I'm a teacher and will ask my students to either bring their laptops with Ubuntu installed with an specific list of packages preinstalled or bring a USB Drive or External Hard Drive with Ubuntu and the packages preinstalled.

For those who are going to bring the USB are two posibilities:

  • Install with the Ubuntu's "Startup disk creator" program, and telling it to reserve some space for persistence.
  • Boot with a LiveCD and Install Ubuntu in the USB drive.

Then, in either case, boot with that media and install the packages.

So, for my purpose or any other purpose:

  • What is the best choice and why?
  • Do we have another option? full explanation please.
  • 1
    When this question was asked, it was possible to use the Ubuntu Startup Disk Creator to make a persistent live system. This is no longer the case with the version in Ubuntu 16.04 LTS and newer versions, where the Startup Disk Creator is a cloning tool, and creates the file system ISO 9660, which is read-only. Instead you should use some other tool, for example mkusb, to create a persistent live drive, help.ubuntu.com/community/mkusb/persistent
    – sudodus
    Commented Mar 1, 2017 at 7:25

7 Answers 7


If I understand you, you want to know the differences between persistent USB and a full install USB.

Persistent Live USB: 8GB or more

First, Persistent Live USB takes less space.

One can create a non-persistent Live USB with a 4GB USB drive. To create a persistent Live USB you would need a slightly bigger one, say 8GB.

Second, Persistent Live USB can be used for installation.

A persistent Live USB is essentially a copy of the installation DVD. The files in the original ISO remains as is. Updates and future installations are saved in the space designated for keeping the changes. Say, you update Firefox. in a normal installation the old one is replaced. In persistent installation the old one stays as is, the newer version is located in the persistent virtual disk (within the USB) taking up extra space and sometimes creating problems, for example for kernel updates. Now if you install Ubuntu from this persistent copy into another hard drive the original version of Firefox in the DVD image will get installed.

Booting a persistent Live USB gives the students access to the "Install Ubuntu" icon on the desktop. Students can "accidentally" start the install process and delete the contents of the hard drive.

Third, Persistent Live USB is less secure.

There is no login process in the Persistent Live USB. The default user has admin rights and does not need a sudo password to exercise it. This means, a malicious student can boot a persistent USB of another student and easily access stored documents, uninstall or reconfigure applications etc.

Fully installed Ubuntu in an USB: 16GB or more

First, Installation takes more space than keeping the image of the installation DVD, about 9GB.

Once installed, the system can be updated, and customized. Uninstalling unneeded software will free up space.

Second, Hardware on which the full install is created is important.

The Live DVD image in the persistent USB is created with compatibility with most computers in mind. However, once installed on a specific hardware, the installation gets a bit customized for the specific components. This is important particularly if the computer has some parts that require proprietary drivers. Once these drivers are installed, the USB may not work on computers that do not have those specific hardware. Conversely, if the installation is done on a computer that does not need any proprietary drivers, that specific installation may not work on the machines that do need them.

Therefore, if the goal is to use the USB in different computers, a persistent Live USB may be a better choice than a full installation.

Third, Full installation is more secure.

Creation of an user ID and a password is required during installation. This password is needed for any administrative action. One can also set it up to require the password at login.

Also see Difference between LiveCD, LiveUSB, full-install, and persistence?

Hope this helps

  • I think your First point under the Persistent Live USB should read that it takes "more" space, not less space. EDIT: no, I guess the explanation under that point is the other way round. It should be "persistent live USB, 1GB", and "full installation USB is slightly bigger, 2GB".
    – Alaa Ali
    Commented May 15, 2013 at 20:08
  • 1
    Yeah, he means to say the persistent live USB needs less, because he later mentions that the full install USB needs a lot more (about 5GB). And it makes sense, a full install would take more space, while a live USB is basically the ISO file.
    – Alaa Ali
    Commented May 15, 2013 at 20:31
  • 1
    @AlaaAli: Thanks for the feedback. I have edited my answer. With the current versions Ubuntu 1GB USB is not enough to make a persistent Live USB. You need at least 2GB. Similarly the recent versions of Full Install don't fit in 4GB USB any more.
    – user68186
    Commented May 15, 2013 at 20:55
  • 1
    @jgomo3, thanks for the feedback. See my previous comment.
    – user68186
    Commented May 15, 2013 at 20:56
  • 1
    Very nice answer. Do you know how it would be possible to get out of the "Hardware on which the full install is created is important." problem of full install ? I'm trying to solve this problem here : askubuntu.com/questions/873550/….
    – tobiasBora
    Commented Jan 19, 2017 at 14:39

Installing Kubuntu on a USB pendrive was a very attractive idea ... and I couldn't resist to do it. At the begining it worked OK, a bit slow but OK ( there is a performance bottleneck on the USB plug, so pretty much better USB 3.0 than USB 2.0 ).

After practicing a bit, upgrading the system, applications and so on ... I was excited ... I went to a tech shop and bought a hi-capacity pendrive (32 Gb) ... I was going to CLONE my Kubuntu main install ( root partition, home partition and swap partition ) on the new pendrive. It was a bit complicated but I managed to do it. I had to adjust Grub, fstab and not many more things ... and it worked, a bit slow ( my laptop hasn't got any USB 3.0 socket ) but worked.

Besides the slowness, I was very happy with my new pendrive ... it got my highly customized Firefox (more than 30 extensions) , my tuned LibreOffice , my custom KDE effects, Thunderbird (with several IMAP and POP accounts) , Dropbox ... everything ... it was pretty nice. In order to mitigate the slugglishness I fine tuned preload parameters (it was already installed in my main install) , I modified a bit fstab so that /temp , /var/lock , /var/log and /var/run went to tmpfs. I also made a Grub profiling and things got a bit better, not comparable with a hard disk install, but a bit snappier than before. By the way Nepomuk and Akonadi were de-activated on my main install, so after cloning they also were no operative on the pendrive.

