title: redis rewrites the dir and dbfilename automatically
body: <p>Recently, I got some weird things while using redis-2.8.19.
  I used redis as memory queues, and my program ran well for some months,
  so I checked the server log, it said:</p>
  
  <pre><code>[19167] 21 Nov 13:49:24.022 * 10 changes in 300 seconds. Saving...
  
  [19167] 21 Nov 13:49:24.023 * Background saving started by pid 15912
  
  [15912] 21 Nov 13:49:24.100 # Error moving temp DB file on the final 
  destination: Is a directory
  
  [19167] 21 Nov 13:49:24.123 # Background saving error
  </code></pre>
  
  <p>so, I used commands <code>:echo "CONFIG GET *" | redis-cli | grep -e "dir" -e "dbfilename" -A1</code>, 
  and it showed as following: </p>
  
  <pre><code>dbfilename
  authorized_keys
  --
  dir
  /root/.ssh
  </code></pre>
  
  <p>Naturally, I changed the <code>dir</code> and <code>dbfilename</code> config and restarted the redis, the program ran well for some hours or some days before broken down again for the same reason. I checked the dir and dbfilename config and found them written exactly same as before. The redis process never restart during the period and no one may change the config.</p>
  
  <p>So I just get confused, how the <code>dir</code> and <code>dbfilename</code> config changed?</p>