Cloned Centos 6.8 on old COMPAQ Using dd to portable SSD but does not show up as bootable drive on DELL laptop
 

Hey all,
My first post, and I am not sure if what I am attempting is possible, so sorry if I sound like a moron.
I would like to be able to boot to Linux residing on a portable SSD from my new Dell laptop running windows 10. Here's how I'm trying to accomplish this:
I have CentOS 6.8 loaded on an old COMPAQ AMD 64 PC. I created a clone of the CentOS 6.8 system using dd onto a portable SSD (SSD is about 20G bigger than the hard drive running the Linux system). I was able to successfully boot to the cloned CentOS system residing on the portable SSD from the old COMPAQ PC (the same one I created the clone from). However, when I tried to boot to the portable SSD from the laptop, only the internal disk shows up on the boot menu. What am I missing?
Thanks in advance for any help anyone can give. I may have to do this a different way.

My guess your new laptop is set to use UEFI, and the cloned ssd was from MBR BIOS system. Check settings in your new laptop BIOS settings for "enable legacy boot" or something similar.

Hello and welcome to LQ.

I agree that without more info, it might be uefi.

Boot machine with usb attached and go to bios. Does the usb show up under a hard drive choice at all?? (in bios not boot menu choice)

You're both exactly right. I changed the BIOS setting to legacy, living life on the edge and ignoring all the red flags, and I now have my Linux system running on my shiny new laptop from my portable storage device, and I was easily able to change BIOS back to UEFI to bring my Windows 10 system back up. Exactly what I wanted to do- THANK YOU!!!

I am *really* surprised that worked. Keep us informed ... :p