grub2-set-default

 1Usage: grub2-set-default [OPTION] MENU_ENTRY
 2Set the default boot menu entry for GRUB.
 3This requires setting GRUB_DEFAULT=saved in /etc/default/grub.
 4
 5  -h, --help              print this message and exit
 6  -v, --version           print the version information and exit
 7  --boot-directory=DIR    expect GRUB images under the directory DIR/grub2
 8                          instead of the /boot/grub2 directory
 9
10MENU_ENTRY is a number, a menu item title or a menu item identifier.
11
12Report bugs to <bug-grub@gnu.org>.

1# awk -F\' '$1=="menuentry " {print $2}' /etc/grub2.cfg
2CentOS Linux (5.4.219-1.el7.elrepo.x86_64) 7 (Core)
3CentOS Linux (3.10.0-1160.76.1.el7.x86_64) 7 (Core)
4CentOS Linux (3.10.0-862.el7.x86_64) 7 (Core)
5CentOS Linux (0-rescue-3221d376917c458992a952d6327f2d6a) 7 (Core)

1# grub2-set-default 0

1~]# init 6
2```[来源](https://github.com/jaywcjlove/linux-command)：https://github.com/jaywcjlove/linux-command