1
<!-- retain these comments for translator revision tracking -->
2
<!-- $Id: parameters.xml 30084 2005-08-20 19:18:11Z fjp $ -->
4
<sect1 id="boot-parms"><title>Boot Parameters</title>
7
Boot parameters are Linux kernel parameters which are generally used
8
to make sure that peripherals are dealt with properly. For the most
9
part, the kernel can auto-detect information about your peripherals.
10
However, in some cases you'll have to help the kernel a bit.
14
If this is the first time you're booting the system, try the default
15
boot parameters (i.e., don't try setting parameters) and see if it works
16
correctly. It probably will. If not, you can reboot later and look for
17
any special parameters that inform the system about your hardware.
21
Information on many boot parameters can be found in the
22
<ulink url="http://www.tldp.org/HOWTO/BootPrompt-HOWTO.html"> Linux
23
BootPrompt HOWTO</ulink>, including tips for obscure hardware. This
24
section contains only a sketch of the most salient parameters. Some
25
common gotchas are included below in
26
<xref linkend="boot-troubleshooting"/>.
30
When the kernel boots, a message
32
<informalexample><screen>
33
Memory:<replaceable>avail</replaceable>k/<replaceable>total</replaceable>k available
34
</screen></informalexample>
36
should be emitted early in the process.
37
<replaceable>total</replaceable> should match the total amount of RAM,
38
in kilobytes. If this doesn't match the actual amount of RAM you have
39
installed, you need to use the
40
<userinput>mem=<replaceable>ram</replaceable></userinput> parameter,
41
where <replaceable>ram</replaceable> is set to the amount of memory,
42
suffixed with <quote>k</quote> for kilobytes, or <quote>m</quote> for
43
megabytes. For example, both <userinput>mem=65536k</userinput> and
44
<userinput>mem=64m</userinput> mean 64MB of RAM.
46
</para><para condition="supports-serial-console">
48
If you are booting with a serial console, generally the kernel will
50
this<phrase arch="mipsel"> (although not on DECstations)</phrase>.
51
If you have a videocard (framebuffer) and a keyboard also attached to
52
the computer which you wish to boot via serial console, you may have
54
<userinput>console=<replaceable>device</replaceable></userinput>
55
argument to the kernel, where <replaceable>device</replaceable> is
56
your serial device, which is usually something like
57
<filename>ttyS0</filename>.
59
</para><para arch="sparc">
61
For &arch-title; the serial devices are <filename>ttya</filename> or
62
<filename>ttyb</filename>.
63
Alternatively, set the <envar>input-device</envar> and
64
<envar>output-device</envar> OpenPROM variables to
65
<filename>ttya</filename>.
70
<sect2 id="installer-args"><title>Debian Installer Parameters</title>
73
The installation system recognizes a few additional boot parameters<footnote>
77
Note that the kernel accepts a maximum of 8 command line options and
78
8 environment options (including any options added by default for the
79
installer). If these numbers are exceeded, 2.4 kernels will drop any
80
excess options and 2.6 kernels will panic.
81
<phrase condition="etch">With kernel 2.6.9 or newer, you can use 32
82
command line options and 32 environment options.</phrase>
86
</footnote> which may be useful.
92
<term>debconf/priority</term>
95
This parameter sets the lowest priority of messages to be displayed.
99
The default installation uses <userinput>debconf/priority=high</userinput>.
100
This means that both high and critical priority messages are shown, but medium
101
and low priority messages are skipped.
102
If problems are encountered, the installer adjusts the priority as needed.
106
If you add <userinput>debconf/priority=medium</userinput> as boot parameter, you
107
will be shown the installation menu and gain more control over the installation.
108
When <userinput>debconf/priority=low</userinput> is used, all messages are shown
109
(this is equivalent to the <emphasis>expert</emphasis> boot method).
110
With <userinput>debconf/priority=critical</userinput>, the installation system
111
will display only critical messages and try to do the right thing without fuss.
118
<term>DEBIAN_FRONTEND</term>
121
This boot parameter controls the type of user interface used for the
122
installer. The current possible parameter settings are:
126
<para><userinput>DEBIAN_FRONTEND=noninteractive</userinput></para>
127
</listitem><listitem>
128
<para><userinput>DEBIAN_FRONTEND=text</userinput></para>
129
</listitem><listitem>
130
<para><userinput>DEBIAN_FRONTEND=newt</userinput></para>
131
</listitem><listitem>
132
<para><userinput>DEBIAN_FRONTEND=slang</userinput></para>
133
</listitem><listitem>
134
<para><userinput>DEBIAN_FRONTEND=ncurses</userinput></para>
135
</listitem><listitem>
136
<para><userinput>DEBIAN_FRONTEND=bogl</userinput></para>
137
</listitem><listitem>
138
<para><userinput>DEBIAN_FRONTEND=gtk</userinput></para>
139
</listitem><listitem>
140
<para><userinput>DEBIAN_FRONTEND=corba</userinput></para>
144
The default front end is <userinput>DEBIAN_FRONTEND=newt</userinput>.
