On 27/08/07, Robert P. J. Day <rpjday@xxxxxxxxxxxxxx> wrote: > > based on a thread or two on some other mailing lists, i'm trying to > clarify what can be de-selected in terms of ramdisk or ramfs or initrd > support when building a kernel. > > it all started when someone noticed this in fs/Kconfig: > > ===== > config RAMFS > bool > default y ... > > i'm sure you can appreciate that it's a little odd to have a Kconfig > option that is hard-selected to yes, while its own help text suggests > that it can be built as a module, and possibly be de-selected in its > entirety. it's also amusing that that same help text claims that > RAMFS is "more of an programming example than a useable file system", > and yet i've been assured that it's absolutely essential to build a > kernel. > I would agree that that help text could do with some updating. Especially since Documentation/filesystems/ramfs-rootfs-initramfs.txt has this to say about it : ... The amount of code required to implement ramfs is tiny, because all the work is done by the existing Linux caching infrastructure. Basically, you're mounting the disk cache as a filesystem. Because of this, ramfs is not an optional component removable via menuconfig, since there would be negligible space savings. ... Which would suggest that we could just nuke it as a config option alltogether... > is it? is there no possible scenario that you might be able to > build a working kernel without RAMFS support? what exactly do you > need it for? > > as i read it, it seems mandatory for initrd support (is that > correct?). but init/Kconfig suggests that initrd is de-selectable: > Initrd is indeed de-selectable. > ===== > config BLK_DEV_INITRD ... > > so maybe i choose to leave out initrd support because i'm working > with an embedded system or something. Or maybe, like me, you just find initrd's / initramfs's to be a royal pain and prefer to do without them. > and on top of all that, RAM > disk support is also de-selectable (from drivers/block/Kconfig): > > ===== > config BLK_DEV_RAM ... > so i'm a bit confused. what's required, and what's not? As far as I know, You can't get rid of RAMFS, but BLK_DEV_RAM and BLK_DEV_INITRD you can do without just fine - I for one never have them enabled for normal use. > and are > all the above properly defined in terms of dependencies? i've just > started to read the appropriate docs, but if someone can clarify this, > i'd be ever so appreciative. > > rday > > p.s. just to sum up, is it possible to build a working kernel without > initrd support? Yes. > without ramfs support? Not as far as I know. > without initramfs support? Yup. > with omitting any combination of the above? You can leave out BLK_DEV_RAM or BLK_DEV_INITRD in any combination you please at least. > and do the Kconfig > entries for those features actually make sense in terms of > dependencies? > As far as I can tell they make resonable sense. Hope that helped a bit. -- Jesper Juhl <jesper.juhl@xxxxxxxxx> Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html Plain text mails only, please http://www.expita.com/nomime.html -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
