securitybreach Posted May 28, 2015 Share Posted May 28, 2015 You may be aware that Debian has switched from SysV to systemd as the init system. As a result systemd is the default init system for the recently released Debian 8. This switch may have some users confused, and the aim of this article is to resolve some of those confusions. Systemd is a System Management daemon. It is responsible for choosing the appropriate drivers upon system boot, enable network connection, start system services and bring the graphical interface upon login. On the other hand the old SysV init (which stands for ‘initialization”) just executed scripts located in the /etc/init.d directory. The change There was a dire need for the successor of the aging init system. Multiple replacements were developed such as Upstart, Epoch and Mudar to tacle some of the challenges of modern systems. The reason for the replacement is within the init daemon and the way it works. Upon system startup init is the first process started. It starts the other tasks, but one tasks starts only if the previous one has loaded successfully. As you can imagine this can cause huge delays during system boot. Systemd starts the daemons at the same time, which makes the boot process much faster. How it works? As mentioned, systemd starts daemons at the same time. This is done by using sockets for all services. It is creating sockets for daemons and organizes them as they start up. This may sound confusing so let me give you an example. Lets say daemon A requires support from daemon B, but daemon B has not started yet. Daemon A will not have to wait for daemon B to start. To avoid delays, systemd writes the request in daemon B’s socket and it continues. That way daemon A does not need to wait for daemon B. That way parallel processing is possible and the system can boot significantly faster. What else you need to know? The configuration for systemd tasks are kept in files called “unit”. Due to this there are different unit types: service socket device mount automount swap timer snapshot target,.......... http://www.linuxveda...stemd-debian-8/ Quote Link to comment Share on other sites More sharing options...
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