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1 | .\" Copyright 1992, 1993 Rickard E. Faith (faith@cs.unc.edu) |
2 | .\" May be distributed under the GNU General Public License | |
3 | .\" Changes from sct@dcs.ed.ac.uk added Sat Oct 9 09:54:00 1993. | |
4 | .TH RDEV 8 "20 November 1993" "Linux 0.99" "Linux Programmer's Manual" | |
5 | .SH NAME | |
6 | rdev \- query/set image root device, swap device, RAM disk size, or video mode | |
7 | .SH SYNOPSIS | |
8 | .nf | |
9 | .BR "rdev [ \-rsvh ] [ \-o " offset " ] [ " image " [ " value " [ " offset " ] ] ]" | |
10 | .BR "rdev [ \-o " offset " ] [ " image " [ " root_device " [ " offset " ] ] ]" | |
11 | .BR "swapdev [ \-o " offset " ] [ " image " [ " swap_device " [ " offset " ] ] ]" | |
12 | .BR "ramsize [ \-o " offset " ] [ " image " [ " size " [ " offset " ] ] ]" | |
13 | .BR "vidmode [ \-o " offset " ] [ " image " [ " mode " [ " offset " ] ] ]" | |
14 | .BR "rootflags [ \-o " offset " ] [ " image " [ " flags " [ " offset " ] ] ]" | |
15 | .fi | |
16 | .SH DESCRIPTION | |
17 | .\" " for emacs hilit19 | |
18 | With no arguments, | |
19 | .B rdev | |
20 | outputs an | |
21 | .I /etc/mtab | |
22 | line for the current root file system. | |
23 | With no arguments, | |
24 | .BR swapdev ", " ramsize ", " vidmode ", and " rootflags | |
25 | print usage information. | |
26 | ||
27 | In a bootable image for the Linux kernel, there are several pairs of bytes | |
28 | which specify the root device, the video mode, the size of the RAM disk, | |
29 | and the swap device. These pairs of bytes, by default, begin at offset 504 | |
30 | (decimal) in the kernel image: | |
31 | ||
32 | .nf | |
33 | .RS | |
34 | 498 Root flags | |
35 | (500 and 502 Reserved) | |
36 | 504 RAM Disk Size | |
37 | 506 VGA Mode | |
38 | 508 Root Device | |
39 | (510 Boot Signature) | |
40 | .RE | |
41 | .fi | |
42 | ||
43 | .B rdev | |
44 | will change these values. | |
45 | ||
46 | Typical values for the | |
47 | .I image | |
66ee8158 | 48 | parameter, which is a bootable Linux kernel image, might be: |
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49 | |
50 | .nf | |
51 | .RS | |
52 | /vmlinux | |
6dbe3af9 | 53 | /vmunix |
66ee8158 | 54 | /boot/bzImage-2.4.0 |
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55 | /dev/fd0 |
56 | /dev/fd1 | |
57 | .RE | |
58 | .fi | |
59 | ||
60 | When using the | |
61 | .BR rdev ", or " swapdev | |
62 | commands, the | |
63 | .IR root_device " or " swap_device | |
66ee8158 | 64 | parameter might be something like: |
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65 | |
66 | .nf | |
67 | .RS | |
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68 | /dev/hda1 |
69 | /dev/hdf13 | |
70 | /dev/sda2 | |
71 | /dev/sdc4 | |
72 | /dev/ida/c0d0p1 | |
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73 | .RE |
74 | .fi | |
75 | ||
76 | For the | |
77 | .B ramsize | |
78 | command, the | |
79 | .B size | |
80 | parameter specifies the size of the RAM disk in kilobytes. | |
81 | ||
82 | For the | |
83 | .B rootflags | |
84 | command, the | |
85 | .B flags | |
86 | parameter contains extra information used when mounting root. | |
87 | Currently the only effect of these flags is to force the kernel to | |
88 | mount the root filesystem in readonly mode if | |
89 | .B flags | |
90 | is non-zero. | |
91 | ||
92 | For the | |
93 | .B vidmode | |
94 | command, the | |
95 | .B mode | |
96 | parameter specifies the video mode: | |
97 | ||
98 | .nf | |
99 | .RS | |
100 | -3 = Prompt | |
101 | -2 = Extended VGA | |
102 | -1 = Normal VGA | |
103 | 0 = as if "0" was pressed at the prompt | |
104 | 1 = as if "1" was pressed at the prompt | |
105 | 2 = as if "2" was pressed at the prompt | |
106 | n = as if "n" was pressed at the prompt | |
107 | .RE | |
108 | .fi | |
109 | ||
110 | If the | |
111 | .I value | |
112 | is not specified, the | |
113 | .I image | |
114 | will be examined to determine the current settings. | |
115 | .SH OPTIONS | |
116 | .TP | |
117 | .B \-s | |
118 | Causes | |
119 | .B rdev | |
120 | to act like | |
121 | .BR swapdev . | |
122 | .TP | |
123 | .B \-r | |
124 | Causes | |
125 | .B rdev | |
126 | to act like | |
127 | .BR ramsize . | |
128 | .TP | |
129 | .B \-R | |
130 | Causes | |
131 | .B rdev | |
132 | to act like | |
133 | .BR rootflags . | |
134 | .TP | |
135 | .B \-v | |
136 | Causes | |
137 | .B rdev | |
138 | to act like | |
139 | .BR vidmode . | |
140 | .TP | |
141 | .B \-h | |
142 | Provides help. | |
143 | .SH BUGS | |
144 | For historical reasons, there are two methods for specifying alternative | |
145 | values for the offset. | |
146 | .sp | |
147 | The user interface is cumbersome, non-intuitive, and should probably be | |
148 | re-written from scratch, allowing multiple kernel image parameters to be | |
149 | changed or examined with a single command. | |
150 | .sp | |
151 | If LILO is used, | |
152 | .B rdev | |
153 | is no longer needed for setting the root device and the VGA mode, since | |
154 | these parameters that | |
155 | .B rdev | |
156 | modifies can be set from the LILO prompt during a boot. However, | |
157 | .B rdev | |
158 | is still needed at this time for setting the RAM disk size. Users are | |
159 | encouraged to find the LILO documentation for more information, and to use | |
160 | LILO when booting their systems. | |
161 | .SH AUTHORS | |
162 | .nf | |
163 | Originally by Werner Almesberger (almesber@nessie.cs.id.ethz.ch) | |
164 | Modified by Peter MacDonald (pmacdona@sanjuan.UVic.CA) | |
165 | rootflags support added by Stephen Tweedie (sct@dcs.ed.ac.uk) | |
166 | .fi |