刚安装了双系统，分别是windows7（先）和Ubuntu10.04（后）（非wubi安装),. 默认是Linux启动,通过下面的操作可把windows7改为默认启动系统
启动Ubuntu后，在终端中输入：
先备份 sudo cp /boot/grub/grub.cfg /boot/grub/grub.cfg.backup
修改启动列表：sudo gedit /boot/grub/grub.cfg(注意不是sudo gedit /boot/grub/menu.lst,
貌似9.10就改为了grub.cfg）
然后找到
default 0
然后往下看，找你想默认启动的操作系统！修改default 后面的数字，0对应第一个，1对应第二个，依次往下！以下是我的grub.cfg
默认是Ubuntu！把0改为4就可以了！(升级内核之后数字酌情修改）
#
# DO NOT EDIT THIS FILE
#
# It is automatically generated by /usr/sbin/grub-mkconfig using templates
# from /etc/grub.d and settings from /etc/default/grub
#
### BEGIN /etc/grub.d/00_header ###
if [ -s $prefix/grubenv ]; then
load_env
fi
set default="0"
if [ ${prev_saved_entry} ]; then
set saved_entry=${prev_saved_entry}
save_env saved_entry
set prev_saved_entry=
save_env prev_saved_entry
set boot_once=true
fi
function savedefault {
if [ -z ${boot_once} ]; then
saved_entry=${chosen}
save_env saved_entry
fi
}
function recordfail {
set recordfail=1
if [ -n ${have_grubenv} ]; then if [ -z ${boot_once} ]; then save_env recordfail; fi; fi
}
insmod ext2
set root='(hd0,3)'
search --no-floppy --fs-uuid --set 0ee185d8-a603-4309-97b7-6440643becb7
if loadfont /usr/share/grub/unicode.pf2 ; then
set gfxmode=640x480
insmod gfxterm
insmod vbe
if terminal_output gfxterm ; then true ; else
# For backward compatibility with versions of terminal.mod that don't
# understand terminal_output
terminal gfxterm
fi
fi
insmod ext2
set root='(hd0,3)'
search --no-floppy --fs-uuid --set 0ee185d8-a603-4309-97b7-6440643becb7
set locale_dir=($root)/boot/grub/locale
set lang=zh
insmod gettext
if [ ${recordfail} = 1 ]; then
set timeout=-1
else
set timeout=10
fi
### END /etc/grub.d/00_header ###
### BEGIN /etc/grub.d/05_debian_theme ###
set menu_color_normal=white/black
set menu_color_highlight=black/light-gray
### END /etc/grub.d/05_debian_theme ###
### BEGIN /etc/grub.d/10_linux ###
menuentry'Ubuntu，Linux 2.6.32-21-generic' --class ubuntu --class gnu-linux --class gnu --class os {
recordfail
insmod ext2
set root='(hd0,3)'
search --no-floppy --fs-uuid --set 0ee185d8-a603-4309-97b7-6440643becb7
linux /boot/vmlinuz-2.6.32-21-generic root=UUID=0ee185d8-a603-4309-97b7-6440643becb7 ro quiet splash
initrd /boot/initrd.img-2.6.32-21-generic
}
menuentry 'Ubuntu，Linux 2.6.32-21-generic (恢复模式)' --class ubuntu --class gnu-linux --class gnu --class os {
recordfail
insmod ext2
set root='(hd0,3)'
search --no-floppy --fs-uuid --set 0ee185d8-a603-4309-97b7-6440643becb7
echo '载入 Linux ...'
linux /boot/vmlinuz-2.6.32-21-generic root=UUID=0ee185d8-a603-4309-97b7-6440643becb7 ro single
echo '载入引导虚拟磁盘 ...'
initrd /boot/initrd.img-2.6.32-21-generic
}
### END /etc/grub.d/10_linux ###
### BEGIN /etc/grub.d/20_memtest86+ ###
menuentry"Memory test (memtest86+)" {
insmod ext2
set root='(hd0,3)'
search --no-floppy --fs-uuid --set 0ee185d8-a603-4309-97b7-6440643becb7
linux16 /boot/memtest86+.bin
}
menuentry "Memory test (memtest86+, serial console 115200)" {
insmod ext2
set root='(hd0,3)'
search --no-floppy --fs-uuid --set 0ee185d8-a603-4309-97b7-6440643becb7
linux16 /boot/memtest86+.bin console=ttyS0,115200n8
}
### END /etc/grub.d/20_memtest86+ ###
### BEGIN /etc/grub.d/30_os-prober ###
menuentry "Windows 7 (loader) (on /dev/sda1)" {
insmod ntfs
set root='(hd0,1)'