145
<userinput>DEBIAN_FRONTEND=text</userinput> may be preferable for
146
serial console installs. Generally only the
147
<userinput>newt</userinput> frontend is available on default install
148
media, so this is not very useful right now.
155
<term>BOOT_DEBUG</term>
158
Setting this boot parameter to 2 will cause the installer's boot process
159
to be verbosely logged. Setting it to 3 makes debug shells
160
available at strategic points in the boot process. (Exit the shells to
161
continue the boot process.)
165
<term><userinput>BOOT_DEBUG=0</userinput></term>
166
<listitem><para>This is the default.</para></listitem>
170
<term><userinput>BOOT_DEBUG=1</userinput></term>
171
<listitem><para>More verbose than usual.</para></listitem>
175
<term><userinput>BOOT_DEBUG=2</userinput></term>
176
<listitem><para>Lots of debugging information.</para></listitem>
180
<term><userinput>BOOT_DEBUG=3</userinput></term>
183
Shells are run at various points in the boot process to allow detailed
184
debugging. Exit the shell to continue the boot.
195
<term>INSTALL_MEDIA_DEV</term>
198
The value of the parameter is the path to the device to load the
199
Debian installer from. For example,
200
<userinput>INSTALL_MEDIA_DEV=/dev/floppy/0</userinput>
204
The boot floppy, which normally scans all floppies and USB storage
205
devices it can to find the root floppy, can be overridden by this
206
parameter to only look at the one device.
212
<term>debian-installer/framebuffer</term>
215
Some architectures use the kernel framebuffer to offer installation in
216
a number of languages. If framebuffer causes a problem on your system
217
you can disable the feature by the parameter
218
<userinput>debian-installer/framebuffer=false</userinput>. Problem
219
symptoms are error messages about bterm or bogl, a blank screen, or
220
a freeze within a few minutes after starting the install.
222
</para><para arch="i386">
224
The <userinput>video=vga16:off</userinput> argument may also be used
225
to disable the framebuffer. Such problems have been reported on a Dell
226
Inspiron with Mobile Radeon card.
228
</para><para arch="m68k">
230
Such problems have been reported on the Amiga 1200 and SE/30.
232
</para><para arch="hppa">
234
Such problems have been reported on hppa.
236
</para><note arch="sparc"><para>
238
Because of display problems on some systems, framebuffer support is
239
<emphasis>disabled by default</emphasis> for &arch-title;. This can result
240
in ugly display on systems that do properly support the framebuffer, like
241
those with ATI graphical cards.
242
If you see display problems in the installer, you can try booting with
243
parameter <userinput>debian-installer/framebuffer=true</userinput>.
245
</para></note></listitem>
249
<term>debian-installer/probe/usb</term>
252
Set to <userinput>false</userinput> to prevent probing for USB on
253
boot, if that causes problems.
259
<term>netcfg/disable_dhcp</term>
262
By default, the &d-i; automatically probes for network configuration
263
via DHCP. If the probe succeeds, you won't have a chance to review and
264
change the obtained settings. You can get to the manual network setup
265
only in case the DHCP probe fails.
269
If you have a DHCP server on your local network, but want to avoid it
270
because e.g. it gives wrong answers, you can use the parameter
271
<userinput>netcfg/disable_dhcp=true</userinput> to prevent configuring
272
the network with DHCP and to enter the information manually.
278
<term>hw-detect/start_pcmcia</term>
281
Set to <userinput>false</userinput> to prevent starting PCMCIA
282
services, if that causes problems. Some laptops are well known for
289
<term>preseed/url</term>
292
Specify the url to a preconfiguration file to download and use in
293
automating the install. See <xref linkend="automatic-install"/>.
299
<term>preseed/file</term>
302
Specify the path to a preconfiguration file to load to
303
automating the install. See <xref linkend="automatic-install"/>.
308
<varlistentry condition="etch">
309
<term>cdrom-detect/eject</term>
312
By default, before rebooting, &d-i; automatically ejects the optical
313
media used during the installation. This can be unnecessary if the system
314
does not automatically boot off the CD. In some cases it may even be
315
undesirable, for example if the optical drive cannot reinsert the media
316
itself and the user is not there to do it manually. Many slot loading,
317
slim-line, and caddy style drives cannot reload media automatically.
321
Set to <userinput>false</userinput> to disable automatic ejection, and
322
be aware that you may need to ensure that the system does not
323
automatically boot from the optical drive after the initial
330
<term>ramdisk_size</term>
333
If you are using a 2.2.x kernel, you may need to set &ramdisksize;.
338
<varlistentry condition="etch">
339
<term>rescue/enable</term>
342
Set to <userinput>true</userinput> to enter rescue mode rather than
343
performing a normal installation. See <xref linkend="rescue"/>.