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Windows 8 Secure Boot – 4sysops

CSM (Compatibility Support Module) to support booting legacy operating systems via a PC-BIOS-like emulation. For more You can find the Enable Secure Boot Support option in the Boot Code Options tab of the Boot Loader Settings dialog. If you have a PC system dating to or earlier it's quite unlikely it has a a BIOS compatibility mode, also sometimes referred to as a CSM. Disabling Secure Boot does not automatically trigger BIOS compatibility mode. Hi, Can anyone please explain what is CSM setting in BIOS and why do I need to have it Some users disable CSM to decrease boot time.

Microsoft denied that the secure boot requirement was intended to serve as a form of lock-inand clarified its requirements by stating that Intel-based systems certified for Windows 8 must allow secure boot to enter custom mode or be disabled, but not on systems using the ARM architecture.

Former Red Hat developer Matthew Garrett noted that conditions in the GNU General Public License version 3 may prevent the use of the GNU Grand Unified Bootloader without a distribution's developer disclosing the private key however, the Free Software Foundation has since clarified its position, assuring that the responsibility to make keys available was held by the hardware manufacturer[88] and that it would also be difficult for advanced users to build custom kernels that could function with secure boot enabled without self-signing them.

What is CSM and do I need it enabled?

Garrett himself developed a minimal bootloader known as a shim, which is a precompiled, signed bootloader that allows the user to individually trust keys provided by distributors. That also allows users to build their own kernels and use custom kernel modules as well, without the need to reconfigure the system. Fedora also uses shim,[ which? However, the proposal was criticized by Linux creator Linus Torvaldswho attacked Red Hat for supporting Microsoft's control over the secure boot infrastructure.

This allows any software to run as though it was genuinely signed by Microsoft and exposes the possibility of rootkit and bootkit attacks.

mjg59 | The current state of UEFI and Linux

However, we can give you some pointers. To do a UEFI-native boot: Make sure all options in the firmware's 'boot' section relating to BIOS compatibility are disabled. To do a BIOS-native boot: If your firmware has an option to turn BIOS compatibility on or off, make sure it's on. If none of the above is working, try intentionally writing a non-UEFI-bootable USB stick, using the livecd-iso-to-disk utility without passing the --efi parameter, or by deleting the EFI system partition from the USB stick, and boot from that.

If none of the above works and you really need to do a BIOS-native installation with Fedora 19 or earlier, you can boot your medium in UEFI-native mode and pass the parameter noefi to the installer from the boot menu. With Fedora 20, you must pass noefi inst. However, this usage of noefi is incorrect, not supported by the kernel developers, and will not work from Fedora 21 onwards.

Checking which mode you booted the Fedora installer or live image in If you are not sure which mode you booted in, there are a few ways to check. In current Fedora releases, the initial boot menu you see looks rather different in each case. If you do a BIOS-native boot, it will look something like this: If you do a UEFI-native boot, it will look something like this: Note that the BIOS-native boot menu is centered on the screen, has a title, and has multi-colored text.

The UEFI-native boot menu has its entries towards the upper-left of the screen, has no title, and all the text is white. If you follow all the instructions above you should not have to worry about this, but it's worth knowing. If you make your partitioning choices during installation such that all existing partitions on your target disk will be erased or the disk is blank to start withthe installer will automatically reformat it to the most appropriate format as part of the installation process.

But if you are installing to a disk and not completely wiping it, Fedora cannot reformat your disk for you, as this would destroy the data on it. Again, though, this shouldn't be something you need to worry about if you follow the above instructions. If you wind up in a situation where you think you need to change your disk format, you should probably ask an expert on IRC, Ask Fedora or the Fedora Forums to make sure.

It doesn't matter that you have a UEFI firmware: If you are doing a UEFI-native installation and use automatic partitioning, the installer will create a correct partition layout for you except in the case that you have an MBR-formatted disk and do not choose to reformat it: You can create a new one instead, though, if you like, and this should work fine.

It's hard to say precisely what size to make it - there isn't really a convention yet - but unless you're really strapped for space, you may as well make it a few hundred MB just to make sure there's plenty of space.

Windows 8 Secure Boot

If you fail to do this correctly, Fedora will give you the rather cryptic error message "you have not created a bootloader stage1 target device". What it's really telling you is you didn't configure an EFI system partition correctly. As stated above, this is unlikely to be what you really want to do.

The installer will configure this to be the default boot menu entry, and so booting the system without any special actions should cause Fedora to start.

Unified Extensible Firmware Interface

The implication of signed files is that you need a key to decrypt them, based on the principles of Public Key Infrastructure PKI. These keys need to be stored in the firmware of your computer. This introduces a significant requirement on your computer: Signatures Database Revoked Signatures Database Key Enrollment Key KEK Database The first two databases contain keys for signers and image hashes of UEFI applications, which identify trusted hardware, firmware, and operating system loader code and a list of keys to identify known malware.

The third database works as an update mechanism for the first two databases. One of the implications of using Secure Boot is that you can no longer dual boot older Windows versions, and you can no longer boot from Linux-based installation media or Linux-based Operating System installations.

Other operating system vendors such as the organizations in the more fragmented Linux ecosystem have had less of an impact on UEFI manufacturers.