This is my first time installing a Linux distro so I don't know much about the prerequisites. I am currently using Windows 7 and would like to install and use Ubuntu alongside Windows. I wanted to ask whether I can use a 3 GB USB stick for the installation? As far as I know the iso is 1.5 GB, so should it be fine?


  • 4
    You haven't said what Ubuntu you are talking about, also whether or not you are talking about desktop, server, IoT appliance software or other, and each has different requirements, let alone release requirements (ie. later ISOs contain more drivers and are thus larger). The desktop for example suggests 25GB, and modern ISOs require a 4GB before installation (are you asking about install to thumb-drive?? OR just the ISO written to thumb-drive to later install on hdd/ssd/other-device? The Ubuntu ISO I downloaded yesterday is 2.6GB in size for example so I'd not expect it to fit (needs 4GB)
    – guiverc
    Jul 17, 2020 at 1:03
  • 4
    If I'm understanding correctly, you mean is your USB large enough to hold the Ubuntu ISO so that you can install it on your computer? If that is your question, the answer is, "Yes, but just barely. It's a 2.5 GB ISO which should be not much larger when written to a device." If your question is if you can install the OS in just 3 GB of space, the answer is not with Ubuntu.
    – KGIII
    Jul 17, 2020 at 1:25
  • 1
    You haven't provided any specific details of what release, or ISO you are intending to use. It is my understanding all will fit on 4GB, however you cannot install to 4GB. Some ISOs are smaller than others, and I still use 2GB thumb-drives for some, but require 4GB for others. (I'm assuming dd or like write of ISO to thumb-drive, and not install onto thumb-drive)
    – guiverc
    Jul 17, 2020 at 1:25
  • 2
    The following link may help you: help.ubuntu.com/community/Installation/FromUSBStick/pre - 'Prerequisites'
    – sudodus
    Jul 17, 2020 at 8:08
  • 1
    Off-topic, but "I am currently using Windows 7" is a massive, massive red flag. Unless your PC is 100% disconnected from the internet and will never be connected, the question is not if you'll be hacked and lose everything, but when. Move to Windows 10 immediately; or wipe it completely and install Linux over the top. Whatever you do, your job today, this minute, should be moving off Windows 7.
    – Graham
    Jul 17, 2020 at 12:00

5 Answers 5


Yes and potentially No.

A netboot or mini.iso will fit on a 384MB thumb-drive/install media (possibly smaller depending on release should you have a thumb-drive that small still lying around).

The last Ubuntu desktop ISO I downloaded (groovy yesterday) was 2.5GB and I used a 4GB thumb-drive to write that onto.

But the size varies on release, and that was a groovy desktop ISO will be larger than older ISOs that contain less or no closed-source drivers, plus released (non-development) ISOs include less diagnostic/development libraries useful in crash reporting which exist only on development ISOs.

However my most common thumb-drives I use are still 2GB as many ISOs will fit on them.

The thumb-drive size required will depend on

  • the release you want (closed source blobs aren't included all releases)
  • the version you want server? desktop? or other?
  • the flavor you want? (some don't include closed source blobs)
  • plus the ISO you choose (options exist)

We have no specifics, so cannot provide a specific answer.

  • 2
    if it's not clear, the closed source blobs include nvidia et.al.
    – guiverc
    Jul 17, 2020 at 2:45

Ubuntu Install Quick Start

The current Ubuntu 20.04 install disk is 2.7GB.

Download Ubuntu 20.04 https://ubuntu.com/download/desktop

Start with a USB of at least 3GB formatted FAT32.

If using Windows, download Rufus. https://rufus.ie/

Double click the Rufus .exe file. (No need to install).

![enter image description here

Select USB Device and Ubuntu ISO file for Boot Selection.

Confirm Persistent partition size is 0 MB.

Select START

When Rufus is done you can use USB to install Ubuntu to BIOS or UEFI machine.


