systemctl命令

systemctl命令是系统服务管理器指令，它实际上将 service 和 chkconfig 这两个命令组合到一起。

任务	旧指令	新指令
使某服务自动启动	chkconfig --level 3 httpd on	systemctl enable httpd.service
使某服务不自动启动	chkconfig --level 3 httpd off	systemctl disable httpd.service
检查服务状态	service httpd status	systemctl status httpd.service(服务详细信息)systemctl is-active httpd.service (仅显示是否 Active)
显示所有已启动的服务	chkconfig --list	systemctl list-units --type=service
启动某服务	service httpd start	systemctl start httpd.service
停止某服务	service httpd stop	systemctl stop httpd.service
重启某服务	service httpd restart	systemctl restart httpd.service

实例

1.启动nfs服务

systemctl start nfs-server.service

2.设置开机自启动

systemctl enable nfs-server.service

3.停止开机自启动

systemctl disable nfs-server.service

4.查看服务当前状态

systemctl status nfs-server.service

5.重新启动某服务

systemctl restart nfs-server.service

6.查看所有已启动的服务

systemctl list -units --type=service

7.开通防火墙22端口

iptables -I INPUT -p tcp --dport 22 -j accept

如果仍然有问题关闭SElinux
修改/etc/selinux/config文件中的SELINUX=disabled，然后重启。

8.彻底关闭防火墙

systemctl status firewalld.service
systemctl stop firewalld.service          
systemctl disable firewalld.service