盘1: ubuntu12.04 win7
盘2: xp
sudo update-grub 的结果只有win7 和 ubuntu,点击win7进入系统，看到了win7和xp,win7可以启动，但是xp不能。于是在网上搜索找到了一个别人的xp和ubuntu共存的grub文件。
发现我的少了一句话，drivemap -s (hd0) ${root},于是加上就ok了。
即在/boot/grub/grub.cfg中添加如下内容即可
menuentry "Windows xp" --class windows --class os {
insmod ntfs
set root="(hd0,1)"
（本文来源于图老师网站，更多请访问https://m.tulaoshi.com/diannaorumen/）search --no-floppy --fs-uuid --set=root 4C844B34844B2036
（本文来源于图老师网站，更多请访问https://m.tulaoshi.com/diannaorumen/）drivemap -s (hd0) ${root}
chainloader +1
}
set root=(hd0,1)，代表第0块磁盘的第一个分区，其中硬盘号是从0开始，分区号是从1开始。我的xp是在第0个分区。我的xp和ubuntu不再同一个磁盘，grub中ubuntu显示在hd1所以xp必然在hd0,而系统在c:盘，所以是第一个分区
整个的grub文件如下：
#
# DO NOT EDIT THIS FILE
#
# It is automatically generated by grub-mkconfig using templates
# from /etc/grub.d and settings from /etc/default/grub
#
### BEGIN /etc/grub.d/00_header ###
if [ -s $prefix/grubenv ]; then
set have_grubenv=true
load_env
fi
set default="0"
if [ "${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 "${boot_once}" ]; then save_env recordfail; fi; fi
}
function load_video {
insmod vbe
insmod vga
insmod video_bochs
insmod video_cirrus
}
insmod part_msdos
insmod ext2
set root="(hd1,msdos6)"
search --no-floppy --fs-uuid --set=root 2636856c-62cc-4195-8995-148eb8cfb30c
if loadfont /usr/share/grub/unicode.pf2 ; then
set gfxmode=auto
load_video
insmod gfxterm
insmod part_msdos
insmod ext2
set root="(hd1,msdos6)"
search --no-floppy --fs-uuid --set=root 2636856c-62cc-4195-8995-148eb8cfb30c
set locale_dir=($root)/boot/grub/locale
set lang=zh_CN
insmod gettext
fi
terminal_output gfxterm
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
if background_color 44,0,30; then
clear
fi
### END /etc/grub.d/05_debian_theme ###
### BEGIN /etc/grub.d/10_linux ###
function gfxmode {
set gfxpayload="$1"
if [ "$1" = "keep" ]; then
set vt_handoff=vt.handoff=7
else
set vt_handoff=
fi
}
if [ ${recordfail} != 1 ]; then
if [ -e ${prefix}/gfxblacklist.txt ]; then
if hwmatch ${prefix}/gfxblacklist.txt 3; then
if [ ${match} = 0 ]; then
set linux_gfx_mode=keep
else
set linux_gfx_mode=text
fi
else
set linux_gfx_mode=text
fi
else
set linux_gfx_mode=keep
fi
else
set linux_gfx_mode=text
fi
export linux_gfx_mode
if [ "$linux_gfx_mode" != "text" ]; then load_video; fi
menuentry "Ubuntu,Linux 3.2.0-23-generic-pae" --class ubuntu --class gnu-linux --class gnu --class os {
recordfail
gfxmode $linux_gfx_mode
insmod gzio
insmod part_msdos
insmod ext2
set root="(hd1,msdos6)"
search --no-floppy --fs-uuid --set=root 2636856c-62cc-4195-8995-148eb8cfb30c
linux /boot/vmlinuz-3.2.0-23-generic-pae root=UUID=2636856c-62cc-4195-8995-148eb8cfb30c ro quiet splash $vt_handoff
initrd /boot/initrd.img-3.2.0-23-generic-pae
}
menuentry "Ubuntu,Linux 3.2.0-23-generic-pae (恢复模式)" --class ubuntu --class gnu-linux --class gnu --class os {
recordfail
insmod gzio
insmod part_msdos
insmod ext2
set root="(hd1,msdos6)"
search --no-floppy --fs-uuid --set=root 2636856c-62cc-4195-8995-148eb8cfb30c
echo "载入 Linux 3.2.0-23-generic-pae "
linux /boot/vmlinuz-3.2.0-23-generic-pae root=UUID=2636856c-62cc-4195-8995-148eb8cfb30c ro recovery nomodeset
echo "载入初始化内存盘"
initrd /boot/initrd.img-3.2.0-23-generic-pae
}
### END /etc/grub.d/10_linux ###
### BEGIN /etc/grub.d/20_linux_xen ###
### END /etc/grub.d/20_linux_xen ###
### BEGIN /etc/grub.d/20_memtest86+ ###
menuentry "Memory test (memtest86+)" {
insmod part_msdos
insmod ext2
set root="(hd1,msdos6)"
search --no-floppy --fs-uuid --set=root 2636856c-62cc-4195-8995-148eb8cfb30c
linux16 /boot/memtest86+.bin
}
menuentry "Memory test (memtest86+, serial console 115200)" {
insmod part_msdos
insmod ext2
set root="(hd1,msdos6)"
search --no-floppy --fs-uuid --set=root 2636856c-62cc-4195-8995-148eb8cfb30c
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)" --class windows --class os {
insmod part_msdos
insmod ntfs
set root="(hd0,msdos1)"
search --no-floppy --fs-uuid --set=root 4C844B34844B2036
（本文来源于图老师网站，更多请访问https://m.tulaoshi.com/diannaorumen/）chainloader +1
}
### END /etc/grub.d/30_os-prober ###
menuentry "Windows xp" --class windows --class os {
insmod ntfs
set root="(hd0,1)"
（本文来源于图老师网站，更多请访问https://m.tulaoshi.com/diannaorumen/）search --no-floppy --fs-uuid --set=root 4C844B34844B2036
（本文来源于图老师网站，更多请访问https://m.tulaoshi.com/diannaorumen/）drivemap -s (hd0) ${root}
chainloader +1
}
### 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 ###
### BEGIN /etc/grub.d/41_custom ###
if [ -f $prefix/custom.cfg ]; then
source $prefix/custom.cfg;
fi
### END /etc/grub.d/41_custom ###
