九、Hadoop节点管理（删除节点）

HDFS删除节点
9.1 删除节点遵循原则
①无数据删除；②查看状态（Normal（正常状态）、Decommissioned in Program（数据正在迁移）、Decommissioned（数据迁移完成））
9.2 导入数据（可省略）
[root@nn01 ~]# /usr/local/hadoop/bin/hadoop fs -put centos.iso /centos.iso
[root@nn01 ~]# /usr/local/hadoop/bin/hadoop fs -ls /
Found 6 items
drwxr-xr-x - root supergroup 0 2021-09-02 10:16 /aaa
-rw-r--r-- 2 root supergroup 177152000 2021-09-06 22:39 /centos.iso
drwxr-xr-x - root supergroup 0 2021-09-02 10:27 /oo
drwxr-xr-x - root supergroup 0 2021-09-02 16:25 /system
drwx------ - root supergroup 0 2021-09-02 10:30 /tmp
drwxr-xr-x - root supergroup 0 2021-09-02 10:30 /xx
9.3 查看集群状态
[root@nn01 hadoop]# ./bin/hdfs dfsadmin -report
Configured Capacity: 68673339392 (63.96 GB)
Present Capacity: 59679309824 (55.58 GB)
DFS Remaining: 59321233408 (55.25 GB)
DFS Used: 358076416 (341.49 MB)
DFS Used%: 0.60%
Under replicated blocks: 0
Blocks with corrupt replicas: 0
Missing blocks: 0
Missing blocks (with replication factor 1): 0

-------------------------------------------------
。。。。。。。。。。。

9.4 卸载node4节点
[root@nn01 hadoop]# ./bin/hdfs dfsadmin -report | grep -P -A 14 'node4'
Name: 192.168.0.22:50010 (node4)
Hostname: node4
Decommission Status : Normal
Configured Capacity: 17168334848 (15.99 GB)
DFS Used: 8192 (8 KB)
Non DFS Used: 2119045120 (1.97 GB)
DFS Remaining: 15049281536 (14.02 GB)
DFS Used%: 0.00%
DFS Remaining%: 87.66%
Configured Cache Capacity: 0 (0 B)
Cache Used: 0 (0 B)
Cache Remaining: 0 (0 B)
Cache Used%: 100.00%
Cache Remaining%: 0.00%
Xceivers: 1
Last contact: Mon Sep 06 23:05:19 CST 2021
此时看看状态Decommission Status : Normal（正常）
9.5 修改配置文件
–增加dfs.hosts.exclude配置
[root@nn01 hadoop]# vim /usr/local/hadoop/etc/hadoop/hdfs-site.xml
<property>
<name>dfs.hosts.exclude</name> #这个配置告诉我们要删除一组主机
<value>/usr/local/hadoop/etc/hadoop/exclude</value> #把删除的主机写入值的文件里
</property>
9.6 增加exclude配置文件，写入要删除的节点主机名
[root@nn01 hadoop]# touch /usr/local/hadoop/etc/hadoop/exclude
[root@nn01 hadoop]# vim /usr/local/hadoop/etc/hadoop/exclude
node4 #删除节点的名称
修改完配置文件后查看状态还是正常的
9.7 开始导出数据
[root@nn01 hadoop]# ./bin/hdfs dfsadmin -refreshNodes
Refresh nodes successful
[root@nn01 hadoop]# ./bin/hdfs dfsadmin -report | grep -P -A 14 'node4'
Name: 192.168.0.22:50010 (node4)
Hostname: node4
Decommission Status : Decommissioned in Program
Configured Capacity: 17168334848 (15.99 GB)
DFS Used: 8192 (8 KB)
Non DFS Used: 2119045120 (1.97 GB)
DFS Remaining: 15049281536 (14.02 GB)
DFS Used%: 0.00%
DFS Remaining%: 87.66%
Configured Cache Capacity: 0 (0 B)
Cache Used: 0 (0 B)
Cache Remaining: 0 (0 B)
Cache Used%: 100.00%
Cache Remaining%: 0.00%
Xceivers: 1
Last contact: Mon Sep 06 23:22:36 CST 2021
过一段时间查看不要下线数据正在迁移
迁移完成如下：
[root@nn01 hadoop]# ./bin/hdfs dfsadmin -report | grep -P -A 14 'node4'
Name: 192.168.0.22:50010 (node4)
Hostname: node4
Decommission Status : Decommissioned
Configured Capacity: 17168334848 (15.99 GB)
DFS Used: 8192 (8 KB)
Non DFS Used: 2119045120 (1.97 GB)
DFS Remaining: 15049281536 (14.02 GB)
DFS Used%: 0.00%
DFS Remaining%: 87.66%
Configured Cache Capacity: 0 (0 B)
Cache Used: 0 (0 B)
Cache Remaining: 0 (0 B)
Cache Used%: 100.00%
Cache Remaining%: 0.00%
Xceivers: 1
Last contact: Mon Sep 06 23:26:01 CST 2021
–注意：只有当状态变成Decommissioned才能down机下线
9.8 出现Decommissioned（数据迁移完成）我们就可以下线node4了
[root@nn01 hadoop]# ssh node4
[root@node4 ~]# cd /usr/local/hadoop/
[root@node4 hadoop]# ./sbin/hadoop-daemon.sh stop datanode
stopping datanode

9.9 更改slaves文件并同步到所有主机

[root@nn01 hadoop]# cat etc/hadoop/slaves
node1
node2
node3

[root@nn01 hadoop]# >exclude 

[root@nn01 hadoop]# for i in node{1..4}; do scp ./etc/hadoop/slaves $i:/usr/local/hadoop/etc/hadoop/; done

这样就彻底删除了