导读 GNU GRUB（GRand Unified Bootloader简称“GRUB”）是一个来自GNU项目的多操作系统启动程序。GRUB是多启动规范的实现，它允许用户可以在计算机内同时拥有多个操作系统，并在计算机启动时选择希望运行的操作系统。GRUB可用于选择操作系统分区上的不同内核，也可用于向这些内核传递启动参数。

环境：Red Hat Enterprise Linux Server release 7.3

查看系统信息并重现故障
[root@localhost ~]# lsb_release -a
LSB Version: :core-4.1-amd64:core-4.1-noarch:cxx-4.1-amd64:cxx-4.1-noarch:desktop-4.1-amd64:desktop-4.1-noarch:languages-4.1-amd64:languages-4.1-noarch:printing-4.1-amd64:printing-4.1-noarch
Distributor ID: RedHatEnterpriseServer
Description: Red Hat Enterprise Linux Server release 7.3 (Maipo)
Release: 7.3
Codename: Maipo
[root@localhost ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/rhel-root 50G 22G 29G 43% /
devtmpfs 1.9G 0 1.9G 0% /dev
tmpfs 1.9G 88K 1.9G 1% /dev/shm
tmpfs 1.9G 9.0M 1.9G 1% /run
tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup
/dev/sda1 1014M 174M 841M 18% /boot
/dev/sr0 3.6G 3.6G 0 100% /media/cdrom
/dev/mapper/rhel-home 46G 33M 46G 1% /home
tmpfs 378M 8.0K 378M 1% /run/user/0
[root@localhost grub2]# grub2-install -V
grub2-install (GRUB) 2.02~beta2
#用grub2-install --version也可以查看grub版本信息
[root@localhost ~]# ls /boot/grub2/
device.map fonts grub.cfg grubenv i386-pc locale themes
[root@localhost ~]# rm -rf /boot/grub2/grub.cfg
[root@localhost ~]# reboot
故障重现

手动引导系统

重装grub
[root@localhost ~]# ls /boot/grub2/
device.map fonts grubenv i386-pc locale themes
[root@localhost ~]# grub2-mkconfig > /boot/grub2/grub.cfg
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-3.10.0-514.el7.x86_64
Found initrd image: /boot/initramfs-3.10.0-514.el7.x86_64.img
Found linux image: /boot/vmlinuz-0-rescue-f0bcb62b11a44643824cde1c7f3833e4
Found initrd image: /boot/initramfs-0-rescue-f0bcb62b11a44643824cde1c7f3833e4.img
done
[root@localhost ~]# ls /boot/grub2/
device.map fonts grub.cfg grubenv i386-pc locale themes
[root@localhost ~]# reboot
#重启验证修复结果



重启后能再次成功进入系统，说明修复成功！

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