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Part VII:

Miscellaneous

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intro

intro—Introduction to miscellany section.

DESCRIPTION

This chapter describes miscellaneous things such as nroff macro packages, tables, C header files, the file hierarchy, general concepts, and other things that don't fit anywhere else.

AUTHORS

Look at the header of the manual page for the authors and copyright conditions. Note that these can be different from page to page!

Linux, 23 April 1993

ascii

ascii—The ASCII character set encoded in octal, decimal, and hexadecimal

DESCRIPTION

The following table contains the 128 ASCII characters.

C program `\X' escapes are noted.

Oct Dec Hex Char Oct Dec Hex Char
000 0 00 NUL `\0' 100 64 40 @
001 1 01 SOH 101 65 41 A
002 2 02 STX 102 66 42 B
003 3 03 ETX 103 67 43 C
004 4 04 EOT 104 68 44 D
005 5 05 ENQ 105 69 45 E
006 6 06 ACK 106 70 46 F
007 7 07 BEL `\a' 107 71 47 G
010 8 08 BS `\b' 110 72 48 H
011 9 09 HT `\t' 111 73 49 I
012 10 0A LF `\n' 112 74 4A J
013 11 0B VT `\v' 113 75 4B K
014 12 0C FF `\f' 114 76 4C L
015 13 0D CR `\r' 115 77 4D M
016 14 0E SO 116 78 4E N
017 15 0F SI 117 79 4F O
020 16 10 DLE 120 80 50 P
021 17 11 DC1 121 81 51 Q
022 18 12 DC2 122 82 52 R
023 19 13 DC3 123 83 53 S
024 20 14 DC4 124 84 54 T
025 21 15 NAK 125 85 55 U
026 22 16 SYN 126 86 56 V

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Oct Dec Hex Char Oct Dec Hex Char
027 23 17 ETB 127 87 57 W
030 24 18 CAN 130 88 58 X
031 25 19 EM 131 89 59 Y
032 26 1A SUB 132 90 5A Z
033 27 1B ESC 133 91 5B [
034 28 1C FS 134 92 5C \'\\'
035 29 1D GS 135 93 5D ]
036 30 1E RS 136 94 5E ^
037 31 1F US 137 95 5F _
040 32 20 SPACE 140 96 60 `
041 33 21 ! 141 97 61 a
042 34 22 " 142 98 62 b
043 35 23 # 143 99 63 c
044 36 24 $ 144 100 64 d
045 37 25 % 145 101 65 e
046 38 26 & 146 102 66 f
047 39 27 ` 147 103 67 g
050 40 28 ( 150 104 68 h
051 41 29 ) 151 105 69 i
052 42 2A * 152 106 6A j
053 43 2B + 153 107 6B k
054 44 2C , 154 108 6C l
055 45 2D _ 155 109 6D m
056 46 2E . 156 110 6E n
057 47 2F / 157 111 6F o
060 48 30 0 160 112 70 p
061 49 31 1 161 113 71 q
062 50 32 2 162 114 72 r
063 51 33 3 163 115 73 s
064 52 34 4 164 116 74 t
065 53 35 5 165 117 75 u
066 54 36 6 166 118 76 v
067 55 37 7 167 119 77 w
070 56 38 8 170 120 78 x
071 57 39 9 171 121 79 y
072 58 3A : 172 122 7A z
073 59 3B ; 173 123 7B {
074 60 3C < 174 124 7C |
075 61 3D = 175 125 7D }
076 62 3E > 176 126 7E ~
077 63 3F ? 177 127 7F DEL

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HISTORY

An ascii manual page appeared in version 7 AT&T UNIX.

SEE ALSO 

iso_8859_1(7)

Linux

bootparam

bootparam—Introduction to boot-time parameters of the Linux kernel.

DESCRIPTION

The Linux kernel accepts certain command-line options or boot-time parameters at the moment it is started. In general, this is used to supply the kernel with information about hardware parameters that the kernel would not be able to determine on its own, or to avoid or override the values that the kernel would otherwise detect.

When the kernel is booted directly by the BIOS (say, from a floppy to which you copied a kernel using cp zImage /dev/fd0), you have no opportunity to specify any parameters. To take advantage of this possibility, you have to use software that is able to pass parameters, such as LILO or loadlin. For a few parameters, one can also modify the kernel image itself, using rdev; see rdev(8) for further details.

The LILO program (LInux LOader) written by Werner Almesberger is the most commonly used. It has the ability to boot various kernels and stores the configuration information in a plain text file. (See lilo(8) and lilo.conf(5).) LILO can boot DOS, OS/2, Linux, FreeBSD, and so on and is quite flexible.

The other commonly used Linux loader is loadlin, which is a DOS program that has the capability to launch a Linux kernel from the DOS prompt (with boot args) assuming that certain resources are available. This is good for people who want to launch Linux from DOS.

It is also very useful if you have certain hardware that relies on the supplied DOS driver to put the hardware into a known state. A common example is SoundBlaster-compatible sound cards that require the DOS driver to twiddle a few mystical registers to put the card into a SB-compatible mode. Booting DOS with the supplied driver and then loading Linux from the DOS prompt with loadlin avoids the reset of the card that happens if one reboots instead.

THE ARGUMENT LIST

Most of the boot args take the form of 

name[=value_1][,value_2]...[,value_11]

name is a unique keyword that is used to identify what part of the kernel the associated values (if any) are to be given to. Multiple boot args are just a space-separated list of the preceding format. Note the limit of 11 is real because the present code handles only 11 comma-separated parameters per keyword. (However, you can reuse the same keyword with up to an additional 11 parameters in unusually complicated situations, assuming the setup function supports it.)

Most of the sorting occurs in linux/init/main.c. First, the kernel checks to see if the argument is any of the special arguments root=, ro, rw, or debug. The meaning of these special arguments is described later in the document.

Then, it walks a list of setup functions (contained in the bootsetups array) to see if the specified argument string (such as foo) is associated with a setup function (foo_setup()) for a particular device or part of the kernel. If you passed the kernel the line foo=3,4,5,6, then the kernel searches the bootsetups array to see if foo is registered. If it is, it calls the setup function associated with foo (foo_setup()) and hands it the arguments 3, 4, 5, and 6 as given on the kernel command line.

Anything of the form foo=bar that is not accepted as a setup function as described is then interpreted as an environment variable to be set. A (useless?) example is to use TERM=vt100 as a boot argument.

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