[Merge] lp:~jamesodhunt/upstart/bug-980917 into lp:upstart

[Steve Langasek]

Review: Needs Fixing

+               if (system_mount ("devtmpfs", "/dev", (MS_NOEXEC | MS_NOSUID)) < 0) {
+                       NihError *err;
+
+                       err = nih_error_get ();
+                       nih_error ("%s: %s", _("Unable to mount /dev filesystem"),
+                               err->message);
+                       nih_free (err);
+               }
+
+               /* Required to exist before /dev/pts accessed */
+               if (mknod ("/dev/ptmx", makedev (5, 2), S_IFCHR) < 0 && errno != EEXIST)
+                       nih_error ("Unable to create /dev/ptmx");
+
+               if (mkdir ("/dev/pts", 0755) < 0 && errno != EEXIST)
+                       nih_error ("%s: %s", _("Cannot create directory"), "/dev/pts");
+

This all assumes that mounting devtmpfs on /dev is required, and that /dev isn't being provided some other way - such as by a static /dev on the root filesystem.  A result of this is that when /dev is not currently a mount point *and is not configured to be*, this code will still mount devtmpfs, potentially clobbering the /dev that the admin has configured.

I think this entire section should be wrapped with a check for whether /dev/pts and /dev/ptmx already exist, and only mount /dev if we determine we need to write to the directory.
-- 
https://code.launchpad.net/~jamesodhunt/upstart/bug-980917/+merge/117863
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