multi_log: only write to /dev/console if it exists.

Some containers lack /dev/console, so when multi_log attempts to open
that device and write to it directly things can start going haywire.

Here we address this problem by sending console-bound output to stdout
and letting init take care of getting it to the console instead.
We already configure upstart with "console output", so we need only
change systemd to use "journal+console".

The one reason that 'console output' might not be sufficient is if
the user redirected output with 'output'.  Ie:
  output:
    init: "> /var/log/my-cloud-init.log"

Would then mean all output would go there, and anything that
*needed* to go to the console (and was explicitly using multi_log for
that purpose) would not get there.

1 files changed, 15 insertions, 5 deletions

diff --git a/cloudinit/util.py b/cloudinit/util.py
index deac8c8d..cd1cc1a4 100644
--- a/cloudinit/util.py
+++ b/cloudinit/util.py
@@ -360,11 +360,21 @@ def multi_log(text, console=True, stderr=True,
     if stderr:
         sys.stderr.write(text)
     if console:
-        # Don't use the write_file since
-        # this might be 'sensitive' info (not debug worthy?)
-        with open('/dev/console', 'wb') as wfh:
-            wfh.write(text)
-            wfh.flush()
+        conpath = "/dev/console"
+        if os.path.exists(conpath):
+            with open(conpath, 'wb') as wfh:
+                wfh.write(text)
+                wfh.flush()
+        else:
+            # A container may lack /dev/console (arguably a container bug).  If
+            # it does not exist, then write output to stdout.  this will result
+            # in duplicate stderr and stdout messages if stderr was True.
+            # 
+            # even though upstart or systemd might have set up output to go to
+            # /dev/console, the user may have configured elsewhere via
+            # cloud-config 'output'.  If there is /dev/console, messages will
+            # still get there.
+            sys.stdout.write(text)
     if log:
         if text[-1] == "\n":
             log.log(log_level, text[:-1])