How to avoid "can't access tty; job control turned off" when boot to initramfs

i'm testing my custom initramfs now, but everytime the log there will have the "can't access tty; job control turned off". The /dev in initramfs has four files: null, sda1, ttyS0. The kernel parameter is 'console=ttyS0'. Also, i test ctrl+c, it works fine.So how could this problem heppen? In busybox documentation, > Why do I keep getting "sh: can't access tty; job control turned off" > errors? Why doesn't Control-C work within my shell? This isn't really > a uClibc question, but I'll answer it here anyways. Job control will > be turned off since your shell can not obtain a controlling terminal. > This typically happens when you run your shell on /dev/console. The > kernel will not provide a controlling terminal on the /dev/console > device. Your should run your shell on a normal tty such as tty1 or > ttyS0 and everything will work perfectly. If you REALLY want your > shell to run on /dev/console, then you can hack your kernel (if you > are into that sortof thing) by changing drivers/char/tty_io.c to > change the lines where it sets "noctty = 1;" to instead set it to "0". > I recommend you instead run your shell on a real console... I type tty and it gives me /dev/console instead of /dev/ttyS0. So, that's all information about this problem, hope some one can help me out:-)