation.

This simple split helps avoid applying a disk fix to a network problem—or wiping a drive to address a boot menu issue.

If the USB won’t boot

Start by verifying the downloaded ISO. On Linux or macOS, calculate its SHA256 checksum and compare it with the official SHA256SUMS file for that Ubuntu release:

sha256sum ubuntu-24.04.3-desktop-amd64.iso

A mismatch means the downloaded file may be corrupted. On Windows, Rufus can calculate a checksum while writing the USB.

Write the ISO as a bootable image with a supported tool, such as Startup Disk Creator, balenaEtcher, or Rufus. Copying the ISO’s files onto a USB drive is not the same thing as writing a bootable image.

If the drive still doesn’t appear in the firmware boot menu, check the computer’s boot mode and how the USB was written. Ubuntu’s amd64 images support both BIOS/Legacy and UEFI boot; a mismatch between the firmware’s expectations and the USB’s partition scheme can prevent it from appearing.

Secure Boot is not usually the reason an official Ubuntu ISO won’t boot: official images are signed and work with Secure Boot on most hardware. If you see a Secure Boot violation, first check how the USB was created. Secure Boot issues are more likely to arise later with some third-party kernel modules, such as proprietary NVIDIA drivers.

If the installer crashes

A generic “Something went wrong” message is not a diagnosis. For the current Ubuntu installer, the useful details are in the installer logs under /var/log/installer/ in the live session.

You may be able to switch to a virtual terminal with Ctrl+Alt+F3 and inspect the logs, though this shortcut doesn’t respond reliably on every system. If the installer offers a terminal from its error dialog, that’s another option. Note which screen you were on when the failure occurred; the stage itself can help narrow the cause.

Look for clues rather than assuming one cause:

• A crash while detecting or partitioning disks points toward storage configuration or a disk-controller issue.
• Different failures on different attempts can be a reason to test the RAM.
• A flaky Wi-Fi connection or captive portal can interfere with network checks.
• A bad USB write or corrupted ISO can cause later failures, too—not only boot problems.

If you can, read the logs before trying the same installation again.

If disk setup fails, pause before changing anything

Disk operations can erase data. Before formatting, deleting, or resizing anything, confirm which drive you’re looking at. In a terminal, this read-only command shows disks, partitions, filesystems, and mount points:

lsblk -f

If you’re unfamiliar with the output, use a guide to identifying Linux disks and filesystems before making changes. Check that the device shown in the terminal matches the drive you intend to install to.

Common partitioning blockers include too little free space and a missing EFI System Partition on a UEFI installation. If the disk has existing LVM or encrypted volumes, manual partitioning may give you more control than asking the guided installer to interpret an old layout.

Take extra care with dual boot. Windows Fast Startup can leave its NTFS partition in a hibernated state, which prevents Linux from safely resizing it. Disable Fast Startup in Windows and fully restart before trying to install alongside it. Also install Ubuntu in the same boot mode as Windows—UEFI with UEFI, not UEFI with Legacy/CSM.

Do not delete or format an existing EFI partition as a general troubleshooting step. Windows and Ubuntu can share one, and removing it may stop Windows from booting.

If package downloads fail

First separate a network problem from a package mirror problem. From a terminal in the live session, you can check basic connectivity and inspect the configured DNS resolver:

ping -c 3 archive.ubuntu.com
cat /etc/resolv.conf

A captive portal may require you to open a browser and sign in before downloads work. DNS problems can also prevent the installer from reaching package servers.

If the connection is unstable, a practical workaround is to uncheck Download updates while installing Ubuntu and Install third-party software during setup. After installation, connect to a reliable network and run:

sudo apt update && sudo apt upgrade

That moves package downloads out of the installation process, where a temporary connection failure can interrupt setup.

If installation succeeds but Ubuntu won’t boot

A successful installer run means it completed the steps it was given; it doesn’t guarantee that your firmware will boot the resulting setup as expected. Separate the symptoms:

• The computer boots straight into Windows: the firmware may be selecting Windows Boot Manager instead of Ubuntu’s entry.
• GRUB appears but doesn’t list Windows: Ubuntu’s GRUB configuration may not have scanned for other operating systems. On recent Ubuntu releases, os-prober is disabled by default. Enabling it involves changing GRUB configuration and regenerating the menu; sudo update-grub alone won’t add Windows if the scan remains disabled.
• A message names a partition during startup: that may be a filesystem check message, not an installer failure. Identify the exact message before attempting repair.

When troubleshooting GRUB, confirm the EFI and root partitions before running repair commands. A wrong target can make a boot problem worse.

The useful rule

Don’t treat “Ubuntu install failed” as one error with one fix. Identify whether the failure happened at boot, inside the installer, during disk setup, while downloading packages, or on the first restart. Then use the evidence—especially /var/log/installer/ and lsblk -f—to choose the next step. If you’re preparing a machine for remote administration after installation, this Ubuntu Server setup walkthrough covers the next part of the job.

I originally published a more detailed version of this guide on the SSHFlow blog.

I'm also building SSHFlow — an SSH client where every server gets its own workspace for terminals, SFTP, code, and databases.