VMBackup: Fix Python 3.12+ compatibility for Azure Linux 4.0

jonathanbrenes · jonathanbrenes · commit 037ab485c0c5 · 2026-05-27T21:22:22.000-06:00
The VMSnapshot extension crashes on Azure Linux 4.0 (Python 3.14) due to
four Python APIs removed in recent versions. The extension fails at import
time, causing Azure Backup jobs to fail with error 400039 after hours of
retries.

Root cause — removed Python APIs used by VMBackup:
  - distutils.version.LooseVersion (removed in 3.12)
  - imp module (removed in 3.12)
  - platform.dist() (removed in 3.8)
  - platform.linux_distribution() (removed in 3.8)

Changes:

WaagentLib.py:
  - Add try/except for LooseVersion import with a minimal shim class
    that provides comparison operators (__lt__, __gt__, __eq__, __le__,
    __ge__) using regex-based version parsing.
    Note: Python never added a stdlib replacement for LooseVersion.
    PEP 632 recommends the third-party `packaging` library, but it is
    not suitable here: (1) it is not in the stdlib and may be absent on
    minimal installs, (2) it enforces strict PEP 440 parsing and rejects
    the loose version strings this codebase passes, and (3) adding a
    dependency to a VM extension that must run on every Linux distro from
    RHEL 7 (Python 2.7) to AZL4 (Python 3.14) is fragile. The inline
    shim is zero-dependency and drop-in compatible.

WAAgentUtil.py:
  - Add try/except around the `import imp` fallback so it does not crash
    on Python 3.12+ when the primary importlib path fails

HandlerUtil.py:
  - Replace platform.dist() in get_dist_info() with /etc/os-release
    parsing (NAME + VERSION fields)
  - Fix invalid escape sequence: replace('\/', '/') was a no-op
    (invalid escape treated as literal char); changed to
    replace('\\/', '/') which correctly replaces \/ with /

patch/__init__.py:
  - Add /etc/os-release ID parsing to DistInfo() fallback
  - Add 'azurelinux' mapping in GetMyPatching() -&gt; AzureLinuxPatching

patch/AzureLinuxPatching.py (new):
  - Dedicated patching class for Azure Linux 4.0
  - All binary paths set to /usr/bin/ (AZL4 merged /usr)
  - Uses dnf for package installation

Tested:
  - End-to-end Azure Backup on AZL4 VM: PASS (26 min, all phases)
  - Backward compat across 10 distros (Python 3.6-3.14): all PASS
    RHEL 8/9, Oracle Linux 9, SLES 15/16, Debian 12,
    Ubuntu 20.04/22.04/24.04, Azure Linux 4.0
diff --git a/VMBackup/main/Utils/HandlerUtil.py b/VMBackup/main/Utils/HandlerUtil.py
@@ -627,8 +627,20 @@ def get_dist_info(self):
                 distinfo[0] = distinfo[0].strip()
                 return  distinfo[0]+"-"+distinfo[1],platform.release()
             else:
-                distinfo = platform.dist()
-                return  distinfo[0]+"-"+distinfo[1],platform.release()
+                # platform.dist() removed in Python 3.8; parse /etc/os-release instead
+                try:
+                    with open("/etc/os-release", "r") as f:
+                        os_name, os_version = "Unknown", "Unknown"
+                        for line in f:
+                            k, _, v = line.strip().partition("=")
+                            v = v.strip('"')
+                            if k == "NAME":
+                                os_name = v
+                            elif k == "VERSION":
+                                os_version = v
+                        return os_name + "-" + os_version, platform.release()
+                except Exception:
+                    return "Unknown", "Unknown"
         except Exception as e:
             errMsg = 'Failed to retrieve the distinfo with error: %s, stack trace: %s' % (str(e), traceback.format_exc())
             self.log(errMsg)
@@ -715,7 +727,7 @@ def do_status_report(self, operation, status, status_code, message, taskId = Non
         stat_rept.timestampUTC = date_place_holder
         date_string = r'\/Date(' + str((int)(time_span)) + r')\/'
         stat_rept = "[" + json.dumps(stat_rept, cls = ComplexEncoder) + "]"
-        stat_rept = stat_rept.replace('\\\/', '\/') # To fix the datetime format of CreationTime to be consumed by C# DateTimeOffset
+        stat_rept = stat_rept.replace('\\/', '/') # To fix the datetime format of CreationTime to be consumed by C# DateTimeOffset
         stat_rept = stat_rept.replace(date_place_holder,date_string)
 
