After a lot of searches I couln't find official minimum required settings in order to make a Bootable USB.

Disclaimer: First of all 3.0 have been renamed 3.1 GEN 1: enter image description here

In order to make a bootable USB (Full Install) for Ubuntu 18.04.2 LTS was wondering what are the specifications needed?

  1. What is the minimum recommanded storage capacity of the USB Key? 4GB? 8GB? 16GB?
  2. Is the speed important ? Is USB 2.0 Enough? Is there an interest to buy a 3.1 GEN 1 just for it?
  • 4GB is enough, but that small drives seem not to be sold any more. Any flash drive you can buy will do. – Pilot6 Mar 5 '19 at 10:21
  • usb 2.0 is enough. A good thing to know: a usb 3.0 stick can be plugged to a usb 2.0 port but could be slowest than a usb 2.0 stick. For better perf, you should choose a stick with the same usb version as your usb port – cmak.fr Mar 5 '19 at 10:26

Bootable USB Size and Speed

There are various ways to make a bootable USB.

Live USB is a read only USB similar to a read only DVD. It only needs to be large enough to fit the Ubuntu ISO, about 2GB. It is good for giving the OS a quick try or for installing Ubuntu. All new data is lost on reboot. The live USB may run in RAM so USB3 is not required but does not hurt.

Persistent USB uses a casper-rw persistent file or partition. Most persistent drive creation programs use syslinux which has a casper-rw size limit of 4GB due to FAT32 file system. YUMI can make a casper-rw file in NTFS of unlimited size. Mkusb uses grub2 rather than syslinux for booting. It will produce a casper-rw partition of unlimited size. Persistent drives will boot "toram" which helps with speed. These drives work as installers, but should not be updated or upgraded.

Full Install USB has Ubuntu installed as it would be to an internal drive. Persistence is only limited by disk size. They are more stable than persistent drives. Over time the need for space seems to increase. About 25-30 GB should last a while. The remaining space on the drive can be used as a NTFS data partition that is accessible to Windows. USB3 is a good choice for Full Install. These drives are upgradeable, updatable, and can use proprietary drivers. A Full install USB is no use installing Ubuntu. Minimum size pendrive for full install is 16GB, 25GB recommended.. Ubuntu Minimal will fit on a 8GB drive but there will not be much room for programs and data.

  • Thank you for your comment, I don't wanna make a Live USB, however I'm not sure if it is called Persistent USB or Full Install USB but I technically wanna make a full installation of Ubuntu from a bootable USB into a SSD. – Ced Mar 5 '19 at 12:54
  • @Ced: If you do not need the drive for installing Ubuntu, this should work for a computer booting BIOS mode: askubuntu.com/questions/1119700/… – C.S.Cameron Mar 5 '19 at 13:15
  • yes that's a full Install USB so, I will update the post, thanks for the details ! – Ced Mar 5 '19 at 13:26
  • @Ced: if you are currently runnung Win 10, you mught need an install that runs in UEFI: askubuntu.com/questions/1107281/… mkusb does not work in Windows but can be installed on a temporary Ubuntu Persistent or Live USB. – C.S.Cameron Mar 5 '19 at 13:26
  • Thanks, I know how to do it because I already did some in the past, but I was planning to make various Full Install USB for differents OS this way I would just be able to pick the right key when I want to, instead of rewritting each of them everytime.everytime. Hence my question, I am looking for the minimum USB requirement in order to build thoses keys. – Ced Mar 5 '19 at 13:33

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