Hi, I am doing linux kernel porting for FPGA board. I am facing issue in getting the shell prompt at the end of kernel booting. Shell prompt is not taking any commands I’m typing. I can place break point in Tx & Rx ISR with Jtag debugger.ISR functions seems working till shell is entered (echo message in the /etc/inittab script & mounting /proc,/devtmpfs and ls command (added to check)are working, I added ls,cat command in the /etc/init.d/rcS file to check uart Tx / Rx) Once the shell is entered with the below message, UART ISR is NOT invoked (using JTAG to put breakpoints) ,if I type any command & I can’t get any message. *Err message: /bin/sh: can't access tty; job control turned off / #* Kindly share any suggestion to fix this issue. * Below are the /etc/initab & /etc/init.d/rcS * /etc/inittab: # This is run first script ::sysinit:/etc/init.d/rcS # Start an "askfirst" shell on the console ttySAC0::askfirst:-/bin/sh ttySAC0::respawn:-/sbin/getty 115200 ttySAC0 # Stuff to do when restarting the init process ::restart:/sbin/init # Stuff to do before rebooting ::ctrlaltdel:/sbin/reboot ::shutdown:/bin/umount a r */etc/init.d/rcS* #!/bin/sh echo -e "\n in rcS script\n" echo -e "\n Mounting proc FS\n" mount t proc none /proc echo -e "\nMounting sysfs \n" mount t sysfs none /sys ls -alh / echo -e "\n\n" ls -alh /dev/ttyS* echo -e "\n" cat /proc/interrupts echo -e "\n ttySAC0 respawning \n" ttySAC0::respawn:-/sbin/getty 115200 ttySAC0 echo -e "\n ttySAC0 respawning finished \n" echo -e "\n exec /bin/sh\n" exec /bin/sh ls #ls -alh /dev *Below are the console message of boot up.* Linux version 3.1.6-00011-g82af784-dirty (pcuser@pcuser-linux) (gcc version 4.6.1 (Ubuntu/Linaro 4.6.1-9ubuntu3) ) #66 Fri May 11 16:21:22 IST 2012 CPU: ARM926EJ-S [41069265] revision 5 (ARMv5TEJ), cr=00053177 CPU: VIVT data cache, VIVT instruction cache Machine: FPGA Board Memory policy: ECC disabled, Data cache writeback Available lowmem size : 32 MB Built 1 zonelists in Zone order, mobility grouping on. Total pages: 8128 Kernel command line: mem=32M console=ttySAC0,115200 root=/dev/ram0 init=/sbin/init initrd=0x80800000,8M user_debug=31 PID hash table entries: 128 (order: -3, 512 bytes) Dentry cache hash table entries: 4096 (order: 2, 16384 bytes) Inode-cache hash table entries: 2048 (order: 1, 8192 bytes) Memory: 32MB = 32MB total Memory: 22456k/22456k available, 10312k reserved, 0K highmem Virtual kernel memory layout: vector : 0xffff0000 - 0xffff1000 ( 4 kB) fixmap : 0xfff00000 - 0xfffe0000 ( 896 kB) DMA : 0xffc00000 - 0xffe00000 ( 2 MB) vmalloc : 0xc2800000 - 0xf6000000 ( 824 MB) lowmem : 0xc0000000 - 0xc2000000 ( 32 MB) modules : 0xbf000000 - 0xc0000000 ( 16 MB) .text : 0xc0008000 - 0xc018c000 (1552 kB) .init : 0xc018c000 - 0xc01a1000 ( 84 kB) .data : 0xc01a2000 - 0xc01afe00 ( 56 kB) .bss : 0xc01afe24 - 0xc01c0f24 ( 69 kB) SLUB: Genslabs=13, HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1 NR_IRQS:32 Console: colour dummy device 80x30 console [ttySAC0] enabled Calibrating delay loop... 1.86 BogoMIPS (lpj=9344) pid_max: default: 32768 minimum: 301 Mount-cache hash table entries: 512 CPU: Testing write buffer coherency: ok devtmpfs: initialized exceptions_init Switching to clocksource timer0 Trying to unpack rootfs image as initramfs... rootfs image is not initramfs (junk in compressed archive); looks like an initrd Freeing initrd memory: 8192K msgmni has been set to 59 io scheduler noop registered (default) brd: module loaded loop: module loaded mousedev: PS/2 mouse device common for all mice RAMDISK: ext2 filesystem found at block 0 RAMDISK: Loading 3072KiB [1 disk] into ram disk... \ done. VFS: Mounted root (ext2 filesystem) readonly on device 1:0. devtmpfs: mounted Freeing init memory: 84K *echo messages from /etc/rcS & /etc/inintab* in rcS script Mounting proc FS Mounting sysfs drwxrwxr-x 12 0 0 1.0K May 9 2012 . drwxrwxr-x 12 0 0 1.0K May 9 2012 .. drwxrwxr-x 2 0 0 2.0K May 11 2012 bin drwxr-xr-x 3 0 0 11.9K Jan 1 00:00 dev drwxr-xr-x 3 0 0 1.0K May 11 2012 etc drwxr-xr-x 2 0 0 1.0K May 9 2012 lib lrwxrwxrwx 1 0 0 11 May 8 2012 linuxrc -> bin/busybox drwx------ 2 0 0 12.0K May 8 2012 lost+found drwxr-xr-x 2 0 0 1.0K May 8 2012 proc drwxrwxr-x 2 0 0 1.0K May 8 2012 sbin drwxr-xr-x 2 0 0 1.0K May 8 2012 sys drwxrwxr-x 4 0 0 1.0K May 8 2012 usr drwxr-xr-x 2 0 0 1.0K May 9 2012 var crw------- 1 0 0 204, 64 Jan 1 00:00 /dev/ttySAC0 ttySAC0 respawning /etc/init.d/rcS: line 20: ttySAC0::respawn:-/sbin/getty: not found ttySAC0 respawning finished -rwxr-xr-x 1 0 0 1.0K May 11 2012 /bin/hello calling hello world /etc/init.d/rcS: line 24: ./hello: not found /etc/init.d/rcS: line 25: hello: not found /etc/init.d/rcS: line 26: ./hello: not found /etc/init.d/rcS: line 27: /bin/hello: not found exec /bin/sh /bin/sh: can't access tty; job control turned off / # I can't type any commad at the shell prompt, shell is not accepting it.