135 lines
4.6 KiB
Plaintext
135 lines
4.6 KiB
Plaintext
EXTLINUX is a new Syslinux derivative, which boots from a Linux
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ext2/ext3 filesystem.
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It works the same way as SYSLINUX (see doc/syslinux.txt), with a few
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slight modifications.
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1. The installer is run on a *mounted* filesystem. Run the extlinux
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installer on the directory in which you want extlinux installed:
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extlinux --install /boot
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Specify --install (-i) to install for the first time, or
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--update (-U) to upgrade a previous installation.
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NOTE: this doesn't have to be the root directory of a filesystem.
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If /boot is a filesystem, you can do:
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mkdir -p /boot/extlinux
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extlinux --install /boot/extlinux
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... to create a subdirectory and install extlinux in it.
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/boot/extlinux is the recommended location for extlinux.
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2. The configuration file is called "extlinux.conf", and is expected
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to be found in the same directory as extlinux is installed in.
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Since 4.00 "syslinux.cfg" is also tried if "extlinux.conf" is not
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found.
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3. Pathnames can be absolute or relative; if absolute (with a leading
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slash), they are relative to the root of the filesystem on which
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extlinux is installed (/boot in the example above), if relative,
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they are relative to the extlinux directory.
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extlinux supports subdirectories, but the total path length is
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limited to 511 characters.
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4. EXTLINUX now supports symbolic links. However, extremely long
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symbolic links might hit the pathname limit. Also, please note
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that absolute symbolic links are interpreted from the root *of the
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filesystem*, which might be different from how the running system
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would interpret it (e.g. in the case of a separate /boot
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partition.) Therefore, use relative symbolic links if at all
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possible.
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5. EXTLINUX now has "boot-once" support. The boot-once information is
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stored in an on-disk datastructure, part of extlinux.sys, called
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the "Auxillary Data Vector". The Auxilliary Data Vector is also
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available to COM32 modules that want to store small amounts of
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information.
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To set the boot-once information, do:
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extlinux --once 'command' /boot/extlinux
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where 'command' is any command you could enter at the Syslinux
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command line. It will be executed on the next boot and then
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erased.
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To clear the boot-once information, do:
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extlinux --clear-once /boot/extlinux
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If EXTLINUX is used on a RAID-1, this is recommended, since under
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certain circumstances a RAID-1 rebuild can "resurrect" the
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boot-once information otherwise.
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To clear the entire Auxillary Data Vector, do:
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extlinux --reset-adv /boot/extlinux
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This will erase all data stored in the ADV, including boot-once.
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The --once, --clear-once, and --reset-adv commands can be combined
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with --install or --update, if desired. The ADV is preserved
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across updates, unless --reset-adv is specified.
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Note that EXTLINUX installs in the filesystem partition like a
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well-behaved bootloader :) Thus, it needs a master boot record in the
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partition table; the mbr.bin shipped with Syslinux should work well.
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To install it just do:
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cat mbr.bin > /dev/XXX
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... where /dev/XXX is the appropriate master device, e.g. /dev/hda,
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and make sure the correct partition in set active.
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If you have multiple disks in a software RAID configuration, the
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preferred way to boot is:
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- Create a separate RAID-1 partition for /boot. Note that the Linux
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RAID-1 driver can span as many disks as you wish.
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- Install the MBR on *each disk*, and mark the RAID-1 partition
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active.
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- Run "extlinux --raid --install /boot" to install extlinux. This
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will install it on all the drives in the RAID-1 set, which means
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you can boot any combination of drives in any order.
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It is not required to re-run the extlinux installer after installing
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new kernels. If you are using ext3 journalling, however, it might be
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desirable to do so, since running the extlinux installer will flush
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the log. Otherwise a dirty shutdown could cause some of the new
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kernel image to still be in the log. This is a general problem for
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boot loaders on journalling filesystems; it is not specific to
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extlinux. The "sync" command does not flush the log on the ext3
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filesystem.
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The Syslinux Project boot loaders support chain loading other
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operating systems via a separate module, chain.c32 (located in
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com32/modules/chain.c32). To use it, specify a LABEL in the
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configuration file with KERNEL chain.c32 and APPEND [hd|fd]<number>
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[<partition>]
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For example:
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# Windows CE/ME/NT, a very dense operating system.
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# Second partition (2) on the first hard disk (hd0);
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# Linux would *typically* call this /dev/hda2 or /dev/sda2.
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LABEL cement
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KERNEL chain.c32
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APPEND hd0 2
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See also doc/menu.txt.
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