kernel with no root filesystem

[sar_van81]

hi

can anyone say me whether is it possible to boot the kernel without a rootfilesystem ? Also can anyone say me what does the kernel image "vmlinux" contains and the rootfilesystem image contains ?


thanks in advance,

saravanan.

[daark.child]

You can have a kernel without support for the root filesystem, but you won't be able to boot the system without using an initial ram disk image. As for vmlinux, take a look here. When you said "root filesystem image" were you referring to the initial ramdisk image? If so, it contains modules and drivers that are used by the kernel during boot up.

[sar_van81]

Hi,

i think its not initial ramdisk image.but i'm not sure. Actually i built linux not for our host but for target board(MIPS based developement board). i created the cross compiler toolchain and the root file system (rootfs.ext2)using buildroot package. mounted this to a directory . then i downloaded the kernel alone and gave the path to the mounted root filesystem in kernel and compiled teh kernel. the final image "vmlinux " was created,ported and the board bootup sucessfully.

is this initial ram disk ?Also in this case does the kernel contains only modules and drivers ?

[kevkim55]

Rootfs is a ramfs inside the kernel itself which is used as a placeholder over which the initrd or other root filesystem gets mounted.

What you did was, to compile and generate a root filesystem which you integrated into the kernel itself using the buildroot package, finally ending up with a monolithic kernel including a root filesystem inside it.

Take a look into the link posted by daark.child to learn a bit more about the kernel image itself. As far as root filesystem is concened, it is like the name says a filesystem with the standard heirarchy of directories which include, the binaries (programs, libraries) and data etc. What exactly are the contents (what programs, libraries etc) of this root filesystem image is dependent upon what you really are trying to use it for.

If what you are wanting is to know the internals of linux kernel, you might wanna read the kernel source. Said that, I couldn't really guess, what exactly you're trying to know.