打开系统文件
vim /boot/grub/grub.conf
默认由0开始计数，因此须将default值改为0即可。
重启服务器
reboot
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#boot=/dev/sda default=1 timeout=5 splashimage=(hd0,0)/grub/splash.xpm.gz hiddenmenu title CentOS (2.6.18-194.17.1.el5) root (hd0,0) kernel /vmlinuz-2.6.18-194.17.1.el5 ro root=LABEL=/ rhgb quiet initrd /initrd-2.6.18-194.17.1.el5.img title CentOS (2.6.18-194.17.1.el5xen) root (hd0,0) kernel /xen.gz-2.6.18-194.17.1.el5 module /vmlinuz-2.6.18-194.17.1.el5xen ro root=LABEL=/ rhgb quiet module /initrd-2.6.18-194.17.1.el5xen.img title CentOS (2.6.18-194.el5xen) root (hd0,0) kernel /xen.gz-2.6.18-194.el5 module /vmlinuz-2.6.18-194.el5xen ro root=LABEL=/ rhgb quiet module /initrd-2.6.18-194.el5xen.img title CentOS-base (2.6.18-194.el5) root (hd0,0) kernel /vmlinuz-2.6.18-194.el5 ro root=LABEL=/ rhgb quiet initrd /initrd-2.6.18-194.el5.img
