Bug 12789

When dumping a filesystem by specifying its mount point (rather than its
special file name) if there is no entry in fstab for the filesystem dump
fails with what can be a misleading error message.

For example if I dump /bsd (which has no fstab entry I get):

bob@luke-pf /usr/src/sbin/dump> dump -0ab 32 -f /dev/null /bsd                 
  DUMP: Date of this level 0 dump: Sat Jul 24 13:21:19 1999
  DUMP: Date of last level 0 dump: the epoch
  DUMP: Dumping /bsd to /dev/null
  DUMP: bad sblock magic number

What has happened here is that dump, because it did not find an entry
for /bsd in /etc/fstab has opened the directory /bsd and tried to dump
it (and, of course, failed since it has no superblock).

Fix: I have implemented a simple additional check to see that the open file
(should be the filesystem) isn't a directory (as it will be in this case).
If it is a directory, the changed code prints a warning message to assist
the user in diagnosing what he has done wrong.

The output from dump will now look like this:

bob@luke-pf /usr/src/sbin/dump> /usr/obj/usr/src/sbin/dump/dump -0ab 32 -f /d >
  DUMP: Date of this level 0 dump: Sat Jul 24 13:47:39 1999
  DUMP: Date of last level 0 dump: the epoch
  DUMP: Dumping /bsd to /dev/null
  DUMP: WARNING: /bsd will be processed as a directory, not a filesystem
  DUMP: bad sblock magic number
  DUMP: The ENTIRE dump is aborted.

There are, no doubt, other and likely better ways to solve this problem
but this worked for me (next time I won't spend so much time tracking
down what's really wrong).

Here is a patch for the change should you be interested:



#include "dump.h"
 #include "pathnames.h"
@@ -104,6 +105,7 @@
        register int ch;
        int i, anydirskipped, bflag = 0, Tflag = 0, honorlevel = 1;
        ino_t maxino;
+       struct stat sb;

        spcl.c_date = 0;
        (void)time((time_t *)&spcl.c_date);
@@ -327,6 +333,11 @@
                msg("Cannot open %s\n", disk);
                exit(X_STARTUP);
        }
+       if (fstat(diskfd, &sb))
+               quit("unable to fstat filesystem");
+       if (S_ISDIR(sb.st_mode))
+               msg("WARNING: %s will be processed as a directory, not a filesystem\n",
+                       disk);
        sync();
        sblock = (struct fs *)sblock_buf;
        bread(SBOFF, (char *) sblock, SBSIZE);--I4VUJ8bqnoj2LHxCkOKTozhyISjpAIYfoyuy279EhA8Easyy
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Index: src/sbin/dump/main.c
===================================================================
RCS file: /usr/cvs/FreeBSD/src/sbin/dump/main.c,v
retrieving revision 1.18
diff -u -r1.18 main.c
--- main.c      1998/09/16 20:52:12     1.18
+++ main.c      1999/07/24 18:47:32
@@ -68,6 +68,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <sys/stat.h>
How-To-Repeat: Run dump against a mounted filesystem that has no entry in /etc/fstab
and specifify its mount point rather than the special file path.