What is this depmod program thingy?
In our exploration of the Linux file system we come across an interestingly named file called "depmod". Normally it resides in your sbin folder. Thinking about this file you wonder if it is a link to Depeche Mode. No it is not a shortcut to Depeche Mode. Instead it is a file used for module dependencies for the Linux kernel. As you know the linux kernel is modular in that parts of the kernel can be loaded and unloaded while it is running. Not only that you can extend the kernel by adding extra modules to it. For example, you go and buy a TV card and plug it in. Unfortunately the Linux kernel you are using doesn't have support for that particular card. Or the current module for that card is a bit flaky. It is very easy to download or compile a module just for that card and insert it into the running kernel. This is a bit like the drivers for windows but you don't have to reboot afterwards. If that module doesn't work then you can easily remove it and try a different one. Sometimes though you will get a kernel panic (this is where the kernel runs around and screams and shouts) where it complains about some symbols not being found. This is because the module libraries have functions in them and to allow programs access to them those functions have symbols attached to them. These symbols are not neat little icons or musical instruments. They are just a unique code that the library and kernel and calling program can all relate to and find a common point. If a program calls a function in a module and the kernel doesn't know about that function then it throws the unable to find symbol error. This is where the "depmod" program comes to the rescue. What "depmod" does is go through the modules libraries and make a list of all of the modules and their dependencies it finds. This is all collected in a file called modules.dep although it could be called something else. This file normally resides in your boot directory snuggled up with your kernel. It is also very important to run this program when you compile your own custom kernels, again for the above reasons. Many distributions run this program automatically as part of their start up routine. So while we are disappointed that "depmod" is not a link to Depeche Mode. We applaud its function in allowing a common point for programs, modules and kernel to access the correct functions and we vow to have it residing on our file system in peace.