         # Add Status as sub-status for Status to be written on Status-File
diff --git a/VMBackup/main/Utils/WAAgentUtil.py b/VMBackup/main/Utils/WAAgentUtil.py
@@ -66,10 +66,11 @@ def searchWAAgentOld():
             spec.loader.exec_module(waagent)       
         except ImportError:
             # For Python 3.4 and earlier, use imp module
-            import imp
-            waagent = imp.load_source('waagent', agentPath)
-        except Exception:
-            raise Exception("Can't load waagent.")
+            try:
+                import imp
+                waagent = imp.load_source('waagent', agentPath)
+            except ImportError:
+                raise Exception("Can't load waagent: importlib.util and imp both unavailable.")
     else:
         raise Exception("Can't load new or old waagent. Agent path not found.")
 except Exception as e:
diff --git a/VMBackup/main/WaagentLib.py b/VMBackup/main/WaagentLib.py
@@ -56,7 +56,48 @@
 import json
 import datetime
 import xml.sax.saxutils
-from distutils.version import LooseVersion
+try:
+    from distutils.version import LooseVersion
+except ImportError:
+    # distutils removed in Python 3.12; minimal shim for version comparisons
+    import re as _re
+    class LooseVersion(object):
+        def __init__(self, vstring):
+            self.vstring = str(vstring)
+            self._cmp_key = self._parse(self.vstring)
+        @staticmethod
+        def _parse(s):
+            parts = []
+            for tok in _re.split(r'(\d+)', s):
+                if tok.isdigit():
+                    parts.append(int(tok))
+                elif tok:
+                    parts.append(tok)
+            return parts
+        def __str__(self):
+            return self.vstring
+        def __repr__(self):
+            return 'LooseVersion(%r)' % self.vstring
+        def _cmp(self, other):
+            if not isinstance(other, LooseVersion):
+                other = LooseVersion(other)
+            a, b = self._cmp_key, other._cmp_key
+            for i in range(max(len(a), len(b))):
+                ai = a[i] if i < len(a) else 0
+                bi = b[i] if i < len(b) else 0
+                if type(ai) != type(bi):
+                    ai, bi = str(ai), str(bi)
+                if ai < bi:
+                    return -1
+                if ai > bi:
+                    return 1
+            return 0
+        def __lt__(self, other): return self._cmp(other) < 0
+        def __le__(self, other): return self._cmp(other) <= 0
+        def __eq__(self, other): return self._cmp(other) == 0
+        def __ge__(self, other): return self._cmp(other) >= 0
+        def __gt__(self, other): return self._cmp(other) > 0
+        def __ne__(self, other): return self._cmp(other) != 0
 
