内容一：只是删除用户
# userdel <user>内容二：删除用户的同时还要删除家目录
# userdel -r <user>补充一：RHEL 系统自带标准用户参考
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/5/html/deployment_guide/s1-users-groups-standard-users
https://access.redhat.com/solutions/225183
补充二：RHEL 系统自带标准组参考
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/5/html/deployment_guide/s1-users-groups-standard-groups