admin:linux:boot [~wiki]

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====== Boot Linux ======

Boot process[(https://documentation.suse.com/sles/12-SP5/html/SLES-all/cha-boot.html)]:

  - Initialization and Boot Loader Phase
  - Kernel Phase
    * Initial Ramdisk (initramfs)
    * init on initramfs
      * Loading Kernel Modules
      * Providing Block Special Files
      * Managing RAID and LVM Setups
      * Managing the Network Configuration
  - (userspace) init phase
    * usually systemd

===== EFI =====

==== EFISTUB (boot kernel directly) ====

=== Arch Linux ===

[[https://wiki.archlinux.org/index.php/EFISTUB|EFISTUB Arch wiki entry]]

<code>efibootmgr --disk /dev/sdX --part Y --create --label "Arch Linux" --loader /vmlinuz-linux --unicode 'root=PARTUUID=XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX rw initrd=\initramfs-linux.img' --verbose</code>

if you need [[https://wiki.archlinux.org/index.php/microcode|ucode]], add it as first initramfs:

<code>… initrd=/cpu_manufacturer-ucode.img initrd=/initramfs-linux.img</code>

==== Grub2 ====

=== Debian ===

<code bash>
grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=debian --recheck
update-grub
</code>

===== dual boot with other systems =====

==== Windows ====

=== Windows gets the time wrong ===

Reason: Clock is set in UTC, Windows thinks it's local time.

Solution:

  * <file reg UseUTCforRTC.reg>Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation]
     "RealTimeIsUniversal"=dword:00000001</file>
  * Disable Windows time service  <code powershell>sc config w32time start= disabled</code>

See also: https://help.ubuntu.com/community/UbuntuTime#Multiple_Boot_Systems_Time_Conflicts

===== Troubleshooting =====
^ show boot options (Kernel command line) | ''cat /proc/cmdline'' |

===== Further reading =====
  * [[https://documentation.suse.com/sles/12-SP5/html/SLES-all/cha-boot.html|Introduction to the boot process (SLES 12 SP5)]]