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<body class="manpage">
<div id="header">
<h1>
syslinux.cfg(5) Manual Page
</h1>
<h2>NAME</h2>
<div class="sectionbody">
<p>syslinux.cfg -
*Syslinux* configuration file
</p>
</div>
</div>
<div id="content">
<div class="sect1">
<h2 id="_description">DESCRIPTION</h2>
<div class="sectionbody">
<div class="paragraph"><p>Configuration for the boot behavior and user experience of <strong>Syslinux</strong>
boot loaders, the format of display files and the boot prompt behavior.</p></div>
<div class="paragraph"><p>Blank lines are ignored.</p></div>
<div class="paragraph"><p>Note that the configuration file is not completely decoded. Syntax
different from the one described above may still work correctly in this
version of <strong>Syslinux</strong>, but may break in a future one.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_location_name">LOCATION/NAME</h2>
<div class="sectionbody">
<div class="paragraph"><p><strong>SYSLINUX</strong> (before 4.00) used the configuration filename of
syslinux.cfg. <strong>EXTLINUX</strong> (merged into <strong>SYSLINUX</strong> as of 4.00) used the
filename extlinux.conf. Both default to searching for the config file
in the installed directory (containing ldlinux.sys/extlinux.sys). As of
4.00, <strong>SYSLINUX</strong> will search for extlinux.conf then syslinux.cfg in each
directory before falling back to the next directory.</p></div>
<div class="paragraph"><p>As of 3.35, <strong>SYSLINUX</strong> also searches /boot/syslinux, /syslinux and /.</p></div>
<div class="paragraph"><p><strong>ISOLINUX</strong> (before 4.02) used the configuration filename of
isolinux.cfg, searching /boot/isolinux (starting 2.00), then /isolinux
and /. As of 4.02, <strong>ISOLINUX</strong> will search for isolinux.cfg then
syslinux.cfg in /boot/isolinux before searching for the same files in
/isolinux, /boot/syslinux, /syslinux, and /.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_global_directives_main">GLOBAL DIRECTIVES - MAIN</h2>
<div class="sectionbody">
<div class="dlist"><dl>
<dt class="hdlist1">
<strong>#</strong> comment
</dt>
<dd>
<p>
A line comment. As of version 3.10, the space between the <strong>#</strong> and the
comment is no longer required.
</p>
</dd>
<dt class="hdlist1">
<strong>MENU</strong> any string
</dt>
<dd>
<p>
(3.00+) A directive for the simple menu system, treated as a comment
outside the menu. See menu.txt.
</p>
</dd>
<dt class="hdlist1">
<strong>INCLUDE</strong> <em>filename</em>
</dt>
<dd>
<p>
Inserts the contents of another file at this point in the configuration
file. Files can currently be nested up to 16 levels deep, but it is not
guaranteed that more than 8 levels will be supported in the future.
</p>
</dd>
<dt class="hdlist1">
<strong>DEFAULT</strong> <em>kernel</em> <em>options…</em>
</dt>
<dd>
<p>
Sets the default command line (which often references a LABEL). If
<strong>Syslinux</strong> boots automatically, it will act just as if the entries after
<strong>DEFAULT</strong> had been typed in at the <em>boot:</em> prompt. Multiple uses will
result in an override.
</p>
<div class="paragraph"><p>If no configuration file is present, or no <strong>DEFAULT</strong> or <strong>UI</strong> entry is
present in the config file, an error message is displayed and the
<em>boot:</em> prompt is shown (3.85+).</p></div>
</dd>
<dt class="hdlist1">
<strong>UI</strong> <em>module</em> <em>options…</em>
</dt>
<dd>
<p>
Selects a specific user interface <em>module</em> (typically menu.c32 or
vesamenu.c32). The command-line interface treats this as a directive
that overrides the <strong>DEFAULT</strong> directive to load this module instead at
startup, for an empty command line and at timeout and <strong>PROMPT</strong> directive
to not prompt (but these directives may have effects on other
configuration parsers). Multiple uses will result in an override.
</p>
</dd>
<dt class="hdlist1">
<strong>LABEL</strong> <em>mylabel</em>
</dt>
<dd>
<p>
Begin a new <strong>LABEL</strong> clause. If <em>mylabel</em> is entered as the kernel to
boot, <strong>Syslinux</strong> should instead boot "image" (specified by a directive
from <strong>KERNEL-LIKE DIRECTIVES</strong>) with any specified <strong>DUAL-PURPOSE
DIRECTIVES</strong> being used instead of the global instance.
