@pritam_konar Looks like SPNEGO (http) authentication is enabled for HDFS. From the machine where we are opening those UIs we will need to make sure that the following things are already done or we can check the following: 1. If it is windows machine then please check if it is pointing to correct Kerberos server by looking at the "C:\Windows\krb5.ini" file (on other Linux/Mac machine check it on "/etc/krb5.conf") Compare it from the Hadoop clusters "/etc/krb5.conf" file once.   2. On the laptop where the browser is trying to open the UI please get a valid HTTP/kerberos ticket:   # kinit -kt $KEYTAB_PATH $PRINCIPAL # klist   NOTE: the principal listed in the above keytab should usually be matching the patterns defined in the "auth_to_local" rules and the you can also find the SPNEGO principal details from HDFS configs.   3. Refer to the following doc to verify if the Browser level settings are already done or not? https://www.cloudera.com/documentation/enterprise/5-6-x/topics/cdh_sg_browser_access_kerberos_protected_url.html (OR) https://docs.hortonworks.com/HDPDocuments/HDP3/HDP-3.1.0/authentication-with-kerberos/content/authe_spnego_enabling_browser_access_to_a_spnego_enabled_web_ui.html   Example : To configure Mozilla Firefox: Open the low level Firefox configuration page by loading the "about:config" page. In the Search text box, enter: "network.negotiate-auth.trusted-uris" Double-click the network.negotiate-auth.trusted-uris preference and enter the hostname or the domain of the web server that is protected by Kerberos HTTP SPNEGO. Separate multiple domains and hostnames with a comma. Click OK.   Similarly you will find settings for Chrome & Internet Explorer as well.   4. Restart the browsers once. Then try to access the UI again.   ... View more

@Manoj690  Better approach will be to change the PORT in yarn config from 53 to something unused.   https://community.cloudera.com/t5/Community-Articles/YARN-REGISTRY-DNS-Port-Conflict-Issue/ta-p/249117 ... View more

@Manoj690  Or try changing the yarn service port to something else.   # kill -9 636   ... View more

@Manoj690    Also please let us know how yarn DNS issue is related to  HST Server issue?  By any chance did you post the yarn dns error in a wrong thread? ... View more

@Manoj690    DNS will use port 53 which seems to be already in use. Please kill the process once which is using port 53 and then retry the operation. Opening TCP and UDP channels on /0.0.0.0 port 53 2019-08-22 12:03:09,775 ERROR dns.PrivilegedRegistryDNSStarter (PrivilegedRegistryDNSStarter.java:init(61)) - Error initializing Registry DNS java.net.BindException: Problem binding to [gaian-lap386.com:53] java.net.BindException: Address already in use; For more details see: <a href="http://wiki.apache.org/hadoop/BindException" target="_blank">http://wiki.apache.org/hadoop/BindException</a> at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)   ... View more

@harry_li  No posting such link will not be an issue. As @denloe  mentioned that you should not face any issue from now.  So it should be all good. Looks like you are able to post new queries now as i see your latest post here:  Ambari-server start error     ... View more

@harry_li    Looks like due to some issue Ambari is not able to connect to MySQL and hence the Connection Pool is not getting populated. Most probably it might be some issue with MySQL / Network issue (firewall..etc)/ Misconfiguration like incorrect host/port in ambari configs for MySQL host/port ...etc So can you please test the connection by running this simple command from ambari server host to see if you get a Successful connection creation response? # /usr/jdk64/jdk1.8.0_112/bin/java -cp /var/lib/ambari-server/resources/DBConnectionVerification.jar:/usr/share/java/mysql-connector-java.jar org.apache.ambari.server.DBConnectionVerification "jdbc:mysql://xxxxxxxxxxx:3306/ambari" "ambari" "bigdata" com.mysql.jdbc.Driver Please use your own MySQL username and passwords in the above query to test the connection. I am using default password as "bigdata" and DB user name as "ambari" in the above example query. If it fails to connect to mysql then Pleas echeck if at n/w level the Port access is allowed to MySQL Server from Ambari Server host? # telnet $MYSQL_FQDN 3306 (OR) # nc -v $MYSQL_FQDN 3306   If possible then can you please try restarting your MysQL server once and then retry. ... View more