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diff --git a/en/preparing/pre-install-bios-setup.xml b/en/preparing/pre-install-bios-setup.xml index 32e3611e4..02bb6a583 100644 --- a/en/preparing/pre-install-bios-setup.xml +++ b/en/preparing/pre-install-bios-setup.xml @@ -20,6 +20,100 @@ hardware; it is most critically invoked during the bootstrap process &bios-setup-s390.xml; &bios-setup-arm.xml; + <sect2 arch="x86" id="UEFI"> + <title>Systems with UEFI firmware</title> + <para> + UEFI (<quote>Unified Extensible Firmware Interface</quote>) is + a new kind of system firmware that is used on many modern + systems and is - among other uses - intended to replace the + classic PC BIOS. + </para> + <para> + Currently most PC systems that use UEFI also have a so-called + <quote>Compatibility Support Module</quote> (CSM) in the firmware, + which provides excatly the same interfaces to an operating system as a + classic PC BIOS, so that software written for the classic PC BIOS + can be used unchanged. Nonetheless UEFI is intended to one day + completely replace the old PC BIOS without being fully + backwards-compatible and there are already a few systems with UEFI but + without CSM. + </para> + <para> + On systems with UEFI there are a few things to take into consideration + when installing an operating system. The way the firmware loads an + operating system is fundamentally different between the classic BIOS + (or UEFI in CSM mode) and native UEFI. One major difference is the + way the harddisk partitions get recorded on the harddisk. While the + classic BIOS and UEFI in CSM mode use a DOS partition table, + native UEFI uses a different partitioning scheme called <quote>GUID + Partition Table</quote> (GPT). On a single disk, for all practical + purposes only one of the two can be used and in case of a multi-boot + setup with different operating systems on one disk, all of them must + therefore use the same type of partition table. Booting from a disk + with GPT is only possible in native UEFI mode, but using GPT becomes + more and more common as hard disk sizes grow, because the classic DOS + partition table cannot address disks larger than about 2 Terabytes + while GPT allows for by far larger disks. The other major difference + between BIOS (or UEFI in CSM mode) and native UEFI is from where boot + code is loaded and in which format it has to be, so that different + bootloaders are needed for both systems. + </para> + <para> + The latter becomes important when booting &d-i; on a UEFI system with + CSM because &d-i; checks whether it was started on a BIOS- or on a + native UEFI system and installs the corresponding bootloader. + Normally this simply works but there can be a problem in multi-boot + environments. On some UEFI systems with CSM the default boot mode for + removable devices can be different from what is actually used when + booting from hard disk, so when booting the installer from a USB stick + in a different mode from what is used when booting another already + installed operating system from the hard disk, the wrong bootloader + might be installed and the system might be unbootable after finishing + the installation. When choosing the boot device from a firmware boot + menu, some systems offer two seperate choices for each device, so that + the user can select whether booting shall happen in CSM or in native + UEFI mode. + </para> + <para> + Another UEFI-related topic is the so-called <quote>secure boot</quote> + mechanism. Secure boot means a function of UEFI implementations that + allows the firmware to only load and execute code that is + cryptographically signed with certain keys and thereby blocking any + (potentially malicious) boot code that is unsigned or signed with + unknown keys. In practice the only key accepted by default on most + UEFI systems with secure boot is a key from Microsoft used for signing + the Windows bootloader. As the boot code used by &d-i; is not signed + by Microsoft, booting the installer requires prior deactivation of + secure boot in case it is enabled. Secure boot is often enabled by + default on systems that come preinstalled with a 64Bit version of + Windows 8 and there is unfortunately no standard where in the UEFI + setup it can be disabled. On some systems, the option to disable + secure boot is only made visible when a BIOS password has been set by + the user, so if you have a system with secure boot enabled, but cannot + find an option to disable it, try setting a BIOS password, powercycle + the machine and look again for an appropriate option. + </para> + </sect2> + + <sect2 arch="x86" id="disable-fast-boot"> + <title>Disabling the Windows 8 <quote>fast boot</quote> feature</title> + <para> + Windows 8 offers a feature called "fast boot" to cut down the time + needed to boot itself. Technically, when this feature is enabled, + Windows 8 does not do a real shutdown and a real cold boot afterwards + when ordered to shut down, but instead does something resembling a + partial suspend to disk to reduce the "boot" time. As long as Windows + 8 is the only operating system on the machine, this is unproblematic, + but it can result in problems and data loss when you have a dual boot + setup in which another operating system accesses the same filesystems + as Windows 8 does. In that case the real state of the filesystem can + be different from what Windows 8 believes it to be after the "boot" + and this could cause filesystem corruption upon further write accesses + to the filesystem. Therefore in a dual boot setup, to avoid + filesystem corruption the "fast boot" feature has to be disabled + within Windows. + </para> + </sect2> <sect2 arch="x86;powerpc" id="hardware-issues"> <title>Hardware Issues to Watch Out For</title> |