第一步:

echo "S0:12345:respawn:/sbin/agetty/ ttyS0 115200" >> /etc/inittab


第二步:

echo "ttyS0" >> /etc/securetty


第三步:

在/etc/grub.conf文件中为内核添加参数:

console=ttyS0


cat  /etc/grub.conf

# grub.conf generated by anaconda

#

# Note that you do not have to rerun grub after making changes to this file

# NOTICE:  You have a /boot partition.  This means that

#          all kernel and initrd paths are relative to /boot/, eg.

#          root (hd0,0)

#          kernel /vmlinuz-version ro root=/dev/mapper/vg_ameim7-lv_root

#          initrd /initrd-[generic-]version.img

#boot=/dev/vda

default=0

timeout=5

splashimage=(hd0,0)/grub/splash.xpm.gz

hiddenmenu

title Red Hat Enterprise Linux (2.6.32-358.el6.x86_64)

        root (hd0,0)

        kernel /vmlinuz-2.6.32-358.el6.x86_64 ro root=/dev/mapper/vg_ameim7-lv_root rd_NO_LUKS rd_LVM_LV=vg_ameim7/lv_swap rd_NO_MD rd_LVM_LV=vg_ameim7/lv_root crashkernel=128M LANG=zh_CN.UTF-8  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM rhgb quiet console=ttyS0

        initrd /initramfs-2.6.32-358.el6.x86_64.img



如果是grub2系统,请修改

vim /etc/default/grub文件, 

GRUB_CMDLINE_LINUX=" console=tty0 console=ttyS0",

然后update-grub 

即执行如下命令,然后重启机器
grub2-mkconfig -o /boot/grub2/grub.cfg