embededed system with CentOS boot setting terminal.

##  CentOS boot setting.

    ** CentOS 6.9 boot setting.
    serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
    terminal --timeout=0 serial console
    default=1
    timeout=5
    #splashimage=(hd0,0)/grub/splash.xpm.gz
    #hiddenmenu
   
    title Accusys 1U Switch Core (3nd Generation V2)
            root (hd0,0)
            kernel /vmlinuz-2.6.32-696.el6.x86_64 ro root=/dev/sda3  crashkernel=auto  console=ttyS0,115200n8 acscfg=1
            initrd /initramfs-2.6.32-696.el6.x86_64.img
   
    title Accusys 1U Switch Core (3nd Generation V2) Dev
            root (hd0,0)
            kernel /bzImage ro root=/dev/sda3  crashkernel=auto  console=ttyS0,115200n8 acscfg=1
            initrd /initramfs-2.6.32-696.el6.x86_64.img
   
    title CentOS 6 (2.6.32-696.el6.x86_64) Default boot setting
            root (hd0,0)
            kernel /vmlinuz-2.6.32-696.el6.x86_64 ro root=UUID=4df0d800-6b42-47f8-99da-5b50987f3824 rd_NO_LUKS rd_NO_LVM LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM rhgb quiet
            initrd /initramfs-2.6.32-696.el6.x86_64.img


    ** CentOS 5.8 boot setting.
    serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
    terminal --timeout=0 serial console
    default=2
    timeout=5
    title Accusys 1U Switch Core (3nd Generation)
            root (hd0,0)
            kernel /boot/vmlinuz-2.6.18-308.el5 ro root=/dev/sda1 crashkernel=128M@16M console=ttyS0,115200n8 acscfg=1
            initrd /boot/initrd-2.6.18-308.el5.img
   
    title Accusys 1U Switch Core (3nd Generation safe mode)
            root (hd0,0)
            kernel /boot/bzImage ro root=/dev/sda1 crashkernel=128M@16M console=ttyS0,115200n8 acscfg=1
            initrd /boot/initrd-2.6.18-308.el5.img
   
   
    title Accusys 1U Switch Core (3nd Generation Sam Debug mode)
            root (hd0,0)
            kernel /root/bzImage ro root=/dev/sda1 crashkernel=128M@16M console=ttyS0,115200n8 acscfg=1
            initrd /boot/initrd-2.6.18-308.el5.img


##  BIOS/GRUB/Kernel/XEN輸出重定向到串口的配置：

    將BIOS輸出重定向到串口
    這一功能需要主板支援，在BIOS中設置，比如我的設置為：
    Server ManagementConsole RedirectionConsole Redirection設置為”Serial Port A”
   
    將GRUB輸出重定向到串口(Edit /boot/grub/grub.conf)
    serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
    terminal --timeout=5 console serial
   
    grub引導過程中,會將輸出同時發送到終端螢幕和串口. grub引導過程中將在終端和連接到串口的超級終端上提示Press any key to continue,
    每秒鐘提示一次,共5次,可修改menu.lst檔terminal行中的--timeout=10改變提示次數,在這一段時間內,可以在終端的鍵盤,
    或者連接到串口的超級終端中按任意鍵進入grub選擇功能表.如果5秒內沒有在終端和連接串口的超級終端上按任意鍵,
    則grub的選擇功能表將出現在console上,如果希望默認情況下, grub選擇功能表出現在串口上,則可修改grub.conf將console serial修改為serial console.
   
    將kernel輸出資訊輸出到串口(編輯/boot/grub/grub.conf有的為menu.lst)
    增加kernel引導參數如下:
   
    kernel  /boot/vmlinuz-2.6.32-29 root=/dev/hda1 ro console=ttyS0,115200n8 console=tty0
   
    則kernel會將輸出資訊同時輸出到串口（ttyS0即COM1）和終端tty0。
    其中，“ttyS0”表示串口使用COM1；“115200”表示串列傳輸速率為115200bps；“n”表示無校驗位；“8”表示有8位元資料位元
   
##  kernel login message 修正為 Accusys login message
    "cat /etc/issue"
    Accusys PCIE SAN 1U Switch
    Kernel \r on an \m
   
##  To auto login to linux console on boot
    edit /etc/init/tty.conf (但是Switch 是ttys0設定方式不同)

    修正 /etc/init/tty.conf
    "exec /sbin/mingetty $TTY"
    改為
    "exec /sbin/mingetty --autologin root $TTY"
   
    [root@localhost ~]# cat /etc/init/tty.conf
    # tty - getty
    #
    # This service maintains a getty on the specified device.
    #
    # Do not edit this file directly. If you want to change the behaviour,
    # please create a file tty.override and put your changes there.
   
    stop on runlevel [S016]
   
    respawn
    instance $TTY
    #exec /sbin/mingetty $TTY
    exec /sbin/mingetty --autologin root $TTY
    usage 'tty TTY=/dev/ttyX  - where X is console id'
    [root@localhost ~]#

##  To auto login to linux serial console on boot
    edit /etc/init/serial.conf

    修正 /etc/init/serial.conf
    "exec /sbin/agetty /dev/$DEV $SPEED vt100-nav"
    改為
    "exec /sbin/agetty -n -l /usr/sbin/autologin /dev/$DEV $SPEED vt100-nav"
    但是 /usr/sbin 找不到 autologin
    我們要自己準備 autologin.c,  code 如下,

    #include "unistd.h"
    int main()
    {
        execlp( "login", "login", "-f", "root", NULL);
    }
    產生執行檔
    gcc autologin.c -o autologin, 將檔案放在你要存放的位子
   
    [root@localhost ~]# cat /etc/init/serial.conf
    # Automatically start a configured serial console
    #
    # How this works:
    #
    # On boot, a udev helper examines /dev/console. If a serial console is the
    # primary console (last console on the commandline in grub),  the event
    # 'fedora.serial-console-available <port name> <speed>' is emitted, which
    # triggers this script. It waits for the runlevel to finish, ensures
    # the proper port is in /etc/securetty, and starts the getty.
    #
    # If your serial console is not the primary console, or you want a getty
    # on serial even if it's not the console, create your own event e.g.
    # /etc/init/ttyS0.conf with content:
    # # ttyS0 - agetty
    # #
    # # This service maintains a agetty on ttyS0.
    #
    # stop on runlevel [S016]
    # start on runlevel [23]
    #
    # respawn
    # exec agetty -h -L -w /dev/ttyS0 115200 vt102
    #
    # Do not edit this file directly. If you want to change the behaviour,
    # please create a file serial.override and put your changes there.
   
    start on fedora.serial-console-available DEV=* and stopped rc RUNLEVEL=[2345]
    stop on runlevel [S016]
   
    instance $DEV
    respawn
    pre-start exec /sbin/securetty $DEV
    #exec /sbin/agetty /dev/$DEV $SPEED vt100-nav
    exec /sbin/agetty -n -l /root/autologin /dev/$DEV $SPEED vt100-nav
    post-stop exec /sbin/initctl emit --no-wait fedora.serial-console-available DEV=$DEV SPEED=$SPEED
    usage 'DEV=ttySX SPEED=Y  - where X is console id and Y is baud rate'