Ubuntu has a default program to create a bootable pen drive.
Follow these steps to create the same.

1. Download the iso image file of the latest Ubuntu from their official site.
2. Now attach an empty USB drive to the system.
3. Start the 'startup disk creator' program.

1. Select the downloaded iso image file as the source file.

1. Select the USB device as the 'disk to use'.
2. Select less than 1 GB Reserved disk space. Click 'Make Startup Disk'.

1. Files will be copied to disk. After some time when OS installation on the disk is complete click the 'quit' button.

1. Detach the USB disk and install the Ubuntu on any system.

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