systemd new features: implement the service started in parallel when the system boots. Demand activation process system state snapshot dependency-based service control logic definition of core concepts: unit (unit) configuration file identification and configuration, file system contains the main service, listening socket, save a snapshot of the system and other relevant information init file is saved to: / usr / lib / systemd / system / RUN / systemd / system / etc / systemd / system Unit type: -service Unit: file extension .service, for defining a service system Target unit: file extension .target, for analog achieve operational level device unit: .device used to define the core recognition device mount unit: .mount definition file system mount point socket unit: .socket, identify the process for inter-socket communication file snapshot unit: management system snapshot swap unit : identifies the swap device automount unit: .automount mount point for the file system path unit: .path definition file system for a file or directory key features: Based on the activation mechanism of the socket, socket and separate service program based on the activation mechanism of the bus; based device activation mechanism of activation mechanism path based system snapshot backward compatibility sysv init scripts. Incompatible: systemctl command fixed, non-started by systemd service, systemctl unable to communicate with management systems and services: CENTIOS 7: Service Unit Note compatible service early script command: systemctl the COMMAND name.service systemctl Start name.service systemctl name.service STOP systemctl status name.service systemctl restart name.service conditions restarted: systemctl try-restart name.service view the current state of service: IS-systemctl the Active name.service ------------- ------------------------------------------------- location: Home »system management» systemctl systemctl command process and the job management service management system systemctl command instructions, it is actually a combination of these two command service and chkconfig together. The new directive tasks the old directive Make a service to start automatically chkconfig --level 3 httpd on systemctl enable httpd.service make a service does not start automatically chkconfig --level 3 httpd off systemctl disable httpd.service check the service status httpd Status systemctl Status httpd.service Service (Service Details ) systemctl is-active httpd.service (display only if Active) shows all the services started chkconfig --list systemctl list-units --type = service to start a service service httpd start systemctl start httpd.service stop a service service httpd stop systemctl stop httpd.service target Units: restart a service service httpd restart systemctl restart httpd.service Show all services: chkconfig --list systemctl list-units --type = service --all View all service startup state-Unit-Files List systemctl --type = Service unit profile .target run level: 0 ==== runlevel0.target poweroff shutdown 1 ==== runlevel1.target rescue.target rescue mode 2 ===== runlevel2.target multi-user.target 3 ==== runlevel3.target multi-user.target = . 4 ==== runlevel4.target multi-user.target # 2. 4. 3 the same level as 5 ==== runlevel5.target GUI level graphical.target . 6 ==== runlevel6.target reboot .target level switching: the init N ==== systemctl the isolate name.target systemctl switched to the isolate # graphical.target graphical interface systemctl list-units --type target # Check load level ------------ -------------------------------------------------- basic.target loaded active active Basic System cryptsetup.target loaded active active Encrypted Volumes getty.target loaded active active Login Prompts graphical.target loaded active active Graphical Interface local-fs-pre.target loaded active active Local File Systems (Pre) local-fs.target loaded active active Local File Systems multi-user.target loaded active active Multi-User System network-online.target loaded active active Network is Online network-pre.target loaded active active Network (Pre) network.target loaded active active Network paths.target loaded active active Paths remote-fs.target loaded active active Remote File Systems the Active Slices loaded the Active slices.target systemctl reboot reboot sockets.target loaded active active Sockets Swap the Active loaded the Active swap.target sysinit.target the Active loaded the Active System the Initialization timers.target the Active loaded the Active Timers ---------------------------- --------------------------- get the default run level: / etc / inittab systemctl gET-default modify the default level of / etc / inittab systemctl set- default graphical.target or modify the configuration file /etc/systemd/system/default.target /usr/lib/systemd/system/multi-user.target. the etc user lib is connected to the file of the soft switch to rescue mode: systemctl emergemcy other commonly used commands systemctl halt shutdown systemctl poweroff shutdown systemctl suspend pending systemctl hiberate snapshot systemctl hybrid-sleep 快照并且挂起 -------------------------------------------------------- System Commands: is-system-running Check whether system is fully running default Enter system default mode rescue Enter system rescue mode emergency Enter system emergency mode halt Shut down and halt the system poweroff Shut down and power-off the system reboot [ARG] Shut down and reboot the system kexec Shut down and reboot the system with kexec the Request User instance Exit Exit switch-root ROOT [INIT] Change to a different root file system Suspend the Suspend The System Hibernate the Hibernate The System Hybrid and the Hibernate Suspend-SLEEP The System ----------------------------- -------------------------------------- systemctl List-view the dependencies httpd.service # dependency systemctl reload-or-restart # reload or restart the service ban is set to boot from Kai: systemctl mask name.service cancel the setting systemctl umask name.service