MapReduce does not connect to HDFS

Time:2019-9-11

Configuration environment Hadoop environment is really fatal, and unexpected problems can arise at any time, such as

Failing this attempt.Diagnostics: Call From Hadoop 001/0.0.0.0 to Hadoop 001:8020 failed on connection exception: java.net.ConnectException: Deny connection; For more details see: http://wiki.apache.org/hadoop/Connection Refused

It’s a strange problem. All the configurations are OK. The problem is on ipv6.

Just disable the IPv6 reboot of the system

vi /etc/default/grub
# cat /etc/default/grub
GRUB_TIMEOUT=5
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT="console"
GRUB_CMDLINE_LINUX="ipv6.disable=1 crashkernel=auto rhgb quiet"
GRUB_DISABLE_RECOVERY="true"
grub2-mkconfig -o /boot/grub2/grub.cfg 
reboot