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    1 EXTLINUX is a new Syslinux derivative, which boots from a Linux
    2 ext2/ext3 filesystem.
    3 
    4 It works the same way as SYSLINUX (see doc/syslinux.txt), with a few
    5 slight modifications.
    6 
    7 1. The installer is run on a *mounted* filesystem.  Run the extlinux
    8    installer on the directory in which you want extlinux installed:
    9 
   10 	extlinux --install /boot
   11 
   12    Specify --install (-i) to install for the first time, or
   13    --update (-U) to upgrade a previous installation.
   14 
   15    NOTE: this doesn't have to be the root directory of a filesystem.
   16    If /boot is a filesystem, you can do:
   17 
   18 	mkdir -p /boot/extlinux
   19 	extlinux --install /boot/extlinux
   20 
   21    ... to create a subdirectory and install extlinux in it.
   22    /boot/extlinux is the recommended location for extlinux.
   23 
   24 
   25 2. The configuration file is called "extlinux.conf", and is expected
   26    to be found in the same directory as extlinux is installed in.
   27    Since 4.00 "syslinux.cfg" is also tried if "extlinux.conf" is not
   28    found.
   29 
   30 
   31 3. Pathnames can be absolute or relative; if absolute (with a leading
   32    slash), they are relative to the root of the filesystem on which
   33    extlinux is installed (/boot in the example above), if relative,
   34    they are relative to the extlinux directory.
   35 
   36    extlinux supports subdirectories, but the total path length is
   37    limited to 511 characters.
   38 
   39 
   40 4. EXTLINUX now supports symbolic links.  However, extremely long
   41    symbolic links might hit the pathname limit.  Also, please note
   42    that absolute symbolic links are interpreted from the root *of the
   43    filesystem*, which might be different from how the running system
   44    would interpret it (e.g. in the case of a separate /boot
   45    partition.)  Therefore, use relative symbolic links if at all
   46    possible.
   47 
   48 
   49 5. EXTLINUX now has "boot-once" support.  The boot-once information is
   50    stored in an on-disk datastructure, part of extlinux.sys, called
   51    the "Auxillary Data Vector".  The Auxilliary Data Vector is also
   52    available to COM32 modules that want to store small amounts of
   53    information.
   54 
   55    To set the boot-once information, do:
   56 
   57 	extlinux --once 'command' /boot/extlinux
   58 
   59    where 'command' is any command you could enter at the Syslinux
   60    command line.  It will be executed on the next boot and then
   61    erased.
   62 
   63    To clear the boot-once information, do:
   64 
   65 	extlinux --clear-once /boot/extlinux
   66 
   67    If EXTLINUX is used on a RAID-1, this is recommended, since under
   68    certain circumstances a RAID-1 rebuild can "resurrect" the
   69    boot-once information otherwise.
   70 
   71    To clear the entire Auxillary Data Vector, do:
   72 
   73 	extlinux --reset-adv /boot/extlinux
   74 
   75    This will erase all data stored in the ADV, including boot-once.
   76 
   77    The --once, --clear-once, and --reset-adv commands can be combined
   78    with --install or --update, if desired.  The ADV is preserved
   79    across updates, unless --reset-adv is specified.
   80 
   81 
   82 Note that EXTLINUX installs in the filesystem partition like a
   83 well-behaved bootloader :)  Thus, it needs a master boot record in the
   84 partition table; the mbr.bin shipped with Syslinux should work well.
   85 To install it just do:
   86 
   87 	cat mbr.bin > /dev/XXX
   88 
   89 ... where /dev/XXX is the appropriate master device, e.g. /dev/hda,
   90 and make sure the correct partition in set active.
   91 
   92 
   93 If you have multiple disks in a software RAID configuration, the
   94 preferred way to boot is:
   95 
   96 - Create a separate RAID-1 partition for /boot.  Note that the Linux
   97   RAID-1 driver can span as many disks as you wish.
   98 
   99 - Install the MBR on *each disk*, and mark the RAID-1 partition
  100   active.
  101 
  102 - Run "extlinux --raid --install /boot" to install extlinux.  This
  103   will install it on all the drives in the RAID-1 set, which means
  104   you can boot any combination of drives in any order.
  105 
  106 
  107 
  108 It is not required to re-run the extlinux installer after installing
  109 new kernels.  If you are using ext3 journalling, however, it might be
  110 desirable to do so, since running the extlinux installer will flush
  111 the log.  Otherwise a dirty shutdown could cause some of the new
  112 kernel image to still be in the log.  This is a general problem for
  113 boot loaders on journalling filesystems; it is not specific to
  114 extlinux.  The "sync" command does not flush the log on the ext3
  115 filesystem.
  116 
  117 
  118 The Syslinux Project boot loaders support chain loading other
  119 operating systems via a separate module, chain.c32 (located in
  120 com32/modules/chain.c32).  To use it, specify a LABEL in the
  121 configuration file with KERNEL chain.c32 and APPEND [hd|fd]<number>
  122 [<partition>]
  123 
  124 For example:
  125 
  126 # Windows CE/ME/NT, a very dense operating system.
  127 # Second partition (2) on the first hard disk (hd0);
  128 # Linux would *typically* call this /dev/hda2 or /dev/sda2.
  129 LABEL cement
  130 	KERNEL chain.c32
  131 	APPEND hd0 2
  132 
  133 See also doc/menu.txt.
  134