diff --git a/lib/spack/spack/cmd/external.py b/lib/spack/spack/cmd/external.py
index d859ad9d7a..6c794a70f2 100644
--- a/lib/spack/spack/cmd/external.py
+++ b/lib/spack/spack/cmd/external.py
@@ -79,6 +79,12 @@ def setup_parser(subparser):
     read_cray_manifest.add_argument(
         "--directory", default=None, help="specify a directory storing a group of manifest files"
     )
+    read_cray_manifest.add_argument(
+        "--ignore-default-dir",
+        action="store_true",
+        default=False,
+        help="ignore the default directory of manifest files",
+    )
     read_cray_manifest.add_argument(
         "--dry-run",
         action="store_true",
@@ -177,11 +183,16 @@ def external_read_cray_manifest(args):
         manifest_directory=args.directory,
         dry_run=args.dry_run,
         fail_on_error=args.fail_on_error,
+        ignore_default_dir=args.ignore_default_dir,
     )
 
 
 def _collect_and_consume_cray_manifest_files(
-    manifest_file=None, manifest_directory=None, dry_run=False, fail_on_error=False
+    manifest_file=None,
+    manifest_directory=None,
+    dry_run=False,
+    fail_on_error=False,
+    ignore_default_dir=False,
 ):
     manifest_files = []
     if manifest_file:
@@ -191,7 +202,7 @@ def _collect_and_consume_cray_manifest_files(
     if manifest_directory:
         manifest_dirs.append(manifest_directory)
 
-    if os.path.isdir(cray_manifest.default_path):
+    if not ignore_default_dir and os.path.isdir(cray_manifest.default_path):
         tty.debug(
             "Cray manifest path {0} exists: collecting all files to read.".format(
                 cray_manifest.default_path
diff --git a/lib/spack/spack/cray_manifest.py b/lib/spack/spack/cray_manifest.py
index 4fdbc095e5..13a7fc43f0 100644
--- a/lib/spack/spack/cray_manifest.py
+++ b/lib/spack/spack/cray_manifest.py
@@ -48,7 +48,8 @@ def translated_compiler_name(manifest_compiler_name):
 def compiler_from_entry(entry):
     compiler_name = translated_compiler_name(entry["name"])
     paths = entry["executables"]
-    version = entry["version"]
+    # to instantiate a compiler class we may need a concrete version:
+    version = "={}".format(entry["version"])
     arch = entry["arch"]
     operating_system = arch["os"]
     target = arch["target"]
diff --git a/lib/spack/spack/platforms/cray.py b/lib/spack/spack/platforms/cray.py
index 3d88285f70..10294676ec 100644
--- a/lib/spack/spack/platforms/cray.py
+++ b/lib/spack/spack/platforms/cray.py
@@ -37,7 +37,9 @@
 
 
 def slingshot_network():
-    return os.path.exists("/opt/cray/pe") and os.path.exists("/lib64/libcxi.so")
+    return os.path.exists("/opt/cray/pe") and (
+        os.path.exists("/lib64/libcxi.so") or os.path.exists("/usr/lib64/libcxi.so")
+    )
 
 
 def _target_name_from_craype_target_name(name):
diff --git a/share/spack/spack-completion.bash b/share/spack/spack-completion.bash
index 1644cffe6f..b06d468aad 100755
--- a/share/spack/spack-completion.bash
+++ b/share/spack/spack-completion.bash
@@ -1060,7 +1060,7 @@ _spack_external_list() {
 }
 
 _spack_external_read_cray_manifest() {
-    SPACK_COMPREPLY="-h --help --file --directory --dry-run --fail-on-error"
+    SPACK_COMPREPLY="-h --help --file --directory --ignore-default-dir --dry-run --fail-on-error"
 }
 
 _spack_fetch() {