[Galaxy S II Android Development] Troubadour666:
i went to see file, and there are some error in lines, some script command are on the same line , all lines have to be ended by ";" and separate.

your code :

unmount("/system");
unmount("/cache");run_program("/sbin/mount", "/dev/block/mmcblk0p9", "/system");
run_program("/sbin/mount", "/dev/block/mmcblk0p10", "/data");
run_program("/sbin/mount", "/dev/block/mmcblk0p7", "/cache");delete_recursive("/system");
delete_recursive("/data/sec_data");delete_recursive("/data/dalvik-cache");
package_extract_dir("data", "/data");
set_perm(2000, 2000, 0771, "/data/local");
set_perm_recursive(1000, 1000, 0771, 0644, "/data/app");
ui_print("Installing system ...");
show_progress(0.500000, 80);
package_extract_dir("system", "/system");package_extract_dir("preload/symlink/system/app", "/data/sec_data");
set_perm(0, 1000, 0755, "/system/xbin/busybox");
run_program("/system/xbin/busybox", "--install", "-s", "/system/xbin");
symlink("/system/xbin/busybox", "/system/bin/busybox");
ui_print("Simlinking ...");

corrected : you see the <> ?

unmount("/system");
unmount("/cache");
run_program("/sbin/mount", "/dev/block/mmcblk0p9", "/system");
run_program("/sbin/mount", "/dev/block/mmcblk0p10", "/data");
run_program("/sbin/mount", "/dev/block/mmcblk0p7", "/cache");
delete_recursive("/system");
delete_recursive("/data/sec_data");
delete_recursive("/data/dalvik-cache");
package_extract_dir("data", "/data");
set_perm(2000, 2000, 0771, "/data/local");
set_perm_recursive(1000, 1000, 0771, 0644, "/data/app");
ui_print("Installing system ...");
show_progress(0.500000, 80);
package_extract_dir("system", "/system");
package_extract_dir("preload/symlink/system/app", "/data/sec_data");
set_perm(0, 1000, 0755, "/system/xbin/busybox");
run_program("/system/xbin/busybox", "--install", "-s", "/system/xbin");
symlink("/system/xbin/busybox", "/system/bin/busybox");
ui_print("Simlinking ...");

I imagine that you already have flash [MENTION=2376110]dorimanx[/MENTION] V8.xx kernel before flash in 2nd ROM, and you wipe data for 2nd rom in recovery to initiate \.secondrom\ folder and DATA.IMG and CACHE.IMG in that folder too.

If you dont change zImage kernel in \sale\ folder (in ZIP ROM), by DorimanX zImage V8.xx, you will lost you dualboot if you let lines relative to flash kernel at end of your updater-script.

Simply delete following code to avoid trouble, for modem too, delete, you have a modem in 1rst rom. Peharps you can let i dont know about it, for me, i delete, but i have two JB 4.1.2 roms so ;) (i remark that if i restore 4.2.2 (4.3) rom in 2nd rom, modem in memory tel is functionnal too.)

ui_print("Flashing kernel ...");
package_extract_file("Sale/flash_image", "/tmp/flash_image");
set_perm(0, 0, 0777, "/tmp/flash_image");
assert(package_extract_file("Sale/zImage", "/tmp/zImage"),
run_program("/tmp/flash_image", "/dev/block/mmcblk0p5", "/tmp/zImage"),
delete("/tmp/zImage"));
ui_print("Flashing modem ...");
assert(package_extract_file("Sale/modem.bin", "/tmp/modem.bin"),
run_program("/tmp/flash_image", "/dev/block/mmcblk0p8", "/tmp/modem.bin"),
delete("/tmp/modem.bin"));

your Symlink_preload is good.

#!/system/bin/mksh
mount -o remount rw /system
mount -o remount rw /data (not necessary)
cd /data/sec_data
apk_list=( `ls | grep .apk` )
odex_list=( `ls | grep .odex` )
items=${apk_list[*]}" "${odex_list[*]}
for item in ${items[@]}
do
ln -s /data/sec_data/$item /system/app/$item
done

Finaly i made a thread in past : prevent error during flash - updater-script editing in Notepad++ , have a look, why not ?

Next time, dont hesitate to put script here before flash (if [MENTION=3690986]_Sale_[/MENTION] is okay for sure) , dont be afraid about response time, [MENTION=4775725]Troubadour666[/MENTION] is here ;)

But i'm perplexe about your phone state now :(

Good luck for good dualbooting test now ;)