</p>
<div class="paragraph"><p><em>mylabel</em> must be unique. Currently the first instance is used but may
result in an error or undesired behavior. <em>mylabel</em> ends at the first
character that is not a non-white-space printable character and should
be restricted to non-white-space typeable characters. Prior to version
3.32, this would transformed to a DOS compatible format of 8.3 with a
restricted character set. A <strong>LABEL</strong> clause must contain exactly 1 of
the <strong>KERNEL-LIKE DIRECTIVES</strong> and may contain 1 each of the <strong>LABEL-ONLY
DIRECTIVES</strong> or <strong>DUAL-PURPOSE DIRECTIVES</strong>.</p></div>
<div class="paragraph"><p>Within a <strong>LABEL</strong>, using multiple <strong>KERNEL-LIKE DIRECTIVES</strong> or reuse of
<strong>LABEL-ONLY DIRECTIVES</strong> or <strong>DUAL-PURPOSE DIRECTIVES</strong> will result in an
override. Otherwise, multiple instances of the same directive will
result in the last being effective.</p></div>
</dd>
</dl></div>
</div>
</div>
<div class="sect1">
<h2 id="_dual_purpose_directives">DUAL-PURPOSE DIRECTIVES</h2>
<div class="sectionbody">
<div class="paragraph"><p>Use of any of the <strong>DUAL-PURPOSE DIRECTIVES</strong> as <strong>GLOBAL DIRECTIVES</strong> is
discouraged if there will be any non-Linux images loaded as <strong>ALL</strong> images
will get these, including those manually entered at the <em>boot:</em> prompt.</p></div>
<div class="dlist"><dl>
<dt class="hdlist1">
<strong>APPEND</strong> <em>options…</em>
</dt>
<dd>
<p>
Add one or more options to the kernel command line. These are added
both for automatic and manual boots. The options are added at the very
beginning of the kernel command line, usually permitting explicitly
entered kernel options to override them. This is the equivalent of the
LILO "append" option.
</p>
<div class="paragraph"><p>Use of the parameter <em>initrd=</em> supports multiple filenames separated by
commas (ie <em>initrd=initrd_file1,initrd_file2</em>) within a single instance.
This is mostly useful for initramfs, which can be composed of multiple
separate cpio or cpio.gz archives.</p></div>
<div class="paragraph"><p>Note: all initrd files except the last one are zero-padded to a 4K page
boundary. This should not affect initramfs.</p></div>
<div class="paragraph"><p>Note: Only the last effective <em>initrd=</em> parameter is used for loading
initrd files.</p></div>
</dd>
<dt class="hdlist1">
<strong>APPEND</strong> -
</dt>
<dd>
<p>
Append nothing. <strong>APPEND</strong> with a single hyphen as argument in a <strong>LABEL</strong>
section can be used to override a global <strong>APPEND</strong>.
</p>
</dd>
</dl></div>
<div class="dlist"><dl>
<dt class="hdlist1">
<strong>SYSAPPEND</strong> <em>bitmask</em>
</dt>
<dt class="hdlist1">
<strong>IPAPPEND</strong> <em>bitmask</em>
</dt>
<dd>
<p>
(<strong>SYSAPPEND</strong>: 5.10+; <strong>IPAPPEND</strong>: <strong>PXELINUX</strong> only)
The <strong>SYSAPPEND</strong> option was introduced in <strong>Syslinux</strong> 5.10; it is an
enhancement of a previous option <strong>IPAPPEND</strong> which was only available on
<strong>PXELINUX</strong>. <em>bitmask</em> is interpreted as decimal format unless prefixed
with "0x" for hexadecimal or "0" (zero) for octal. The <em>bitmask</em> is an
OR (sum) of the following integer options:
</p>
<div class="dlist"><dl>
<dt class="hdlist1">
<strong>1</strong>
</dt>
<dd>
<p>
An option of the following format should be generated, based on
the input from the DHCP/BOOTP or PXE boot server and added to the kernel
command line(see note below; empty for non-PXELINUX variants):
</p>
<div class="listingblock">
<div class="content">
<pre><code>ip=<client-ip>:<boot-server-ip>:<gw-ip>:<netmask></code></pre>
</div></div>
<div class="admonitionblock">
<table><tr>
<td class="icon">
<div class="title">Note</div>
</td>
<td class="content">The use of option 1 is no substitute for running a DHCP client in
the booted system and should instead only be used to seed the client for
a request. Without regular renewals, the lease acquired by the PXE BIOS
will expire, making the IP address available for reuse by the DHCP
server.</td>
</tr></table>
</div>
</dd>
<dt class="hdlist1">
<strong>2</strong>
</dt>
<dd>
<p>
An option of the following format should be generated, in
dash-separated hexadecimal with leading hardware type (same as for the
configuration file; see pxelinux.txt.) and added to the kernel command
line, allowing an initrd program to determine from which interface the
system booted(empty for non-PXELINUX variants):
</p>
<div class="listingblock">
<div class="content">
<pre><code>BOOTIF=<hardware-address-of-boot-interface></code></pre>
</div></div>
</dd>
<dt class="hdlist1">
