This is my error logs ......    ==========================Creating target directory...========================== Command start time 2019-09-02 17:01:05 Connection to master closed.SSH command execution finishedhost=master, exitcode=0Command end time 2019-09-02 17:01:05 ==========================Copying ambari sudo script...========================== Command start time 2019-09-02 17:01:05 scp /var/lib/ambari-server/ambari-sudo.shhost=master, exitcode=0Command end time 2019-09-02 17:01:05 ==========================Copying common functions script...========================== Command start time 2019-09-02 17:01:05 scp /usr/lib/python2.6/site-packages/ambari_commonshost=master, exitcode=0Command end time 2019-09-02 17:01:06 ==========================Copying OS type check script...========================== Command start time 2019-09-02 17:01:06 scp /usr/lib/python2.6/site-packages/ambari_server/os_check_type.pyhost=master, exitcode=0Command end time 2019-09-02 17:01:06 ==========================Running OS type check...========================== Command start time 2019-09-02 17:01:06Cluster primary/cluster OS family is ubuntu16 and local/current OS family is ubuntu16 Connection to master closed.SSH command execution finishedhost=master, exitcode=0Command end time 2019-09-02 17:01:06 ==========================Checking 'sudo' package on remote host...========================== Command start time 2019-09-02 17:01:06 Connection to master closed.SSH command execution finishedhost=master, exitcode=0Command end time 2019-09-02 17:01:06 ==========================Copying repo file to 'tmp' folder...========================== Command start time 2019-09-02 17:01:06 scp /etc/apt/sources.list.d/ambari.listhost=master, exitcode=0Command end time 2019-09-02 17:01:07 ==========================Moving file to repo dir...========================== Command start time 2019-09-02 17:01:07 Connection to master closed.SSH command execution finishedhost=master, exitcode=0Command end time 2019-09-02 17:01:07 ==========================Changing permissions for ambari.repo...========================== Command start time 2019-09-02 17:01:07 Connection to master closed.SSH command execution finishedhost=master, exitcode=0Command end time 2019-09-02 17:01:07 ==========================Update apt cache of repository...========================== Command start time 2019-09-02 17:01:07 0% [Working]0% [Connecting to public-repo-1.hortonworks.com] [Waiting for headers]Hit:1 http://ppa.launchpad.net/webupd8team/java/ubuntu xenial InRelease 0% [Connecting to public-repo-1.hortonworks.com]0% [1 InRelease gpgv 17.6 kB] [Connecting to public-repo-1.hortonworks.com]0% [Connecting to public-repo-1.hortonworks.com]0% [Connecting to public-repo-1.hortonworks.com]0% [Connecting to public-repo-1.hortonworks.com]0% [Connecting to public-repo-1.hortonworks.com]0% [Connecting to public-repo-1.hortonworks.com]0% [Connecting to public-repo-1.hortonworks.com]0% [Connecting to public-repo-1.hortonworks.com]0% [Connecting to public-repo-1.hortonworks.com]0% [Connecting to public-repo-1.hortonworks.com]Hit:2 http://public-repo-1.hortonworks.com/ambari/ubuntu14/2.x/updates/2.4.2.0 Ambari InRelease 0% [Working]0% [2 InRelease gpgv 3,190 B]20% [Working] Reading package lists... 0% Reading package lists... 0% Reading package lists... 0% Reading package lists... 0% Reading package lists... 5% Reading package lists... Done W: http://public-repo-1.hortonworks.com/ambari/ubuntu14/2.x/updates/2.4.2.0/dists/Ambari/InRelease: Signature by key DF52ED4F7A3A5882C0994C66B9733A7A07513CAD uses weak digest algorithm (SHA1) Connection to master closed.SSH command execution finishedhost=master, exitcode=0Command end time 2019-09-02 17:01:13 ==========================Copying setup script file...========================== Command start time 2019-09-02 17:01:13 scp /usr/lib/python2.6/site-packages/ambari_server/setupAgent.pyhost=master, exitcode=0Command end time 2019-09-02 17:01:13 ==========================Running setup agent script...