Add initial commit outlining scale-build python structure

scale_build/preflight.py

@@ -0,0 +1,57 @@
+import logging
+import os
+import shutil
+
+from .exceptions import CallError, MissingPackagesException
+from .utils.manifest import get_manifest
+from .utils.system import has_low_ram
+from .utils.variables import TMP_DIR, HASH_DIR, LOG_DIR, PKG_DIR
+
+
+logger = logging.getLogger(__name__)
+
+WANTED_PACKAGES = {
+    'make',
+    'debootstrap',
+    'git',
+    'xorriso',
+    'grub-mkrescue',
+    'mksquashfs',
+    'unzip',
+}
+
+
+def is_root():
+    return os.geteuid() == 0
+
+
+def retrieve_missing_packages():
+    missing = {pkg for pkg in WANTED_PACKAGES if not shutil.which(pkg)}
+    if not os.path.exists('/lib/grub/x86_64-efi') and not os.path.exists('/usr/lib/grub/x86_64-efi'):
+        missing.add('grub-efi-amd64-bin')
+
+    if not os.path.exists('/lib/grub/i386-pc') and not os.path.exists('/usr/lib/grub/i386-pc'):
+        missing.add('grub-pc-bin')
+
+    return missing
+
+
+def setup_dirs():
+    for d in (TMP_DIR, HASH_DIR, LOG_DIR, PKG_DIR):
+        os.makedirs(d, exist_ok=True)
+
+
+def preflight_check():
+    # TODO: Please see how we should delete overlayfs/bootstrapdir when exceptions are raised
+    if not is_root():
+        raise CallError('Must be run as root (or using sudo)!')
+
+    missing_packages = retrieve_missing_packages()
+    if missing_packages:
+        raise MissingPackagesException(missing_packages)
+
+    if has_low_ram():
+        logging.warning('WARNING: Running with less than 16GB of memory. Build may fail...')
+
+    setup_dirs()
+    get_manifest()