On 08.05.2017 18:33, Carl Karsten wrote: > On Mon, May 8, 2017 at 11:29 AM, Eric Blake <ebl...@redhat.com> wrote: > >> On 05/08/2017 10:56 AM, Carl Karsten wrote: >> >>>>>>> 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. >> >>> "write operations on block 0 will be restricted." >>> >>> Is there a way to explicitly enable that? >> >> Yes. Pass format=raw at the right place (in other words, instead of >> getting the 'raw' format driver by default, explicitly mentioning that >> you KNOW you want the 'raw' format driver is enough to shut up the >> warning). >> > > according to the warning: "Specify the 'raw' format explicitly to remove > the restrictions." > > I want the restriction. > > format=raw, (write operations on block 0)=restricted
Well, the restriction won't prevent all writes to the first sector, though; it will only prevent writes which would make the image look like it was in some non-raw format. So this is probably not what you want anyway. Unfortunately, I don't know any current way to "soft" write-protect an image. It sounds like an interesting idea, though, and should be simple enough to implement e.g. in the raw driver. Max
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