From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44650) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VUWtN-0004gb-JS for qemu-devel@nongnu.org; Fri, 11 Oct 2013 03:12:14 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VUWtE-0005Eu-4o for qemu-devel@nongnu.org; Fri, 11 Oct 2013 03:12:09 -0400 Received: from mail.univention.de ([82.198.197.8]:1801) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VUWtD-0005EP-UA for qemu-devel@nongnu.org; Fri, 11 Oct 2013 03:12:00 -0400 From: Philipp Hahn Date: Fri, 11 Oct 2013 09:11:56 +0200 References: In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Message-Id: <201310110911.56498.hahn@univention.de> Subject: Re: [Qemu-devel] Qemu Boot failure with /dev/ram0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Saptarshi Sen Hello, On Monday 16 September 2013 07:40:08 Saptarshi Sen wrote: > I want to use a ram disk as a block device for my kernel.( i am > measuring file io on ram ) > > I am trying to boot a kernel from using /dev/ram0. However I am getting > "No root Device found" > > qemu-system-x86_64 -m 8G -hda disk.img -kernel vmlinuz-3.10.0-rc6 > -initrd initramfs-3.10.0-rc6.img -append "root=/dev/ram0 selinux=0 > enforcing=0 rw" -vnc :0 Perhaps you're mixing "Initial*RamFS*" and "Initial*RootDisk*"? Your filename "initramfs" indicates you're going for the former, but your "root=/dev/ram0" is required fror InitRD. InitRamFS is a (compressed) CPIO archive, which is extracted to a dynamically growing "tmpfs" by the kernel. InitRD is a (compressed) ext2/3/4/jfs/xfs/whatever filesystem, which is backed by a fixed portion of you RAM; you probably need to explicitly specify a "ramdisk_size=250000" parameter to be large enougth to contain the uncompressed file-system. If the size is too small, you will have a corrupt FS where you also get the error you mention above. Sincerely Philipp -- Philipp Hahn Open Source Software Engineer hahn@univention.de Univention GmbH be open. fon: +49 421 22 232- 0 Mary-Somerville-Str.1 D-28359 Bremen fax: +49 421 22 232-99 http://www.univention.de/ Director:Peter H. Ganten HRB 20755 Amtsgericht Bremen UID:DE 220 051 310