Linux initialization init system-sysvinit, Upstart, SYSTEMD

Start by understanding the following changes to the Ubuntu runlevel (init) corresponding tool history:

1, Ubuntu 6.10 and previous versions use Sysvinit.

2, Ubuntu 14.10 and the previous version of the use of upstart but still keep sysvinit coexist.

Https://wiki.ubuntu.com/Upstart

Https://help.ubuntu.com/community/UpstartHowto

3, Ubuntu 15.04 started using SYSTEMD, but you can choose to use the SYSTEMD or upstart in the boot option, but not the same time using sysvinit or upstart coexist.

Https://wiki.ubuntu.com/SystemdForUpstartUsers

The entire Linux init development history:

Https://zh.wikipedia.org/wiki/Init

Detailed introduction of three systems: Sysvinit, Upstart, SYSTEMD

Sysvinit:https://www.ibm.com/developerworks/cn/linux/1407_liuming_init1/index.html

Upstart:https://www.ibm.com/developerworks/cn/linux/1407_liuming_init2/index.html

Systemd:https://www.ibm.com/developerworks/cn/linux/1407_liuming_init3/index.html

Summary sysvinit:

For the other two items that have been introduced on Ubuntu, the main thing is that Sysvinit has a long history, primarily a shell script, and is placed under the/etc/init.d folder. The start of the service is then performed by the UPDATE-RC.D command at run-level operations. Here are some of the service scripts that are written as references:

In fact the system provides the documentation in/ETC/INIT.D/README

https://gist.github.com/naholyr/4275302

Https://www.cyberciti.biz/tips/linux-write-sys-v-init-script-to-start-stop-service.html

Linux initialization init system-sysvinit, Upstart, SYSTEMD