So, after follow all steps in this tuto: "digitalhermit.com/linux/Kernel-Build-HOWTO.html" whe I rebooted my pc I obtained this error message:

VFS cannot open root device "LABEL=/" or unknown-block(0,0)
please append a correct "root=" boot opt

kernel panic-not syncing:VFS: Unable to mount root fs on unknown-block (0,0)

so what is that? what did I wrong?

thanks for your advices

Have you compiled the FileSystem into your kernel or have you made it a module? This is the most common mistake that causes this error.

It has to be compiled in for root, since you can't mount root to read the module.

Thanks Ieonscape but, forgive me, I don´t understand what do you mean?, do you talk about some options in "make menuconfig" step?, I think that you´re trying to tell me that the filesystems option I put it as a "module", and It has to be as a root, is it right?, if it doesn´t, can you explain me?

thanks

Okay I'll try and explain, as I wasn't to clear before

The filesystem of root ( ext2, ext3, reiserfs etc.. ) has to be compiled into the kernel ( marked with a * ), and not made as a module ( marked with a M ). when you do make menuconfig.

Otherwise the kernel can't read the root partition.

If you think about it you'll see that the kernel reads the modules from root.
Now if you've compiled the filesystem of root as a module, then the kernel can't read root to get the module to read root. Its hard to explain, but read it again and you'll get it

The other reason to get this error is a configuration error in your bootloader either LILO or GRUB, but thats less common.