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In this video, you'll learn about the system V init legacy boot procedure. So what is this

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about? Well, this is about how we booted before system D. System D has been the standard for

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over a decade. So you won't find many systems anymore that use system V, also known as system

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V, which is named after the system V Unix distribution that already used this way of

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booting. System D booting replaces the system V legacy boot, where slash sbin slash init

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was the PID1 loaded by the kernel and responsible for booting everything else. Now in system

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V boot, the run level was used to define the state that the system should start in. And

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the etc init tab file was used to set the default run level in which the system would

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enter. So in system V boot, we had etc init tab to set the default run level. And you

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could use init or tell init commands to manage the current run level temporarily. Where run

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level five was for graphical, run level three was for multi-user. So if you would be in

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graphical, and you wanted to go to multi-user, you would use init three. And to start a

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different run level while booting, the number of the run level could be added at the end

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of the line that boots a kernel in grub. System V services were managed with service

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commands. So you would have service followed by the name of the service, followed by start,

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stop, status, or restart to perform one of the respective operations on them. And every

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now and then you still might have to do that if system D is not available. Now the service

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commands are for managing services individually. If you wanted to make sure that the service

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was toggled to be automatically enabled or disabled, you would use check config. So check

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config, HTTP on would make sure that on Red Hat the HTTP service would be started

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automatically. System V booting is legacy. It's old. And for that reason, you should not

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search for system V compatibility while using system D, but use system D solutions. So nobody

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is using these options anymore unless you encounter a distribution where you get a system

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CTL command not found. If that is the case, use the service command instead. But fortunately,

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that's going to be pretty rare.