Consider not download automatically (all) kernel modules

[moul]

On some kernels, we have about 470MB of optional kernel modules.

On the on the Alpine Linux image, it is ridiculusly 15 times higher than the 30MB original image size 😳.

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Potential ways of optimization:

• disable some loadable kernel modules
• build more loadable kernel modules in the kernel (seems smaller in size when built-in)
• do not call the sync-kernel-modules automatically but document it
• find a way to "lazy-download" needed kernel modules
• mount /lib/modules as a read-only network block device/nfs
• use a compressed file system for /lib/modules

cc @QuentinPerez, @brmzkw, @bchatelard, @aimxhaisse

[ElNounch]

A PoC using CephFs, mounting /lib/modules read-only.
master...ElNounch:PoC-CephFs-KernelModules

[moul]

@ElNounch, you're awesome

Thank you for this PoC, we will discuss it internally, but I clearly like the idea

And thank you for the other non-POC related updated (typos, init script headers)