更改系统默认加载的内核

可修改启动配置文件，更改系统默认加载的内核！
查看有两个grub.conf，分别是/etc/grub.conf，还有/boot/grub/grub.conf
两个文件应该是一样的
/etc/grub.conf: symbolic link to `../boot/grub/grub.conf'
#vi /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/sda2
#       initrd /initrd-version.img
#boot=/dev/sda
default=1
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title Red Hat Enterprise Linux Server (2.6.18-53.el5PAE)
       root (hd0,0)
       kernel /vmlinuz-2.6.18-53.el5PAE ro root=LABEL=/1 3 rhgb quiet
       initrd /initrd-2.6.18-53.el5PAE.img
title Red Hat Enterprise Linux Server-xen (2.6.18-53.el5xen)
       root (hd0,0)
       kernel /xen.gz-2.6.18-53.el5
       module /vmlinuz-2.6.18-53.el5xen ro root=LABEL=/1 3 rhgb quiet
       module /initrd-2.6.18-53.el5xen.img
title Red Hat Enterprise Linux Server-base (2.6.18-53.el5)
       root (hd0,0)
       kernel /vmlinuz-2.6.18-53.el5 ro root=LABEL=/1 3 rhgb quiet
       initrd /initrd-2.6.18-53.el5.img
将其中的default =1改为你需要的。（注：默认顺序是从0开始）