<strong>4</strong>
</dt>
<dd>
<p>
An option of the following format should be generated, in lower
case hexadecimal in the format normally used for UUIDs (same as for the
configuration file; see pxelinux.txt.) and added to the kernel command
line:
</p>
<div class="listingblock">
<div class="content">
<pre><code>SYSUUID=<system uuid></code></pre>
</div></div>
</dd>
<dt class="hdlist1">
<strong>8</strong>
</dt>
<dd>
<p>
(5.10+) indicate the CPU family and certain particularly
significant CPU feature bits:
</p>
<div class="listingblock">
<div class="content">
<pre><code>CPU=<family><features></code></pre>
</div></div>
<div class="paragraph"><p>The <family> is a single digit from 3 (i386) to 6 (i686 or higher.) The
following CPU features are currently reported; additional flags may be
added in the future:</p></div>
<div class="literalblock">
<div class="content">
<pre><code>P Physical Address Extension (PAE)
V Intel Virtualization Technology (VT/VMX)
T Intel Trusted Exection Technology (TXT/SMX)
X Execution Disable (XD/NX)
L Long Mode (x86-64)
S AMD SMX virtualization</code></pre>
</div></div>
</dd>
<dt class="hdlist1">
<strong>DMI</strong>
</dt>
<dd>
<p>
(5.10+) The following strings are derived from DMI/SMBIOS
information if available:
</p>
<div class="literalblock">
<div class="content">
<pre><code>Bit String Significance
-------------------------------------------------------------
0x00010 SYSVENDOR= System vendor name
0x00020 SYSPRODUCT= System product name
0x00040 SYSVERSION= System version
0x00080 SYSSERIAL= System serial number
0x00100 SYSSKU= System SKU
0x00200 SYSFAMILY= System family
0x00400 MBVENDOR= Motherboard vendor name
0x00800 MBVERSION= Motherboard version
0x01000 MBSERIAL= Motherboard serial number
0x02000 MBASSET= Motherboard asset tag
0x04000 BIOSVENDOR= BIOS vendor name
0x08000 BIOSVERSION= BIOS version
0x10000 SYSFF= System form factor</code></pre>
</div></div>
<div class="paragraph"><p>If these strings contain white-space characters, they are replaced with
underscores (_).</p></div>
<div class="paragraph"><p>The system form factor value is a number defined in the SMBIOS
specification, available at <a href="http://www.dmtf.org/">http://www.dmtf.org/</a>. As of version 2.7.1
of the specification, the following values are defined:</p></div>
<div class="literalblock">
<div class="content">
<pre><code> 1 Other
2 Unknown
3 Desktop
4 Low profile desktop
5 Pizza box
6 Mini tower
7 Tower
8 Portble
9 Laptop
10 Notebook
11 Handheld
12 Docking station
13 All-in-one
14 Subnotebook
15 Space-saving
16 Lunch box
17 Main server chassis
18 Expansion chassis
19 Subchassis
20 Bus expansion chassis
21 Peripheral chassis
22 RAID chassis
23 Rack mount chasss
24 Sealed-case PC
25 Multi-system chassis
26 Compact PCI
27 Advanced TCI
28 Blade
29 Blade enclosure</code></pre>
</div></div>
</dd>
</dl></div>
</dd>
</dl></div>
</div>
</div>
<div class="sect1">
<h2 id="_kernel_like_directives">KERNEL-LIKE DIRECTIVES</h2>
<div class="sectionbody">
<div class="dlist"><dl>
<dt class="hdlist1">
<strong>KERNEL</strong> <em>image</em>
</dt>
<dd>
<p>
Load a kernel-like file <em>image</em> with automatic filetype detection based
on file extension, listed under the non-auto-detecting directives,
defaulting to <strong>LINUX</strong>.
</p>
</dd>
</dl></div>
<div class="paragraph"><p><strong>LINUX</strong> is used as an example]
<strong>LINUX</strong> <em>image</em>::
Load <em>image</em> as a Linux-like kernel. MEMDISK is an example of a
non-Linux kernel loaded in a Linux-like fashion.</p></div>
<div class="dlist"><dl>
<dt class="hdlist1">
<strong>BOOT</strong> <em>image</em>
</dt>
<dd>
<p>
(<strong>ISOLINUX</strong> only: .bin; <strong>SYSLINUX</strong> only: .bs) Load a boot sector. .bin
is a "CD boot sector" and .bs is a regular disk boot sector.
</p>
</dd>
<dt class="hdlist1">
<strong>BSS</strong> <em>image</em>
</dt>
<dd>
<p>
(<strong>SYSLINUX</strong> only: .bss) Load a BSS image, a .bs image with the DOS
superblock patched in.
</p>
</dd>
<dt class="hdlist1">
<strong>COMBOOT</strong> <em>image</em>
</dt>
<dd>
<p>
(.com, .cbt; Removed as of 5.00) Load a <strong>Syslinux</strong> COMBOOT image. .com
images may also be runnable from DOS while .cbt images are not. See
also <strong>comboot.txt</strong>
</p>
</dd>
<dt class="hdlist1">
<strong>COM32</strong> <em>image</em>
</dt>
<dd>
<p>
(.c32) Load a <strong>Syslinux</strong> COM32 (32-bit <strong>COMBOOT</strong>) image. See also
<strong>comboot.txt</strong>
</p>
</dd>
<dt class="hdlist1">
<strong>CONFIG</strong> <em>image</em>
</dt>
<dd>
<p>
Load a new configuration file. The configuration file is read, the
working directory is changed (if specified via an <strong>APPEND</strong>), then the
configuration file is parsed.
