Does Linux reinstall when I boot LinuxCNC install from USB?

Hello All,
I've been unable to determine the answer to my topic question by searching this part of the forum, and as a Linux noob I have this question: when I install LinuxCNC from a bootable USB (made with Balena Etcher for AMD64) the process appears to reinstall Linux.  I have always cancelled the install when it asks for a password (for root?) since looks like it's about to overwrite my existing Linux Debian 12 install.
Should I continue without a password?
When will the process actually get to the  LinuxCNC installation?
My thanks in advance, and Cheers.

If you chose the Install option it will overwrite an existing install if you have no extra space on your drive.

linuxcnc.org/docs/stable/html/getting-st...ml#_testing_linuxcnc

You can just save a copy of your ~/linuxcnc folder to other media/usb stick
Then install the later version and restore the folder
You will loose any customisations you have made to the linux operating system but linuxcnc will remain the same once restored.

Thank you. Can you tell me how to get to the LinuxCNC install and bypass the Linux installation?
I guess that coming from a Windows background the need for a bootable application installation media seems weird.

Thanks> Can I get to the LinuxCNC install with a keystroke combination or ? It seems strange to me to have to reinstall and OS to install an application.
Thanks again!

Check out section 7 of the install instructions:

linuxcnc.org/docs/html/getting-started/g..._installing_linuxcnc
 

Specifically there is an installation script under 7,1 of PCW's link which will allow you to install if you installed Debian from the Debian web site.
But thats not what you want to upgrade from one version to the next release of linuxcnc
The ISO installer sets up the environment correctly including choosing the XFCE desktop graphical environment (te default gnome desktop is not a good choice
Assuming you are not using a raspberry pi, to upgrade from say the 2.9.1 release to the latest 2.9.2 release, all you need to do is to:
open a terminal window and typeThis will install any new security fixes and upgrade Debian to its 12.4 release if running an earlier version.
It will also install the latest version of Linuxcnc 2.9.x if one has been released.
This will keep any changes you have made to the Linux environment and you should end up with an identical environment if you installed the 2.9.2 ISO (pus any security releases Debian has released)

What is so different about installing software on Linux vs Windows is software applications are distributed as .deb files. Debian maintains a central repository of approved applications. You can install any of these packages from the command line or by using the Synaptic package manager. You can modify some system files to allow third party applications (like Linuxcnc) can add their repositories to your PC so they are also accessible (we do this on this for Linuxcnc on our installers)

Unfortunately, for the Pi, this does not woak as we have had to build the Linux kernel from source so doing an apt update will try to replace the current kernel with a debian One and it breaks.

Actually, I was on that page when I read your recommendation.