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In this lesson, I will explain Linux hardware management.

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So the Linux kernel is responsible for device management.

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So any hardware you want to use needs to be addressed by a Linux kernel module.

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And these modules work with specific device types.

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Kernel modules are included in InitRAMFS, and InitRAMFS is created when you install

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Linux.

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So it's created according to the hardware that was found and makes sure that all the

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essential drivers are available while booting.

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There's also a part of the hardware that can be loaded by the plug-and-play manager.

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And this plug-and-play manager is systemd-udev-d.

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So automatic on-demand device initialization is done by systemd-udev-d.

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And systemd-udev-d is defined by rules in uselib-udev-rules.d and etc-udev-rules.d.

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And that's pretty cool.

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You can customize these rules to make sure that specific actions will happen when a specific

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device is plugged in.

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So if you want a message to be logged to your syslog, or a file to be created, or whatever,

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if a device is plugged in, systemd-udev-d rules is what you need to do.

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That's beyond what you need to know for Linux Plus, so I won't explain it right here.

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So systemd-udev-d detects devices and will load the required kernel modules.

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And there's also a manual way of doing it, and that would be modprobe.

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And if you want to interface with devices, many, but not all of the devices have a device

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node file in slash dev.

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If you are going to use a hard disk, for instance, you use commands like mount slash dev slash

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sda1.

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Well, the dev sda1 is referring to your first partition, and this first partition addresses

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the appropriate kernel module to make sure that the device is initialized.

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And in this, the device nodes in the slash dev directory have a major number, and they

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have a minor number.

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And that indicates which kernel driver to use.

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And also, hardware-related parameters are stored in slash sys and its subdirectories.

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Let me show you a little bit of what's going on in this slash dev directory.

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So the part that I need you to be aware of is ls minus l slash dev slash, well, just

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slash dev.

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Here we can see all these device nodes.

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And in my list of device nodes, I'm looking up my storage device.

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I have an NVMe disk, and my NVMe disk is right here.

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And it's 259 comma 0.

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This is what matters.

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259 is the major, and the minor is 0.

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So the major addresses the driver.

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So here we can see 259 comma 1 for partition number 1, and so on.

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All of these devices have a major.

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And if you want to find out what that is, you need to have a look at the PROCFILE system,

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because in the PROCFILE system, there is a file with the name devices.

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The PROCFILE system is about kernel settings, about the current kernel state.

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If you investigate the PROCFILE system, you can learn so much about what is going on on

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your system.

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I'm going to use less on devices.

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And there we can see that it starts with a list of character devices.

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And then there is a list of block devices, where 259 is identified as a block ext.

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And block ext, well, that addresses the kernel functionality that is required.

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So there is a kernel module that makes sure that this device can be used.