sshdriver: reduce loglevel when running commands

This avoids potential SSH log messages from ending up in the command output,
especially when using stderr_merge.

Signed-off-by: Jan Luebbe <[email protected]>
Signed-off-by: Rouven Czerwinski <[email protected]>

Author: jluebbe

doc/configuration.rst

@@ -1575,10 +1575,10 @@ Arguments:
     explicitly use the SFTP protocol for file transfers instead of scp's default protocol
   - su_username(str, default="root"): only used if su_password is set
   - su_prompt(str, default="Passowrd:"): prompt string for su
-  - su_password(str, default=None): su password for the user set via su_username
+  - su_password(str): optional, su password for the user set via su_username
 
 .. note::
-   Using the su support will automatically enable stderr_merge, since ssh this
+   Using the su support will automatically enable ``stderr_merge``, since ssh this
    is required to interact with the password prompt.
 
 UBootDriver

labgrid/driver/sshdriver.py

@@ -206,7 +206,7 @@ def handle_password(self, fd, stdin, marker):
             # no password needed
             return p.after
 
-        stdin.write(f"{self.su_password}".encode("utf-8"))
+        stdin.write(self.su_password.encode("utf-8"))
         # It seems we need to close stdin here to reliably get su to accept the
         # password. \n doesn't seem to work.
         stdin.close()
@@ -233,7 +233,7 @@ def _run(self, cmd, codec="utf-8", decodeerrors="strict", timeout=None):
         if not self._check_keepalive():
             raise ExecutionError("Keepalive no longer running")
 
-        complete_cmd = ["ssh", "-x", *self.ssh_prefix,
+        complete_cmd = ["ssh", "-x", "-o", "LogLevel=QUIET", *self.ssh_prefix,
                         "-p", str(self.networkservice.port), "-l", self.networkservice.username,
                         self.networkservice.address
                         ]
@@ -263,14 +263,11 @@ def _run(self, cmd, codec="utf-8", decodeerrors="strict", timeout=None):
             )
 
         if self.su_password:
-            fd = sub.stdout if self.stderr_merge else sub.stderr
+            fd = sub.stdout
             output = self.handle_password(fd, sub.stdin, marker)
             sub.stdin.close()
-            self.logger.debug(f"su leftover output: %s", output)
-            if self.stderr_merge:
-                stderr += output
-            else:
-                stdout += output
+            self.logger.debug("su leftover output: %s", output)
+            stderr += output
 
         sub.stdin = None  # never try to write to stdin here
         comout, comerr = sub.communicate(timeout=timeout)