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(grub.info)Features

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GRUB features
=============

   The primary requirement for GRUB is that it be compliant with the
"Multiboot Specification", which is described in Note: Multiboot
Specification.

   The other goals, listed in approximate order of importance, are:

   * Basic functions must be straightforward for end-users.

   * Rich functionality to support kernel experts and designers.

   * Backward compatibility for booting FreeBSD, NetBSD, OpenBSD, and
     Linux. Proprietary kernels (such as DOS, Windows NT, and OS/2) are
     supported via a chain-loading function.

   Except for specific compatibility modes (chain-loading and the Linux
"piggyback" format), all kernels will be started in much the same state
as in the Multiboot Specification. Only kernels loaded at 1 megabyte or
above are presently supported. Any attempt to load below that boundary
will simply result in immediate failure and an error message reporting
the problem.

   In addition to the requirements above, GRUB has the following
features (note that the Multiboot Specification doesn't require all the
features that GRUB supports):

Recognize multiple executable formats
     Support many of the "a.out" variants plus "ELF". Symbol tables are
     also loaded.

Support non-Multiboot kernels
     Support many of the various free 32-bit kernels that lack Multiboot
     compliance (primarily FreeBSD, NetBSD, OpenBSD, and Linux).
     Chain-loading of other boot loaders is also supported.

Load multiples modules
     Fully support the Multiboot feature of loading multiple modules.

Load a configuration file
     Support a human-readable text configuration file with preset boot
     commands. You can also load another configuration file dynamically
     and embed a preset configuration file in a GRUB image file. The
     list of commands (Note: Commands) are a superset of those
     supported on the command-line. An example configuration file is
     provided in Note: Configuration.

Provide a menu interface
     A menu interface listing the preset boot commands, with a
     programmable timeout, is available. There is no fixed limit on the
     number of boot entries, and the current implementation has space
     for several hundred.

Have a flexible command-line interface
     A fairly flexible command-line interface, accessible from the menu,
     is available to edit any preset commands, or write a new boot
     command set from scratch. If no configuration file is present,
     GRUB drops to the command-line.

     The list of commands (Note: Commands) are a subset of those
     supported for configuration files. Editing commands closely
     resembles the Bash command-line (Note: Bash.
), with <TAB>-completion of commands, devices,
     partitions, and files in a directory depending on context.

Support multiple filesystem types
     Support multiple filesystem types transparently, plus a useful
     explicit blocklist notation. The currently supported filesystem
     types are "BSD FFS", "DOS FAT16 and FAT32", "Minix fs", "Linux
     ext2fs", "ReiserFS", "JFS", "XFS", and "VSTa fs". Note:
     Filesystem, for more information.

Support automatic decompression
     Can decompress files which were compressed by `gzip'. This
     function is both automatic and transparent to the user (i.e. all
     functions operate upon the uncompressed contents of the specified
     files). This greatly reduces a file size and the loading time, a
     particularly major benefit for floppies.(1) (Note:
     Features-Footnote-1)

     It is conceivable that some kernel modules should be loaded in a
     compressed state, so a different module-loading command can be
     specified to avoid uncompressing the modules.

Access data on any installed device
     Support reading data from any or all floppy or hard disk(s)
     recognized by the BIOS, independent of the setting of the root
     device.

Be independent of drive geometry translations
     Unlike many other boot loaders, GRUB makes the particular drive
     translation irrelevant. A drive installed and running with one
     translation may be converted to another translation without any
     adverse effects or changes in GRUB's configuration.

Detect all installed RAM
     GRUB can generally find all the installed RAM on a PC-compatible
     machine. It uses an advanced BIOS query technique for finding all
     memory regions. As described on the Multiboot Specification (Note:
     Multiboot Specification.), not all kernels make
     use of this information, but GRUB provides it for those who do.

Support Logical Block Address mode
     In traditional disk calls (called "CHS mode"), there is a geometry
     translation problem, that is, the BIOS cannot access over 1024
     cylinders, so the accessible space is limited to at least 508 MB
     and to at most 8GB. GRUB can't universally solve this problem, as
     there is no standard interface used in all machines. However,
     several newer machines have the new interface, Logical Block
     Address ("LBA") mode. GRUB automatically detects if LBA mode is
     available and uses it if available. In LBA mode, GRUB can access
     the entire disk.

Support network booting
     GRUB is basically a disk-based boot loader but also has network
     support. You can load OS images from a network by using the "TFTP"
     protocol.

Support remote terminals
     To support computers with no console, GRUB provides remote terminal
     support, so that you can control GRUB from a remote host. Only
     serial terminal support is implemented at the moment.