I just build my first PC, turned it on for the first time, and attempting to install Linux Ubuntu 20.04.1 LTS from a bootable USB.

As many others have had the "decoding failed" problem I cannot seem to figure out how to use any of the solutions posted to fix the issue regarding my situation.

Any or some advice would be greatly appreciated as I have no idea what I am doing nor have any technical knowledge.


Thank You

Image of error when attempting to boot

Ubuntu prompt (I clicked enter on the first line ubuntu)

  • Is this error occurring when booted to the Ubuntu Live DVD/USB and trying to install Ubuntu, or after you've installed Ubuntu, and are booting it from your HDD/SSD?
    – heynnema
    Commented Sep 24, 2020 at 19:36
  • I believe the first one. I turned on the PC for the first time. Then plugged the USB that I have Ubuntu downloaded on. I rebooted the PC, and was prompted with the image for which I added to the above question under "Ubuntu prompt"
    – user1130013
    Commented Sep 24, 2020 at 19:41
  • When you boot to the Ubuntu Live USB, it does a file check... did that pass for you, or were there errors? Once you see the GRUB menu, select Ubuntu.
    – heynnema
    Commented Sep 24, 2020 at 19:50
  • After I clicked on Ubuntu from the GRUB menu I was greeted with the image that I posted above, which said the decoding failed.
    – user1130013
    Commented Sep 24, 2020 at 20:23
  • When you downloaded the .iso file, did you checksum it before burning it to flash? How/where did you burn it to flash?
    – heynnema
    Commented Sep 24, 2020 at 20:28

2 Answers 2


You can see here: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1835660

The workaround that I applied to solve the issue was:

changing setting in initramfs.conf editting the file with sudo rights


then change the line with COMPRESS=lz4 to COMPRESS=gzip

boot time with lz4 was:

Startup finished in 10.074s (firmware) + 6.687s (loader) + 6.451s (kernel) + 30.951s (userspace) = 54.164s 
graphical.target reached after 29.969s in userspace

now with gzip:

Startup finished in 10.046s (firmware) + 8.307s (loader) + 7.636s (kernel) + 27.035s (userspace) = 53.026s 
graphical.target reached after 26.279s in userspace

I actually had that problem just now along with coloured lines on the black screen (heard a lot of people had a similar issue). Not an expert on the topic but I'll share what happened on my end that resolved the issue.

Changing /etc/initramfs-tools/initramf.conf

COMPRESS=lz4 to COMPRESS=gzip did the trick of the error message.

There was still a problem in that it still booted to a black screen with coloured lines (I'm hearing a lot of people with this issue also have that). What I found was that by updating the video card driver to the Nvidia one (assuming you're using an Nvidia GPU) as well as doing all the software updates then restarting seemed to not only work (in removing the lines), but I also got a notification on boot-up from that point on that the blocks were cleaned (probably from the first step).

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