You can also pass the initramfs location and size to the kernel via ATAGs in ARM builds. Please see my previous replies to this thread and the arm booting documentation in the kernel docs directory.
[Peter Oh <p...@innopath.com>] > > Thanks! Brian, > > This is my knowledge so far about initramfs. > To use initramfs as root filesystem, > > 1. initramfs.img is required to link with kernel image in the stage of kernel > build > Using the kernel option CONFIG_INITRAMFS_SOURCE="ramdisk.img" > > Using this option, kernel can link the ramdisk.img during the kernel build > stage. > But I haven't verified it yet. > > Regards. > Peter Oh > -----Original Message----- > From: android-porting@googlegroups.com > [mailto:android-port...@googlegroups.com] On Behalf Of Brian Swetland > Sent: Wednesday, February 11, 2009 9:28 PM > To: android-porting@googlegroups.com > Subject: [android-porting] Re: How to use initramfs for root filesystem? > > > > [Peter Oh <p...@innopath.com>] > > > > Thank you a lot for your reply. > > > > Now I'm almost clear except this one. > > If I assume that I have initramfs file as the name of 'ramdisk.img' > > Yup. ramdisk.img is a gzip'd cpio image. > > > How can android kernel find the location of 'ramdisk.img' exists? > > If there is 'root=' option, kernel can try to find the location of > > 'ramdisk.img' from the location of 'root='. > > But if kernel option does not have 'root=' option, > > How kernel knows the location of ramdisk.img? > > The bootloader passes the ramdisk size and location via ATAGs. > See Documentation/arm/Booting in the linux kernel sources. > > > Does android kernel also usr 'root=' option to find out the location of > > 'ramdisk.img'? > > Can I see what the typical 'Kernel command line' option for android is? > > Nothing special really. I used "mem=101M console=ttyMSM2" on 7201A > SURF, for example. > > > Really my best regards. > > Peter Oh > > > > -----Original Message----- > > From: android-porting@googlegroups.com > > [mailto:android-port...@googlegroups.com] On Behalf Of Brian Swetland > > Sent: Wednesday, February 11, 2009 12:28 AM > > To: android-porting@googlegroups.com > > Subject: [android-porting] Re: How to use initramfs for root filesystem? > > > > > > > > When booting with initramfs, the kernel creates a tmpfs at /, unpacking > > the initramfs (typically a gzip'd cpio archive) into it. Then it runs > > /init (I believe there is actually a short list of programs it tries to > > run on / in a specific order, but I'd have to look at the kernel sources > > to verify this). > > > > It's expected that the init process started from initramfs will know how > > to get everything else going. In the android world, this involves > > /init.rc scripting what to mount where, etc. > > > > Brian > > > > [ebmajor <p...@innopath.com>] > > > > > > Dear all, > > > > > > I'm trying to understand how initramfs, especially 'init' program is > > > used as a root filesystem. > > > Usually I've used 'root=/dev/mtdblock0 rootfstype=jffs2' in kernel > > > command line for root filesystem and my 'init' program > > > is laid in mtdblock0 so kernel can find where the 'init' program > > > exists. > > > > > > But I read initramfs does not required 'root=' command line. > > > So, if I don't type 'root=' in kernel command line, how the kernel > > > finds out where the 'init' program exists? > > > and what kind of filesystem is using for the block that 'init' program > > > exists? > > > > > > Simply asking, > > > Can I use kernel command line without 'root=' option? If I can, how > > > can I use? > > > > > > Sincerely. > > > > > > > > > > > > > > > > > > > > > > > > --~--~---------~--~----~------------~-------~--~----~ unsubscribe: android-porting+unsubscr...@googlegroups.com website: http://groups.google.com/group/android-porting -~----------~----~----~----~------~----~------~--~---
