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Pocket Linux Guide
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7.3. Construction

7.3.1. Verify presence of getty and login

bash# ls ~/staging/sbin/getty
bash# ls ~/staging/bin/login

7.3.2. Modify inittab for multi-user mode

Modify ~/staging/etc/inittab by changing the default runlevel and adding getty entries as shown below.

# /etc/inittab - init daemon configuration file
#
# Default runlevel
id:2:initdefault:
#
# System initialization
si:S:sysinit:/etc/init.d/rc S
#
# Runlevel scripts
r0:0:wait:/etc/init.d/rc 0
r1:1:respawn:/bin/sh
r2:2:wait:/etc/init.d/rc 2
r3:3:wait:/etc/init.d/rc 3
r4:4:wait:/etc/init.d/rc 4
r5:5:wait:/etc/init.d/rc 5
r6:6:wait:/etc/init.d/rc 6
#
# Spawn virtual terminals
1:235:respawn:/sbin/getty 38400 tty1 linux
2:235:respawn:/sbin/getty 38400 tty2 linux
3:235:respawn:/sbin/getty 38400 tty3 linux
4:235:respawn:/sbin/getty 38400 tty4 linux
5:235:respawn:/sbin/getty 38400 tty5 linux
6:2345:respawn:/sbin/getty 38400 tty6 linux
#
# end of /etc/inittab

7.3.3. Create tty devices

bash# cd ~/staging/dev
bash# mknod ~/staging/dev/tty0 c 4 0
bash# mknod ~/staging/dev/tty1 c 4 1
bash# mknod ~/staging/dev/tty2 c 4 2
bash# mknod ~/staging/dev/tty3 c 4 3
bash# mknod ~/staging/dev/tty4 c 4 4
bash# mknod ~/staging/dev/tty5 c 4 5
bash# mknod ~/staging/dev/tty6 c 4 6
bash# mknod ~/staging/dev/tty c 5 0

7.3.4. Create support files in /etc

7.3.4.1. /etc/issue

Create the file ~/staging/etc/issue using the example below or design a customized message.

Connected to \l at \b bps.

Be sure that "\l" is a lowercase letter L and not the number one.

7.3.4.2. /etc/passwd

Use a text editor to create a minimal passwd file conforming to the Linux Standards Base (LSB) document. Save the file as ~/staging/etc/passwd

root::0:0:Super User:/root:/bin/sh
bin:x:1:1:Legacy UID:/bin:/bin/false
daemon:x:2:2:Legacy UID:/sbin:/bin/false

7.3.4.3. /etc/group

Use a text editor to create an LSB conforming group file and save it as ~/staging/etc/group

root::0:root
bin:x:1:root,bin,daemon
daemon:x:2:root,bin,daemon

7.3.4.4. /etc/nsswitch.conf

Create the following file and save it as ~/staging/etc/nsswitch.conf

passwd: files
group:  files

7.3.5. Copy required libraries

bash# cp /lib/libnss_files.so.2 ~/staging/lib
bash# strip --strip-unneeded ~/staging/lib/*

7.3.6. Set directory and file permissions

Set minimal privileges on all files and directories under ~/staging. Everything is owned by the root user and the root group. Permissions are read-write for the owner and read-only for the group. Exceptions to the blanket permissions are handled case by case.

bash# cd ~/staging
bash# chown -R 0:0 ~/staging/*
bash# chmod -R 640 ~/staging/*

Set execute permission on all directories. (Note the capital "X")

bash# chmod -R +X ~/staging/*

Files in /bin are read and execute for all, but su is an exception.

bash# chmod 755 ~/staging/bin/*
bash# chmod 4750 ~/staging/bin/su

Files in /dev have various permissions. Disk devices should be accessible to administrators only. Other files like /dev/null should have full privileges granted to everyone.

bash# chmod 660 ~/staging/dev/fd0 dev/ram0
bash# chmod 666 ~/staging/dev/null
bash# chmod 622 ~/staging/dev/console
bash# chmod 600 ~/staging/dev/initctl
bash# chmod 622 ~/staging/dev/tty
bash# chmod 622 ~/staging/dev/tty?

The passwd and group files must be world readable.

bash# chmod 644 ~/staging/etc/passwd
bash# chmod 644 ~/staging/etc/group

The scripts in /etc/init.d are read and execute for administrators.

bash# chmod 750 ~/staging/etc/init.d/*

Libraries need read and execute permissions for everyone.

bash# chmod 755 ~/staging/lib/*

Only root should have access to the /root directory.

bash# chmod 700 ~/staging/root

Make files in /sbin read and execute for administrators.

bash# chmod 750 ~/staging/sbin/*

Temp should be read-write for all with the sticky bit set.

bash# chmod 1777 ~/staging/tmp

7.3.7. Create the root disk image

bash# cd /
bash# dd if=/dev/zero of=/dev/ram7 bs=1k count=4096
bash# mke2fs -m0 /dev/ram7 4096
bash# mount /dev/ram7 /mnt
bash# cp -dpR ~/staging/* /mnt
bash# umount /dev/ram7
bash# dd if=/dev/ram7 of=~/phase6-image bs=1k count=4096
bash# gzip -9 ~/phase6-image

7.3.8. Copy the image to diskette

Insert the diskette labeled "root disk" into drive fd0.

bash# dd if=~/phase6-image.gz of=/dev/fd0 bs=1k
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