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Explain init for the newbier

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Ciro Santilli
2017-10-29 20:27:13 +00:00
parent 6a17c51131
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README.md
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@@ -264,6 +264,20 @@ For convenience, we also setup a symlink from `S99` to `rootfs_overlay/etc/init.
Scripts under `/etc/init.d` are run by `/etc/init.d/rcS`, which gets called by the line `::sysinit:/etc/init.d/rcS` in `/etc/inittab`. Scripts under `/etc/init.d` are run by `/etc/init.d/rcS`, which gets called by the line `::sysinit:/etc/init.d/rcS` in `/etc/inittab`.
### What is the init executable?
When the Linux kernel finishes booting, it runs an executable as the first and only userland process.
The default path is `/init`, but we an set a custom one with the `init=` kernel command line argument.
This process is then responsible for setting up the entire userland (or destroying everything when you want to have fun).
This typically means reading some configuration files (e.g. `/etc/initrc`) and forking a bunch of userland executables based on those files.
systemd is a "popular" `/init` implementation for desktop distros as of 2017.
BusyBox provides its own minimalistic init implementation which Buildroot uses by default.
### Custom init ### Custom init
Is the default BusyBox `/init` too bloated for you, minimalism freak? Is the default BusyBox `/init` too bloated for you, minimalism freak?