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1 EXTLINUX is a new Syslinux derivative, which boots from a Linux
2 ext2/ext3 filesystem.
4 It works the same way as SYSLINUX (see doc/syslinux.txt), with a few
5 slight modifications.
7 1. The installer is run on a *mounted* filesystem. Run the extlinux
8 installer on the directory in which you want extlinux installed:
10 extlinux --install /boot
12 Specify --install (-i) to install for the first time, or
13 --update (-U) to upgrade a previous installation.
15 NOTE: this doesn't have to be the root directory of a filesystem.
16 If /boot is a filesystem, you can do:
18 mkdir -p /boot/extlinux
19 extlinux --install /boot/extlinux
21 ... to create a subdirectory and install extlinux in it.
22 /boot/extlinux is the recommended location for extlinux.
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
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.
36 extlinux supports subdirectories, but the total path length is
37 limited to 511 characters.
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
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
55 To set the boot-once information, do:
57 extlinux --once 'command' /boot/extlinux
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
63 To clear the boot-once information, do:
65 extlinux --clear-once /boot/extlinux
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.
71 To clear the entire Auxillary Data Vector, do:
73 extlinux --reset-adv /boot/extlinux
75 This will erase all data stored in the ADV, including boot-once.
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.
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:
87 cat mbr.bin > /dev/XXX
89 ... where /dev/XXX is the appropriate master device, e.g. /dev/hda,
90 and make sure the correct partition in set active.
93 If you have multiple disks in a software RAID configuration, the
94 preferred way to boot is:
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.
99 - Install the MBR on *each disk*, and mark the RAID-1 partition
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.
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
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>
124 For example:
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
133 See also doc/menu.txt.