Fix application for multiple cached layers

This is work towards tern-tools#1082

When using the default method of overlaying the container image's
layers, in the event of a cache hit the current implementation does
not copy over the filesystem into the merge directory. As a result,
the overlaying fails. To fix this issue, we check to see if there
was a cache hit and if the driver is the default one. If this is
the case, we prep the merge directory anyway.

In some situations, the operations to build container images create
whiteout files owned by the root user. In order to delete these files
and directories, tern needs to be able to run these operations as the
root user. Hence we use the root_command utility to remove whiteout
files and directories.

Signed-off-by: Nisha K <[email protected]>

Author: Nisha K

tern/analyze/default/container/multi_layer.py

@@ -10,7 +10,6 @@
 import glob
 import logging
 import os
-import shutil
 
 from tern.report import errors
 from tern.utils import constants
@@ -53,9 +52,9 @@ def apply_layers(image_obj, top_layer):
             delpath = os.path.join(target, os.path.dirname(fd.path), deleted)
             if os.path.exists(delpath):
                 if os.path.isfile(delpath):
-                    os.remove(delpath)
+                    rootfs.root_command(['rm'], delpath)
                 else:
-                    shutil.rmtree(delpath)
+                    rootfs.root_command(rootfs.remove, delpath)
                 os.remove(os.path.join(layer_dir, fd.path))
     # Finally, bulk copy the layer contents into the target directory
     # if there are any files to move
@@ -128,6 +127,10 @@ def analyze_subsequent_layers(image_obj, prereqs, master_list, options):
         fresh analysis
         package information and bundle it into the image object
         3. Update the master list"""
+    # if the driver is 'default' then the first layer needs to be extracted
+    mergepath = os.path.join(rootfs.get_working_dir(), constants.mergedir)
+    if not os.listdir(mergepath):
+        prep_layers(image_obj, 0, 'default')
     curr_layer = 1
     # get list of environment variables
     prereqs.envs = lock.get_env_vars(image_obj)
@@ -151,6 +154,9 @@ def analyze_subsequent_layers(image_obj, prereqs, master_list, options):
         if not common.load_from_cache(image_obj.layers[curr_layer],
                                       options.redo):
             fresh_analysis(image_obj, curr_layer, prereqs, options)
+        # If the driver is 'default' apply the current layer anyway
+        if options.driver == 'default':
+            apply_layers(image_obj, curr_layer)
         # update the master list
         dcom.update_master_list(master_list, image_obj.layers[curr_layer])
         curr_layer = curr_layer + 1