</p>
</dd>
<dt class="hdlist1">
<strong>FDIMAGE</strong> <em>image</em>
</dt>
<dd>
<p>
(Removed as of 4.05, added 1.65; <strong>ISOLINUX</strong> only: .img) Load a disk
image.
</p>
</dd>
<dt class="hdlist1">
<strong>LOCALBOOT</strong> <em>type</em>
</dt>
<dd>
<p>
(<strong>PXELINUX</strong> 1.53+; <strong>ISOLINUX</strong> ??3.10+; <strong>SYSLINUX</strong> 3.70+)Attempt a
different local boot method. The special value -1 causes the boot
loader to report failure to the BIOS, which, on recent BIOSes, should
mean that the next boot device in the boot sequence should be activated.
Values other than those documented may produce undesired results.
</p>
<div class="paragraph"><p>On <strong>PXELINUX</strong>, <em>type</em> 0 means perform a normal boot. <em>type</em> 4 will
perform a local boot with the Universal Network Driver Interface (UNDI)
driver still resident in memory. Finally, <em>type</em> 5 will perform a local
boot with the entire PXE stack, including the UNDI driver, still
resident in memory. All other values are undefined. If you don’t know
what the UNDI or PXE stacks are, don’t worry — you don’t want them,
just specify 0.</p></div>
<div class="paragraph"><p>On <strong>ISOLINUX</strong>/<strong>SYSLINUX</strong>, the <em>type</em> specifies the local drive number to
boot from; 0x00 is the primary floppy drive and 0x80 is the primary hard
drive.</p></div>
</dd>
<dt class="hdlist1">
<strong>PXE</strong> <em>image</em>
</dt>
<dd>
<p>
(<strong>PXELINUX</strong> only: .0) Load a PXE NBP (Network Boot Program) image. The
PXE protocol does not provide any means for specifiying or using a
command line or initrd.
</p>
</dd>
</dl></div>
</div>
</div>
<div class="sect1">
<h2 id="_label_only_directives">LABEL-ONLY DIRECTIVES</h2>
<div class="sectionbody">
<div class="dlist"><dl>
<dt class="hdlist1">
<strong>INITRD</strong> <em>initrd_file</em>
</dt>
<dd>
<p>
(3.71+) An initrd can be specified in a separate statement (INITRD)
instead of as part of the <strong>APPEND</strong> statement; this functionally appends
"initrd=initrd_file" to the kernel command line. Like <em>initrd=</em>, this
also supports multiple comma separated file names (see <strong>APPEND</strong>).
</p>
</dd>
</dl></div>
</div>
</div>
<div class="sect1">
<h2 id="_global_directives_secondary">GLOBAL DIRECTIVES - SECONDARY</h2>
<div class="sectionbody">
<div class="paragraph"><p>These are global directives that are of lesser importance, often
affecting the user experience and not the boot process.</p></div>
<div class="dlist"><dl>
<dt class="hdlist1">
<strong>ALLOWOPTIONS</strong> <em>flag_val</em>
</dt>
<dd>
<p>
If <em>flag_val</em> is 0, the user is not allowed to specify any arguments on
the kernel command line. The only options recognized are those
specified in an <strong>APPEND</strong>) statement. The default is 1.
</p>
</dd>
<dt class="hdlist1">
<strong>IMPLICIT</strong> <em>flag_val</em>
</dt>
<dd>
<p>
If <em>flag_val</em> is 0, do not load a kernel image unless it has been
explicitly named in a <strong>LABEL</strong> statement. The default is 1.
</p>
</dd>
<dt class="hdlist1">
<strong>TIMEOUT</strong> <em>timeout</em>
</dt>
<dd>
<p>
Indicates how long to wait at the <em>boot:</em> prompt until booting
automatically, in units of 1/10 s. The timeout is cancelled as soon as
the user types anything on the keyboard, the assumption being that the
user will complete the command line already begun. The timer is reset
to 0 upon return from an unsuccessful attempt to boot or from a module.
A timeout of zero (the default) will disable the timeout completely.
</p>
</dd>
<dt class="hdlist1">
<strong>TOTALTIMEOUT</strong> <em>timeout</em>
</dt>
<dd>
<p>
Indicates how long to wait until booting automatically, in units of
1/10 s. This timeout is <strong>not</strong> cancelled by user input, and can thus be
used to deal with serial port glitches or "the user walked away" type
situations. A timeout of zero (the default) will disable the timeout
completely.
</p>
<div class="paragraph"><p>Both <strong>TIMEOUT</strong> and <strong>TOTALTIMEOUT</strong> can be used together, for example:</p></div>
<div class="listingblock">
<div class="content">
<pre><code># Wait 5 seconds unless the user types something, but
# always boot after 15 minutes.
TIMEOUT 50
TOTALTIMEOUT 9000</code></pre>
</div></div>
</dd>
</dl></div>
<div class="dlist"><dl>
<dt class="hdlist1">
<strong>ONTIMEOUT</strong> <em>kernel options…</em>
</dt>
<dd>
<p>
Sets the command line invoked on a timeout (which often references a
LABEL). If not specified, <em>UI</em> (if used) or 'DEFAULT is used.