========================== Command start time 2019-09-02 17:01:13('INFO 2019-09-02 17:01:47,369 logger.py:71 - call returned (0, \'\')INFO 2019-09-02 17:01:47,369 logger.py:71 - call[[\'test\', \'-w\', \'/run/user/0\']] {\'sudo\': True, \'timeout\': 5}INFO 2019-09-02 17:01:47,372 logger.py:71 - call returned (0, \'\')INFO 2019-09-02 17:01:47,378 Facter.py:194 - Directory: \'/etc/resource_overrides\' does not exist - it won\'t be used for gathering system resources.INFO 2019-09-02 17:01:47,449 Controller.py:160 - Registering with master (127.0.1.1) (agent=\'{"hardwareProfile": {"kernel": "Linux", "domain": "", "physicalprocessorcount": 4, "kernelrelease": "4.15.0-45-generic", "uptime_days": "3", "memorytotal": 16390376, "swapfree": "0.95 GB", "memorysize": 16390376, "osfamily": "ubuntu", "swapsize": "0.95 GB", "processorcount": 4, "netmask": null, "timezone": "KST", "hardwareisa": "x86_64", "memoryfree": 12196540, "operatingsystem": "ubuntu", "kernelmajversion": "4.15", "kernelversion": "4.15.0", "macaddress": "30:9C:23:43:F8:99", "operatingsystemrelease": "16.04", "ipaddress": "127.0.1.1", "hostname": "master", "uptime_hours": "73", "fqdn": "master", "id": "root", "architecture": "x86_64", "selinux": false, "mounts": [{"available": "8165416", "used": "0", "percent": "0%", "device": "udev", "mountpoint": "/dev", "type": "devtmpfs", "size": "8165416"}, {"available": "1627856", "used": "11184", "percent": "1%", "device": "tmpfs", "mountpoint": "/run", "type": "tmpfs", "size": "1639040"}, {"available": "903763276", "used": "7750156", "percent": "1%", "device": "/dev/sda1", "mountpoint": "/", "type": "ext4", "size": "960317832"}, {"available": "8195008", "used": "180", "percent": "1%", "device": "tmpfs", "mountpoint": "/dev/shm", "type": "tmpfs", "size": "8195188"}, {"available": "5116", "used": "4", "percent": "1%", "device": "tmpfs", "mountpoint": "/run/lock", "type": "tmpfs", "size": "5120"}, {"available": "1638984", "used": "56", "percent": "1%", "device": "tmpfs", "mountpoint": "/run/user/1000", "type": "tmpfs", "size": "1639040"}, {"available": "1639040", "used": "0", "percent": "0%", "device": "tmpfs", "mountpoint": "/run/user/0", "type": "tmpfs", "size": "1639040"}], "hardwaremodel": "x86_64", "uptime_seconds": "264311", "interfaces": "enp0s31f6,lo,wlx909f330d4aff"}, "currentPingPort": 8670, "prefix": "/var/lib/ambari-agent/data", "agentVersion": "2.4.2.0", "agentEnv": {"transparentHugePage": "madvise", "hostHealth": {"agentTimeStampAtReporting": 1567411307448, "activeJavaProcs": [], "liveServices": [{"status": "Healthy", "name": "ntp", "desc": ""}]}, "reverseLookup": true, "alternatives": [], "umask": "18", "firewallName": "ufw", "stackFoldersAndFiles": [], "existingUsers": [], "firewallRunning": false}, "timestamp": 1567411307380, "hostname": "master", "responseId": -1, "publicHostname": "master"}\')INFO 2019-09-02 17:01:47,449 NetUtil.py:62 - Connecting to https://192.168.56.101 master master.hadoop.com:8440/connection_infoWARNING 2019-09-02 17:01:47,460 NetUtil.py:85 - GET https://192.168.56.101 master master.hadoop.com:8440/connection_info -> 400, body:INFO 2019-09-02 17:01:47,461 security.py:100 - SSL Connect being called.. connecting to the serverINFO 2019-09-02 17:01:47,461 security.py:67 - Insecure connection to https://192.168.56.101 master master.hadoop.com:8441/ failed. Reconnecting using two-way SSL authentication..INFO 2019-09-02 17:01:47,461 security.py:186 - Server certicate not exists, downloadingINFO 2019-09-02 17:01:47,461 security.py:209 - Downloading server cert from https://192.168.56.101 master master.hadoop.com:8440/cert/ca/ERROR 2019-09-02 17:01:47,471 Controller.py:212 - Unable to connect to: https://192.168.56.101 master master.hadoop.com:8441/agent/v1/register/masterTraceback (most recent call last):File "/usr/lib/python2.6/site-packages/ambari_agent/Controller.py", line 165, in registerWithServerret = self.sendRequest(self.registerUrl, data)File "/usr/lib/python2.6/site-packages/ambari_agent/Controller.py", line 496, in sendRequestraise IOError(\'Request to {0} failed due to {1}\'.format(url, str(exception)))IOError: Request to https://192.168.56.101 master master.hadoop.com:8441/agent/v1/register/master failed due to <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:590)>ERROR 2019-09-02 17:01:47,471 Controller.py:213 - Error:Request to https://192.168.56.101 master master.hadoop.com:8441/agent/v1/register/master failed due to <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:590)>WARNING 2019-09-02 17:01:47,471 Controller.py:214 - Sleeping for 19 seconds and then trying again', None)('INFO 2019-09-02 17:01:47,369 logger.py:71 - call returned (0, \'\')INFO 2019-09-02 17:01:47,369 logger.py:71 - call[[\'test\', \'-w\', \'/run/user/0\']] {\'sudo\': True, \'timeout\': 5}INFO 2019-09-02 17:01:47,372 logger.py:71 - call returned (0, \'\')INFO 2019-09-02 17:01:47,378 Facter.py:194 - Directory: \'/etc/resource_overrides\' does not exist - it won\'t be used for gathering system resources.INFO 2019-09-02 17:01:47,449 Controller.py:160 - Registering with master (127.0.1.1) (agent=\'{"hardwareProfile": {"kernel": "Linux", "domain": "", "physicalprocessorcount": 4, "kernelrelease": "4.15.0-45-generic", "uptime_days": "3", "memorytotal": 16390376, "swapfree": "0.95 GB", "memorysize": 16390376, "osfamily": "ubuntu", "swapsize": "0.95 GB", "processorcount": 4, "netmask": null, "timezone": "KST", "hardwareisa": "x86_64", "memoryfree": 12196540, "operatingsystem": "ubuntu", "kernelmajversion": "4.15", "kernelversion": "4.15.0", "macaddress": "30:9C:23:43:F8:99", "operatingsystemrelease": "16.04", "ipaddress": "127.0.1.1", "hostname": "master", "uptime_hours": "73", "fqdn": "master", "id": "root", "architecture": "x86_64", "selinux": false, "mounts": [{"available": "8165416", "used": "0", "percent": "0%", "device": "udev", "mountpoint": "/dev", "type": "devtmpfs", "size": "8165416"}, {"available": "1627856", "used": "11184", "percent": "1%", "device": "tmpfs", "mountpoint": "/run", "type": "tmpfs", "size": "1639040"}, {"available": "903763276", "used": "7750156", "percent": "1%", "device": "/dev/sda1", "mountpoint": "/", "type": "ext4", "size": "960317832"}, {"available": "8195008", "used": "180", "percent": "1%", "device": "tmpfs", "mountpoint": "/dev/shm", "type": "tmpfs", "size": "8195188"}, {"available": "5116", "used": "4", "percent": "1%", "device": "tmpfs", "mountpoint": "/run/lock", "type": "tmpfs", "size": "5120"}, {"available": "1638984", "used": "56", "percent": "1%", "device": "tmpfs", "mountpoint": "/run/user/1000", "type": "tmpfs", "size": "1639040"}, {"available": "1639040", "used": "0", "percent": "0%", "device": "tmpfs", "mountpoint": "/run/user/0", "type": "tmpfs", "size": "1639040"}], "hardwaremodel": "x86_64", "uptime_seconds": "264311", "interfaces": "enp0s31f6,lo,wlx909f330d4aff"}, "currentPingPort": 8670, "prefix": "/var/lib/ambari-agent/data", "agentVersion": "2.4.2.0", "agentEnv": {"transparentHugePage": "madvise", "hostHealth": {"agentTimeStampAtReporting": 1567411307448, "activeJavaProcs": [], "liveServices": [{"status": "Healthy", "name": "ntp", "desc": ""}]}, "reverseLookup": true, "alternatives": [], "umask": "18", "firewallName": "ufw", "stackFoldersAndFiles": [], "existingUsers": [], "firewallRunning": false}, "timestamp": 1567411307380, "hostname": "master", "responseId": -1, "publicHostname": "master"}\')INFO 2019-09-02 17:01:47,449 NetUtil.py:62 - Connecting to https://192.168.56.101 master master.hadoop.com:8440/connection_infoWARNING 2019-09-02 17:01:47,460 NetUtil.py:85 - GET https://192.168.56.101 master master.hadoop.com:8440/connection_info -> 400, body:INFO 2019-09-02 17:01:47,461 security.py:100 - SSL Connect being called.. connecting to the serverINFO 2019-09-02 17:01:47,461 security.py:67 - Insecure connection to https://192.168.56.101 