flume出现org.apache.hadoop.fs.UnsupportedFileSystemException: No FileSystem for scheme “hdfs“

flume没有hadoop环境
排查：

1. flume-env.sh加上export JAVA_HOME=/opt/module/jdk

2. 把hadoop的配置文件core-site.xml和hdfs-site.xml放在$FLUME_HOME/conf

3. jar包依赖问题
   /opt/module/hadoop/share/hadoop/hdfs/lib/hadoop-annotations-3.1.3.jar
   /opt/module/hadoop/share/hadoop/hdfs/lib/hadoop-auth-3.1.3.jar
   /opt/module/hadoop/share/hadoop/hdfs/lib/htrace-core4-4.1.0-incubating.jar
   /opt/module/hadoop/share/hadoop/common/lib/commons-io-2.5.jar
   /opt/module/hadoop/share/hadoop/common/lib/commons-configuration2-2.1.1.jar
   /opt/module/hadoop/share/hadoop/common/lib/guava-27.0-jre.jar 替换成高版本的
   /opt/module/hadoop/share/hadoop/hdfs/hadoop-hdfs-3.1.3.jar
   /opt/module/hadoop/share/hadoop/common/hadoop-common-3.1.3.jar
   /opt/module/hadoop/share/hadoop/common/lib/woodstox-core-5.0.3.jar

4. 没有which命令！！！！！！！
   在flume-ng脚本里，有一个which hadoop，用来查找有没有hadoop命令的
   which前面是自动添加hadoop环境变量的。
   但是如果没有which命令，他就永远也找不到hadoop在哪里！！！！！

可以再命令行里面用which hadoop测试一下有没有which，如果是command not found就是没有which命令，下载一下就行了
yum install which -y

#Debian
apt-get install which
 
#Ubuntu
apt-get install which
 
#Alpine
apk add which
 
#Arch Linux
pacman -S which
 
#Kali Linux
apt-get install which
 
#CentOS
yum install which
 
#Fedora
dnf install which
 
#Raspbian
apt-get install which
 
#Docker
docker run cmd.cat/which which

没有网下载which的，把HADOOP_IN_PATH变成hadoop的目录就行