</p>
</dd>
<dt class="hdlist1">
<strong>ONERROR</strong> <em>kernel options…</em>
</dt>
<dd>
<p>
If a kernel image is not found (either due to it not existing, or
because <strong>IMPLICIT</strong> is set), run the specified command. The faulty
command line is appended to the specified options, so if the <strong>ONERROR</strong>
directive reads as:
</p>
<div class="listingblock">
<div class="content">
<pre><code>ONERROR xyzzy plugh</code></pre>
</div></div>
<div class="paragraph"><p>and the command line as entered by the user is:</p></div>
<div class="listingblock">
<div class="content">
<pre><code>foo bar baz</code></pre>
</div></div>
<div class="paragraph"><p><strong>Syslinux</strong> will execute the following as if entered by the user:</p></div>
<div class="listingblock">
<div class="content">
<pre><code>xyzzy plugh foo bar baz</code></pre>
</div></div>
</dd>
<dt class="hdlist1">
<strong>SERIAL</strong> <em>port [baudrate [flowcontrol]]</em>
</dt>
<dd>
<p>
Enables a serial port to act as the console. <em>port</em> is a number (0 =
/dev/ttyS0 = COM1, etc.) or an I/O port address (e.g. 0x3F8); if
<em>baudrate</em> is omitted, the baud rate defaults to 9600 bps. The serial
parameters are hardcoded to be 8 bits, no parity, 1 stop bit.
</p>
<div class="paragraph"><p><em>flowcontrol</em> is a combination of the following bits:</p></div>
<div class="literalblock">
<div class="content">
<pre><code>0x001 - Assert DTR
0x002 - Assert RTS
0x008 - Enable interrupts
0x010 - Wait for CTS assertion
0x020 - Wait for DSR assertion
0x040 - Wait for RI assertion
0x080 - Wait for DCD assertion
0x100 - Ignore input unless CTS asserted
0x200 - Ignore input unless DSR asserted
0x400 - Ignore input unless RI asserted
0x800 - Ignore input unless DCD asserted</code></pre>
</div></div>
<div class="paragraph"><p>All other bits are reserved.</p></div>
<div class="paragraph"><p>Typical values are:</p></div>
<div class="literalblock">
<div class="content">
<pre><code> 0 - No flow control (default)
0x303 - Null modem cable detect
0x013 - RTS/CTS flow control
0x813 - RTS/CTS flow control, modem input
0x023 - DTR/DSR flow control
0x083 - DTR/DCD flow control</code></pre>
</div></div>
<div class="paragraph"><p>For the <strong>SERIAL</strong> directive to be guaranteed to work properly, it should
be the first directive in the configuration file.</p></div>
<div class="admonitionblock">
<table><tr>
<td class="icon">
<div class="title">Note</div>
</td>
<td class="content"><em>port</em> values from 0 to 3 means the first four serial ports
detected by the BIOS. They may or may not correspond to the legacy port
values 0x3F8, 0x2F8, 0x3E8, 0x2E8.</td>
</tr></table>
</div>
<div class="paragraph"><p>Enabling interrupts (setting the 0x008 bit) may give better
responsiveness without setting the <strong>NOHALT</strong> option, but could
potentially cause problems with buggy BIOSes.</p></div>
<div class="paragraph"><p>This option is "sticky" and is not automatically reset when loading a
new configuration file with the CONFIG command.</p></div>
</dd>
<dt class="hdlist1">
<strong>NOHALT</strong> <em>flag_val</em>
</dt>
<dd>
<p>
If <em>flag_val</em> is 1, don’t halt the processor while idle. Halting the
processor while idle significantly reduces the power consumption, but
can cause poor responsiveness to the serial console, especially when
using scripts to drive the serial console, as opposed to human
interaction.
</p>
</dd>
<dt class="hdlist1">
<strong>CONSOLE</strong> <em>flag_val</em>
</dt>
<dd>
<p>
If <em>flag_val</em> is 0, disable output to the normal video console. If
<em>flag_val</em> is 1, enable output to the video console (this is the
default.)
</p>
<div class="paragraph"><p>Some BIOSes try to forward this to the serial console and sometimes make
a total mess thereof, so this option lets you disable the video console
on these systems.</p></div>
</dd>
<dt class="hdlist1">
<strong>FONT</strong> <em>filename</em>
</dt>
<dd>
<p>
Load a font in .psf format before displaying any output (except the
copyright line, which is output as ldlinux.sys itself is loaded.)
<strong>Syslinux</strong> only loads the font onto the video card; if the .psf file
contains a Unicode table it is ignored. This only works on EGA and VGA
cards; hopefully it should do nothing on others.
</p>
</dd>
<dt class="hdlist1">
<strong>KBDMAP</strong> <em>keymap</em>
</dt>
<dd>
<p>
Install a simple keyboard map. The keyboard remapper used is <strong>very</strong>
simplistic (it simply remaps the keycodes received from the BIOS, which
means that only the key combinations relevant in the default layout — usually U.S. English — can be mapped) but should at least help people
with AZERTY keyboard layout and the locations of = and , (two special
characters used heavily on the Linux kernel command line.)
