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Full Discussion: Right place to install Linux bootloader
Top Forums UNIX for Dummies Questions & Answers Right place to install Linux bootloader Post 302867801 by bakunin on Friday 25th of October 2013 04:41:35 AM
Old 10-25-2013
OK, first a few words about the booting process of a PC. That will make it clearer, hopefully:

When a PC starts, the BIOS holds the first program to be loaded. It scans several busses (IDE-controllers, SCSI-controllers, ...) for prospective devices to boot from and creates a list. Then this is worked from top to bottom (though it is possible to exclude certain devices or rearrange list entries - this is a common option in BIOSes).

Every device found that way - usually disks, USB sticks, CD-ROM-drives, diskette drives and so on - is in turn scanned for a so-called "Master boot record". This is a certain disk block, which contains a boot-loader program - if the disk is bootable. If not, then this space is simply left free and the process tries the next device in its list and searches there for a MBR.

If such a boot-loader is found, it is loaded by the BIOS and started. The boot-loader is NOT an OS by itself, it just loads an OS. GRUB, the older lilo and some other boot-loaders work that way. Usually the boot-loader presents a selection of kernels to boot from and a list of root volumes (aka "partitions" to use as the root of the FS - to mount as "/" in case of Unix-systems, as "C:" in case of DOS/Windows-systems or as "[SYS]" in case of VMS-systems.

Once a kernel image and/or boot partition is selected the boot-loader program tries to pass control to an OS-bootstrap program located in certain parts of the selected partition (this is why you need to flag a partition "active" to boot from - this certain space is set apart) and starts that. This in turn loads the OS kernel and the rest is OS specific. Note, that the whole process up to the initialization of the OS kernel happens in the CPUs "real mode", even for protected mode/virtual mode OSes. They have to switch the CPU into their respective mode of operation themselves.

So, to answer your question: yes, you will have to install the boot loader (perhaps "GRUB", less likely "lilo") to the MBR ("/dev/sda", which signifies the disk, rather than "/dev/sdaX", which denotes a certain partition on that disk), otherwise it will not get executed automatically. You need to do that as root, not as normal user, because files involved in the boot process have mostly permissions set to be accessible only by root.

I hope this helps.

bakunin
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LEARN ABOUT PHP

grub-install

GRUB-INSTALL(8) 					  System Administration Utilities					   GRUB-INSTALL(8)

NAME

       grub-install - install GRUB to a device

SYNOPSIS

       grub-install [OPTION...] [OPTION] [INSTALL_DEVICE]

DESCRIPTION

       Install GRUB on your drive.

       --compress=no|xz|gz|lzo
	      compress GRUB files [optional]

       -d, --directory=DIR
	      use images and modules under DIR [default=/usr/lib/grub/<platform>]

       --fonts=FONTS
	      install FONTS [default=unicode]

       --install-modules=MODULES
	      install only MODULES and their dependencies [default=all]

       -k, --pubkey=FILE
	      embed FILE as public key for signature checking

       --locale-directory=DIR use translations under DIR
	      [default=/usr/share/locale]

       --locales=LOCALES
	      install only LOCALES [default=all]

       --modules=MODULES
	      pre-load specified modules MODULES

       --themes=THEMES
	      install THEMES [default=starfield]

       -v, --verbose
	      print verbose messages.

       --allow-floppy
	      make the drive also bootable as floppy (default for fdX devices). May break on some BIOSes.

       --auto-nvram
	      only update NVRAM variables if possible. This option is only available on EFI and IEEE1275 targets.

       --boot-directory=DIR
	      install GRUB images under the directory DIR/grub instead of the boot/grub directory

       --bootloader-id=ID
	      the ID of bootloader. This option is only available on EFI and Macs.

       --core-compress=xz|none|auto
	      choose the compression to use for core image

       --disk-module=MODULE
	      disk module to use (biosdisk or native). This option is only available on BIOS target.

       --efi-directory=DIR
	      use DIR as the EFI System Partition root.

       --force
	      install even if problems are detected

       --force-file-id
	      use identifier file even if UUID is available

       --label-bgcolor=COLOR
	      use COLOR for label background

       --label-color=COLOR
	      use COLOR for label

       --label-font=FILE
	      use FILE as font for label

       --macppc-directory=DIR use DIR for PPC MAC install.

       --no-bootsector
	      do not install bootsector

       --no-extra-removable
	      Do not install bootloader code to the removable media path. This option is only available on EFI.

       --no-nvram
	      don't update the `boot-device'/`Boot*' NVRAM variables. This option is only available on EFI and IEEE1275 targets.

       --no-rs-codes
	      Do not apply any reed-solomon codes when embedding core.img. This option is only available on x86 BIOS targets.

