LXR syslinux/doc/extlinux.txt

   1EXTLINUX is a new Syslinux derivative, which boots from a Linux
   2ext2/ext3 filesystem.
   3
   4It works the same way as SYSLINUX (see doc/syslinux.txt), with a few
   5slight modifications.
   6
   71. 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
  252. 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
  313. 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
  404. 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
  495. 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
  82Note that EXTLINUX installs in the filesystem partition like a
  83well-behaved bootloader :)  Thus, it needs a master boot record in the
  84partition table; the mbr.bin shipped with Syslinux should work well.
  85To 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,
  90and make sure the correct partition in set active.
  91
  92
  93If you have multiple disks in a software RAID configuration, the
  94preferred 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
 108It is not required to re-run the extlinux installer after installing
 109new kernels.  If you are using ext3 journalling, however, it might be
 110desirable to do so, since running the extlinux installer will flush
 111the log.  Otherwise a dirty shutdown could cause some of the new
 112kernel image to still be in the log.  This is a general problem for
 113boot loaders on journalling filesystems; it is not specific to
 114extlinux.  The "sync" command does not flush the log on the ext3
 115filesystem.
 116
 117
 118The Syslinux Project boot loaders support chain loading other
 119operating systems via a separate module, chain.c32 (located in
 120com32/modules/chain.c32).  To use it, specify a LABEL in the
 121configuration file with KERNEL chain.c32 and APPEND [hd|fd]<number>
 122[<partition>]
 123
 124For 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.
 129LABEL cement
 130        KERNEL chain.c32
 131        APPEND hd0 2
 132
 133See also doc/menu.txt.
 134
 135