[Android] Modding.MyMind:
# Adds kernel's Init.d
INITD() {
if [[ -e "/PATH/TO/init.rc" ]]; then
sed -i -e '0,/class_start /s//start sysinit\n\n class_start /' "/PATH/TO/init.rc"
sed -i -e 's/service media /service sysinit \/system\/bin\/logwrapper \/system\/xbin\/busybox run-parts \/system\/etc\/init.d\n disabled\n oneshot\n\nservice media /' "/PATH/TO/init.rc"
cd "$(dirname "$0")"
cd ..
# Call other methods
MOUNT
INSTALL_RECOVERY
SYSINT
PERMISSIONS
else
ui_print "ERROR, missing needed contents from the ramdisk?!";
rm -rf "$ACTIVE_PROJECT/TEMP"
return 1
fi
}

# Mount system as R/W
MOUNT() {
busybox mount -o remount,rw -t auto /system
}

# Build and write to install-recovery.sh
INSTALL_RECOVERY() {
if [ -e /system/etc/install-recovery.sh ]
then
busybox echo "# init.d support" >> /system/etc/install-recovery.sh
busybox echo "busybox run-parts /system/etc/init.d/" >> /system/etc/install-recovery.sh
busybox echo "" >> /system/etc/install-recovery.sh
busybox awk '!x[$0]++' /system/etc/install-recovery.sh > /tmp/install-recovery.sh
busybox cat /tmp/install-recovery.sh > /system/etc/install-recovery.sh
busybox echo "" >> /system/etc/install-recovery.sh
else
cat > /system/etc/install-recovery.sh
busybox echo "#!/system/bin/sh" >> /system/etc/install-recovery.sh
busybox echo "# init.d support" >> /system/etc/install-recovery.sh
busybox echo "busybox run-parts /system/etc/init.d/" >> /system/etc/install-recovery.sh
busybox echo "" >> /system/etc/install-recovery.sh
fi
}

# Build and write to systint
SYSINT() {
if [ -e /system/bin/sysint ]
then
busybox echo "#!/system/bin/sh" >> /system/bin/sysint
busybox echo "# init.d support" >> /system/bin/sysint
busybox echo "" >> /system/bin/sysint
busybox echo "export PATH=/sbin:/system/sbin:/system/bin:/system/xbin" >> /system/bin/sysint
busybox echo "/system/bin/logwrapper run-parts /system/etc/init.d" >> /system/bin/sysint
busybox echo "" >> /system/bin/sysint
busybox awk '!x[$0]++' /system/bin/sysint > /tmp/sysint
busybox cat /tmp/sysint > /system/bin/sysint
busybox echo "" >> /system/bin/sysint
else
busybox echo "#!/system/bin/sh" > /system/bin/sysint
busybox echo "# init.d support" >> /system/bin/sysint
busybox echo "" >> /system/bin/sysint
busybox echo "export PATH=/sbin:/system/sbin:/system/bin:/system/xbin" >> /system/bin/sysint
busybox echo "/system/bin/logwrapper run-parts /system/etc/init.d" >> /system/bin/sysint
busybox echo "" >> /system/bin/sysint
fi
}

# Set permissions accordingly
PERMISSIONS() {
busybox chmod 755 /system/etc/install-recovery.sh
busybox chown 0.0 /system/etc/install-recovery.sh
busybox chmod 755 /system/bin/sysint
busybox chown 0.2000 /system/bin/sysint
}

# Start process here
INITD

Here is a small snippet from my script that I use with MyMinds_Kernel_Swap for flashing in my recovery to pull my boot.img using dd, unpack using my unmkbootimg binary, edit init.rc and amongst other things in /system, swap kernel, build ramdisk with mkbootfs, build boot.img with mkbootimg, and flash using dd. Pretty much like AnyKernel, but I wrote my own because AnyKernel just didn't work.

Anyways, here you go. Remember, some adjustments are needed more in less but should give you an idea for init.rc support. If you wish to see my entire script then just look up my github and find my repo as named above.