-a, --all
print all information, in the following order, except omit -p
and -i if unknown:
-s, --kernel-name
print the kernel name
-n, --nodename
print the network node hostname
-r, --kernel-release
print the kernel release
cat /etc/redhat-release 看linux的版本
原文：https://www.cnblogs.com/todayORtomorrow/p/10507389.html