From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52004) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d7ke2-0006Pd-Rq for qemu-devel@nongnu.org; Mon, 08 May 2017 11:32:19 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1d7kdz-0006CP-IH for qemu-devel@nongnu.org; Mon, 08 May 2017 11:32:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35276) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1d7kdz-0006C3-BS for qemu-devel@nongnu.org; Mon, 08 May 2017 11:32:15 -0400 References: <87wp9r689l.fsf@dusky.pond.sub.org> From: John Snow Message-ID: Date: Mon, 8 May 2017 11:32:12 -0400 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] format=raw,readonly errors List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Carl Karsten , Markus Armbruster Cc: qemu-devel@nongnu.org On 05/08/2017 10:15 AM, Carl Karsten wrote: > On Mon, May 8, 2017 at 3:51 AM, Markus Armbruster wrote: > >> Carl Karsten writes: >> >>> juser@gator:~/temp$ qemu-system-x86_64 -m 256 -display curses -drive >>> file=disk.cow -drive file=boot.img >>> WARNING: Image format was not specified for 'boot.img' and probing >> guessed >>> raw. >>> Automatically detecting the format is dangerous for raw images, >>> write operations on block 0 will be restricted. >>> Specify the 'raw' format explicitly to remove the restrictions. >>> >>> This is OK, as I don't want anything writing to that thing anyway. So to >>> get rid of the waring: >>> >>> juser@gator:~/temp$ qemu-system-x86_64 -drive >>> file=boot.img,format=raw,readonly qemu-system-x86_64: Can't use a >> read-only >>> drive >>> qemu-system-x86_64: Initialization of device ide-hd failed: Device >>> initialization failed. >> >> -drive without if=... creates an IDE disk[*]. IDE disks can't do >> read-only. Have you tried omitting ",readonly"? >> > > > omitting works, but my goal was for the drive to be read only. > > I don't think there's a way to make physical IDE drives "read only." I don't think there's any jumper settings or any of the like which can accomplish this. Unlike floppy disks (which you could notch the corner of) or SD cards (which have the write lock), I don't think ATA disks have a method for being "read only," so this isn't a feature QEMU can support. What you CAN do, however, is to use -snapshot or otherwise use something like a qcow2 overlay to trap all writes to a temporary file that you can discard at a later point in time, effectively keeping your original image "read only." I believe that SCSI disks support a read-only mode, though.