Systemd system and service manager in Fedora17

Systemd is a Linux system and service manager compatible with the SysV initialization script. It uses socket and D-Bus to enable the Service and provides a daemon-demand startup policy based on the daemon process, it can be used to manage started services, adjust running levels, and manage logs. To accelerate the entire system startup and start more processes in parallel, systemd creates a listening socket before the daemon starts, and then passes the socket to the daemon. During system initialization

Systemd is a Linux system and service manager compatible with the SysV initialization script. It uses socket and D-Bus to enable the Service and provides a daemon-demand startup policy based on the daemon process, it can be used to manage started services, adjust running levels, and manage logs.

To accelerate the entire system startup and start more processes in parallel, systemd creates a listening socket before the daemon starts, and then passes the socket to the daemon. During system initialization, first create a socket for all daemon and then start all daemon. If a service is not fully started because it requires the support of another service, and the connection may be queuing in the queue that provides the service, the client process will be blocked in this request. However, only this client process will be blocked, and it will only be blocked in this request. The dependencies between services no longer need to be configured to implement real parallel startup (because all sockets are enabled at a time, if a service needs other services, it can obviously connect to the corresponding socket ).

D-Bus activation policy starts the service: By using the Bus activation policy, the service can be started immediately upon access. At the same time, the Bus activation policy allows the system to use small consumption to enable synchronous requests between the provider and consumer of the D-Bus service. (Enable multiple services at the same time. If one service is faster than other services in the Bus activation policy, it queues its requests in D-Bus until other management determines its service information ).

Systemctl is the most important tool. It integrates the functions of service and chkconfig. You can use it to enable or disable services permanently or only in the current session. The following table lists the systemd commands and the equivalent commands corresponding to sysVinit.

/Sbin/service and/sbin/chkconfig can still work in the systemd environment, and will be translated as native equivalent commands if necessary.

Systemd introduces a concept: goal. Its usage is similar to the running level, but it runs differently. Each target is named by name rather than number, serving a specific purpose. Some goals are achieved by inheriting another goal and adding other additional services. Some systemd targets mimic the common sysvinit running level, so you can still switch the target through the familiar telinit RUNLEVEL. Run the 1:1 ing between 0, 1, 3, 5, and 6 on the pure Fedora system and a specific target. Unfortunately, similar conversions cannot be implemented for user-defined runtime Level 2 and Level 4. If you use these running levels, we recommend that you use the/etc/systemd/system/$ YOURTARGET method to create a new systemd target, create a directory named/etc/systemd/system/$ YOURTARGET based on an existing running level (you can view/lib/systemd/system/graphical.tar get as an example. wants, and then symbolic links to the extra services you want to enable to this directory (the services linked by symbolic links are located in/lib/systemd/system ).

For more information about Fedora, see Fedora topics page http://www.linuxidc.com/topicnews.aspx? Tid = 5