[Libguestfs] [INCOMPLETE PATCH nbdkit] ssh: Allow the remote file to be created

This patch is incomplete (missing tests) so for discussion only, but it implements nbdkit-ssh-plugin create=true option which creates the remote file. Example: $ nbdkit ssh host=foo /var/tmp/newdisk create=true create-size=100M $ nbdsh -u nbd://localhost The disk is only created on first connection (which works the same way as nbdkit-vddk-plugin). So if you just want to create the remote disk and not do anything else, you should do something like this: nbdkit -U - ssh host=foo /var/tmp/newdisk create=true create-size=100M \ --run 'nbdinfo --can connect $uri' If the remote disk already exists, it is truncated but not recreated (in this case you'll notice the remote ctime is not touched). For some reason I don't understand, create-mode=0777 is ineffective. sftp-server has a -u option to set the umask, or else it uses the remote user's umask. I verified that openssh does *not* use the -u option and that the umask of sftp-server is 0002, yet the permissions on the file are still 0700. Rich.