The initial planned use for my pendrive was homemaking, tinkering and disaster recovery lifeboat.

I was able to upgrade the system, the kernel, applications ... everything went smooth.

But there was one factor I haven't previously thought about ... ... ... the limited amount of write cycles a nand-flash cell can survive before getting corrupt.

After some time LibreOffice stop booting with no apparent reason ... some days later other application followed the same path ... some weeks later the pendrive died. But the first time it happened I sincerely was not fully aware what the problem was ... so I 'decided' it was a low-quality pendrive ... and I bought another (different brand) ... and I repited everything ... and after some weeks the pendrive began suffering the same problems. Then I run badblocks utility and it became more clear ... the nand-flash cells were getting corrupt after some weeks of use ... what a pity !!!

I pretty much prefer running a fully ultra-customized pendrive than a generic persistent USB live session ... but this was a real showstopper for me. I guess a persistent USB live session will not suffer this kind of problem due to I believe there is less I/O activity in that configuration.

On the other hand USB flash installs sometimes has some little problems other USB installs (HDD or SSD) do not have ... regarding with Hibernation and Suspending to memory.

I would consider two options : internal drive (HDD or SSD) or USB external drive (HDD or SSD).


  • 1
    +1 For your advise about limited nand-flash cell.
    – jgomo3
    Commented Aug 29, 2014 at 16:38
  • Maybe using ext2 or disable journaling would cause less trouble ?
    – tobiasBora
    Commented Jan 19, 2017 at 14:41
  • Greetings from The Future. These days you can get m.2 USB enclosures that are very similar to normal USB sticks, but without the issues you mention. The Future is NICE! :) Commented Dec 9, 2021 at 9:09

Using a persistent USB "LiveCD" has some disadvantages in my experience:

  • On some systems you can get error messages while booting, making the boot time dramatically longer, or even preventing the computer from booting altogether (my computers all do this, unfortunately :p ). I have not found a solution for this (yet)

  • There will be a default user with sudo rights and without a password (it can be disabled, but it is not so easy)

  • Kernel updates can cause problems, since update-initramfs will trigger something with grub (or something :D), and that doesn't work because casper does not use grub (this should not break the system, but will leave the kernel unconfigured)

So if you are just having your class try Ubuntu out, this is a good way to taste the OS, but if you are planning on using Ubuntu full-time, you might consider using a full install instead (either on an internal or an external drive).


To be honest the only difference I see is that the non-live sytem will be usually faster and applications can be optimized to work on that specific hardware but you will lost versatility as you'll no longer be able to jump from one computer to another without some compatibility issues. Installations take more space and because of the nature of a thumb drive I think is a priority to keep compatibility and versatility over performance. Another difference is you can install Ubuntu from a live system and your personal configuration in your persistent file won't affect it.

Now, in my experience I have been using Lubuntu during almost a year in a persistent USB install and I can tell you that it works GREAT! I can install any program I want and keep the system updated. I use my system for development, audio editing sometimes, networking, general internet use, watch movies and video games (wine and common emulation). I don't think your students have any problems installing packages on a live system.

My system has a good performance even with the very low writing speed on the device (5 MB/s max). I use a very old computer (Presario F700) and the system has to be tweaked in order to work properly. I had to uninstall the Nouveau drivers and install proprietary drivers from Nvidia so I can have the drive to boot on any computer so far (but not apple computers because they need a special configuration). The system can use hardware acceleration with Nvidia hardware and works fine without hardware acceleration with open source drivers for other brands like AMD or Intel with no issues so far.

I also have a web server with MySQL working right now. I'm currently writing this from the computer after-mentioned while downloading some stuff. The system can be locked to avoid other users from using it, but as I said it needs some tweaking. Persistent USB works great if the user have the time and will to get it work the way they want and I think is great for learning.

Please correct me if I made a mistake in my assumptions. I'm a Linux fan but not an expert. :)



From a technical point of view there is not much difference in either method.

I think your decision should be based on more practical considerations. I presume that not all students have the exact same make/model. In fact I would expect pretty much everyone to have a different model. There is a chance that some machines do not include an optical drive. Assuming these are relatively new models, you will be able to boot them from USB. For older models you can only tell by trial and error. Also keep in mind that laptops are notoriously difficult to configure because of the often specialized hardware they contain. Going for a full install on such systems may result in endless hours of troubleshooting.

I am not trying to disappoint you here - after all installing on such a system can be very educational about the inner workings of computers and operating systems. I am just suggesting you go about this starting as simple as possible. Give your students -and yourself - the flexibility to use ANY of those methods.

  • Good idea let the students decide.
    – jgomo3
    Commented May 15, 2013 at 19:51

In a test I did, a Full install to USB booted about five times faster than a Persistent install.

It is also true that a Full install can be made more secure and can be updated and upgraded.

If the drive will also be used to transfer files to a Windows machine it will need the first partition to be FAT.

A Persistent install initially has a persistence limit of 4GB however this can be increased using casper-rw and home-rw ext2 partitions.

Proprietary video drivers do not work on a persistent install.


Persistent Ubuntu on USB is better, because a persistent setup gives makes it possible to create user accounts with passwords. (Although other people say different, you just have to go to System Settings → User Accounts and create admin account.)

It uses less space than a normal full installation, so the USB flash drive will take longer to wear out, and leaves more space for other files.

  • Its not true, my answer is a improvement. As I said in my answer I tried to create user account and it worked. I dont know what is he/she talking about.
    – Enforcer
    Commented Sep 3, 2017 at 19:49

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