Quick Fix: Cannot boot to bootable Linux media on older Toshiba laptops
You can have problems booting to Linux LiveCD, LiveUSB or DVD installation media on older Toshiba laptops due to the following issues:
1. Boot Speed is set to Fast in Setup Utility.
2. You are using an external USB optical drive.
3. The system boots immediately to the primary disk with a Linux distribution already installed due to a fast SSD.
4. The F12 option to display Boot options fails.
If you encounter this issue with an older Toshiba laptop or netbook such as the NB520, what normally happens is that the LiveUSB or Live media will appear to be active but the system boots directly to the primary disk.
You can try the following solution to boot to the Linux bootable medium:
Hold down the F2 button on boot. Do not tap the button repeatedly to get to the BIOS settings as you would on a Dell or HP system.
On the Boot tab in the Setup Utility, move the external optical drive or bootable USB option using the F6/F5 button regardless if the device is detected. Save settings and exit. The system should boot directly to the USB optical drive or flash drive assuming the Linux installation media was created properly.
Note: If you foresee that you will be booting to external storage devices regularly, you can change the Boot Speed option to Normal in the Advanced tab in the Setup Utility.