search --no-floppy --fs-uuid --set 6e40b6ff40b6ccd9
chainloader +1
}
### END /etc/grub.d/30_os-prober ###
### BEGIN /etc/grub.d/40_custom ###
# This file provides an easy way to add custom menu entries. Simply type the
# menu entries you want to add after this comment. Be careful not to change
# the 'exec tail' line above.
### END /etc/grub.d/40_custom ###
→→此处分割←←
上面的自己修改default后面的数字。！··
如果你觉得这样不方便到话，我建议你把win7的那一项剪切到Ubuntu前面
也就是这个样子，这样既美观又方便（不用修改default后面的数字）。
#
# DO NOT EDIT THIS FILE
#
# It is automatically generated by /usr/sbin/grub-mkconfig using templates
# from /etc/grub.d and settings from /etc/default/grub
#
### BEGIN /etc/grub.d/00_header ###
if [ -s $prefix/grubenv ]; then
load_env
fi
set default="0"
if [ ${prev_saved_entry} ]; then
set saved_entry=${prev_saved_entry}
save_env saved_entry
set prev_saved_entry=
save_env prev_saved_entry
set boot_once=true
fi
function savedefault {
if [ -z ${boot_once} ]; then
saved_entry=${chosen}
save_env saved_entry
fi
}
function recordfail {
set recordfail=1
if [ -n ${have_grubenv} ]; then if [ -z ${boot_once} ]; then save_env recordfail; fi; fi
}
insmod ext2
set root='(hd0,3)'
search --no-floppy --fs-uuid --set 0ee185d8-a603-4309-97b7-6440643becb7
if loadfont /usr/share/grub/unicode.pf2 ; then
set gfxmode=640x480
insmod gfxterm
insmod vbe
if terminal_output gfxterm ; then true ; else
# For backward compatibility with versions of terminal.mod that don't
# understand terminal_output
terminal gfxterm
fi
fi
insmod ext2
set root='(hd0,3)'
search --no-floppy --fs-uuid --set 0ee185d8-a603-4309-97b7-6440643becb7
set locale_dir=($root)/boot/grub/locale
set lang=zh
insmod gettext
if [ ${recordfail} = 1 ]; then
set timeout=-1
else
set timeout=10
fi
### END /etc/grub.d/00_header ###
### BEGIN /etc/grub.d/05_debian_theme ###
set menu_color_normal=white/black
set menu_color_highlight=black/light-gray
### END /etc/grub.d/05_debian_theme ###
### BEGIN /etc/grub.d/30_os-prober ###
menuentry "Windows 7 (loader) (on /dev/sda1)" {
insmod ntfs
set root='(hd0,1)'
search --no-floppy --fs-uuid --set 6e40b6ff40b6ccd9
chainloader +1
}
### END /etc/grub.d/30_os-prober ###
### BEGIN /etc/grub.d/10_linux ###
menuentry 'Ubuntu，Linux 2.6.32-21-generic' --class ubuntu --class gnu-linux --class gnu --class os {
recordfail
insmod ext2
set root='(hd0,3)'
search --no-floppy --fs-uuid --set 0ee185d8-a603-4309-97b7-6440643becb7
linux /boot/vmlinuz-2.6.32-21-generic root=UUID=0ee185d8-a603-4309-97b7-6440643becb7 ro quiet splash
initrd /boot/initrd.img-2.6.32-21-generic
}
menuentry 'Ubuntu，Linux 2.6.32-21-generic (恢复模式)' --class ubuntu --class gnu-linux --class gnu --class os {
recordfail
insmod ext2
set root='(hd0,3)'
search --no-floppy --fs-uuid --set 0ee185d8-a603-4309-97b7-6440643becb7
echo '载入 Linux ...'
linux /boot/vmlinuz-2.6.32-21-generic root=UUID=0ee185d8-a603-4309-97b7-6440643becb7 ro single
echo '载入引导虚拟磁盘 ...'
initrd /boot/initrd.img-2.6.32-21-generic
}
### END /etc/grub.d/10_linux ###
### BEGIN /etc/grub.d/20_memtest86+ ###
menuentry "Memory test (memtest86+)" {
insmod ext2
set root='(hd0,3)'
search --no-floppy --fs-uuid --set 0ee185d8-a603-4309-97b7-6440643becb7
linux16 /boot/memtest86+.bin
}
menuentry "Memory test (memtest86+, serial console 115200)" {
insmod ext2
set root='(hd0,3)'
search --no-floppy --fs-uuid --set 0ee185d8-a603-4309-97b7-6440643becb7
linux16 /boot/memtest86+.bin console=ttyS0,115200n8
}
### END /etc/grub.d/20_memtest86+ ###
### BEGIN /etc/grub.d/40_custom ###
# This file provides an easy way to add custom menu entries. Simply type the
# menu entries you want to add after this comment. Be careful not to change
# the 'exec tail' line above.
### END /etc/grub.d/40_custom ###
每次更新内核，你都要重新修改这个启动项
原帖地址：http://www.linuxidc.com/Linux/2010-10/29101.htm