hadoop如何恢复namenode

Namenode恢复

1.修改 conf/core-site.xml,增加

Xml代码

<property>
<name>fs.checkpoint.period</name>
<value>3600</value>
<description>The number of seconds between two periodic checkpoints. </description>
</property>
<property>
<name>fs.checkpoint.size</name>
<value>67108864</value>
<description>The size of the current edit log (in bytes) that triggers a periodic checkpoint even if the fs.checkpoint.period hasn't expired. </description>
</property>
<property>
<name>fs.checkpoint.dir</name>
<value>/data/work/hdfs/namesecondary</value>
<description>Determines where on the local filesystem the DFS secondary name node should store the temporary images to merge. If this is a comma-delimited list of directories then the image is replicated in all of the directories for redundancy. </description>
</property>

        <property>
                <name>fs.checkpoint.period</name>  
                <value>3600</value>  
                <description>The number of seconds between two periodic checkpoints.  </description>
        </property>
        <property>  
                <name>fs.checkpoint.size</name>  
                <value>67108864</value>  
                <description>The size of the current edit log (in bytes) that triggers       a periodic checkpoint even if the fs.checkpoint.period hasn't expired.  </description>
        </property>

        <property>  
                <name>fs.checkpoint.dir</name>  
                <value>/data/work/hdfs/namesecondary</value>  
                <description>Determines where on the local filesystem the DFS secondary      name node should store the temporary images to merge.      If this is a comma-delimited list of directories then the image is      replicated in all of the directories for redundancy.  </description>
        </property>

fs.checkpoint.period表示多长时间记录一次hdfs的镜像。默认是1小时。
fs.checkpoint.size表示一次记录多大的size，默认64M

2.修改 conf/hdfs-site.xml,增加

Xml代码

<property>
<name>dfs.http.address</name>
<value>master:50070</value>
<description> The address and the base port where the dfs namenode web ui will listen on. If the port is 0 then the server will start on a free port. </description>
</property>

        <property>  
                <name>dfs.http.address</name>  
                <value>master:50070</value>  
                <description>    The address and the base port where the dfs namenode web ui will listen on.    If the port is 0 then the server will start on a free port.  </description>
        </property>

0.0.0.0改为namenode的IP地址

3.重启hadoop，然后检查是否启动是否成功。
登录secondarynamenode所在的机器，输入jps查看secondarynamenode进程
进入secondarynamenode的目录/data/work/hdfs/namesecondary
正确的结果：

如果没有，请耐心等待，只有到了设置的checkpoint的时间或者大小，才会生成。

4.恢复
制造namenode宕机的情况
1) kill 掉namenode的进程

Java代码

[root@master name]# jps
11749 NameNode
12339 Jps
11905 JobTracker
[root@master name]# kill 11749

[root@master name]# jps
11749 NameNode
12339 Jps
11905 JobTracker
[root@master name]# kill 11749

2)删除dfs.name.dir所指向的文件夹，这里是/data/work/hdfs/name

Java代码

[root@master name]# rm -rf *

[root@master name]# rm -rf *

删除name目录下的所有内容，但是必须保证name这个目录是存在的

3）从secondarynamenode远程拷贝namesecondary文件到namenode的namesecondary

Java代码

[root@master hdfs]# scp -r slave-001:/data/work/hdfs/namesecondary/ ./

[root@master hdfs]# scp -r slave-001:/data/work/hdfs/namesecondary/ ./

4）启动namenode

Java代码

[root@master /data]# hadoop namenode –importCheckpoint

[root@master /data]# hadoop namenode –importCheckpoint

正常启动以后，屏幕上会显示很多log，这个时候namenode就可以正常访问了

5)检查
使用hadoop fsck /user命令检查文件Block的完整性

6）停止namenode，使用crrl+C或者会话结束

7）删除namesecondary目录下的文件（保存干净）

Java代码

[root@master namesecondary]# rm -rf *

[root@master namesecondary]# rm -rf *

8）正式启动namenode

Java代码

[root@master bin]# ./hadoop-daemon.sh start namenode

[root@master bin]# ./hadoop-daemon.sh  start namenode

恢复工作完成，检查hdfs的数据

balancer

在使用start-balancer.sh时，
默认使用1M/S(1048576)的速度移动数据(so slowly...)
修改hdfs-site.xml配置，这里我们使用的是20m/S
<property>
<name>dfs.balance.bandwidthPerSec</name>
<value>20971520</value>
<description> Specifies the maximum bandwidth that each datanode can utilize for the balancing purpose in term of the number of bytes per second. </description>
</property>

