hadoop配置文件之hadoop-env.sh

参考文档地址：https://blog.csdn.net/zhanglong_4444/article/details/99471211

#使用jdk的路径（指定本地安装的路径）
export JAVA_HOME=${JAVA_HOME}

#配置文件的路径如果$HADOOP_CONF_DIR 没有值时，会赋予默认值/etc/hadoop
export HADOOP_CONF_DIR=${HADOOP_CONF_DIR:-"/etc/hadoop"}

# The maximum amount of heap to use, in MB. Default is 1000.
#如果不指定大小会默认指定1000MB
#namenode,secondarynamenode,jobtracker,datanode,tasktracker守护进程内存
export HADOOP_HEAPSIZE=

#NameNode的初始化堆内存大小，默认也是1000M
export HADOOP_NAMENODE_INIT_HEAPSIZE=""

# Enable extra debugging of Hadoop's JAAS binding, used to set up
# Kerberos security.
#设置jaas绑定、开启Kerberos 安全认证
export HADOOP_JAAS_DEBUG=true

#使用Ipv4禁用Ipv6
export HADOOP_OPTS="$HADOOP_OPTS -Djava.net.preferIPv4Stack=true"

#大部分情况下，这个统一设置的值可能并不适合。例如对于namenode节点，
#1000M的内存只能存储几百万个文件的数据块的引用。
# 单独设置namenode、secondrynamenode、datanode、blancer 、jobtrackerde 的内存，可以通过下面的参数来设置
HADOOP_NAMENODE_OPTS=2048
HADOOP_SECONDARYNAMENODE_OPTS
HADOOP_DATANODE_OPTS
HADOOP_BALANCER_OPTS
HADOOP_JOBTRACKER_OPTS

# Command specific options appended to HADOOP_OPTS when specified
#DataNode、NameNode、secondrynamenode、nfs3、 的JVM参数设置
export HADOOP_NAMENODE_OPTS="-Dhadoop.security.logger=${HADOOP_SECURITY_LOGGER:-INFO,RFAS} -Dhdfs.audit.logger=${HDFS_AUDIT_LOGGER:-INFO,NullAppender} $HADOOP_NAMENODE_OPTS"
export HADOOP_DATANODE_OPTS="-Dhadoop.security.logger=ERROR,RFAS $HADOOP_DATANODE_OPTS"
export HADOOP_SECONDARYNAMENODE_OPTS="-Dhadoop.security.logger=${HADOOP_SECURITY_LOGGER:-INFO,RFAS} -Dhdfs.audit.logger=${HDFS_AUDIT_LOGGER:-INFO,NullAppender} $HADOOP_SECONDARYNAMENODE_OPTS"
export HADOOP_NFS3_OPTS="$HADOOP_NFS3_OPTS"

#这个是在HDFS格式化时需要的JVM配置，也就是执行hdfs namenode -format时的JVM配置　
export HADOOP_PORTMAP_OPTS="-Xmx512m $HADOOP_PORTMAP_OPTS"

# The following applies to multiple commands (fs, dfs, fsck, distcp etc)
#设置 HADOOP_CLIENT 参数    fs, dfs, fsck,distcp etc 命令涉及
export HADOOP_CLIENT_OPTS="$HADOOP_CLIENT_OPTS"

# set heap args when HADOOP_HEAPSIZE is empty
#如果未设置HADOOP_CLIENT_OPTS，则会设置默认值512m
if [ "$HADOOP_HEAPSIZE" = "" ]; then
  export HADOOP_CLIENT_OPTS="-Xmx512m $HADOOP_CLIENT_OPTS"
fi

#配置日志路径
# Where log files are stored.  $HADOOP_HOME/logs by default.
export HADOOP_LOG_DIR=${HADOOP_LOG_DIR}/$USER

# Where log files are stored in the secure data environment.
export HADOOP_SECURE_DN_LOG_DIR=${HADOOP_LOG_DIR}/${HADOOP_HDFS_USER}

# The directory where pid files are stored. /tmp by default.
# NOTE: this should be set to a directory that can only be written to by 
#       the user that will run the hadoop daemons.  Otherwise there is the
#       potential for a symlink attack.
#配置hadoop pid文件路径
export HADOOP_PID_DIR=${HADOOP_PID_DIR}
export HADOOP_SECURE_DN_PID_DIR=${HADOOP_PID_DIR}

# A string representing this instance of hadoop. $USER by default.
#hadoop默认用户$USER为当前用户
export HADOOP_IDENT_STRING=$USER