bash 使用 Hadoop：本地主机：错误：未设置 JAVA_HOME
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Working With Hadoop: localhost: Error: JAVA_HOME is not set
提问by Ali Ismail
I'm working with Ubuntu 12.04 LTS.
我正在使用 Ubuntu 12.04 LTS。
I'm going through the hadoop quickstart manual to make a pseudo-distributed operation. It seems simple and straightforward (easy!).
我正在阅读 hadoop 快速入门手册以进行伪分布式操作。它看起来简单明了（简单！）。
However, when I try to run start-all.shI get:
但是，当我尝试运行时，start-all.sh我得到：
localhost: Error: JAVA_HOME is not set.
I've read all the other advice on stackoverflow for this issue and have done the following to ensure JAVA_HOMEis set:
我已经阅读了有关此问题的所有其他关于 stackoverflow 的建议，并已执行以下操作以确保JAVA_HOME已设置：
In /etc/hadoop/conf/hadoop-env.shI have set
在/etc/hadoop/conf/hadoop-env.sh我已经设置
JAVA_HOME=/usr/lib/jvm/java-6-oracle
export JAVA_HOME
In /etc/bash.bashrcI have set
在/etc/bash.bashrc我已经设置
JAVA_HOME=/usr/lib/jvm/java-6-oracle
export JAVA_HOME
PATH=$PATH:$JAVA_HOME/bin
export PATH
which javareturns:
which java返回：
/usr/bin/java
java –versionworks
java –version作品
echo $JAVA_HOMEreturns:
echo $JAVA_HOME返回：
/usr/lib/jvm/java-6-oracle
I've even tried becoming root and explicitly writing the in the terminal:
我什至尝试成为 root 并在终端中明确写入：
$ JAVA_HOME=/usr/lib/jvm/java-6-oracle
$ export JAVA_HOME
$ start-all.sh
If you could show me how to resolve this error it would be greatly appreciated.
I'm thinking that my JAVA_HOMEis being overridden somehow. If that is the case, could you explain to me how to make my exports global?
如果您能告诉我如何解决此错误，将不胜感激。我在想我的JAVA_HOME不知何故被覆盖了。如果是这种情况，您能否向我解释如何使我的出口全球化？
回答by Krishna
I am using hadoop 1.1, and faced the same problem.
我正在使用 hadoop 1.1，并面临同样的问题。
I got it solved through changing JAVA_HOMEvariable in /etc/hadoop/hadoop-env.shas:
我通过将JAVA_HOME变量更改/etc/hadoop/hadoop-env.sh为以下内容来解决它：
export JAVA_HOME=/usr/lib/jvm/<jdk folder>
回答by bitek
The way to solve this problem is to export the JAVA_HOME variable inside the conf/hadoop-env.sh file.
解决这个问题的方法是在conf/hadoop-env.sh文件中导出JAVA_HOME变量。
It doesn't matter if you already exported that variable in ~/.bashrc, it'll still show the error.
如果您已经在 ~/.bashrc 中导出该变量并不重要，它仍然会显示错误。
So editconf/hadoop-env.shand uncomment the line "export JAVA_HOME" and add a proper filesystem path to it, i.e. the path to your Java JDK.
因此，编辑conf/hadoop-env.sh并取消注释“export JAVA_HOME”行并为其添加正确的文件系统路径，即 Java JDK 的路径。
# The Java implementation to use. Required.
export JAVA_HOME="/path/to/java/JDK/"
# 要使用的 Java 实现。必需的。
导出 JAVA_HOME="/path/to/java/JDK/"
回答by Nitesh Chaturvedi
extract from etc/hadoop/hadoop-env.sh
从 etc/hadoop/hadoop-env.sh 中提取
The only required environment variable is JAVA_HOME. All others are optional. When running a distributed configuration it is best to set JAVA_HOME in this file, so that it is correctly defined on remote nodes.
唯一需要的环境变量是 JAVA_HOME。所有其他都是可选的。运行分布式配置时，最好在此文件中设置 JAVA_HOME，以便在远程节点上正确定义。
This means its better and advised to set JAVA_HOME here.. even though the existing definition reads the JAVA_HOME variable. Perhaps its not getting the value of JAVA_HOME from previously set value... standard apache manual does not tell this :( :(
这意味着它更好，建议在此处设置 JAVA_HOME .. 即使现有定义读取 JAVA_HOME 变量。也许它没有从先前设置的值中获得 JAVA_HOME 的值......标准 apache 手册没有说明这一点:( :(
回答by whitewalker
This error is coming from Line 180
此错误来自第 180 行
if [[ -z $JAVA_HOME ]]; then
echo "Error: JAVA_HOME is not set and could not be found." 1>&2
exit 1
fi
in libexec/hadoop-config.sh.
