1、ubuntu@ubun:/usr/local$ cat /etc/default/grub
#If you change this file, run ‘update-grub’ afterwards to update
#/boot/grub/grub.cfg.
#For full documentation of the options in this file, see:
#info -f grub -n ‘Simple configuration’
#GRUB_DEFAULT=0
GRUB_DEFAULT="Advanced options for Ubuntu>Ubuntu, with Linux 4.15.0-72-generic"
#GRUB_DEFAULT=“1> 2”
#GRUB_TIMEOUT_STYLE=hidden
GRUB_TIMEOUT=10
GRUB_DISTRIBUTOR=lsb_release -i -s 2> /dev/null || echo Debian
GRUB_CMDLINE_LINUX_DEFAULT=“text”
#GRUB_CMDLINE_LINUX_DEFAULT=“quiet splash”
#GRUB_CMDLINE_LINUX=""
#Uncomment to enable BadRAM filtering, modify to suit your needs
#This works with Linux (no patch required) and with any kernel that obtains
#the memory map information from GRUB (GNU Mach, kernel of FreeBSD …)
#GRUB_BADRAM=“0x01234567,0xfefefefe,0x89abcdef,0xefefefef”
#Uncomment to disable graphical terminal (grub-pc only)
#GRUB_TERMINAL=console
#The resolution used on graphical terminal
#note that you can use only modes which your graphic card supports via VBE
#you can see them in real GRUB with the command `vbeinfo’
#GRUB_GFXMODE=640x480
#Uncomment if you don’t want GRUB to pass “root=UUID=xxx” parameter to Linux
#GRUB_DISABLE_LINUX_UUID=true
#Uncomment to disable generation of recovery mode menu entries
#GRUB_DISABLE_RECOVERY=“true”
#Uncomment to get a beep at grub start
#GRUB_INIT_TUNE=“480 440 1”
2、ubuntu@ubun: sudo update-grub
3、重新启动，现在应该默认启动旧的内核版本
ubuntu@ubun: sudo reboot