Hdfs commands-EditsFsImage-Configfiles

sudo useradd  juan
#add password to user juan
sudo passwd juan

#create a group
groupadd supergroup
#assaign a group to user juan
usermod -g supergroup juan

#the folder owner is hdfs:supergroup
sudo -su hfds hdfs dfs -mkdir /work

#change owner and permissions of the folder
sudo -su hdfs hdfs dfs -chown juan:supergroup /work  #being root
sudo -su juan
hdfs dfs -chmod 755 /work

//edits files and fsimages

#go to /dfs/nn/current to see the files edits files of the namenode
cd /dfs/nn/current
ls -ltr
#go to /dfs/snn/current to see the files edits files of the Secundary namenode
cd /dfs/snn/current
ls -ltr

# in order to generate a new fsimage and edit log 
#first get into safe mode
sudo -u hdfs hdfs dfsadmin -safemode enter
#this line create the new edit log and fsimage
sudo -u hdfs hdfs dfsadmin -saveNamespace
#leave the safemode
sudo -u hdfs hdfs dfsadmin -safemode leave

###find the config files in the cluster
#go to the cluster where is the namenode service
find / -name "core-site.xml"
#go to 
cd /var/run/cloudera-scm-agent/process/  #you will see varios namenode, there are various because
# in this way cloudera handle rollbacks 


###find log files
cd /var/log/hadoop-hdfs