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From: | Anthony Liguori |
Subject: | Re: [Qemu-devel] [PATCH] Add readonly flag to -drive command |
Date: | Mon, 12 Oct 2009 09:30:05 -0500 |
User-agent: | Thunderbird 2.0.0.23 (X11/20090825) |
Jamie Lokier wrote:
Kevin Wolf wrote:Am 12.10.2009 14:47, schrieb Naphtali Sprei:In order to safely share an image between guests (as read only drive), add a 'readonly' flag to the -drive command (qemu command line and monitor).Heh. I've been sharing images between guests for ages - using "chmod -r" :-)
Were it not for backwards compatibility, I would remove that and have it error out.
I've had multiple people end up with strangely broken guests because they didn't realize the image was read only.
Still missing passing the read only attribute to the guest, where possible. I don't know which device types supports read only, and don't know how to pass this information to guests.This was discussed in a thread some months ago. You might look it up. SCSI, USB, and floppy can pass the information to guests - see the Linux kernel for how the flag is read. CD-ROMs are read-only already of course. I don't know if virtio-blk can; if not, it would be good to add it.
virtio-blk can support read-only images now. Regards, Anthony Liguori
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