= Hadoop分佈式文件系統使用指南二 =

= 升級 =
 * 由於換版本的話，資料夾內的conf設定檔也勢必被更改，因此目前作法為： 把conf 移至/opt/conf ，hadoop 0.16 與 hadoop 0.18用 ln 做捷徑代換。由於conf已不在hadoop_home內，因此記得匯入conf/hadoop-env.sh
{{{
$ source /opt/conf/hadoop-env.sh
}}}

 * 先看狀態
{{{
$ bin/hadoop dfsadmin -upgradeProgress status

There are no upgrades in progress.
}}}

 * 停止hdfs
   * 注意不可使用bin/stop-all.sh來停止
{{{
$ bin/stop-dfs.sh
}}}

 * 部署新版本的Hadoop
   * 注意每個node的版本都要統一，否則會出現問題


 * 啟動
{{{
$ bin/start-dfs.sh -upgrade
}}}

 * namenode管理網頁會出現升級狀態

= 退回 =

 * 停止集群
{{{
$ bin/stop-dfs.sh
}}}
 * 部署老版本的Hadoop

 * 退回之前版本
{{{
$ bin/start-dfs.sh -rollback
}}}

= 檢查hdfs磁碟狀況 = 
 * fsck 可以
{{{
$ bin/hadoop fsck /

.
/user/waue/input/1.txt:  Under replicated blk_-90085106852013388_1001. Target Replicas is 3 but found 2 replica(s).
/user/waue/input/1.txt:  Under replicated blk_-4027196261436469955_1001. Target Replicas is 3 but found 2 replica(s).
.
/user/waue/input/2.txt:  Under replicated blk_-2300843106107816641_1002. Target Replicas is 3 but found 2 replica(s).
.
/user/waue/input/3.txt:  Under replicated blk_-1561577350198661966_1003. Target Replicas is 3 but found 2 replica(s).
.
/user/waue/input/4.txt:  Under replicated blk_1316726598778579026_1004. Target Replicas is 3 but found 2 replica(s).
Status: HEALTHY
 Total size:	143451003 B
 Total dirs:	8
 Total files:	4
 Total blocks (validated):	5 (avg. block size 28690200 B)
 Minimally replicated blocks:	5 (100.0 %)
 Over-replicated blocks:	0 (0.0 %)
 Under-replicated blocks:	5 (100.0 %)
 Mis-replicated blocks:		0 (0.0 %)
 Default replication factor:	3
 Average block replication:	2.0
 Corrupt blocks:		0
 Missing replicas:		5 (50.0 %)
 Number of data-nodes:		2
 Number of racks:		1
The filesystem under path '/' is HEALTHY
}}}

 * 加不同的參數有不同的用處，如
{{{
$ bin/hadoop fsck / -files


/tmp <dir>

/tmp/hadoop <dir>

/tmp/hadoop/hadoop-waue <dir>

/tmp/hadoop/hadoop-waue/mapred <dir>

/tmp/hadoop/hadoop-waue/mapred/system <dir>

/user <dir>

/user/waue <dir>

/user/waue/input <dir>

/user/waue/input/1.txt 115045564 bytes, 2 block(s):  Under replicated blk_-90085106852013388_1001. Target Replicas is 3 but found 2 replica(s).

 Under replicated blk_-4027196261436469955_1001. Target Replicas is 3 but found 2 replica(s).

/user/waue/input/2.txt 987864 bytes, 1 block(s):  Under replicated blk_-2300843106107816641_1002. Target Replicas is 3 but found 2 replica(s).

/user/waue/input/3.txt 1573048 bytes, 1 block(s):  Under replicated blk_-1561577350198661966_1003. Target Replicas is 3 but found 2 replica(s).

/user/waue/input/4.txt 25844527 bytes, 1 block(s):  Under replicated blk_1316726598778579026_1004. Target Replicas is 3 but found 2 replica(s).

Status: HEALTHY

....（同上）
}}}