source: MondoRescue/branches/stable/mindi-busybox/examples/bootfloppy/bootfloppy.txt @ 821

Last change on this file since 821 was 821, checked in by Bruno Cornec, 14 years ago

Addition of busybox 1.2.1 as a mindi-busybox new package
This should avoid delivering binary files in mindi not built there (Fedora and Debian are quite serious about that)

File size: 4.5 KB
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1Building a Busybox Boot Floppy
2==============================
3
4This document describes how to buid a boot floppy using the following
5components:
6
7 - Linux Kernel (http://www.kernel.org)
8 - uClibc: C library (http://www.uclibc.org/)
9 - Busybox: Unix utilities (http://busybox.net/)
10 - Syslinux: bootloader (http://syslinux.zytor.com)
11
12It is based heavily on a paper presented by Erik Andersen at the 2001 Embedded
13Systems Conference.
14
15
16
17Building The Software Components
18--------------------------------
19
20Detailed instructions on how to build Busybox, uClibc, or a working Linux
21kernel are beyond the scope of this document. The following guidelines will
22help though:
23
24    - Stock Busybox from CVS or a tarball will work with no modifications to
25      any files. Just extract and go.
26    - Ditto uClibc.
27    - Your Linux kernel must include support for initrd or else the floppy
28      won't be able to mount it's root file system.
29
30If you require further information on building Busybox uClibc or Linux, please
31refer to the web pages and documentation for those individual programs.
32
33
34
35Making a Root File System
36-------------------------
37
38The following steps will create a root file system.
39
40 - Create an empty file that you can format as a filesystem:
41
42    dd if=/dev/zero of=rootfs bs=1k count=4000
43
44 - Set up the rootfs file we just created to be used as a loop device (may not
45   be necessary)
46
47    losetup /dev/loop0 rootfs
48
49 - Format the rootfs file with a filesystem:
50
51    mkfs.ext2 -F -i 2000 rootfs
52
53 - Mount the file on a mountpoint so we can place files in it:
54
55    mkdir loop
56    mount -o loop rootfs loop/
57
58    (you will probably need to be root to do this)
59
60 - Copy on the C library, the dynamic linking library, and other necessary
61   libraries. For this example, we copy the following files from the uClibc
62   tree:
63
64    mkdir loop/lib
65    (chdir to uClibc directory)
66    cp -a libc.so* uClibc*.so \
67        ld.so-1/d-link/ld-linux-uclibc.so* \
68        ld.so-1/libdl/libdl.so* \
69        crypt/libcrypt.so* \
70        (path to)loop/lib
71
72 - Install the Busybox binary and accompanying symlinks:
73
74    (chdir to busybox directory)
75    make PREFIX=(path to)loop/ install
76
77 - Make device files in /dev:
78
79    This can be done by running the 'mkdevs.sh' script. If you want the gory
80    details, you can read the script.
81
82 - Make necessary files in /etc:
83
84    For this, just cp -a the etc/ directory onto rootfs. Again, if you want
85    all the details, you can just look at the files in the dir.
86
87 - Unmount the rootfs from the mountpoint:
88
89    umount loop
90
91 - Compress it:
92
93    gzip -9 rootfs
94
95
96Making a SYSLINUX boot floppy
97-----------------------------
98
99The following steps will create the boot floppy.
100
101Note: You will need to have the mtools package installed beforehand.
102
103 - Insert a floppy in the drive and format it with an MSDOS filesystem:
104
105    mformat a:
106
107    (if the system doesn't know what device 'a:' is, look at /etc/mtools.conf)
108
109 - Run syslinux on the floppy:
110
111    syslinux -s /dev/fd0
112
113    (the -s stands for "safe, slow, and stupid" and should work better with
114    buggy BIOSes; it can be omitted)
115
116 - Put on a syslinux.cfg file:
117
118    mcopy syslinux.cfg a:
119
120    (more on syslinux.cfg below)
121
122 - Copy the root file system you made onto the MSDOS formatted floppy
123
124    mcopy rootfs.gz a:
125
126 - Build a linux kernel and copy it onto the disk with the filename 'linux'
127
128    mcopy bzImage a:linux
129
130
131Sample syslinux.cfg
132~~~~~~~~~~~~~~~~~~~
133
134The following simple syslinux.cfg file should work. You can tweak it if you
135like.
136
137----begin-syslinux.cfg---------------
138DEFAULT linux
139APPEND initrd=rootfs.gz root=/dev/ram0
140TIMEOUT 10
141PROMPT 1
142----end-syslinux.cfg---------------
143
144Some changes you could make to syslinux.cfg:
145
146 - This value is the number seconds it will wait before booting. You can set
147   the timeout to 0 (or omit) to boot instantly, or you can set it as high as
148   10 to wait awhile.
149
150 - PROMPT can be set to 0 to disable the 'boot:' prompt.
151
152 - you can add this line to display the contents of a file as a welcome
153   message:
154
155    DISPLAY display.txt
156
157
158
159Additional Resources
160--------------------
161
162Other useful information on making a Linux bootfloppy is available at the
163following URLs:
164
165http://www.linuxdoc.org/HOWTO/Bootdisk-HOWTO/index.html
166http://www.linux-embedded.com/howto/Embedded-Linux-Howto.html
167http://linux-embedded.org/howto/LFS-HOWTO.html
168http://linux-embedded.org/pmhowto.html
169http://recycle.lbl.gov/~ldoolitt/embedded/ (Larry Doolittle's stuff)
170
171
172
173Possible TODOs
174--------------
175
176The following features that we might want to add later:
177
178 - support for additional filesystems besides ext2, i.e. minix
179 - different libc, static vs dynamic loading
180 - maybe using an alternate bootloader
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