Monday, January 24, 2011

Will modules installed by insmod command persist after rebooting?

There is how the book I'm reading describe the insmod utility:

The program loads the module code and data into the kernel, which, in turn, performs a function similar to that of ld, in that it links any unresolved symbol in the module to the symbol table of the kernel. Unlike the linker, however, the kernel doesn’t modify the module’s disk file, but rather an in-memory copy.

It looks like it won't persist since it's in-memory, but I'm not sure.

  • No, they won't. After rebooting, you begin from scratch.

    Normally, for modules that you want loaded after every reboot, there's a configuration file listing modules to be auto-loaded at boot time.

    Look at /etc/modules.

    man modules:

    NAME
       /etc/modules - kernel modules to load at boot time
    
    DESCRIPTION
       The  /etc/modules file contains the names of kernel modules that are to
       be loaded at boot time, one per line. Arguments can  be  given  in  the
       same line as the module name. Lines beginning with a '#' are ignored.
    
  • Modules manually loaded using insmod do not persist when your system is rebooted (for that behavior see the manpage for modules.confmodules, which essentially runs insmod automatically on reboot, but with a bit more intelligence).

    ed: modules, not modules.conf (the latter is useful if you're writing a custom module with dependencies)

    From voretaq7

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