After creating the Live CD or Live USB of your favorite distribution, all you need to do is configure the BIOS to boot from the appropriate drive.
As a short explanation, let’s assume that the first thing to load when starting a computer is the BIOS (Basic Input / Output System), whose main goal is to execute routines that check the hardware’s correct function and later load the operating system. In other words, it’s this screen you see before the operating system starts loading (be it Windows or any other).
What we need to do to test and / or install Linux is to call the BIOS configuration screen and tell it that instead of the operating system installed on the hard disk, the one in our live CD or live USB, as the case may be.
How to call up the BIOS setup screen
Unfortunately, there is no universal method to accomplish this task, as each motherboard model has a specific BIOS and it is impossible to document the full range of configuration managers. However, if we let ourselves be carried along by intuition, the process is quite simple.
When you connect the device and the first messages are displayed, you can press the "Pause" button to stop the startup process and see for sure what is displayed on the screen. This has to be done quickly, because the mentioned messages are only visible for a few seconds.
If you can’t stop the start process, take a close look at the start screen. At the bottom of this screen, there is usually a similar line: "Press F2 to enter SETUP". Of course, the key can be any other. Most common are: [DEL] or [Delete], [Insert], [Esc], [F2], [F1], [F10] or another function key.
In some newer BIOSes, you can also select the startup device with a different key without having to access the BIOS setup page. This is because these settings are usually changed frequently and the user can’t accidentally make another change as a result. If the BIOS has this "shortcut has, simply use the keyboard arrows and select the appropriate startup device.
This "link" However, only works for 1 boot; On the next boot of the operating system installed on the hard disk. To summarize: To make the change "permanent" or if the BIOS does not have the above mentioned "shortcut" you must press the appropriate key to bring up the BIOS configuration screen that may be present A completely different aspect than the one shown here, but with similar features and benefits.
Configure the startup drive
Here we can only give general guidelines, as the BIOS setup screen varies from card to card. Generally, though, you need to find a tab similar to "Boot" or an entry called "Boot Sequence" or "Boot Priority" on a more general tab of the "Advanced BIOS Features" style.
At this point, it is important to remember that Sequence boats. This means that we set a chain of priorities: first, trying to boot from the CD or USB (depending on how we want to test our distribution); if this fails, trying to boot from the operating system installed on the hard disk, etc. to start.
tab selection or changing the settings is very different. Sometimes you just need to use the arrows, sometimes you need to use the PgUp and PgDn keys, etc. use. However, in a column on the right, you will always find an explanatory table that lists the steps to follow. The buttons to press to perform the most common tasks appear below. Basic English knowledge is sufficient to understand what to do.
Save your changes and exit the setup program. To do this you have to press the corresponding key (in the case of the previous screenshot F10).
Some older BIOSes do not support booting from a USB drive. In this case, it is usually the best option to use a live CD to test your favorite Linux distribution. However, it is also possible to force boot from USB (without corresponding BIOS support for this) with PLOP Boot Manager.
Other older BIOS don’t even support booting from CD-ROM drive. In this case, the natural alternative would be to use boot disks, which only a few are Linux mini-distributions have available to. Fortunately, if the computer has a CD reader, it is possible to boot from a live CD even if the BIOS does not support it Smart Boot Manager o PLOP Boot Manager.
UEFI and Secure Boot
The Unified Extensible Firmware Interface (UEFI) is a specification designed to replace the old BIOS interface, which for many has become too "eighty" and has a similar aspect to the old DOS. In addition, it contains several additional features that do not meet the objective of this article, including the so-called "Secure Boot" or "Secure Boot.
Secure Boot prevents the computer from booting the operating system if the boot loader does not have a valid digital certificate resulting from an arbitrary change of malicious code. In this way, malware of the bootkit type cannot work effectively.
However, the fact that Microsoft forced manufacturers to distribute their computers with this option enabled in order to get Windows 8 certification was great stirring. In particular it is to be feared that this function serves only to prevent users from starting another operating system than Windows. In this case, the requirement is more of a limitation for users than a safety feature.
According to Microsoft there are two "guarantees, that this will not happen. On the one hand, you can disable both UEFI (by booting with a "BIOS-compatible mode") and Secure Boot, also known as "Legacy Boot mode) as well as Secure Boot. On the other hand, the authorization required by Secure Boot for a digital signature is issued by an independent authority, which is not the manufacturer or Microsoft.
The truth is that currently Linux distributions only give their first steps to run on computers with UEFI and Secure Boot enabled.
As things stand, it is best to disable Secure Boot before installing Linux. Support for UEFI, on the other hand, is more developed, although there are still some shortcomings. In case of failure, there is no choice but to use the "legacy boot" option select and disable the UEFI.
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Full path to the article: On Linux " UseLinux from FileLet " How to change BIOS settings to boot Linux from Live CD / USB