From 5626a4d593df9384fff5129e7bdb6c909f5f2b11 Mon Sep 17 00:00:00 2001
From: Maurizio Lombardi <mlombard@redhat.com>
Date: Fri, 8 Feb 2019 14:36:34 +0100
Subject: [PATCH] save_to_file() function breaks symbolic link when saving
 configuration

Currently the location of the targetcli configuration file is not
configurable (saveconfig.json). The location is : /etc/target
Some users use stateless VMs, with just a persistent device
mounted under /var/lib/diskless.

In order to circumvent the non configurable location of
saveconfig.json, they create a symbolic link in /etc/target
pointing to /var/lib/diskless

Unfortunately, the rtslib save_to_file() function breaks
this symbolic link and creates a new regular file in place of it,
due to the creation of a saveconfig.json.temp file which is
then renamed to saveconfig.json using the os.rename() function.

This patch replace os.rename() with shutil.copyfile() + os.remove(),
using copyfile() instead of rename() will preserve the symbolic link

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
---
 rtslib/root.py | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/rtslib/root.py b/rtslib/root.py
index 5c0a98c..c93e65b 100644
--- a/rtslib/root.py
+++ b/rtslib/root.py
@@ -23,6 +23,7 @@ import stat
 import json
 import glob
 import errno
+import shutil
 
 from .node import CFSNode
 from .target import Target
@@ -386,7 +387,9 @@ class RTSRoot(CFSNode):
         else:
             saveconf = self.dump()
 
-        with open(save_file+".temp", "w+") as f:
+        tmp_file = save_file + ".temp"
+
+        with open(tmp_file, "w+") as f:
             os.fchmod(f.fileno(), stat.S_IRUSR | stat.S_IWUSR)
             f.write(json.dumps(saveconf, sort_keys=True, indent=2))
             f.write("\n")
@@ -394,7 +397,8 @@ class RTSRoot(CFSNode):
             os.fsync(f.fileno())
             f.close()
 
-        os.rename(save_file+".temp", save_file)
+        shutil.copyfile(tmp_file, save_file)
+        os.remove(tmp_file)
 
     def restore_from_file(self, restore_file=None, clear_existing=True, abort_on_error=False):
         '''
-- 
2.21.0