 if not hasattr(subprocess, 'check_output'):
     def check_output(*popenargs, **kwargs):
@@ -4514,6 +4555,8 @@ def GetMyDistro(dist_class_name=''):
                 Distro = 'oracle'
             elif ('redhat'.lower() in Distro.lower()):
                 Distro = 'redhat'
+            elif ('azurelinux' in Distro.lower()):
+                Distro = 'fedora'
             elif ('Kali'.lower() in Distro.lower()):
                 Distro = 'Kali'
             elif ('FreeBSD'.lower() in  Distro.lower() or 'gaia'.lower() in Distro.lower() or 'panos'.lower() in Distro.lower()):
@@ -4555,6 +4598,21 @@ def DistInfo(fullname=0):
             return distinfo
         if 'Linux' in platform.system():
             distinfo = ["Default"]
+            # On Python 3.8+ linux_distribution is removed; detect via /etc/os-release
+            try:
+                with open("/etc/os-release", "r") as f:
+                    os_id, os_version = "", ""
+                    for line in f:
+                        k, _, v = line.strip().partition("=")
+                        v = v.strip('"')
+                        if k == "ID":
+                            os_id = v
+                        elif k == "VERSION_ID":
+                            os_version = v
+                    if os_id == "azurelinux":
+                        return ["azurelinux", os_version]
+            except Exception:
+                pass
             if "ubuntu" in platform.version().lower():
                 distinfo[0] = "Ubuntu"
             elif 'suse' in platform.version().lower():
diff --git a/VMBackup/main/patch/AzureLinuxPatching.py b/VMBackup/main/patch/AzureLinuxPatching.py
@@ -0,0 +1,49 @@
+#!/usr/bin/python
+#
+# Copyright 2015 Microsoft Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+import subprocess
+from patch.AbstractPatching import AbstractPatching
+from common import *
+
+
+class AzureLinuxPatching(AbstractPatching):
+    def __init__(self,logger,distro_info):
+        super(AzureLinuxPatching,self).__init__(distro_info)
+        self.logger = logger
+        self.base64_path = '/usr/bin/base64'
+        self.bash_path = '/usr/bin/bash'
+        self.blkid_path = '/usr/bin/blkid'
+        self.cat_path = '/usr/bin/cat'
+        self.cryptsetup_path = '/usr/bin/cryptsetup'
+        self.dd_path = '/usr/bin/dd'
+        self.e2fsck_path = '/usr/bin/e2fsck'
+        self.echo_path = '/usr/bin/echo'
+        self.getenforce_path = '/usr/bin/getenforce'
+        self.setenforce_path = '/usr/bin/setenforce'
+        self.lsblk_path = '/usr/bin/lsblk'
+        self.usr_flag = 1
+        self.lsscsi_path = '/usr/bin/lsscsi'
+        self.mkdir_path = '/usr/bin/mkdir'
+        self.mount_path = '/usr/bin/mount'
+        self.openssl_path = '/usr/bin/openssl'
+        self.resize2fs_path = '/usr/bin/resize2fs'
+        self.umount_path = '/usr/bin/umount'
+
+    def install_extras(self):
+        common_extras = ['cryptsetup','lsscsi']
+        for extra in common_extras:
+            self.logger.log("installation for " + extra + ' result is ' + str(subprocess.call(['dnf', 'install','-y', extra])))
diff --git a/VMBackup/main/patch/__init__.py b/VMBackup/main/patch/__init__.py
@@ -31,6 +31,7 @@
 from patch.DefaultPatching import DefaultPatching
 from patch.FreeBSDPatching import FreeBSDPatching
 from patch.NSBSDPatching import NSBSDPatching
+from patch.AzureLinuxPatching import AzureLinuxPatching
 
 # Define the function in case waagent(<2.0.4) doesn't have DistInfo()
 def DistInfo():
@@ -60,6 +61,21 @@ def DistInfo():
             return distinfo
         if 'Linux' in platform.system():
             distinfo = ["Default"]
+            # On Python 3.8+ linux_distribution is removed; detect via /etc/os-release
+            try:
+                with open("/etc/os-release", "r") as f:
+                    os_id, os_version = "", ""
+                    for line in f:
+                        k, _, v = line.strip().partition("=")
+                        v = v.strip('"')
+                        if k == "ID":
+                            os_id = v
+                        elif k == "VERSION_ID":
+                            os_version = v
+                    if os_id == "azurelinux":
+                        return ["azurelinux", os_version]
+            except Exception:
+                pass
             if "ubuntu" in platform.version().lower():
                 distinfo[0] = "Ubuntu"
             elif 'suse' in platform.version().lower():
@@ -114,6 +130,8 @@ def GetMyPatching(logger):
             Distro = 'oracle'
         elif ('redhat'.lower() in Distro.lower()):
             Distro = 'redhat'
+        elif ('azurelinux' in Distro.lower()):
+            Distro = 'AzureLinux'
         elif ("Kali".lower() in Distro.lower()):
             Distro = 'Kali'
         elif ('FreeBSD'.lower() in  Distro.lower() or 'gaia'.lower() in Distro.lower() or 'panos'.lower() in Distro.lower()):