</p>
<div class="paragraph"><p>The included program keytab-lilo.pl from the LILO distribution can be
used to create such keymaps. The file keytab-lilo.txt contains the
documentation for this program.</p></div>
</dd>
<dt class="hdlist1">
<strong>DISPLAY</strong> <em>filename</em>
</dt>
<dd>
<p>
Displays the indicated file on the screen at boot time (before the boot:
prompt, if displayed). Please see the section below on <strong>DISPLAY</strong> files.
</p>
<div class="admonitionblock">
<table><tr>
<td class="icon">
<div class="title">Note</div>
</td>
<td class="content">If the file is missing, this option is simply ignored.</td>
</tr></table>
</div>
</dd>
<dt class="hdlist1">
<strong>SAY</strong> <em>message</em>
</dt>
<dd>
<p>
Prints the message on the screen.
</p>
</dd>
<dt class="hdlist1">
<strong>PROMPT</strong> <em>flag_val</em>
</dt>
<dd>
<p>
If <em>flag_val</em> is 0, display the boot: prompt only if the Shift or Alt
key is pressed, or Caps Lock or Scroll lock is set (this is the
default). If <em>flag_val</em> is 1, always display the boot: prompt.
</p>
</dd>
<dt class="hdlist1">
<strong>NOESCAPE</strong> <em>flag_val</em>
</dt>
<dd>
<p>
If <em>flag_val</em> is set to 1, ignore the Shift/Alt/Caps Lock/Scroll Lock
escapes. Use this (together with PROMPT 0) to force the default boot
alternative.
</p>
</dd>
<dt class="hdlist1">
<strong>NOCOMPLETE</strong> <em>flag_val</em>
</dt>
<dd>
<p>
If <em>flag_val</em> is set to 1, the Tab key does not display labels at the
boot: prompt.
</p>
</dd>
</dl></div>
<div class="dlist"><dl>
<dt class="hdlist1">
<strong>F1</strong> <em>filename</em>
</dt>
<dt class="hdlist1">
<strong>F2</strong> <em>filename</em>
</dt>
<dt class="hdlist1">
<strong>F3</strong> <em>filename</em>
</dt>
<dt class="hdlist1">
<strong>F4</strong> <em>filename</em>
</dt>
<dt class="hdlist1">
<strong>F5</strong> <em>filename</em>
</dt>
<dt class="hdlist1">
<strong>F6</strong> <em>filename</em>
</dt>
<dt class="hdlist1">
<strong>F7</strong> <em>filename</em>
</dt>
<dt class="hdlist1">
<strong>F8</strong> <em>filename</em>
</dt>
<dt class="hdlist1">
<strong>F9</strong> <em>filename</em>
</dt>
<dt class="hdlist1">
<strong>F10</strong> <em>filename</em>
</dt>
<dt class="hdlist1">
<strong>F11</strong> <em>filename</em>
</dt>
<dt class="hdlist1">
<strong>F12</strong> <em>filename</em>
</dt>
<dd>
<p>
Displays the indicated file on the screen when a function key is pressed
at the boot: prompt. This can be used to implement pre-boot online help
(presumably for the kernel command line options.) Please see the
section below on DISPLAY files.
</p>
<div class="paragraph"><p>When using the serial console, press <Ctrl-F><digit> to get to the help
screens, e.g. <Ctrl-F><2> to get to the F2 screen. For F10-F12, hit
<Ctrl-F><A>, <Ctrl-F>B, <Ctrl-F>C. For compatibility with earlier
versions, F10 can also be entered as <Ctrl-F>0.</p></div>
</dd>
<dt class="hdlist1">
<strong>PATH</strong> <em>path</em>
</dt>
<dd>
<p>
(5.00+) Specify a space-separated (' <em>; 5.00-5.10 was a colon ':</em>) list
of directories to search when attempting to load modules. This directive
is useful for specifying the directories containing the lib*.c32 library
files as other modules may be dependent on these files, but may not
reside in the same directory. Multiple instances will append additional
paths.
</p>
</dd>
<dt class="hdlist1">
<strong>SENDCOOKIES</strong> <em>bitmask</em>
</dt>
<dd>
<p>
(<strong>PXELINUX</strong> 5.10+) When downloading files over http, the SYSAPPEND
strings are prepended with <em>Syslinux</em> and sent to the server as cookies.
The cookies are URL-encoded; whitespace is <strong>not</strong> replaced with
underscores.
