GNU/Linux Installing Unetbootin Guide
The Tutorial shows you How to Install Unetbootin Package on the most diffused GNU/Linux Distributions.
And the UNetbootin Tool allows you to Create Bootable Live Linux USB without burning a CD.
Especially relevant, currently for a Better and Easier Alternative with Multi-OS USB Boot you should see: Ventoy Setup Guide.
Finally, UNetbootin loads distributions either by Downloading a ISO (CD image) files for you, or by Using an ISO file you’ve already downloaded.

Unetbootin Installation on Linux
For Ubuntu Linux Based Systems
like Lubuntu, Kubuntu, Xubuntu, Linux Mint, Elementary OS, Zorin, Bodhi, Lite, LXLE… See:
How to Install UNetbootin on Ubuntu Like.For Debian Linux Based Systems
like Linux Mint Debian, Kali, Deepin, MX, antiX…:
How to Install UNetbootin on Debian Like.For Red-Hat Linux Based Systems
like CentOS, Fedora, Oracle…:sudo su -c "yum install unetbootin"
For SUSE Linux Based Systems
like openSUSE:sudo su -c "zypper in unetbootin"
For Mandriva Linux Based Systems
like Mageia, OpenMandriva:su -c urpmi unetbootin
For Arch Linux Based Systems
like Antergos, ArchBang, Bridge-Linux, Manjaro…:sudo pacman -Sy unetbootin
For Gentoo Linux Based Systems
like Sabayon:sudo emerge -a sys-boot/unetbootin
For Slackware Linux Based Systems
like Salix, VectorLinux, Absolute-Linux, Zenwalk…:slackpkg install unetbootin