CentOS6服务用chkconfig控制，CentOS7改为systemd控制
1 systemd
systemd is a suite of basic building blocks for a Linux system. It provides a system and service manager that runs as PID 1 and starts the rest of the system. systemd provides aggressive parallelization capabilities, uses socket and D-Bus activation for starting services, offers on-demand starting of daemons, keeps track of processes using Linux control groups, maintains mount and automount points, and implements an elaborate transactional dependency-based service control logic. systemd supports SysV and LSB init scripts and works as a replacement for sysvinit. Other parts include a logging daemon, utilities to control basic system configuration like the hostname, date, locale, maintain a list of logged-in users and running containers and virtual machines, system accounts, runtime directories and settings, and daemons to manage simple network configuration, network time synchronization, log forwarding, and name resolution.
service位于/usr/lib/systemd/system/
列出所有的unit
# systemctl list-unit-files
# systemctl list-unit-files --type=service
启动、停止、重启、查询状态
# systemctl start docker
# systemctl stop docker
# systemctl restart docker
# systemctl status docker
查看日志
# journalctl -u docker
# journalctl -u docker -f
开机启动设置、取消
# systemctl enable docker
# systemctl disable docker
参考：https://www.freedesktop.org/wiki/Software/systemd/
2 chkconfig
chkconfig provides a simple command-line tool for maintaining the /etc/rc[0-6].d directory hierarchy by relieving system administrators of the task of directly manipulating the numerous symbolic links in those directories.
This implementation of chkconfig was inspired by the chkconfig command present in the IRIX operating system. Rather than maintaining configuration information outside of the /etc/rc[0-6].d hierarchy, however, this version directly manages the symlinks in /etc/rc[0-6].d. This leaves all of the configuration information regarding what services init starts in a single location.
chkconfig has five distinct functions: adding new services for management, removing services from management, listing the current startup information for services, changing the startup information for services, and checking the startup state of a particular service.
将service放到目录/etc/init.d/
列出服务
# chkconfig --list
添加、删除服务
# chkconfig --add httpd
# chkconfig --del httpd
开机启动设置、取消
# chkconfig httpd on
# chkconfig httpd off
参考：https://linux.die.net/man/8/chkconfig