On Thu, Mar 21, 2013 at 01:38:58PM +0000, Richard W.M. Jones wrote: > From: "Richard W.M. Jones" <rjo...@redhat.com> > > qemu-system-x86_64 -drive file=ssh://hostname/some/image > > QEMU will ssh into 'hostname' and open '/some/image' which is made > available as a standard block device. > > You can specify a username (ssh://user@host/...) and/or a port number > (ssh://host:port/...).
I can see this being handy for qemu-img since it gives you the ability to work with remote image files. > Current limitations: > > - Authentication must be done without passwords or passphrases, using > ssh-agent. Other authentication methods are not supported. (*) > > - Does not check host key. (*) > > - New remote files cannot be created. (*) Would be important to fix these limitations. Authentication methods to make this more usable. Host key check for security. File creation for qemu-img. > - Uses coroutine read/write, instead of true AIO. (libssh2 supports > non-blocking access, so this could be fixed with some effort). This patch does not really use coroutines - the SSH I/O is blocking! Coroutines must submit the SSH I/O and then yield so the QEMU event loop can get on with other work. When SSH I/O finishes the request's coroutine is re-entered and the request gets completed. > - Blocks during connection and authentication. Right now the code also blocks while SSH I/O takes place. > (*) = potentially easy fix > > This is implemented using libssh2 on the client side. The server just > requires a regular ssh daemon with sftp-server support. Most ssh > daemons on Unix/Linux systems will work out of the box. How much of a win over sshfs is this? sshfs can be mounted by unprivileged users and QEMU accesses it like a regular file. So the sshfs approach already works today. Stefan
