title: mongod shell doesn't start, data/db doesn't exsist
body: <p>When I start mongod trowed error. What is the problem?</p>
  
  <pre><code>root@cs12867:~# mongod
  mongod --help for help and startup options
  Sun Dec 22 15:37:44.081 [initandlisten] MongoDB starting : pid=18415 port=27017 dbpath=/data/db/ 64-bit host=cs12867
  Sun Dec 22 15:37:44.081 [initandlisten] db version v2.4.6
  Sun Dec 22 15:37:44.081 [initandlisten] git version: b9925db5eac369d77a3a5f5d98a145eaaacd9673
  Sun Dec 22 15:37:44.081 [initandlisten] build info: Linux ip-10-2-29-40 2.6.21.7-2.ec2.v1.2.fc8xen #1 SMP Fri Nov 20 17:48:28 EST 2009 x86_64 BOOST_LIB_VERSION=1_49
  Sun Dec 22 15:37:44.081 [initandlisten] allocator: tcmalloc
  Sun Dec 22 15:37:44.081 [initandlisten] options: {}
  Sun Dec 22 15:37:44.081 [initandlisten] exception in initAndListen: 10296
  *********************************************************************
   ERROR: dbpath (/data/db/) does not exist.
   Create this directory or give existing directory in --dbpath.
   See http://dochub.mongodb.org/core/startingandstoppingmongo
  *********************************************************************
  , terminating
  Sun Dec 22 15:37:44.081 dbexit:
  Sun Dec 22 15:37:44.081 [initandlisten] shutdown: going to close listening sockets...
  Sun Dec 22 15:37:44.081 [initandlisten] shutdown: going to flush diaglog...
  Sun Dec 22 15:37:44.081 [initandlisten] shutdown: going to close sockets...
  Sun Dec 22 15:37:44.081 [initandlisten] shutdown: waiting for fs preallocator...
  Sun Dec 22 15:37:44.081 [initandlisten] shutdown: lock for final commit...
  Sun Dec 22 15:37:44.081 [initandlisten] shutdown: final commit...
  Sun Dec 22 15:37:44.081 [initandlisten] shutdown: closing all files...
  Sun Dec 22 15:37:44.081 [initandlisten] closeAllFiles() finished
  Sun Dec 22 15:37:44.081 dbexit: really exiting now
  </code></pre>
  