</p>
<div class="paragraph"><p>This command limits the cookies send; 0 means no cookies. The default
is -1, meaning send all cookies.</p></div>
<div class="paragraph"><p>This option is "sticky" and is not automatically reset when loading a
new configuration file with the CONFIG command.</p></div>
</dd>
</dl></div>
</div>
</div>
<div class="sect1">
<h2 id="_display_file_format">DISPLAY FILE FORMAT</h2>
<div class="sectionbody">
<div class="paragraph"><p>DISPLAY and function-key help files are text files in either DOS or UNIX
format (with or without <CR>). In addition, the following special codes
are interpreted:</p></div>
<div class="paragraph"><p>identical to #3</p></div>
<div class="dlist"><dl>
<dt class="hdlist1">
<strong><FF></strong>
</dt>
<dd>
<p>
                                 = <Ctrl-L> = ASCII 12<br />
Clear the screen, home the cursor. Note that the screen is filled with
the current display color.
</p>
</dd>
<dt class="hdlist1">
<strong><FF></strong>
</dt>
<dd>
<p>
= <Ctrl-L> = ASCII 12; Clear the screen, home the cursor. Note that the
screen is filled with the current display color.
</p>
</dd>
<dt class="hdlist1">
<strong><FF></strong>
</dt>
<dd>
<p>
<FF> = <Ctrl-L> = ASCII 12
</p>
<div class="paragraph"><p>Clear the screen, home the cursor. Note that the screen is filled with
the current display color.</p></div>
</dd>
<dt class="hdlist1">
<strong><FF></strong>
</dt>
<dd>
<p>
<FF> = <Ctrl-L> = ASCII 12<br />
Clear the screen, home the cursor. Note that the screen is filled with
the current display color.
</p>
</dd>
<dt class="hdlist1">
<strong><SI></strong><em><bg><fg></em>
</dt>
<dd>
<p>
<SI> = <Ctrl-O> = ASCII 15
</p>
<div class="paragraph"><p>Set the display colors to the specified background and foreground
colors, where <bg> and <fg> are the 2 hex digits representing 1 byte,
corresponding to the standard PC display attributes:</p></div>
<div class="literalblock">
<div class="content">
<pre><code>0 = black 8 = dark grey
1 = dark blue 9 = bright blue
2 = dark green a = bright green
3 = dark cyan b = bright cyan
4 = dark red c = bright red
5 = dark purple d = bright purple
6 = brown e = yellow
7 = light grey f = white</code></pre>
</div></div>
<div class="paragraph"><p>Picking a bright color (8-f) for the background results in the
corresponding dark color (0-7), with the foreground flashing.</p></div>
<div class="paragraph"><p>Colors are not visible over the serial console.</p></div>
</dd>
<dt class="hdlist1">
<strong><CAN></strong><em>filename<newline></em>
</dt>
<dd>
<p>
<CAN> = <Ctrl-X> = ASCII 24
</p>
<div class="paragraph"><p>If a VGA display is present, enter graphics mode and display the graphic
included in the specified file. The file format is an ad hoc format
called LSS16; the included Perl program "ppmtolss16" can be used to
produce these images. This Perl program also includes the file format
specification.</p></div>
<div class="paragraph"><p>The image is displayed in 640x480 16-color mode. Once in graphics mode,
the display attributes (set by <SI> code sequences) work slightly
differently: the background color is ignored, and the foreground colors
are the 16 colors specified in the image file. For that reason,
ppmtolss16 allows you to specify that certain colors should be assigned
to specific color indicies.</p></div>
<div class="paragraph"><p>Color indicies 0 and 7, in particular, should be chosen with care: 0 is
the background color, and 7 is the color used for the text printed by
<strong>Syslinux</strong> itself.</p></div>
</dd>
<dt class="hdlist1">
<strong><EM></strong>
</dt>
<dd>
<p>
<EM> = <Ctrl-Y> = ASCII 25<br />
If we are currently in graphics mode, return to text mode.
</p>
</dd>
<dt class="hdlist1">
<strong><DLE></strong>..<strong><ETB></strong>
</dt>
<dd>
<p>
<Ctrl-P>..<Ctrl-W> = ASCII 16-23
</p>
<div class="paragraph"><p>These codes can be used to select which modes to print a certain part of
the message file in. Each of these control characters select a specific
set of modes (text screen, graphics screen, serial port) for which the
output is actually displayed:</p></div>
<div class="literalblock">
<div class="content">
<pre><code>Character Text Graph Serial
------------------------------------------------------
<DLE> = <Ctrl-P> = ASCII 16 No No No
<DC1> = <Ctrl-Q> = ASCII 17 Yes No No
<DC2> = <Ctrl-R> = ASCII 18 No Yes No
<DC3> = <Ctrl-S> = ASCII 19 Yes Yes No
<DC4> = <Ctrl-T> = ASCII 20 No No Yes
<NAK> = <Ctrl-U> = ASCII 21 Yes No Yes
<SYN> = <Ctrl-V> = ASCII 22 No Yes Yes
<ETB> = <Ctrl-W> = ASCII 23 Yes Yes Yes</code></pre>
</div></div>
<div class="paragraph"><p>For example, the following will actually print out which mode the
console is in:</p></div>
<div class="literalblock">
<div class="content">
<pre><code><DC1>Text mode<DC2>Graphics mode<DC4>Serial port<ETB></code></pre>
</div></div>
</dd>
<dt class="hdlist1">
<strong><SUB></strong>
</dt>
<dd>
<p>
<SUB> = <Ctrl-Z> = ASCII 26
</p>
<div class="paragraph"><p>End of file (DOS convention).</p></div>
</dd>
<dt class="hdlist1">
<strong><BEL></strong>
</dt>
<dd>
<p>
<BEL> = <Ctrl-G> = ASCII 7<br />
Beep the speaker.
