HDFS垃圾回收站的配置及使用方法

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HDFS会为每一个用户创建一个回收站目录：/user/用户名/.Trash/，
每一个被用户通过shell删除的文件/目录，在系统回收站中都一个周期，也就是当系统回收站中的文件/目录在一段时间之后没有被用户恢复的话，HDFS就会自动的把这个文件/目录彻底删除，之后，用户就永远也找不回这个文件/目录了。

1. HDFS默认会关闭回收站功能。默认情况下HDFS删除文件,无法恢复。
    [hadoop@hadoop002 hadoop]$ hdfs dfs -rm /gw_test.log2
    Deleted /gw_test.log2
2. 启用回收站功能，需要配置core-site.xml文件
    [hadoop@hadoop002 hadoop]$ vi etc/hadoop/core-site.xml 
    <?xml version="1.0" encoding="UTF-8"?>
    <?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
    <!--
    Licensed 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 language Governing permissions and
    limitations under the License. See accompanying LICENSE file.
    -->

    <!-- Put site-specific property overrides in this file. -->
    
    <configuration>
    <property>
    <name>fs.defaultFS</name>
    <value>hdfs://hadoop002:9000</value>
    </property>
    <!--多长时间创建CheckPoint Namenode截点上运行的CheckPointer 从Current文件夹创建CheckPoint;默认：0 由fs.trash.interval项指定 -->
    <property>
         <name>fs.trash.checkpoint.interva</name>
         <value>0</value>
    </property>
    <!--多少分钟.Trash下的CheckPoint目录会被删除,该配置服务器设置优先级大于客户端，默认:不启用 -->
    <property>
          <name>fs.trash.interval</name>
         <value>1440</value>  -- 清除周期分钟(24小时)
    </property>
    
    </configuration>
    [hadoop@hadoop002 hadoop]
3. 重启hdfs服务
    #停止hdfs服务
    [hadoop@hadoop002 hadoop]$ sbin/stop-dfs.sh 
    Stopping namenodes on [hadoop002]
    hadoop002: no namenode to stop
    hadoop002: no datanode to stop
    Stopping secondary namenodes [hadoop002]
    hadoop002: no secondarynamenode to stop
    #启动hdfs服务
    [hadoop@hadoop002 hadoop]$ sbin/start-dfs.sh 
    Starting namenodes on [hadoop002]
    hadoop002: starting namenode, logging to /opt/software/hadoop-2.8.1/logs/hadoop-hadoop-namenode-hadoop002.out
    hadoop002: starting datanode, logging to /opt/software/hadoop-2.8.1/logs/hadoop-hadoop-datanode-hadoop002.out
    Starting secondary namenodes [hadoop002]
    hadoop002: starting secondarynamenode, logging to /opt/software/hadoop-2.8.1/logs/hadoop-hadoop-secondarynamenode-hadoop002.out
    [hadoop@hadoop002 hadoop]$
4. HDFS删除文件,删除的文件被存放在回收站下面；/user/hadoop/.Trash/Current
    #删除文件/gw_test.log3，
    [hadoop@hadoop002 hadoop]$ hdfs dfs -rm  /gw_test.log3
    18/05/25 15:27:47 INFO fs.TrashPolicyDefault: Moved: 'hdfs://hadoop002:9000/gw_test.log3' to trash at: hdfs://hadoop002:9000/user/hadoop/.Trash/Current/gw_test.log3
    #查看根目录下，gw_test.log3文件不存在
    [hadoop@hadoop002 hadoop]$ hdfs dfs -ls /
    Found 3 items
    drwxr-xr-x   - root   root                0 2018-05-23 13:16 /root
    drwx------   - hadoop supergroup          0 2018-05-22 11:23 /tmp
    drwxr-xr-x   - hadoop supergroup          0 2018-05-22 11:22 /user
    [hadoop@hadoop002 hadoop]$ 
    #查看回收站目录下的文件，
    [hadoop@hadoop002 hadoop]$ hdfs dfs -ls /user/hadoop/.Trash/Current
    Found 1 items
    -rw-r--r--   1 hadoop supergroup         25 2018-05-23 13:04 /user/hadoop/.Trash/Current/gw_test.log3

5. 恢复文件
    #恢复文件操作
    [hadoop@hadoop002 hadoop]$ hdfs dfs -mv /user/hadoop/.Trash/Current/gw_test.log3 /gw_test.log3
    #查看根目录下文件是否被恢复
    [hadoop@hadoop002 hadoop]$ hdfs dfs -ls /
    Found 4 items
    -rw-r--r--   1 hadoop supergroup         25 2018-05-23 13:04 /gw_test.log3
    drwxr-xr-x   - root   root                0 2018-05-23 13:16 /root
    drwx------   - hadoop supergroup          0 2018-05-22 11:23 /tmp
    drwxr-xr-x   - hadoop supergroup          0 2018-05-22 11:22 /user

6. 删除文件跳过回收站 
    #  -skipTrash参数表示跳过回收站
    [hadoop@hadoop002 hadoop]$ hdfs dfs -rm -skipTrash /gw_test.log3
    Deleted /gw_test.log3

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