  <p>I set <code>--dbpath</code>:</p>
  
  <pre><code>root@cs12867:~# mongod --dbpath /var/lib/mongodb/data/db
  Sun Dec 22 15:29:25.121 [initandlisten] MongoDB starting : pid=17739 port=27017 dbpath=/var/lib/mongodb/data/db 64-bit host=cs12867
  Sun Dec 22 15:29:25.121 [initandlisten] db version v2.4.6
  Sun Dec 22 15:29:25.121 [initandlisten] git version: b9925db5eac369d77a3a5f5d98a145eaaacd9673
  Sun Dec 22 15:29:25.121 [initandlisten] build info: Linux ip-10-2-29-40 2.6.21.7-2.ec2.v1.2.fc8xen #1 SMP Fri Nov 20 17:48:28 EST 2009 x86_64 BOOST_LIB_VERSION=1_49
  Sun Dec 22 15:29:25.121 [initandlisten] allocator: tcmalloc
  Sun Dec 22 15:29:25.121 [initandlisten] options: { dbpath: "/var/lib/mongodb/data/db" }
  Sun Dec 22 15:29:25.121 [initandlisten]
  Sun Dec 22 15:29:25.121 [initandlisten] ** WARNING: Readahead for /var/lib/mongodb/data/db is set to 2048KB
  Sun Dec 22 15:29:25.121 [initandlisten] **          We suggest setting it to 256KB (512 sectors) or less
  Sun Dec 22 15:29:25.121 [initandlisten] **          http://dochub.mongodb.org/core/readahead
  Sun Dec 22 15:29:25.123 [initandlisten] journal dir=/var/lib/mongodb/data/db/journal
  Sun Dec 22 15:29:25.123 [initandlisten] recover : no journal files present, no recovery needed
  Sun Dec 22 15:29:25.134 [initandlisten] waiting for connections on port 27017
  Sun Dec 22 15:29:25.134 [websvr] admin web console waiting for connections on port 28017
  Sun Dec 22 15:29:26.179 [initandlisten] connection accepted from 127.0.0.1:37164 #1 (1 connection now open)
  Sun Dec 22 15:29:26.179 [FileAllocator] allocating new datafile /var/lib/mongodb/data/db/Tester.ns, filling with zeroes...
  Sun Dec 22 15:29:26.179 [FileAllocator] creating directory /var/lib/mongodb/data/db/_tmp
  Sun Dec 22 15:29:26.181 [FileAllocator] done allocating datafile /var/lib/mongodb/data/db/Tester.ns, size: 16MB,  took 0 secs
  Sun Dec 22 15:29:26.181 [FileAllocator] allocating new datafile /var/lib/mongodb/data/db/Tester.0, filling with zeroes...
  Sun Dec 22 15:29:26.181 [FileAllocator] done allocating datafile /var/lib/mongodb/data/db/Tester.0, size: 64MB,  took 0 secs
  Sun Dec 22 15:29:26.182 [FileAllocator] allocating new datafile /var/lib/mongodb/data/db/Tester.1, filling with zeroes...
  Sun Dec 22 15:29:26.182 [FileAllocator] done allocating datafile /var/lib/mongodb/data/db/Tester.1, size: 128MB,  took 0 secs
  Sun Dec 22 15:29:26.184 [conn1] build index Tester.user { _id: 1 }
  Sun Dec 22 15:29:26.184 [conn1] build index done.  scanned 0 total records. 0 secs
  Sun Dec 22 15:29:26.184 [conn1] end connection 127.0.0.1:37164 (0 connections now open)
  Sun Dec 22 15:29:26.192 [initandlisten] connection accepted from 127.0.0.1:37165 #2 (1 connection now open)
  Sun Dec 22 15:29:26.732 [initandlisten] connection accepted from 127.0.0.1:37166 #3 (2 connections now open)
  Sun Dec 22 15:29:26.733 [conn3] end connection 127.0.0.1:37166 (1 connection now open)
  Sun Dec 22 15:29:26.740 [initandlisten] connection accepted from 127.0.0.1:37167 #4 (2 connections now open)
  Sun Dec 22 15:29:26.740 [conn4] end connection 127.0.0.1:37167 (1 connection now open)
  Sun Dec 22 15:29:26.834 [initandlisten] connection accepted from 127.0.0.1:37168 #5 (2 connections now open)
  Sun Dec 22 15:29:26.835 [conn5] end connection 127.0.0.1:37168 (1 connection now open)
  Sun Dec 22 15:29:26.843 [initandlisten] connection accepted from 127.0.0.1:37169 #6 (2 connections now open)
  Sun Dec 22 15:29:27.252 [initandlisten] connection accepted from 127.0.0.1:37170 #7 (3 connections now open)
  Sun Dec 22 15:29:27.253 [conn7] end connection 127.0.0.1:37170 (2 connections now open)
  Sun Dec 22 15:29:27.304 [initandlisten] connection accepted from 127.0.0.1:37171 #8 (3 connections now open)
  Sun Dec 22 15:29:27.304 [conn8] end connection 127.0.0.1:37171 (2 connections now open)
  Sun Dec 22 15:29:28.332 [initandlisten] connection accepted from 127.0.0.1:37173 #9 (3 connections now open)
  Sun Dec 22 15:29:28.333 [conn9] end connection 127.0.0.1:37173 (2 connections now open)
  Sun Dec 22 15:29:28.352 [initandlisten] connection accepted from 127.0.0.1:37174 #10 (3 connections now open)
  Sun Dec 22 15:29:28.842 [conn10] end connection 127.0.0.1:37174 (2 connections now open)
  Sun Dec 22 15:29:28.862 [initandlisten] connection accepted from 127.0.0.1:37176 #11 (3 connections now open)
  Sun Dec 22 15:29:28.863 [conn11] end connection 127.0.0.1:37176 (2 connections now open)
  Sun Dec 22 15:29:30.362 [initandlisten] connection accepted from 127.0.0.1:37178 #12 (3 connections now open)
  Sun Dec 22 15:29:30.363 [initandlisten] connection accepted from 127.0.0.1:37179 #13 (4 connections now open)
  Sun Dec 22 15:29:30.364 [conn13] end connection 127.0.0.1:37179 (3 connections now open)
  Sun Dec 22 15:37:36.523 [signalProcessingThread] shutdown: closing all files...
  Sun Dec 22 15:37:36.523 [signalProcessingThread] closeAllFiles() finished
  Sun Dec 22 15:37:36.523 [signalProcessingThread] journalCleanup...
  Sun Dec 22 15:37:36.523 [signalProcessingThread] removeJournalFiles
  Sun Dec 22 15:37:36.525 [signalProcessingThread] shutdown: removing fs lock...
  Sun Dec 22 15:37:36.525 dbexit: really exiting now
  </code></pre>
  
  <p>Then again:</p>
  
  <pre><code>root@cs12867:~# mongod
  mongod --help for help and startup options
  Sun Dec 22 15:37:44.081 [initandlisten] MongoDB starting : pid=18415 port=27017 dbpath=/data/db/ 64-bit host=cs12867
  Sun Dec 22 15:37:44.081 [initandlisten] db version v2.4.6
  Sun Dec 22 15:37:44.081 [initandlisten] git version: b9925db5eac369d77a3a5f5d98a145eaaacd9673
  Sun Dec 22 15:37:44.081 [initandlisten] build info: Linux ip-10-2-29-40 2.6.21.7-2.ec2.v1.2.fc8xen #1 SMP Fri Nov 20 17:48:28 EST 2009 x86_64 BOOST_LIB_VERSION=1_49
  Sun Dec 22 15:37:44.081 [initandlisten] allocator: tcmalloc
  Sun Dec 22 15:37:44.081 [initandlisten] options: {}
  Sun Dec 22 15:37:44.081 [initandlisten] exception in initAndListen: 10296
  *********************************************************************
   ERROR: dbpath (/data/db/) does not exist.
   Create this directory or give existing directory in --dbpath.
   See http://dochub.mongodb.org/core/startingandstoppingmongo
  *********************************************************************
  , terminating
  Sun Dec 22 15:37:44.081 dbexit:
  Sun Dec 22 15:37:44.081 [initandlisten] shutdown: going to close listening sockets...
  Sun Dec 22 15:37:44.081 [initandlisten] shutdown: going to flush diaglog...
  Sun Dec 22 15:37:44.081 [initandlisten] shutdown: going to close sockets...
  Sun Dec 22 15:37:44.081 [initandlisten] shutdown: waiting for fs preallocator...
  Sun Dec 22 15:37:44.081 [initandlisten] shutdown: lock for final commit...
  Sun Dec 22 15:37:44.081 [initandlisten] shutdown: final commit...
  Sun Dec 22 15:37:44.081 [initandlisten] shutdown: closing all files...
  Sun Dec 22 15:37:44.081 [initandlisten] closeAllFiles() finished
  Sun Dec 22 15:37:44.081 dbexit: really exiting now
  </code></pre>