CentOS 7 修改开机顺序.doc

CentOS 7 修改开机顺序

在笔记本电脑安装了win8与centOS 7。按照以往的惯例，安装完centOS时，会在／boot／grub／grub.conf里自动加入安装系统前其它系统的引导控制，但是实际上是没有的。
此文不探讨如何将先系统引导加入centOS 7的/boot/grub2/grub.cfg当中。
先查看我电脑上grub.cfg当中的内容如下（注意加粗内容）：

[root@localhost grub2]# cat grub.cfg
# DO NOT EDIT THIS FILE
#
# It is automatically generated by grub2-mkconfig using templates
# from /etc/grub.d and settings from /etc/default/grub
#

### BEGIN /etc/grub.d/00_header ###
set pager=1

if [ -s $prefix/grubenv ]; then
load_env
fi
if [ "${next_entry}" ] ; then
set default="${next_entry}"
set next_entry=
save_env next_entry
set boot_once=true
else
set default="${saved_entry}"
fi

if [ x"${feature_menuentry_id}" = xy ]; then
menuentry_id_option="--id"
else
menuentry_id_option=""
fi

export menuentry_id_option

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 load_video {
if [ x$feature_all_video_module = xy ]; then
insmod all_video
else
insmod efi_gop
insmod efi_uga
insmod ieee1275_fb
insmod vbe
insmod vga
insmod video_bochs
insmod video_cirrus
fi
}

terminal_output console
if [ x$feature_timeout_style = xy ] ; then
set timeout_style=menu
set timeout=5
# Fallback normal timeout code in case the timeout_style feature is
# unavailable.
else
set timeout=5
fi
### END /etc/grub.d/00_header ###
### Begin with windows 8##########

menuentry 'CentOS Linux (3.10.0-123.13.2.el7.x86_64) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-123.el7.x86_64-advanced-337b5933-c8eb-4c4e-8e7d-3a1f7aaa1e73' {
load_video
set gfxpayload=keep
insmod gzio
insmod part_msdos
insmod xfs
set root='hd0,msdos2'
if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos2 --hint-efi=hd0,msdos2 --hint-baremetal=ahci0,msdos2 --hint='hd0,msdos2' 337b5933-c8eb-4c4e-8e7d-3a1f7aaa1e73
else
search --no-floppy --fs-uuid --set=root 337b5933-c8eb-4c4e-8e7d-3a1f7aaa1e73
fi
linux16 /boot/vmlinuz-3.10.0-123.13.2.el7.x86_64 root=UUID=337b5933-c8eb-4c4e-8e7d-3a1f7aaa1e73 ro vconsole.keymap=us vconsole.font=latarcyrheb-sun16 rhgb quiet LANG=zh_CN.UTF-8
initrd16 /boot/initramfs-3.10.0-123.13.2.el7.x86_64.img
}
menuentry 'Windows 8(loader)(on /dev/sda1)' --class windows --class or $menuentry_id_option 'osprober-chain-140E68540E6830C2'{
insmod part_msdos
insmod ntfs
set root='hd0,msdos1'
chainloader +1
}

### BEGIN /etc/grub.d/10_linux ###
menuentry 'CentOS Linux, with Linux 3.10.0-123.el7.x86_64' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-123.el7.x86_64-advanced-337b5933-c8eb-4c4e-8e7d-3a1f7aaa1e73' {
load_video
set gfxpayload=keep
insmod gzio
insmod part_msdos
insmod xfs
set root='hd0,msdos2'
if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos2 --hint-efi=hd0,msdos2 --hint-baremetal=ahci0,msdos2 --hint='hd0,msdos2' 337b5933-c8eb-4c4e-8e7d-3a1f7aaa1e73
else
search --no-floppy --fs-uuid --set=root 337b5933-c8eb-4c4e-8e7d-3a1f7aaa1e73
fi
linux16 /boot/vmlinuz-3.10.0-123.el7.x86_64 root=UUID=337b5933-c8eb-4c4e-8e7d-3a1f7aaa1e73 ro vconsole.keymap=us vconsole.font=latarcyrheb-sun16 rhgb quiet LANG=zh_CN.UTF-8
initrd16 /boot/initramfs-3.10.0-123.el7.x86_64.img
}
menuentry 'CentOS Linux, with Linux 0-rescue-96f17ff7113c494a98433dd3c1be3974' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-0-rescue-96f17ff7113c494a98433dd3c1be3974-advanced-337b5933-c8eb-4c4e-8e7d-3a1f7aaa1e73' {
load_video
insmod gzio
insmod part_msdos
insmod xfs
set root='hd0,msdos2'
if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos2 --hint-efi=hd0,msdos2 --hint-baremetal=ahci0,msdos2 --hint='hd0,msdos2' 337b5933-c8eb-4c4e-8e7d-3a1f7aaa1e73
else
search --no-floppy --fs-uuid --set=root 337b5933-c8eb-4c4e-8e7d-3a1f7aaa1e73
fi
linux16 /boot/vmlinuz-0-rescue-96f17ff7113c494a98433dd3c1be3974 root=UUID=337b5933-c8eb-4c4e-8e7d-3a1f7aaa1e73 ro vconsole.keymap=us vconsole.font=latarcyrheb-sun16 rhgb quiet
initrd16 /boot/initramfs-0-rescue-96f17ff7113c494a98433dd3c1be3974.img
}
if [ "x$default" = 'CentOS Linux, with Linux 3.10.0-123.el7.x86_64' ]; then default='Advanced options for CentOS Linux>CentOS Linux, with Linux 3.10.0-123.el7.x86_64'; fi;
### 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_ppc_terminfo ###
### END /etc/grub.d/20_ppc_terminfo ###

### BEGIN /etc/grub.d/30_os-prober ###
### 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 ###

### BEGIN /etc/grub.d/41_custom ###
if [ -f ${config_directory}/custom.cfg ]; then
source ${config_directory}/custom.cfg
elif [ -z "${config_directory}" -a -f $prefix/custom.cfg ]; then
source $prefix/custom.cfg;
fi

细心查看上面的引导脚本，发现还有一个文件，就是grub2文件夹里面的文件grubenv。发现，开机引导那个系统是以这个文件里面的参数来确定的。
再查看这个文件里面的内容是什么。
[root@localhost grub2]# cat grubenv
# GRUB Environment Block

saved_entry=CentOS Linux (3.10.0-123.13.2.el7.x86_64) 7 (Core)
###########################################################################################################################################################################################################################################

于是按照grub.cfg里面的内容来修改grubenv的内容，先注释原来的内容，再加上自己需要引导的标题，内容如下：

[root@localhost grub2]# cat grubenv
# GRUB Environment Block

#saved_entry=CentOS Linux (3.10.0-123.13.2.el7.x86_64) 7 (Core)
#########################################################################################################################################
saved_entry=Windows 8(loader)(on /dev/sda1)

再保存一下文件。这样就可以自己的需要来改变开机引导顺序了。