A Boot Loader Called Grub

Hello, Harry N. Hacker here to discuss grub. I was out in the back yard the other day, and noticed a bunch of… what? We aren’t talking about worms in the yard?

Oh, Harry, just give it up!

GRUB, the GRand Unified Bootloader was originally designed and implemented by a guy named Erich Stefan Boleyn. His bootloader is the first software program that runs when your computer starts up. GRUB loads and transfers control to the operating system kernel software such as Linux. The kernel then initializes the rest of the operating system.

GRUB Legacy is no longer actively developed, however, bug fixes will be made so that GRUB Legacy can still be used for older systems.

GRUB Legacy has the following features:

• Compliance with the Multiboot Specification

• Basic functions are easy for an end-user to use.

• Good functionality for OS experts/designers.

• Compatibility for booting FreeBSD, NetBSD, OpenBSD, and GNU/Linux. Proprietary OS's such as most current Windows releases and OS/2 are supported via a chain-loading function.

In addition to the requirements above, GNU GRUB Legacy has the following additional features:

• Support multiple executable formats.

• Support non-Multiboot OS's.

• Load multiple modules.

• Support a human-readable configuration file.

• Menu interface.

• Flexible command-line interface.

• Support for multiple filesystem types.

• Support for automatic decompression.

• Data accessability on any installed device.

• Geometry translation independence.

• Detection of all installed RAM.

• Support for Logical Block Address (LBA) mode.

• Ability to download OS images from a network.

• Support for diskless systems.

• Support for remote terminals.

This information may be viewed in the documentation of GNU GRUB by "info grub" on your shell prompt (or use your favorite Info browser, if you don't like info).

GRUB 2 has replaced the GRUB Legacy, and all though enhancements are still being made, the currently released version is quite usable. This statement came from an older article about GRUB. The following information comes from an article which was written in 2015. Quite a bit of difference I’d say:

GRUB vs GRUB 2

GRUB 2's default menu will look familiar to GRUB users but there are a great number of differences beneath the surface.

1. On a new installation of Ubuntu 9.10 or later with no other installed operating systems, GRUB 2 will boot directly to the login prompt or Desktop. No menu will be displayed.

2. Hold down (right) SHIFT to display the menu during boot. In certain cases, pressing the ESC key may also display the menu.

3. No /boot/grub/menu.lst. It has been replaced by /boot/grub/grub.cfg.

4. There is no "/find boot/grub/stage1" at the grub prompt. Stage 1.5 has been eliminated.

5. The main Grub 2 configuration file, normally located in the /boot/grub folder, is grub.cfg. It is the product of various scripts and should not normally be edited directly.

6. grub.cfg is overwritten by certain Grub 2 package updates, whenever a kernel is added or removed, or when the user runs update-grub.

7. The menu list of available Linux kernels is automatically generated by running update-grub.

8. The user can create a custom file in which the user can place his own menu entries. This file will not be overwritten. By default, a custom file named 40_custom is available for use in the /etc/grub.d folder.

9. The primary configuration file for changing menu display settings is called grub and by default is located in the /etc/default folder.

10. There are multiple files for configuring the menu - /etc/default/grub mentioned above, and all the files in the /etc/grub.d/ directory.

11. Partition numbering has changed. The first partition is now 1 rather than 0. The first device/drive is still hd0 by default (no change). These designations can be altered if necessary in the device.map file in the /boot/grub folder.

12. Automated searches for other operating systems, such as Windows, are accomplished whenever update-grub is executed. Operating systems found will be placed in the Grub 2 menu.

13. Changes made in the configuration files will not take effect until the update-grub command is executed.

This article also states GRUB 2 is the current bootloader for Ubuntu since 9.10 (Karmic Koala). The article can be found at "Ubuntu Documentation." Grub2. Web. 18 Apr. 2016.

Systemd-boot is an alternative boot loader for Linux systems. systemd-boot (previously called gummiboot), is a simple UEFI boot manager which executes configured EFI images. The default entry is selected by a configured pattern (glob) or an on-screen menu. It is included with systemd since systemd 220-2.

It is simple to configure, but can only start EFI executables, such as the Linux kernel EFISTUB, UEFI Shell, GRUB, the Windows Boot Manager, and such.

This commentary was located on wiki.archlinux.org/index.php/Systemd-boot, and Citation “monster” is not working properly again. Sorry.

So there you have it, GRUB, GRUB2 and systemd-boot all in a nut shell. Ha, get it? Nut SHELL. (been hanging around Harry too much).

Thanks for stopping in, and “Happy Researching”.

Resources:

"GNU GRUB." - GNU Project. Web. 18 Apr. 2016.

"PUPA.": Home. Web. 18 Apr. 2016.

"Fedora." Features/Grub2. Web. 18 Apr. 2016.