systemctl

System Service Manager Directives

Supplementary instructions

systemctl command is a system service manager command, which actually combines the two commands service and chkconfig.

Tasks	Old Commands	New Commands
Make a service start automatically	chkconfig --level 3 httpd on	systemctl enable httpd.service
Prevent a service from starting automatically	chkconfig --level 3 httpd off	systemctl disable httpd.service
Check service status	service httpd status	systemctl status httpd.service (service details) systemctl is-active httpd.service (only shows whether Active)
Show all started services	chkconfig --list	systemctl list-units --type=service
Start service	service httpd start	systemctl start httpd.service
Stop service	service httpd stop	systemctl stop httpd.service
Restart service	service httpd restart	systemctl restart httpd.service
Reload service	service httpd reload	systemctl reload httpd.service

Example

systemctl start nfs-server.service . # Start nfs service
systemctl enable nfs-server.service # Set up auto-start at boot
systemctl disable nfs-server.service # Stop auto-start at boot
systemctl status nfs-server.service # View the current status of the service
systemctl restart nfs-server.service # Restart a service
systemctl list-units --type=service # View all started services

Open firewall port 22

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

If you still have problems, it may be caused by SELinux

Turn off SElinux:

Modify SELINUX="" in the /etc/selinux/config file to disabled, and then restart.

Turn off the firewall completely:

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