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]#