centos view system and kernel version

1. Check the system version / etc / redhat-release

[root@gitlab ~]# cat /etc/redhat-release 
CentOS Linux release 7.5.1804 (Core)

2. Check the kernel version uname -a or / proc / version

a/

[root@gitlab ~]# uname -a
Linux gitlab 3.10.0-862.el7.x86_64 #1 SMP Fri Apr 20 16:44:24 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

b/

[root@gitlab ~]# cat /proc/version 
Linux version 3.10.0-862.el7.x86_64 ([email protected]) (gcc version 4.8.5 20150623 (Red Hat 4.8.5-28) (GCC) ) #1 SMP Fri Apr 20 16:44:24 UTC 2018