Contents of /trunk/mkinitrd-magellan/busybox/examples/bootfloppy/bootfloppy.txt
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Fri Apr 24 18:33:46 2009 UTC (15 years, 1 month ago) by niro
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-updated to busybox-1.13.4
1 | Building a Busybox Boot Floppy |
2 | ============================== |
3 | |
4 | This document describes how to buid a boot floppy using the following |
5 | components: |
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 | |
12 | It is based heavily on a paper presented by Erik Andersen at the 2001 Embedded |
13 | Systems Conference. |
14 | |
15 | |
16 | |
17 | Building The Software Components |
18 | -------------------------------- |
19 | |
20 | Detailed instructions on how to build Busybox, uClibc, or a working Linux |
21 | kernel are beyond the scope of this document. The following guidelines will |
22 | help 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 | |
30 | If you require further information on building Busybox uClibc or Linux, please |
31 | refer to the web pages and documentation for those individual programs. |
32 | |
33 | |
34 | |
35 | Making a Root File System |
36 | ------------------------- |
37 | |
38 | The 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 CONFIG_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 | |
96 | Making a SYSLINUX boot floppy |
97 | ----------------------------- |
98 | |
99 | The following steps will create the boot floppy. |
100 | |
101 | Note: 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 | |
131 | Sample syslinux.cfg |
132 | ~~~~~~~~~~~~~~~~~~~ |
133 | |
134 | The following simple syslinux.cfg file should work. You can tweak it if you |
135 | like. |
136 | |
137 | ----begin-syslinux.cfg--------------- |
138 | DEFAULT linux |
139 | APPEND initrd=rootfs.gz root=/dev/ram0 |
140 | TIMEOUT 10 |
141 | PROMPT 1 |
142 | ----end-syslinux.cfg--------------- |
143 | |
144 | Some 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 | |
159 | Additional Resources |
160 | -------------------- |
161 | |
162 | Other useful information on making a Linux bootfloppy is available at the |
163 | following URLs: |
164 | |
165 | http://www.linuxdoc.org/HOWTO/Bootdisk-HOWTO/index.html |
166 | http://www.linux-embedded.com/howto/Embedded-Linux-Howto.html |
167 | http://linux-embedded.org/howto/LFS-HOWTO.html |
168 | http://linux-embedded.org/pmhowto.html |
169 | http://recycle.lbl.gov/~ldoolitt/embedded/ (Larry Doolittle's stuff) |
170 | |
171 | |
172 | |
173 | Possible TODOs |
174 | -------------- |
175 | |
176 | The 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 |