以我的Fedora12为例，系统启动时默认等待时间为15秒。
这个参数的值是在文件/boot/grub/grub.conf
打开这个文件，可以看到内容如下：
# 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_linux-lv_root
# initrd /initrd-[generic-]version.img
#boot=/dev/sda
default=0
timeout=15
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title Fedora (2.6.31.5-127.fc12.i686.PAE)
root (hd0,0)
kernel /vmlinuz-2.6.31.5-127.fc12.i686.PAE ro root=/dev/mapper/vg_linux-lv_root LANG=zh_CN.UTF-8 KEYBOARDTYPE=pc KEYTABLE=us rhgb quiet
initrd /initramfs-2.6.31.5-127.fc12.i686.PAE.img
其中的timeout=15就表示等待时间为15秒，如果将它改为5，再保存重启机器，就能看到效果了！