</p>
</dd>
</dl></div>
</div>
</div>
<div class="sect1">
<h2 id="_boot_loader_ids_used">BOOT LOADER IDS USED</h2>
<div class="sectionbody">
<div class="paragraph"><p>The Linux boot protocol supports a "boot loader ID", a single byte where
the upper nybble specifies a boot loader family (3 = <strong>Syslinux</strong>) and the
lower nybble is version or, in the case of <strong>Syslinux</strong>, media:</p></div>
<div class="literalblock">
<div class="content">
<pre><code>0x31 (49) = SYSLINUX
0x32 (50) = PXELINUX
0x33 (51) = ISOLINUX
0x34 (52) = EXTLINUX</code></pre>
</div></div>
<div class="paragraph"><p>In recent versions of Linux, this ID is available as
/proc/sys/kernel/bootloader_type.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_novice_protection">NOVICE PROTECTION</h2>
<div class="sectionbody">
<div class="paragraph"><p><strong>Syslinux</strong> will attempt to detect booting on a machine with too little
memory, which means the Linux boot sequence cannot complete. If so, a
message is displayed and the boot sequence aborted. Holding down the
Ctrl key while booting disables this feature.</p></div>
<div class="paragraph"><p>Any file that <strong>Syslinux</strong> uses can be marked hidden, system or readonly
if so is convenient; <strong>Syslinux</strong> ignores all file attributes. The
<strong>SYSLINUX</strong> installer automatically sets the readonly/hidden/system
attributes on LDLINUX.SYS.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_example">EXAMPLE</h2>
<div class="sectionbody">
<div class="paragraph"><p>Here are some sample config files:</p></div>
<div class="listingblock">
<div class="content">
<pre><code># SERIAL 0 115200
DEFAULT linux
PROMPT 1
TIMEOUT 600
LABEL linux
LINUX vmlinuz
APPEND initrd=initrd1.gz,initrd2.gz
LABEL m
COM32 menu.c32</code></pre>
</div></div>
<div class="paragraph"><p>In this example, serial port use is disabled but can be enabled by
uncommenting the first line and utilize serial port 0 at 115200 bps. If
<em>linux</em> is typed on the command line, the kernel-like file <em>vmlinuz</em> is
executed as a Linux kernel, initrd files initrd1.gz and initrd2.gz are
loaded as initial ramdisk files (like cpio.gz files for initramfs). If
<em>m</em> is typed on the command line, the COM32 module <em>menu.c32</em> is
executed to launch a menu system.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_known_bugs">KNOWN BUGS</h2>
<div class="sectionbody">
<div class="paragraph"><p>Several known bugs/common problems are listed at
<a href="http://www.syslinux.org/wiki/index.php/Common_Problems">http://www.syslinux.org/wiki/index.php/Common_Problems</a> and known
hardware compatibility issues are listed at
<a href="http://www.syslinux.org/wiki/index.php/Hardware_Compatibility">http://www.syslinux.org/wiki/index.php/Hardware_Compatibility</a> with
filename translation difficulty and early PXE stacks being some of the
most common. Reporting of other encountered issues is welcome and
appreciated.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_bug_reports">BUG REPORTS</h2>
<div class="sectionbody">
<div class="paragraph"><p>I would appreciate hearing of any problems you have with Syslinux. I
would also like to hear from you if you have successfully used Syslinux,
<strong>especially</strong> if you are using it for a distribution.</p></div>
<div class="paragraph"><p>If you are reporting problems, please include all possible information
about your system and your BIOS; the vast majority of all problems
reported turn out to be BIOS or hardware bugs, and I need as much
information as possible in order to diagnose the problems.</p></div>
<div class="paragraph"><p>There is a mailing list for discussion among Syslinux users and for
announcements of new and test versions. To join, or to browse the
archive, go to:</p></div>
<div class="paragraph"><p><a href="http://www.zytor.com/mailman/listinfo/syslinux">http://www.zytor.com/mailman/listinfo/syslinux</a></p></div>
<div class="paragraph"><p>Please DO NOT send HTML messages or attachments to the mailing list
(including multipart/alternative or similar.) All such messages will be
bounced.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_author">AUTHOR</h2>
<div class="sectionbody">
<div class="paragraph"><p>This AsciiDoc derived document is a modified version of the original
<strong>SYSLINUX</strong> documentation by H. Peter Anvin <<a href="mailto:hpa@zytor.com">hpa@zytor.com</a>>. The conversion
to an AsciiDoc was made by Gene Cumm <<a href="mailto:gene.cumm@gmail.com">gene.cumm@gmail.com</a>></p></div>
</div>
</div>
</div>
<div id="footnotes"><hr /></div>
<div id="footer">
<div id="footer-text">
Last updated 2014-01-17 16:09:56 PST
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