然后结果是导致job运行变得不稳定，出现一些意外的长map单元，某些reduce时间处理变长(整个集群负载满满的情况下，外加20m/s的balance)，据说淘宝的为10m/s，需要调整后实验，看看情况如何。

Java代码

hadoop balancer -threshold 5

hadoop balancer -threshold 5

安全模式
有两个方法离开这种安全模式：
（1）修改dfs.safemode.threshold.pct为一个比较小的值，缺省是0.999。
dfs.safemode.threshold.pct（缺省值0.999f）
HDFS启动的时候，如果DataNode上报的block个数达到了元数据记录的block个数的0.999倍才可以离开安全模式，否则一直是这种只读模式。如果设为1则HDFS永远是处于SafeMode。

（2）hadoop dfsadmin -safemode leave命令强制离开
dfsadmin -safemode value 参数value的说明：
enter - 进入安全模式
leave - 强制NameNode离开安全模式
get - 返回安全模式是否开启的信息
wait - 等待，一直到安全模式结束。

大小: 8.1 KB

Namenode恢复

1.修改 conf/core-site.xml,增加

Xml代码

<property>
<name>fs.checkpoint.period</name>
<value>3600</value>
<description>The number of seconds between two periodic checkpoints. </description>
</property>
<property>
<name>fs.checkpoint.size</name>
<value>67108864</value>
<description>The size of the current edit log (in bytes) that triggers a periodic checkpoint even if the fs.checkpoint.period hasn't expired. </description>
</property>
<property>
<name>fs.checkpoint.dir</name>
<value>/data/work/hdfs/namesecondary</value>
<description>Determines where on the local filesystem the DFS secondary name node should store the temporary images to merge. If this is a comma-delimited list of directories then the image is replicated in all of the directories for redundancy. </description>
</property>

        <property>
                <name>fs.checkpoint.period</name>  
                <value>3600</value>  
                <description>The number of seconds between two periodic checkpoints.  </description>
        </property>
        <property>  
                <name>fs.checkpoint.size</name>  
                <value>67108864</value>  
                <description>The size of the current edit log (in bytes) that triggers       a periodic checkpoint even if the fs.checkpoint.period hasn't expired.  </description>
        </property>

        <property>  
                <name>fs.checkpoint.dir</name>  
                <value>/data/work/hdfs/namesecondary</value>  
                <description>Determines where on the local filesystem the DFS secondary      name node should store the temporary images to merge.      If this is a comma-delimited list of directories then the image is      replicated in all of the directories for redundancy.  </description>
        </property>

fs.checkpoint.period表示多长时间记录一次hdfs的镜像。默认是1小时。
fs.checkpoint.size表示一次记录多大的size，默认64M

2.修改 conf/hdfs-site.xml,增加

Xml代码

<property>
<name>dfs.http.address</name>
<value>master:50070</value>
<description> The address and the base port where the dfs namenode web ui will listen on. If the port is 0 then the server will start on a free port. </description>
</property>

        <property>  
                <name>dfs.http.address</name>  
                <value>master:50070</value>  
                <description>    The address and the base port where the dfs namenode web ui will listen on.    If the port is 0 then the server will start on a free port.  </description>
        </property>

如果没有，请耐心等待，只有到了设置的checkpoint的时间或者大小，才会生成。

4.恢复
制造namenode宕机的情况
1) kill 掉namenode的进程

Java代码

[root@master name]# jps
11749 NameNode
12339 Jps
11905 JobTracker
[root@master name]# kill 11749

[root@master name]# jps
11749 NameNode
12339 Jps
11905 JobTracker
[root@master name]# kill 11749

2)删除dfs.name.dir所指向的文件夹，这里是/data/work/hdfs/name

Java代码

[root@master name]# rm -rf *

[root@master name]# rm -rf *

删除name目录下的所有内容，但是必须保证name这个目录是存在的

3）从secondarynamenode远程拷贝namesecondary文件到namenode的namesecondary

Java代码

[root@master hdfs]# scp -r slave-001:/data/work/hdfs/namesecondary/ ./

[root@master hdfs]# scp -r slave-001:/data/work/hdfs/namesecondary/ ./

4）启动namenode

Java代码

[root@master /data]# hadoop namenode –importCheckpoint

[root@master /data]# hadoop namenode –importCheckpoint

Java代码

[root@master namesecondary]# rm -rf *

[root@master namesecondary]# rm -rf *

8）正式启动namenode

Java代码

[root@master bin]# ./hadoop-daemon.sh start namenode

[root@master bin]# ./hadoop-daemon.sh  start namenode

Java代码

hadoop balancer -threshold 5

hadoop balancer -threshold 5

hadoop如何恢复namenode

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