master master.hadoop.com:8441/ failed. Reconnecting using two-way SSL authentication..INFO 2019-09-02 17:01:47,461 security.py:186 - Server certicate not exists, downloadingINFO 2019-09-02 17:01:47,461 security.py:209 - Downloading server cert from https://192.168.56.101 master master.hadoop.com:8440/cert/ca/ERROR 2019-09-02 17:01:47,471 Controller.py:212 - Unable to connect to: https://192.168.56.101 master master.hadoop.com:8441/agent/v1/register/masterTraceback (most recent call last):File "/usr/lib/python2.6/site-packages/ambari_agent/Controller.py", line 165, in registerWithServerret = self.sendRequest(self.registerUrl, data)File "/usr/lib/python2.6/site-packages/ambari_agent/Controller.py", line 496, in sendRequestraise IOError(\'Request to {0} failed due to {1}\'.format(url, str(exception)))IOError: Request to https://192.168.56.101 master master.hadoop.com:8441/agent/v1/register/master failed due to <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:590)>ERROR 2019-09-02 17:01:47,471 Controller.py:213 - Error:Request to https://192.168.56.101 master master.hadoop.com:8441/agent/v1/register/master failed due to <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:590)>WARNING 2019-09-02 17:01:47,471 Controller.py:214 - Sleeping for 19 seconds and then trying again', None) Connection to master closed.SSH command execution finishedhost=master, exitcode=0Command end time 2019-09-02 17:01:48 Registering with the server...Registration with the server failed. And this is my ambari-agent.ini # Licensed to the Apache Software Foundation (ASF) under one or more# contributor license agreements. See the NOTICE file distributed with# this work for additional information regarding copyright ownership.# The ASF licenses this file to You under the Apache License, Version 2.0# (the "License"); you may not use this file except in compliance with# the License. You may obtain a copy of the License at## http://www.apache.org/licenses/LICENSE-2.0## Unless required by applicable law or agreed to in writing, software# distributed under the License is distributed on an "AS IS" BASIS,# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.# See the License for the specific [server]hostname=192.168.56.101 master master.hadoop.comurl_port=8440secured_url_port=8441 [agent]logdir=/var/log/ambari-agentpiddir=/var/run/ambari-agentprefix=/var/lib/ambari-agent/data;loglevel=(DEBUG/INFO)loglevel=INFOdata_cleanup_interval=86400data_cleanup_max_age=2592000data_cleanup_max_size_MB = 100ping_port=8670cache_dir=/var/lib/ambari-agent/cachetolerate_download_failures=truerun_as_user=rootparallel_execution=0alert_grace_period=5alert_kinit_timeout=14400000system_resource_overrides=/etc/resource_overrides; memory_threshold_soft_mb=400; memory_threshold_hard_mb=1000 [security]keysdir=/var/lib/ambari-agent/keysserver_crt=ca.crtpassphrase_env_var_name=AMBARI_PASSPHRASEssl_verify_cert=0 [services]pidLookupPath=/var/run/ [heartbeat]state_interval_seconds=60dirs=/etc/hadoop,/etc/hadoop/conf,/etc/hbase,/etc/hcatalog,/etc/hive,/etc/oozie,/etc/sqoop,/etc/ganglia,/var/run/hadoop,/var/run/zookeeper,/var/run/hbase,/var/run/templeton,/var/run/oozie,/var/log/hadoop,/var/log/zookeeper,/var/log/hbase,/var/run/templeton,/var/log/hive; 0 - unlimitedlog_lines_count=300idle_interval_min=1idle_interval_max=10 [logging]syslog_enabled=0 and This is my /etc/hosts 127.0.0.1 localhost127.0.1.1 master 192.168.56.101 master master.hadoop.com192.168.56.102 slave1 slave1.hadoop.com192.168.56.103 slave2 slave2.hadoop.com192.168.56.104 slave3 slave3.hadoop.com192.168.56.105 slave4 slave4.hadoop.com192.168.56.106 slave5 slave5.hadoop.com # The following lines are desirable for IPv6 capable hosts::1 ip6-localhost ip6-loopbackfe00::0 ip6-localnetff00::0 ip6-mcastprefixff02::1 ip6-allnodesff02::2 ip6-allrouters root@master:~# hostnamemasterroot@master:~# hostname -fmaster   How can i fix it???   ... 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