Yes 3 GB USB drive will fit for Live Ubuntu ISO. I have installed Ubuntu 18.04 (1.8 GB disk image) in multi boot with windows with 3.66 GB USB drive. If you use a mini ISO then the you even don't need a 3 GB ISO, and old USB drive about 386MB is enough. Though if you want to create persistent USB stick, then to create the persistent partition file, you need a USB drive greater than 4 GB.

  • "Fit the live ISO" is not quite the same as installing it, though. I think persistence would be needed in order to match the OP's expectation.
    – jpaugh
    Jul 17, 2020 at 18:26

You can, but it's not necessarily so straightforward. Most live images use a compressed root filesystem, which is much smaller than an uncompressed root. The obvious solution is to install less packages, replace the desktop environment with a lighter one, etc., but this is not always a reasonable solution. That's why you'll most likely need to use a compressed root too.

Some numbers: A minimal installation of most linux distros with a Desktop Environment and very common packages (office, music, video, browser, etc.) weighs around 3-5 GB. Because CDs only have a capacity of 650-700 MB, and binaries and text files (both which are the bulk of those 3-5 GB) compress very well, all live images of the distributions that I know of use a compressed root.

The easiest way to have a compressed root filesystem is to use btrfs with compression enabled (but beware that btrfs is somewhat less stable, especially if the system hangs or experiences sudden power loss). See this thread for ideas about how to install on btrfs with compression: Trick installer to use btrfs root with compression

Another way is to do it the way live images work, but this is much more involved: In many distros, live images have the root mounted as an overlayfs, which combines two mountpoints, with the bottom layer a squashfs image (a filesystem designed to compress very well files to fit distros onto a CD), and an tmpfs upper layer (a volatile, in-RAM filesystem) which holds the changes to the system.

  • 1
    "I've stopped using ISOs and Ubuntu a long time ago" -> I'd be curious, what did you switch to? Jul 18, 2020 at 13:35
  • @StéphaneGourichon , I'm using Arch almost exclusively nowadays. Usually I just drop a root image where I need it, a bootloader if needed and I'm done. It's more convenient for me and also much easier if the system does not have optical drives, can't boot off usb or is headless (my laptop and phones are 1&2, my workstation is 1&3, all my Raspberry Pis are 1,2&3).
    – mostanes
    Jul 19, 2020 at 11:22
  • @Nmath , my solution is to do the thing ISOs do: compress the root filesystem.
    – mostanes
    Jul 19, 2020 at 11:24
  • @mostanes thanks for the details and welcome to this Q&A site. I happen to also use headless Raspberry Pis (as servers), and deeper embedded systems, too, where I fiddle with the GNU toolchain linker scripts (no joke). That said, given the OP mentions using Windows, they most probably need an "ordinary" setup. Also your answer explains how a live-CD or live-USB works, which is interesting but not what the OP asked. You'll find plenty of other questions where your detailed knowledge will be useful to others and appreciated, just try to stick to the questions asked. Jul 19, 2020 at 12:08
  • Thanks for the feedback. I'll try to edit to match a clear answer.
    – mostanes
    Jul 19, 2020 at 12:13

Not exactly what you were originally asking, but I really like the "Live" USB drives @Wasif_Hasan mentioned above. You can try your 3GB drive first, it might fit. Otherwise use a larger drive and create a "Live" boot drive. You can boot to Ubuntu without actually repartitioning your Windows machine for dual boot. This way you can test and see if all your hardware is supported (such as laptop camera). Also you can get a taste of Ubuntu before you take the larger step. This tutorial should help:


You will get a slower experience, but if you like what you see there is a link on the "Live" desktop to do a full side-by-side desktop install (or replace Windows completely on that machine - but see below).

What ever you do, I suggests backing up all your data on your Windows 7 machine first. Good practice even if you are doing a major Windows upgrade. If your hardware and budget allow, I would also recommend moving to Windows 10 ASAP (as in one of the comments above), or just move to a new Windows 10 machine and completely replace Windows 7 with Ubuntu. I've always found a second machine to be more useful than a dual boot (although that's how I started).

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