I have come to put the ISO in 2GB, but 4GB is recommended. A pendrive to install the operating system.
HOW TO INSTALL UBUNTU FROM USB ON PC WITHOUT OS HOW TO
How to install Ubuntu on a USB Requirements
2 What we gain by performing a complete installation. 1.3 Installation process 2: installing Ubuntu. 1.2 Installation process: preparing the USB. On the other hand, I would like to make it clear that this is something that can happen, so I would create a Live USB with the operating system that I have on my PC to reinstall it (without formatting), so that it can happen. Of course, the first step that I would do would be to avoid some problems of this type: unmount the hard drive from Nautilus. Apparently all of this has changed and now can be installed without problems and used on any other PC. In addition, it did not work at all well if we used it on other computers. When installing the operating system on a pendrive, I moved the / boot (or EFI) partition to the USB, which meant that the PC would not start without the USB connected. Until recently, if I remember correctly, Ubiquity didn't do as well as it does now.
In this article we will explain how to install a full Ubuntu on a pendrive as if it were a hard drive. Also, not everything is updated as it should because the configuration is not the same as a full installation. For testing or as a recovery tool that keeps the changes going very well, but the performance is not as good as we would like. At the end of March we publish an article in which we explain how to create an Ubuntu Live USB with persistent storage.