[Nexus S Android Development] androidphone2012:
init.d (busybox run-parts)

1. init.rc in the ramdisk - CM differs

service userinit /system/xbin/busybox run-parts /system/etc/init.d
oneshot
class late_start
user root
group root

2. 1) busybox in /system/xbin/

2) and permission

set_perm(0, 0, 04755, "/system/xbin/busybox");

3) and install-related stuff in updater-script

run_program("/system/xbin/busybox", "--install", "-s", "/system/xbin");

or

symlink("busybox", "/system/xbin/[", "/system/xbin/[[",
"/system/xbin/adjtimex", "/system/xbin/arp", "/system/xbin/ash",
"/system/xbin/awk", "/system/xbin/base64", "/system/xbin/basename",
"/system/xbin/bbconfig", "/system/xbin/blkid", "/system/xbin/blockdev",
"/system/xbin/brctl", "/system/xbin/bunzip2", "/system/xbin/bzcat",
"/system/xbin/bzip2", "/system/xbin/cal", "/system/xbin/cat",
"/system/xbin/catv", "/system/xbin/chattr", "/system/xbin/chgrp",
"/system/xbin/chmod", "/system/xbin/chown", "/system/xbin/chroot",
"/system/xbin/clear", "/system/xbin/cmp", "/system/xbin/comm",
"/system/xbin/cp", "/system/xbin/cpio", "/system/xbin/crond",
"/system/xbin/crontab", "/system/xbin/cut", "/system/xbin/date",
"/system/xbin/dc", "/system/xbin/dd", "/system/xbin/depmod",
"/system/xbin/devmem", "/system/xbin/df", "/system/xbin/diff",
"/system/xbin/dirname", "/system/xbin/dmesg", "/system/xbin/dnsd",
"/system/xbin/dos2unix", "/system/xbin/du", "/system/xbin/echo",
"/system/xbin/ed", "/system/xbin/egrep", "/system/xbin/env",
"/system/xbin/expand", "/system/xbin/expr", "/system/xbin/false",
"/system/xbin/fdisk", "/system/xbin/fgrep", "/system/xbin/find",
"/system/xbin/flash_lock", "/system/xbin/flash_unlock",
"/system/xbin/flashcp", "/system/xbin/flock", "/system/xbin/fold",
"/system/xbin/free", "/system/xbin/freeramdisk", "/system/xbin/fsync",
"/system/xbin/ftpget", "/system/xbin/ftpput", "/system/xbin/fuser",
"/system/xbin/getopt", "/system/xbin/grep", "/system/xbin/groups",
"/system/xbin/gunzip", "/system/xbin/gzip", "/system/xbin/halt",
"/system/xbin/head", "/system/xbin/hexdump", "/system/xbin/id",
"/system/xbin/ifconfig", "/system/xbin/insmod", "/system/xbin/install",
"/system/xbin/iostat", "/system/xbin/ip", "/system/xbin/kill",
"/system/xbin/killall", "/system/xbin/killall5", "/system/xbin/length",
"/system/xbin/less", "/system/xbin/ln", "/system/xbin/losetup",
"/system/xbin/ls", "/system/xbin/lsattr", "/system/xbin/lsmod",
"/system/xbin/lsusb", "/system/xbin/lzcat", "/system/xbin/lzma",
"/system/xbin/lzop", "/system/xbin/lzopcat", "/system/xbin/man",
"/system/xbin/md5sum", "/system/xbin/mesg", "/system/xbin/mkdir",
"/system/xbin/mke2fs", "/system/xbin/mkfifo", "/system/xbin/mkfs.ext2",
"/system/xbin/mkfs.vfat", "/system/xbin/mknod", "/system/xbin/mkswap",
"/system/xbin/mktemp", "/system/xbin/modinfo", "/system/xbin/modprobe",
"/system/xbin/more", "/system/xbin/mount", "/system/xbin/mountpoint",
"/system/xbin/mpstat", "/system/xbin/mv", "/system/xbin/nanddump",
"/system/xbin/nandwrite", "/system/xbin/netstat", "/system/xbin/nice",
"/system/xbin/nohup", "/system/xbin/nslookup", "/system/xbin/ntpd",
"/system/xbin/od", "/system/xbin/patch", "/system/xbin/pgrep",
"/system/xbin/pidof", "/system/xbin/ping", "/system/xbin/pkill",
"/system/xbin/pmap", "/system/xbin/poweroff", "/system/xbin/printenv",
"/system/xbin/printf", "/system/xbin/ps", "/system/xbin/pstree",
"/system/xbin/pwd", "/system/xbin/pwdx", "/system/xbin/rdev",
"/system/xbin/readlink", "/system/xbin/realpath", "/system/xbin/renice",
"/system/xbin/reset", "/system/xbin/resize", "/system/xbin/rev",
"/system/xbin/rm", "/system/xbin/rmdir", "/system/xbin/rmmod",
"/system/xbin/route", "/system/xbin/run-parts", "/system/xbin/rx",
"/system/xbin/sed", "/system/xbin/seq", "/system/xbin/setconsole",
"/system/xbin/setserial", "/system/xbin/setsid", "/system/xbin/sh",
"/system/xbin/sha1sum", "/system/xbin/sha256sum",
"/system/xbin/sha512sum", "/system/xbin/sleep", "/system/xbin/sort",
"/system/xbin/split", "/system/xbin/stat", "/system/xbin/strings",
"/system/xbin/stty", "/system/xbin/sum", "/system/xbin/swapoff",
"/system/xbin/swapon", "/system/xbin/sync", "/system/xbin/sysctl",
"/system/xbin/tac", "/system/xbin/tail", "/system/xbin/tar",
"/system/xbin/taskset", "/system/xbin/tee", "/system/xbin/telnet",
"/system/xbin/telnetd", "/system/xbin/test", "/system/xbin/tftp",
"/system/xbin/tftpd", "/system/xbin/time", "/system/xbin/timeout",
"/system/xbin/top", "/system/xbin/touch", "/system/xbin/tr",
"/system/xbin/traceroute", "/system/xbin/true", "/system/xbin/ttysize",
"/system/xbin/tune2fs", "/system/xbin/umount", "/system/xbin/uname",
"/system/xbin/uncompress", "/system/xbin/unexpand", "/system/xbin/uniq",
"/system/xbin/unix2dos", "/system/xbin/unlzma", "/system/xbin/unlzop",
"/system/xbin/unxz", "/system/xbin/unzip", "/system/xbin/uptime",
"/system/xbin/usleep", "/system/xbin/uudecode", "/system/xbin/uuencode",
"/system/xbin/vi", "/system/xbin/watch", "/system/xbin/wc",
"/system/xbin/wget", "/system/xbin/which", "/system/xbin/whoami",
"/system/xbin/xargs", "/system/xbin/xz", "/system/xbin/xzcat",
"/system/xbin/yes",
"/system/xbin/zcat");

3. 1) /system/etc/init.d/

2) and permission

set_perm_recursive(0, 0, 0755, 0755, "/system/etc/init.d");

○ v0.5.2 does not have 2.2) / 2.3) / 3.

flash Busybox_v1.20.2_by.Stericson.zip and int.d_scripts.zip

○ v0.8 does not have 3.

flash int.d_scripts.zip

place your own scripts in int.d_scripts.zip/system/etc/init.d directory before flashing

anyway, most of the rom installer zips "formatting system" so you need to install scripts on each occasion

Edit : ○v1.0 has everything :)