rhel7 升级内核，保证grub2启动时为默认项目
[root@server0 ~]# uname-r
3.10.0-123.el7.x86_64
[root@server0 ~]#cd Downloads/
[root@server0 Downloads]# ls
kernel-3.10.0-123.el7.x86_64.rpm
[root@server0 Downloads]# rpm -ivh kernel-3.10.0-123.el7.x86_64.rpm
warning:kernel-3.10.0-123.el7.x86_64.rpm: Header V3 RSA/SHA256 Signature, key IDfd431d51: NOKEY
Preparing... ################################# [100%]
package kernel-3.10.0-123.el7.x86_64 isalready installed
[root@server0 Downloads]#
