Can I install Linux using the entire disk without a USB drive?

The simplest and safest option is still to borrow or buy a basic USB drive. It doesn’t need to be large or expensive. Workarounds involving shrinking a partition, extracting the ISO, configuring the bootloader, and then deleting the old system are more complicated and could leave the computer unable to boot if something goes wrong.

Yes, it’s possible, but the installation method and the choice between full-disk and dual-boot are separate issues. You can use network booting, a CD/DVD, or sometimes boot an ISO stored on the internal drive. The full-disk installer option will still work once you reach the installer.

Network installation tools such as netboot.xyz may work if your computer supports booting from the network and you have a reliable wired connection. The exact steps depend on your computer’s firmware and the Linux distribution, so this is usually less beginner-friendly than using installation media.

Booting an ISO directly from the hard drive with a bootloader can work, but it’s an advanced and riskier approach. Also, full-disk encryption adds another layer of complexity. If this is your first Linux installation, it’s better to use normal installation media and get comfortable with an unencrypted setup before attempting a more complicated method.