Merge pull request #780 from jsmeix/add_basic_stuff_to_move_away_rest…

…ored_files_issue779

new usr/share/rear/restore/default/99_move_away_restored_files.sh

usr/share/rear/conf/default.conf

@@ -763,6 +763,57 @@ EXTERNAL_IGNORE_ERRORS=( 23 24 )
 # output on STDOUT by rerouting that to FD 8, the progress bar
 EXTERNAL_CHECK="ssh vms date >&8"
 
+##
+# BACKUP_RESTORE_MOVE_AWAY
+#
+# Move away restored files or directories that should not have been restored:
+#
+# Do not confuse it with EXCLUDE_RESTORE in the EXCLUDES section below.
+# With EXCLUDE_RESTORE items are excluded during backup restore
+# where each particular backup method must explicitly implement support
+# for the EXCLUDE_RESTORE functionality (most do not support it).
+# In contrast BACKUP_RESTORE_MOVE_AWAY works generically
+# for any backup restore method.
+#
+# See https://github.com/rear/rear/issues/779
+#
+# After backup restore rear should move away files or directories
+# that should not have been restored - maily files or directories
+# that are created and maintained by system tools where
+# a restore from the backup results wrong/outdated
+# content that conflicts with the actual system.
+#
+# The generic traditional example of such a file was /etc/mtab.
+# As long as it was a regular file it must not have been restored
+# with outdated content from a backup. Nowadays it is a symbolic link
+# to /proc/self/mounts which should probably be restored to ensure
+# that link is available.
+#
+# rear will not remove any file (any user data is sacrosanct).
+# Instead rear moves those files away into a rear-specific directory
+# so that the admin can inspect that directory to see what rear thinks
+# should not have been restored:
+readonly BACKUP_RESTORE_MOVE_AWAY_DIRECTORY="$VAR_DIR/moved_away_after_backup_restore/"
+#
+# There is nothing hardcoded in the scripts.
+# Instead BACKUP_RESTORE_MOVE_AWAY_FILES is a documented list
+# that explains why each file or directory is moved away.
+# The BACKUP_RESTORE_MOVE_AWAY_FILES list is not readonly
+# so that it can be modified as needed by the scripts.
+# The items in the BACKUP_RESTORE_MOVE_AWAY_FILES list do not need to be only files.
+# Also a whole directory tree can be moved away (automatically recursively).
+# Already existing stuff in the BACKUP_RESTORE_MOVE_AWAY_DIRECTORY that would be (partially)
+# overwritten by the items in the BACKUP_RESTORE_MOVE_AWAY_FILES list is removed before
+# (because such stuff is considered as outdated leftover e.g. from a previous recovery)
+# but already existing stuff in the BACKUP_RESTORE_MOVE_AWAY_DIRECTORY that is not
+# in the curent BACKUP_RESTORE_MOVE_AWAY_FILES list is kept.
+# Example:
+# Perhaps stuff in the /var/tmp directory is not needed after a system recovery
+# and /etc/udev/rules.d/70-persistent-net.rules is created and maintained
+# by systemd/udev (see https://github.com/rear/rear/issues/770):
+# BACKUP_RESTORE_MOVE_AWAY_FILES=( /var/tmp /etc/udev/rules.d/70-persistent-net.rules )
+BACKUP_RESTORE_MOVE_AWAY_FILES=()
+
 ##
 # How to exclude something ----- EXCLUDES -------
 #

usr/share/rear/restore/default/99_move_away_restored_files.sh

@@ -0,0 +1,66 @@
+#
+# Move away restored files or directories that should not have been restored:
+#
+# See https://github.com/rear/rear/issues/779
+#
+# After backup restore rear should move away files or directories
+# that should not have been restored - maily files or directories
+# that are created and maintained by system tools where
+# a restore from the backup results wrong/outdated
+# content that conflicts with the actual system.
+#
+# The generic traditional example of such a file was /etc/mtab.
+# As long as it was a regular file it must not have been restored
+# with outdated content from a backup. Nowadays it is a symbolic link
+# to /proc/self/mounts which should probably be restored to ensure
+# that link is available.
+#
+# rear will not remove any file (any user data is sacrosanct).
+# Instead rear moves those files away into a rear-specific directory
+# (specified by BACKUP_RESTORE_MOVE_AWAY_DIRECTORY in default.conf)
+# so that the admin can inspect that directory to see what rear thinks
+# should not have been restored.
+#
+# There is nothing hardcoded in the scripts.
+# Instead BACKUP_RESTORE_MOVE_AWAY_FILES is a documented predefined list
+# in default.conf what files or directories are moved away by default.
+
+# Go to the recovery system root directory:
+pushd $TARGET_FS_ROOT >&8
+# Artificial 'for' clause that is run only once to be able to 'continue' in case of errors
+# (because the 'for' loop is run only once 'continue' is the same as 'break'):
+for dummy in "once" ; do
+    # The following code is only meant to be used for the "recover" workflow:
+    test "recover" = "$WORKFLOW" || continue
+    # Nothing to do if the BACKUP_RESTORE_MOVE_AWAY_FILES list is empty
+    # (that list is considered to be empty when its first element is empty):
+    test "$BACKUP_RESTORE_MOVE_AWAY_FILES" || continue
+    # Strip leading '/' from $BACKUP_RESTORE_MOVE_AWAY_DIRECTORY
+    # to get a relative path that is needed inside the recovery system:
+    move_away_dir="${BACKUP_RESTORE_MOVE_AWAY_DIRECTORY#/}"
+    # Do nothing if no real BACKUP_RESTORE_MOVE_AWAY_DIRECTORY is specified
+    # (it has to be specified in default.conf and must not be only '/'):
+    test "$move_away_dir" || continue
+    # Create the move away directory with mode 0700 (rwx------)
+    # so that only root can access files and subdirectories therein
+    # because the files therein could contain security relevant information:
+    mkdir -p -m 0700 $move_away_dir || continue
+    # Copy each file or directory in BACKUP_RESTORE_MOVE_AWAY_FILES with full path:
+    for file in ${BACKUP_RESTORE_MOVE_AWAY_FILES[@]} ; do
+        # Strip leading '/' from $file to get it with relative path that is needed inside the recovery system:
+        file_relative="${file#/}"
+        # Skip files or directories listed in BACKUP_RESTORE_MOVE_AWAY_FILES that do not actually exist:
+        test -e $file_relative || continue
+        # Clean up already existing stuff in the move away directory
+        # that would be (partially) overwritten by the current copy
+        # (such stuff is considered as outdated leftover e.g. from a previous recovery)
+        # but keep already existing stuff in the move away directory
+        # that is not in the curent BACKUP_RESTORE_MOVE_AWAY_FILES list:
+        rm -rf $move_away_dir/$file_relative
+        # Only if the copy was successful remove the original file or directory:
+        cp -a --parents $file_relative $move_away_dir && rm -rf $file_relative
+    done
+done
+# Go back from the recovery system root directory:
+popd >&8
+