Fall back to mount if guestmount is not available

Relates: https://pagure.io/pungi/issue/803

Signed-off-by: Ondrej Nosek <onosek@redhat.com>

pungi.spec

@@ -42,7 +42,6 @@ Requires:       gettext
 Requires:       syslinux
 Requires:       git
 Requires:       python-jsonschema
-Requires:       libguestfs-tools-c
 Requires:       python-enum34
 Requires:       python2-dnf
 Requires:       python2-multilib

pungi/phases/product_img.py

@@ -131,6 +131,9 @@ def create_product_img(compose, arch, variant):
 
     shutil.rmtree(po_tmp)
 
+    ret, __ = run(["which", "guestmount"], can_fail=True)
+    guestmount_available = not bool(ret)  # return code 0 means that guestmount is available
+
     mount_tmp = compose.mkdtemp(prefix="product_img_mount_")
     cmds = [
         # allocate image
@@ -139,7 +142,8 @@ def create_product_img(compose, arch, variant):
         "mke2fs -F %s" % shlex_quote(image),
         # use guestmount to mount the image, which doesn't require root privileges
         # LIBGUESTFS_BACKEND=direct: running qemu directly without libvirt
-        "LIBGUESTFS_BACKEND=direct guestmount -a %s -m /dev/sda %s" % (shlex_quote(image), shlex_quote(mount_tmp)),
+        "LIBGUESTFS_BACKEND=direct guestmount -a %s -m /dev/sda %s" % (shlex_quote(image), shlex_quote(mount_tmp)) if guestmount_available
+        else "mount -o loop %s %s" % (shlex_quote(image), shlex_quote(mount_tmp)),
         "mkdir -p %s/run/install/product" % shlex_quote(mount_tmp),
         "cp -rp %s/* %s/run/install/product/" % (shlex_quote(product_tmp), shlex_quote(mount_tmp)),
         "mkdir -p %s/run/install/product/pyanaconda" % shlex_quote(mount_tmp),
@@ -149,7 +153,8 @@ def create_product_img(compose, arch, variant):
         "ln -s run/install/product/locale %s" % shlex_quote(mount_tmp),
         # compat symlink: run/install/product/pyanaconda/installclasses -> ../installclasses
         "ln -s ../installclasses %s/run/install/product/pyanaconda/installclasses" % shlex_quote(mount_tmp),
-        "fusermount -u %s" % shlex_quote(mount_tmp),
+        "fusermount -u %s" % shlex_quote(mount_tmp) if guestmount_available
+        else "umount %s" % shlex_quote(mount_tmp),
         # tweak last mount path written in the image
         "tune2fs -M /run/install/product %s" % shlex_quote(image),
     ]

pungi/util.py

@@ -36,6 +36,7 @@ from productmd.common import get_major_version
 # Patterns that match all names of debuginfo packages
 DEBUG_PATTERNS = ["*-debuginfo", "*-debuginfo-*", "*-debugsource"]
 
+
 def _doRunCommand(command, logger, rundir='/tmp', output=subprocess.PIPE, error=subprocess.PIPE, env=None):
     """Run a command and log the output.  Error out if we get something on stderr"""
 
@@ -609,11 +610,6 @@ def temp_dir(log=None, *args, **kwargs):
                 log.warning('Error removing %s: %s', dir, exc.strerror)
 
 
-def fusermount(path, **kwargs):
-    """Run fusermount -u on a given path."""
-    run_unmount_cmd(['fusermount', '-u', path], path=path, **kwargs)
-
-
 def run_unmount_cmd(cmd, max_retries=10, path=None, logger=None):
     """Attempt to run the command to unmount an image.
 

pungi/wrappers/iso.py

@@ -385,11 +385,17 @@ def mount(image, logger=None):
     The yielded path will only be valid in the with block and is removed once
     the image is unmounted.
     """
-    # use guestmount to mount the image, which doesn't require root privileges
-    # LIBGUESTFS_BACKEND=direct: running qemu directly without libvirt
     with util.temp_dir(prefix='iso-mount-') as mount_dir:
-        env = {'LIBGUESTFS_BACKEND': 'direct', 'LIBGUESTFS_DEBUG': '1', 'LIBGUESTFS_TRACE': '1'}
+        ret, __ = run(["which", "guestmount"], can_fail=True)
-        cmd = ["guestmount", "-a", image, "-m", "/dev/sda", mount_dir]
+        guestmount_available = not bool(ret)  # return code 0 means that guestmount is available
+        if guestmount_available:
+            # use guestmount to mount the image, which doesn't require root privileges
+            # LIBGUESTFS_BACKEND=direct: running qemu directly without libvirt
+            env = {'LIBGUESTFS_BACKEND': 'direct', 'LIBGUESTFS_DEBUG': '1', 'LIBGUESTFS_TRACE': '1'}
+            cmd = ["guestmount", "-a", image, "-m", "/dev/sda", mount_dir]
+        else:
+            env = {}
+            cmd = ["mount", "-o", "loop", image, mount_dir]
         ret, out = run(cmd, env=env, can_fail=True, universal_newlines=True)
         if ret != 0:
             # The mount command failed, something is wrong. Log the output and raise an exception.
@@ -400,4 +406,7 @@ def mount(image, logger=None):
         try:
             yield mount_dir
         finally:
-            util.fusermount(mount_dir, logger=logger)
+            if guestmount_available:
+                util.run_unmount_cmd(['fusermount', '-u', mount_dir], path=mount_dir)
+            else:
+                util.run_unmount_cmd(['umount', mount_dir], path=mount_dir)