在libexec/hadoop-config.sh。
Try echo $JAVA_HOMEin that script. If it doesn't recognize,
$JAVA_HOME在该脚本中尝试 echo 。如果不认识，
Find your JAVA_HOMEusing this:
找到你的JAVA_HOME用法：
$(readlink -f /usr/bin/javac | sed "s:/bin/javac::")
$(readlink -f /usr/bin/javac | sed "s:/bin/javac::")
and replace the line
并更换线
export JAVA_HOME=${JAVA_HOME}in /etc/hadoop/hadoop-env.shwith JAVA_HOME you got from above command.
export JAVA_HOME=${JAVA_HOME}在/etc/hadoop/hadoop-env.shJAVA_HOME 中，您从上面的命令中获得。
回答by codeguru
I also had faced the similar problem in hadoop 1.1I had not noticed that the JAVA_HOMEwas commented in: hadoop/conf/hadoop-env.sh
我在hadoop 1.1 中也遇到过类似的问题，
我没有注意到在以下内容中JAVA_HOME进行了评论：hadoop/conf/hadoop-env.sh
It was
它是
/#JAVA_HOME=/usr/lib/jvm/java-6-oracle
Had to change it to
不得不把它改成
JAVA_HOME=/usr/lib/jvm/java-6-oracle
回答by Mr. Crowley
regardless of debian or any linux flavor, just know that ~/.bash_profilebelongs to specific user and is not system wide.
in pseudo-distributed environment hadoop works on localhostso the $JAVA_HOMEin .bash_profile is no use anymore.
无论是 debian 还是任何 linux 风格，只要知道它~/.bash_profile属于特定用户，而不是系统范围内的。在伪分布式环境中 hadoop 可以工作，localhost因此$JAVA_HOME.bash_profile 不再有用。
just export the JAVA_HOME in ~/.bashrcand use it system wide.
只需导出 JAVA_HOME~/.bashrc并在系统范围内使用它。
回答by kometen
Ran into the same issue on ubuntu LTS 16.04. Running bash -vx ./bin/hadoopshowed it tested whether java was a directory. So I changed JAVA_HOME to a folder and it worked.
在 ubuntu LTS 16.04 上遇到了同样的问题。运行bash -vx ./bin/hadoop表明它测试了 java 是否是一个目录。所以我将 JAVA_HOME 更改为一个文件夹并且它起作用了。
++ [[ ! -d /usr/bin/java ]]
++ hadoop_error 'ERROR: JAVA_HOME /usr/bin/java does not exist.'
++ echo 'ERROR: JAVA_HOME /usr/bin/java does not exist.'
ERROR: JAVA_HOME /usr/bin/java does not exist.
So I changed JAVA_HOME in ./etc/hadoop/hadoop-env.shto
所以我在改变JAVA_HOME./etc/hadoop/hadoop-env.sh到
export JAVA_HOME=/usr/lib/jvm/java-8-oracle/jre/
and hadoop starts fine. This is also mentioned in this article.
和 hadoop 开始很好。这篇文章中也提到了这一点。
回答by Paul Sanwald
The way to debug this is to put an "echo $JAVA_HOME" in start-all.sh. Are you running your hadoop environment under a different username, or as yourself? If the former, it's very likely that the JAVA_HOME environment variable is not set for that user.
调试它的方法是在 start-all.sh 中放置一个“echo $JAVA_HOME”。您是使用不同的用户名还是以您自己的身份运行您的 hadoop 环境？如果是前者，很可能没有为该用户设置 JAVA_HOME 环境变量。
The other potential problem is that you have specified JAVA_HOME incorrectly, and the value that you have provided doesn't point to a JDK/JRE. Note that "which java" and "java -version" will both work, even if JAVA_HOME is set incorrectly.
另一个潜在问题是您错误地指定了 JAVA_HOME，并且您提供的值未指向 JDK/JRE。请注意，即使 JAVA_HOME 设置不正确，"which java" 和 "java -version" 都可以工作。
回答by Rajarsh
Check if your alternatives is pointing to the right one, you might actually be pointing to a different version and trying to alter the hadoop-env.sh on another installed version.
检查您的替代品是否指向正确的替代品，您实际上可能指向不同的版本并尝试更改另一个已安装版本的 hadoop-env.sh。
-alternatives --install /etc/hadoop/conf [generic_name] [your correct path] priority {for further check man page of alternatives}
-alternatives --install /etc/hadoop/conf [generic_name] [您的正确路径] 优先级{进一步检查替代品的手册页}
to set alternatives manually,
手动设置备选方案，
alternatives --set [generic name] [your current path].
替代方案 --set [通用名称] [您当前的路径]。
回答by Raja Sekaran
Change the JAVA_HOMEvariable in conf/hadoop-env.sh
改变JAVA_HOME变量conf/hadoop-env.sh
export JAVA_HOME=/etc/local/java/<jdk folder>
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