The Cloudera Community has been helping users find answers to their Hadoop questions for over three years now. Over that time the community, along with the Hadoop ecosystem, has grown and changed in many ways. As a result, we are assessing the current and future state of this community to ensure that we are offering an environment that best meets the needs of our users. This is where we need your help. We are opening this thread to collect your feedback on what you like, what can be improved and any new features you would like on the community.   Some potential areas we would like feedback on are:   Segmentation of the forums - Currently the boards are mostly based on components and their function.   This makes it difficult to know where to post your new question and can also reduce the number of people who see your topic. Discussion style: is the current discussion thread style working for you?  Are there examples of other communities with a more intuitive style? Your total community hub: we are considering a large revamp of how you interact with us and find content and connections that you need.  Instead of just being discussion boards, would you like a single portal for all your community needs?  Including local meetup and conference registration, documentation, rich media tutorials, blogs, contests and fun rewards like quests, points, and badges that can earn you not only reputation but other real-world benefits? Are there other ways we can make it easier and more fun to interact with Cloudera, our content, and your peers? Improvements to current features - What features do we have that you would like to improve? A few examples: Improved site search Advanced user profile linked to your social media and allowing you to add and connect with others based on skills/interests Personalizable views/home screens Anything else you would like to add. ... View more

Symptoms   "Permission denied" errors can present in a variety of use cases and from nearly any application that utilizes CDH.   For example, when attempting to start the jobtracker using this command   service hadoop-0.20-mapreduce-jobtracker start    You may see this error, or one similar   org.apache.hadoop.security.AccessControlException: Permission denied: user=mapred, access=WRITE, inode="/":hdfs:supergroup:drwxr-xr-x at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.check(FSPermissionChecker.java:224) at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.check(FSPermissionChecker.java:204) at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.checkPermission(FSPermissionChecker.java:149) at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkPermission(FSNamesystem.java:4891) at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkPermission(FSNamesystem.java:4873) at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.checkAncestorAccess(FSNamesystem.java:4847) at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirsInternal(FSNamesystem.java:3192) at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirsInt(FSNamesystem.java:3156) at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.mkdirs(FSNamesystem.java:3137) at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.mkdirs(NameNodeRpcServer.java:669)    While the steps to reproduce this error can vary widely, the root causes are very well defined and you'll know you're suffering from this issue by finding the following line either on stdout or in the relevant log files:   org.apache.hadoop.security.AccessControlException: Permission denied: user=XXX, access=WRITE, inode="/someDirectory":hdfs:supergroup:drwxr-xr-x   Applies To   CDH (all versions), Mapreduce, HDFS, other services that rely on reading from or writing to HDFS   Cause   Access to the HDFS filesystem and/or permissions on certain directories are not correctly configured.   Troubleshooting Steps   There are several solutions to attempt:   1) The /user/ directory is owned by "hdfs" with 755 permissions. As a result only hdfs can write to that directory. Unlike unix/linux, hdfs is the superuser and not root. So you would need to do this: sudo -u hdfs hadoop fs -mkdir /user/,,myfile,, sudo -u hdfs hadoop fs -put myfile.txt /user/,,/,, If you want to create a home directory for root so you can store files in his directory, do: sudo -u hdfs hadoop fs -mkdir /user/root sudo -u hdfs hadoop fs -chown root /user/root Then as root you can do "hadoop fs -put file /user/root/". 2) You may also be getting denied on the network port where the NameNode is supposed to be listening:   Fix this by changing the address that the service is listening on in /etc/hadoop/conf/core-site.xml. By default your NameNode may be listening on "localhost:8020." (127.0.0.1)   So to be clear, implement this value for the following property: <property>     <name>fs.defaultFS</name>     <value>hdfs://0.0.0.0:8020</value> </property>   then bounce the service with hadoop-hdfs-namenode restart optional: validate with netstat -tupln | grep '8020'    References ... View more