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3.3. Construction
This section is written using ramdisk seven
(/dev/ram7) to build the root image. There is nothing
particularly special about ramdisk seven and it is possible to use any of
the other available ramdisks provided they are not already in use.
3.3.1. Create a ramdisk
bash# dd if=/dev/zero of=/dev/ram7 bs=1k count=4096
bash# mke2fs -m0 /dev/ram7 4096
bash# mount /dev/ram7 /mnt
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3.3.2. Rebuild the BASH shell
bash# cd /usr/src/bash-3.0
bash# make distclean
bash# export CC="gcc -mcpu=i386"
bash# ./configure --enable-minimal-config --host=i386-pc-linux-gnu
bash# make
bash# strip bash
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3.3.3. Determine which libraries are required
View the output from the ldd command. It should
look similar to the example below.
bash# ldd bash
libdl.so.2 => /lib/libdl.so.2 (0x4001d000)
libc.so.6 => /lib/libc.so.6 (0x40020000)
/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000) |
Some systems may have a slightly different library set up. For
example, you may see libc.so.6 =>
/lib/tls/libc.so.6 rather than
libc.so.6 => /lib/libc.so.6 as
shown in the example. If your ldd output does not
match the example then use the path given by your
ldd command when completing the next step. |
3.3.4. Copy BASH and its libraries to the ramdisk
bash# mkdir /mnt/bin
bash# cp bash /mnt/bin
bash# ln -s bash /mnt/bin/sh
bash# mkdir /mnt/lib
bash# strip --strip-unneeded -o /mnt/lib/libdl.so.2 /lib/libdl.so.2
bash# strip --strip-unneeded -o /mnt/lib/libc.so.6 /lib/libc.so.6
bash# strip --strip-unneeded -o /mnt/lib/ld-linux.so.2 /lib/ld-linux.so.2
bash# chmod +x /mnt/lib/ld-linux.so.2
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Using strip -o might seem an odd way to
copy library files from the development system to the ramdisk. What
it does is strip the symbols while the file is in transit from the
source location to the destination. This has the effect of stripping
symbols from the library on the ramdisk without altering the
libraries on the development system. Unfortunately file permissions
are lost when copying libraries this way which is why the
chmod +x command is then used to set the execute
flag for the rootdisk's dynamic loader. |
3.3.5. Create a console device
bash# mkdir /mnt/dev
bash# mknod /mnt/dev/console c 5 1
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3.3.6. Compress the ramdisk image
bash# cd /
bash# umount /dev/ram7
bash# dd if=/dev/ram7 of=~/phase2-image bs=1k count=4096
bash# gzip -9 ~/phase2-image
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3.3.7. Copy the compressed image to diskette
Insert the floppy labeled "root disk" into drive fd0.
bash# dd if=~/phase2-image.gz of=/dev/fd0 bs=1k
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