tests/test_iso_wrapper.py

@@ -20,6 +20,7 @@ INCORRECT_OUTPUT = '''This should never happen: File not found'''
 
 
 class TestIsoUtils(unittest.TestCase):
+
     @mock.patch('pungi.wrappers.iso.run')
     def test_get_implanted_md5_correct(self, mock_run):
         mock_run.return_value = (0, CORRECT_OUTPUT)
@@ -44,24 +45,48 @@ class TestIsoUtils(unittest.TestCase):
     @mock.patch('pungi.util.run_unmount_cmd')
     @mock.patch('pungi.wrappers.iso.run')
     def test_mount_iso(self, mock_run, mock_unmount):
-        mock_run.return_value = (0, '')
+        # first tuple is return value for command 'which guestmount'
+        # value determines type of the mount/unmount command ('1' - guestmount is not available)
+        # for approach as a root, pair commands mount-umount are used
+        mock_run.side_effect = [(1, ''), (0, '')]
         with iso.mount('dummy') as temp_dir:
             self.assertTrue(os.path.isdir(temp_dir))
-        self.assertEqual(len(mock_run.call_args_list), 1)
+        self.assertEqual(len(mock_run.call_args_list), 2)
+        mount_call_str = str(mock_run.call_args_list[1])
+        self.assertTrue(mount_call_str.startswith("call(['mount'"))
         self.assertEqual(len(mock_unmount.call_args_list), 1)
+        unmount_call_str = str(mock_unmount.call_args_list[0])
+        self.assertTrue(unmount_call_str.startswith("call(['umount'"))
+        self.assertFalse(os.path.isdir(temp_dir))
+
+    @mock.patch('pungi.util.run_unmount_cmd')
+    @mock.patch('pungi.wrappers.iso.run')
+    def test_guestmount(self, mock_run, mock_unmount):
+        # first tuple is return value for command 'which guestmount'
+        # value determines type of the mount/unmount command ('0' - guestmount is available)
+        # for approach as a non-root, pair commands guestmount-fusermount are used
+        mock_run.side_effect = [(0, ''), (0, '')]
+        with iso.mount('dummy') as temp_dir:
+            self.assertTrue(os.path.isdir(temp_dir))
+        self.assertEqual(len(mock_run.call_args_list), 2)
+        mount_call_str = str(mock_run.call_args_list[1])
+        self.assertTrue(mount_call_str.startswith("call(['guestmount'"))
+        self.assertEqual(len(mock_unmount.call_args_list), 1)
+        unmount_call_str = str(mock_unmount.call_args_list[0])
+        self.assertTrue(unmount_call_str.startswith("call(['fusermount'"))
         self.assertFalse(os.path.isdir(temp_dir))
 
     @mock.patch('pungi.util.run_unmount_cmd')
     @mock.patch('pungi.wrappers.iso.run')
     def test_mount_iso_always_unmounts(self, mock_run, mock_unmount):
-        mock_run.return_value = (0, '')
+        mock_run.side_effect = [(1, ''), (0, '')]
         try:
             with iso.mount('dummy') as temp_dir:
                 self.assertTrue(os.path.isdir(temp_dir))
                 raise RuntimeError()
         except RuntimeError:
             pass
-        self.assertEqual(len(mock_run.call_args_list), 1)
+        self.assertEqual(len(mock_run.call_args_list), 2)
         self.assertEqual(len(mock_unmount.call_args_list), 1)
         self.assertFalse(os.path.isdir(temp_dir))
 
@@ -69,11 +94,11 @@ class TestIsoUtils(unittest.TestCase):
     @mock.patch('pungi.wrappers.iso.run')
     def test_mount_iso_raises_on_error(self, mock_run, mock_unmount):
         log = mock.Mock()
-        mock_run.return_value = (1, 'Boom')
+        mock_run.side_effect = [(1, ''), (1, 'Boom')]
         with self.assertRaises(RuntimeError):
             with iso.mount('dummy', logger=log) as temp_dir:
                 self.assertTrue(os.path.isdir(temp_dir))
-        self.assertEqual(len(mock_run.call_args_list), 1)
+        self.assertEqual(len(mock_run.call_args_list), 2)
         self.assertEqual(len(mock_unmount.call_args_list), 0)
         self.assertEqual(len(log.mock_calls), 1)
 

tests/test_util.py

@@ -446,7 +446,7 @@ class TestUnmountCmd(unittest.TestCase):
                                  self._fakeProc(0, out='It is very busy'),
                                  self._fakeProc(1, out='lsof output')]
         with self.assertRaises(RuntimeError) as ctx:
-            util.fusermount('/path', max_retries=3, logger=logger)
+            util.run_unmount_cmd(['fusermount', '-u', '/path'], path='/path', max_retries=3, logger=logger)
         cmd = ['fusermount', '-u', '/path']
         expected = [mock.call(cmd, stderr=subprocess.PIPE, stdout=subprocess.PIPE,
                               universal_newlines=True),