Lately, Debian has chosen systemd as the service manager. Now, systemd will be default. First discussion was started two years ago. A lot of team members would like to change the archaic system and put changes. They did not want to SysVinit. Lately, systemd was popular on the RedHat systems like Fedora, CentOS and Mandriva. If system supports systemd then it has not to sign CLA. One of developers from Redhat told: "And yeah, without the CLA, we would very likely have worked on upstart, instead of starting the systemd project." Ok, but at first the question is: “What is systemd? What is SysVinit?” In that case, let us to start from the beginning.
Init is first program who was run with Linux by kernel. Init runs all the processes. It uses a lot of start scripts. A lot of implementations of init exist on Linux and Unix systems. The most popular are systemd, sysvinit and upstart. Scripts are run from /etc/rc.d or /etc/init.d directories. They are sort according to the level of action. Regular files in /etc/rc.d or /etc.init.d are starting scripts and they are run by boot of system. Sysvinit package contains programs to control the startup, operation and shutdown of all other programs. Sysvinit depends on: Binutils, Coreutils, GCC, Glibc and Make. For the issue of 7.0 Wheezy including init daemon default in Debian is sysvinit. It is old, sequential model of system startup System V style.One of the implementation of init is systemd. Systemd is a new default implementation of the init Debian GNU / Linux. It is compatible with SysVinit and Linux Standard Base. It has a possibility of running services parallel. It runs services through the slot and launches services on-demand. It can follow operation processes using cgroups. It has support for saving and restoration of the service in the system and maintains of mounting point. It is run as a replacement for sysvinit and implements the service control transaction logic based on the relationship. Deamon calls systemd (system deamon) because on Linux name of deamons are written in lowercase. Upstart is a replacement for init daemon too. It supports running tasks during power on system and stopping tasks during shutdown. It controls of the task after running. It was designed to eliminate the problem of connected devices. It organizes boot sequence dynamically. However, it has many advantages - it`s fast, handles depending on when you start, it has backwards compatibility and is actively developed - many people also draws attention to its shortcomings. It serves not only the init function, but also deals with other tasks, which raise concerns about security and stability. Use certain features found only on this operating system, developers are not even interested in running systemd on other UNIX systems (hence the decision to change does not apply to non-Linux Debian architecture). Die-hard opponents of systemd, however do not have to overly worry: other implementations of init continue to be available in Debian and you will be able to use them just as they are now.