       --no-uefi-secure-boot
	      do  not install an image usable with UEFI Secure Boot, even if the system was currently started using it. This option is only avail-
	      able on EFI.

       --product-version=STRING
	      use STRING as product version

       --recheck
	      delete device map if it already exists

       --removable
	      the installation device is removable. This option is only available on EFI.

       -s, --skip-fs-probe
	      do not probe for filesystems in DEVICE

	      Usage: grub-install [OPTION...] [OPTION] [INSTALL_DEVICE]

       Install GRUB on your drive.

       --compress=no|xz|gz|lzo
	      compress GRUB files [optional]

       -d, --directory=DIR
	      use images and modules under DIR [default=/usr/lib/grub/<platform>]

       --fonts=FONTS
	      install FONTS [default=unicode]

       --install-modules=MODULES
	      install only MODULES and their dependencies [default=all]

       -k, --pubkey=FILE
	      embed FILE as public key for signature checking

       --locale-directory=DIR use translations under DIR
	      [default=/usr/share/locale]

       --locales=LOCALES
	      install only LOCALES [default=all]

       --modules=MODULES
	      pre-load specified modules MODULES

       --themes=THEMES
	      install THEMES [default=starfield]

       -v, --verbose
	      print verbose messages.

       --allow-floppy
	      make the drive also bootable as floppy (default for fdX devices). May break on some BIOSes.

       --auto-nvram
	      only update NVRAM variables if possible. This option is only available on EFI and IEEE1275 targets.

       --boot-directory=DIR
	      install GRUB images under the directory DIR/grub instead of the boot/grub directory

       --bootloader-id=ID
	      the ID of bootloader. This option is only available on EFI and Macs.

       --core-compress=xz|none|auto
	      choose the compression to use for core image

       --disk-module=MODULE
	      disk module to use (biosdisk or native). This option is only available on BIOS target.

       --efi-directory=DIR
	      use DIR as the EFI System Partition root.

       --force
	      install even if problems are detected

       --force-file-id
	      use identifier file even if UUID is available

       --label-bgcolor=COLOR
	      use COLOR for label background

       --label-color=COLOR
	      use COLOR for label

       --label-font=FILE
	      use FILE as font for label

       --macppc-directory=DIR use DIR for PPC MAC install.

       --no-bootsector
	      do not install bootsector

       --no-extra-removable
	      Do not install bootloader code to the removable media path. This option is only available on EFI.

       --no-nvram
	      don't update the `boot-device'/`Boot*' NVRAM variables. This option is only available on EFI and IEEE1275 targets.

       --no-rs-codes
	      Do not apply any reed-solomon codes when embedding core.img. This option is only available on x86 BIOS targets.

       --no-uefi-secure-boot
	      do not install an image usable with UEFI Secure Boot, even if the system was currently started using it. This option is only  avail-
	      able on EFI.

       --product-version=STRING
	      use STRING as product version

       --recheck
	      delete device map if it already exists

       --removable
	      the installation device is removable. This option is only available on EFI.

       -s, --skip-fs-probe
	      do not probe for filesystems in DEVICE

       --target=TARGET
	      install  GRUB  for  TARGET  platform  [default=i386-pc];	available targets: arm-efi, arm-uboot, arm64-efi, i386-coreboot, i386-efi,
	      i386-ieee1275, i386-multiboot, i386-pc,  i386-qemu,  i386-xen,  ia64-efi,  mips-arc,  mips-qemu_mips,  mipsel-arc,  mipsel-loongson,
	      mipsel-qemu_mips, powerpc-ieee1275, sparc64-ieee1275, x86_64-efi, x86_64-xen

       --uefi-secure-boot
	      install  an  image  usable  with UEFI Secure Boot.  This option is only available on EFI and if the grub-efi-amd64-signed package is
	      installed.

       -?, --help
	      give this help list

       --usage
	      give a short usage message

       -V, --version
	      print program version

       Mandatory or optional arguments to long options are also mandatory or optional for any corresponding short options.

       INSTALL_DEVICE must be system device filename.  grub-install copies GRUB images into boot/grub.	On some platforms,  it	may  also  install
       GRUB into the boot sector.

REPORTING BUGS

       Report bugs to <bug-grub@gnu.org>.

SEE ALSO

       grub-mkconfig(8), grub-mkimage(1), grub-mkrescue(1)

       The full documentation for grub-install is maintained as a Texinfo manual.  If the info and grub-install programs are properly installed at
       your site, the command

	      info grub-install

       should give you access to the complete manual.

grub-install (GRUB) 2.02-2ubuntu8.3				     July 2018							   GRUB-INSTALL(8)
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