利用secondarynamenode 回复namenode

1主要：把secondarynamenode 数据 迁移到namenode数据目录里，然后重启namenode

2首先知道：secondarynamenode 默认每隔一小时备份一次数据

core-site.xml

<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>/home/hadoop/soft/hadoop-2.6.4/hdpdata/dfs/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

3制造namenode宕机的情形 ：kill -9  把namenode 杀掉

4把secondarynamenode数据拷贝到namenode目录下，然后重启namenode就ok

scp -r /home/hadoop/soft/hadoop-2.6.4/hdpdata/dfs/namesecondary hadoop@mina0:/home/hadoop/soft/hadoop-2.6.4/hdpdata/dfs/name/

5重启：先stop-all.sh,然后：start-all.sh