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- [Instructor] Let's talk more

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about the Linux kernel modules,

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dependencies, and the use count.

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So remember,

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the last two columns from lsmod show the use count,

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typically a small integer value

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like one or zero or maybe a little bit more.

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And then we have a list of modules separated by commas.

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Those are the used by modules.

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So the last one here, LLC, is used by STP and GARP.

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And the use count does not have to match those dependencies.

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A module can be in use

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even if another module doesn't need it.

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For example,

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if a process has opened up a file associated with a module,

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a driver module typically,

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then that would increment the use count.

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In general, the use count is used by the kernel

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to say a module's in use, and don't remove it.

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In the old days, the kernel

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would remove modules automatically that weren't in use.

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That turned out to be a bad idea (laughing)

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because removing modules is kind of risky.

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So the use counts may be not all that important

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'cause you don't want to be removing modules, typically.

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Dependency list is sometimes important

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because you can struggle to get a module loaded,

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because it needs modules

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and there's some sort of issue there.

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So the modules.dep file,

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and then there's a binary version of it

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that's actually faster to use,

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but modprobe uses the modules.dep files.

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When you modprobe a module,

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it's going to look up that module in the file,

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get the path to the module,

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and then also see what that module depends on

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and will load those modules.

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Incidentally, that's a comprehensive list,

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it doesn't have to like keep lookin' through the file

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to see if there's more.

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So here I grepped garp.ko,

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and I see the first line is the entry for the garp.ko.zst,

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and it depends on two other modules, STP and LLC.

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And then we see the line for the 8021q.

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And that depends on GARP,

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and that also depends on several other modules.

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So the GARP showed up in two cases,

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the module itself, and a module that depended on it.

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That's what modules.dep is all about.