tests/vm: avoid extra compressed image copy

The image copy is only really needed because xz doesn't know to
properly decompress a file not named properly.  Instead of
decompressing to stdout, and having to rely on a shell, let's just
create a link instead of copying the file.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20190613130718.3763-2-crosa@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

tests/vm/centos

@@ -66,8 +66,8 @@ class CentosVM(basevm.BaseVM):
         cimg = self._download_with_cache("https://cloud.centos.org/centos/7/images/CentOS-7-x86_64-GenericCloud-1802.qcow2.xz")
         img_tmp = img + ".tmp"
         sys.stderr.write("Extracting the image...\n")
-        subprocess.check_call(["cp", "-f", cimg, img_tmp + ".xz"])
-        subprocess.check_call(["xz", "-dvf", img_tmp + ".xz"])
+        subprocess.check_call(["ln", "-f", cimg, img_tmp + ".xz"])
+        subprocess.check_call(["xz", "--keep", "-dvf", img_tmp + ".xz"])
         subprocess.check_call(["qemu-img", "resize", img_tmp, "50G"])
         self.boot(img_tmp, extra_args = ["-cdrom", self._gen_cloud_init_iso()])
         self.wait_ssh()

tests/vm/freebsd

@@ -34,8 +34,8 @@ class FreeBSDVM(basevm.BaseVM):
         img_tmp_xz = img + ".tmp.xz"
         img_tmp = img + ".tmp"
         sys.stderr.write("Extracting the image...\n")
-        subprocess.check_call(["cp", "-f", cimg, img_tmp_xz])
-        subprocess.check_call(["xz", "-dvf", img_tmp_xz])
+        subprocess.check_call(["ln", "-f", cimg, img_tmp_xz])
+        subprocess.check_call(["xz", "--keep", "-dvf", img_tmp_xz])
         if os.path.exists(img):
             os.remove(img)
         os.rename(img_tmp, img)

tests/vm/netbsd

@@ -34,8 +34,8 @@ class NetBSDVM(basevm.BaseVM):
         img_tmp_xz = img + ".tmp.xz"
         img_tmp = img + ".tmp"
         sys.stderr.write("Extracting the image...\n")
-        subprocess.check_call(["cp", "-f", cimg, img_tmp_xz])
-        subprocess.check_call(["xz", "-dvf", img_tmp_xz])
+        subprocess.check_call(["ln", "-f", cimg, img_tmp_xz])
+        subprocess.check_call(["xz", "--keep", "-dvf", img_tmp_xz])
         if os.path.exists(img):
             os.remove(img)
         os.rename(img_tmp, img)

tests/vm/openbsd

@@ -36,8 +36,8 @@ class OpenBSDVM(basevm.BaseVM):
         img_tmp_xz = img + ".tmp.xz"
         img_tmp = img + ".tmp"
         sys.stderr.write("Extracting the image...\n")
-        subprocess.check_call(["cp", "-f", cimg, img_tmp_xz])
-        subprocess.check_call(["xz", "-dvf", img_tmp_xz])
+        subprocess.check_call(["ln", "-f", cimg, img_tmp_xz])
+        subprocess.check_call(["xz", "--keep", "-dvf", img_tmp_xz])
         if os.path.exists(img):
             os.remove(img)
         os.rename(img_tmp, img)