Update nfs config for image mode

Fix mount issue(RHEL-84861) in image mode.

Signed-off-by: lcheng <lcheng@redhat.com>

Author: cliping

virttest/nfs.py

@@ -158,7 +158,6 @@ class Nfs(object):
     def __init__(self, params):
         self.mount_dir = params.get("nfs_mount_dir")
         self.mount_options = params.get("nfs_mount_options")
-        self.mount_src = params.get("nfs_mount_src")
         self.nfs_setup = False
         path.find_command("mount")
         self.rm_mount_dir = False
@@ -167,10 +166,16 @@ def __init__(self, params):
         distro_details = distro.detect().name
         self.session = None
         self.setup_nfs_ip = params.get("nfs_server_ip", "127.0.0.1")
-        self.export_dir = params.get("export_dir") or self.mount_src.split(":")[-1]
         self.export_ip = params.get("export_ip", "*")
-        self.export_options = params.get("export_options", "").strip()
         self.run_mount = params.get("run_mount", True)
+        migration_setup = params.get("migration_setup", "no") == "yes"
+        if migration_setup and utils_sys.is_image_mode():
+            self.mount_src = "/"
+            self.export_options = params.get("export_options", "").strip() + ",fsid=0"
+        else:
+            self.mount_src = params.get("nfs_mount_src")
+            self.export_options = params.get("export_options", "").strip()
+        self.export_dir = params.get("export_dir") or self.mount_src.split(":")[-1]
 
         if params.get("setup_remote_nfs") == "yes":
             self.nfs_setup = True
@@ -307,7 +312,6 @@ def __init__(self, params):
         self.mkdir_mount_remote = False
         self.mount_dir = params.get("nfs_mount_dir")
         self.mount_options = params.get("nfs_mount_options")
-        self.mount_src = params.get("nfs_mount_src")
         self.nfs_server_ip = params.get("nfs_server_ip")
         self.ssh_user = params.get("ssh_username", "root")
         self.remote_nfs_mount = params.get("remote_nfs_mount", "yes")
@@ -316,6 +320,12 @@ def __init__(self, params):
         if not self.ssh_hostkey_check:
             self.ssh_cmd += "-o StrictHostKeyChecking=no "
 
+        migration_setup = params.get("migration_setup", "no") == "yes"
+        if migration_setup and utils_sys.is_image_mode():
+            self.mount_src = "/"
+        else:
+            self.mount_src = params.get("nfs_mount_src")
+
     def is_mounted(self):
         """
         Check the NFS is mounted or not.