15 Advanced Linux Interview Questions and Answers - http://linoxide.com/linux-how-to/advanc ... s-answers/
9) systemd over init system, What do you think?
Systemd is well designed. It was conceived from the top, not just to fix bugs, but to be a correct implementation of the base system services. A systemd, may refer to all the packages, utilities and libraries around daemon. It was designed to overcome the shortcomings of init. It itself is a background process which is designed to start processes in parallel, thus reducing the boot time and computational overhead. It has a lot other features as compared to init while Sysvinit was never designed to cope with the dynamic/event-based architecture of the current Linux kernel. The only reason why we still use it today is the cost of a migration.
Systemd ships a growing number of useful, unified command-line interfaces for system settings and control (timedatectl, bootctl, hostnamectl, loginctl, machinectl, kernel-install, localectl). In Debian, they use the existing configuration files without breaking compatibility.
Systemd makes the boot process much simpler, entirely removing the need to specify dependencies in many cases thanks to D-Bus activation, socket activation, file/inotify activation and udev integration.
Systemd supports SELinux integration while SysV doesn't
Systemd can handle the boot process from head to toe, without needing to use any of the existing shell scripts. Systemd extends the logging features of the system in many ways with journald, and can remain integrated with the existing rsyslog daemon. Logs are in a structured format, attributed to filename, line of code, PID and service. They include the early boot (starting from initramfs). They can be quickly filtered and programmatically accessed through an efficient interface.
Systemd unit files, unlike SysV scripts, can usually be shipped by upstream, or at least shared with other distributions (already more than 1000 existing unit files in Fedora) without any changes, the Debian specifics being handled by systemd itself.
Systemd is incredibly fast (1 second to boot). It was not designed with speed in mind, but doing things correctly avoids all the delays currently incurred by the boot process.
The transition plan is easy, since existing init scripts are treated as first-class services: scripts can depend (using LSB headers) on units, units can depend on scripts. More than 99% of init scripts can be used without a modification.
It is not just init. It unifies, in fewer lines of code, everything that is related to starting services and managing session groups: user login, cron jobs, network services (inetd), virtual TTY management… Having a single system to handle all of that allows us to remove a lot of cruft, and to use less memory on the system.
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