VMBackup: Document vmbackup.conf options including df -kl local flag

VMBackup/README.txt

@@ -2,6 +2,41 @@ VMBackup extension is used by Azure Backup service to provide application consis
 
 **Note:** This extension is not recommended to be installed outside Azure Backup service context. 
 
-## Deploying the extension to a VM
+Configuration
+-------------
+
+The VMBackup extension reads optional configuration from /etc/azure/vmbackup.conf.
+Below are the available options under the [SnapshotThread] section:
+
+  fsfreeze (default: True)
+    Whether to freeze filesystems (fsfreeze/thaw) before taking a snapshot.
+    Freezing ensures application-consistent backups by flushing pending I/O.
+    Set to False only if fsfreeze causes issues (e.g., unresponsive mounts).
+
+  onlyLocalFilesystems (default: False)
+    When set to True, the extension uses 'df -kl' instead of 'df -k' for size
+    calculation, restricting the listing to local filesystems only. This prevents
+    the df command from hanging when network mounts (NFS, CIFS, FUSE, etc.) are
+    unreachable or slow to respond. Recommended for VMs with network-mounted
+    filesystems.
+
+  MountsToSkip (default: empty)
+    Comma-separated list of mount points to exclude from filesystem freeze.
+    Useful when specific mounts should not be frozen during backup (e.g., large
+    shared storage that cannot be safely frozen).
+
+  seqsnapshot (default: 0)
+    Controls snapshot ordering. 0 = parallel snapshots, 1 = sequential (set
+    programmatically), 2 = sequential (set by customer). Use 2 to force
+    sequential disk snapshots if parallel snapshots cause issues.
+
+Example /etc/azure/vmbackup.conf:
+
+  [SnapshotThread]
+  fsfreeze = True
+  onlyLocalFilesystems = True
+  MountsToSkip = /mnt/nfs_share,/mnt/cifs_share
+
+Deploying the extension to a VM
 This extension gets deployed as part of first scheduled backup of the VM post you configure VM for backup. You can configure VM to be backed up using [Azure Portal](https://docs.microsoft.com/azure/backup/quick-backup-vm-portal), [Azure PowerShell](https://docs.microsoft.com/azure/backup/quick-backup-vm-powershell) or Azure CLI(https://docs.microsoft.com/azure/backup/quick-backup-vm-cli). 
 

VMBackup/main/tempPlugin/vmbackup.conf

@@ -1,3 +1,20 @@
 [SnapshotThread]
+
+# Whether to freeze filesystems (fsfreeze/thaw) before taking a snapshot.
+# Freezing ensures application-consistent backups by flushing pending I/O.
+# Set to False only if fsfreeze causes issues (e.g., unresponsive mounts).
+# Default: True
 fsfreeze: True
 
+# Set to True to use 'df -kl' (local filesystems only) instead of 'df -k' for
+# size calculation. This prevents df from hanging when network mounts (NFS,
+# CIFS, FUSE, etc.) are unreachable or slow. Recommended for VMs with
+# network-mounted filesystems. Default: False
+# onlyLocalFilesystems: True
+
+# Comma-separated mount points to exclude from filesystem freeze.
+# MountsToSkip:
+
+# Snapshot ordering: 0=parallel, 1=sequential (programmatic), 2=sequential (customer).
+# seqsnapshot: 0
+