All,

Currently the "virsh save" command opens a file to save a domain's XML and memory state, does the save, and then re-opens the file to simulate seeking to the beginning to update the header to indicate that the file is complete.

For pipes this is not possible, attempting to re-open the pipe will not connect you to the same consumer. Seeking is also not possible on a pipe.

Attached is a patch that detects if the file being written to is not seekable, and if so writes the completed header initially, then writes the normal data, and avoids re-opening the file.

This is useful to me for saving a VM state directly to Ceph RBD images without having an intermediate file.

I've tested this patch successfully (against v1.3.5) for both saving and restoring a domain:

# ( fifo="$(mktemp -u)"; mkfifo "${fifo}" && virsh save one-0 "${fifo}" & cat "${fifo}" | rbd import - rbd/test1234 & wait; rm -f "${fifo}" )Domain one-0 saved to /tmp/tmp.HK4hChiQqB#

# ( fifo="$(mktemp -u)"; mkfifo "${fifo}" && rbd export rbd/test1234 - > "${fifo}" & virsh restore "${fifo}" & wait; rm -f "${fifo}" ) Exporting image: 100% complete...done.Domain restored from /tmp/tmp.0YaUZ5Y2yT# virsh list Id Name State---------------------------------------------------- 11 one-0 running#

-- 
	Roy Keene
	Knight Point Systems, LLC
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