hadoop yarn 获取 作业 内存大小

语法：

hdfs dfs -cat <HDFS文件路径>

示例：

[root@master local]# hdfs dfs -cat /input/text.txt
hello ,hadoop

[root@master local]# hdfs dfs -tail /input/text.txt
hello ,hadoop

删除文件

语法：

hadoop fs -rm <HDFS文件路径>

示例：

# 删除文件夹
[root@master ~]# hdfs dfs -mkdir /user/resource
[root@master ~]# hdfs dfs -rmdir /user/resource
[root@master ~]# hadoop fs -rm -f /user/resource

# 删除文件
[root@master ~]# hdfs dfs -rm /user/resoure/text.txt
[root@master ~]# hadoop fs -rm -r /user/resource/text.txt

文件重命名

语法：

hadoop fs -mv <HDFS文件路径> <HDFS文件路径>

示例：

[root@master ~]# hadoop fs -mv /input/test.txt /input/demo.txt

查看集群的基本信息

[root@master ~]# hdfs fsck /
Connecting to namenode via http://192.168.184.130:50070/fsck?ugi=root&path=%2F
FSCK started by root (auth:SIMPLE) from /192.168.184.130 for path / at Tue May 23 10:42:27 CST 2023


/input/text.txt:  Under replicated BP-399935676-192.168.184.130-1684307575827:blk_1073741825_1001. Target Replicas is 3 but found 1 live replica(s), 0 decommissioned replica(s), 0 decommissioning replica(s).

Status: HEALTHY
 Number of data-nodes:  1
 Number of racks:               1
 Total dirs:                    6
 Total symlinks:                0

Replicated Blocks:
 Total size:    13 B
 Total files:   3
 Total blocks (validated):      1 (avg. block size 13 B)
 Minimally replicated blocks:   1 (100.0 %)
 Over-replicated blocks:        0 (0.0 %)
 Under-replicated blocks:       1 (100.0 %)
 Mis-replicated blocks:         0 (0.0 %)
 Default replication factor:    3
 Average block replication:     1.0
 Missing blocks:                0
 Corrupt blocks:                0
 Missing replicas:              2 (66.666664 %)
 Blocks queued for replication: 0

Erasure Coded Block Groups:
 Total size:    0 B
 Total files:   0
 Total block groups (validated):        0
 Minimally erasure-coded block groups:  0
 Over-erasure-coded block groups:       0
 Under-erasure-coded block groups:      0
 Unsatisfactory placement block groups: 0
 Average block group size:      0.0
 Missing block groups:          0
 Corrupt block groups:          0
 Missing internal blocks:       0
 Blocks queued for replication: 0
FSCK ended at Tue May 23 10:42:27 CST 2023 in 18 milliseconds


The filesystem under path '/' is HEALTHY

在Hadoop的集群的基本信息主要包含分布式文件系统HDFS和分布式资源管理YARN

分布式文件系统HDFS主要包含文件系统的状态，是否有块丢失，备份丢失等，同时包含集群节点状态等。

分布式资源管理YARN主要包含集群节点状态，节点资源（内存，CPU等），队列状态等

Hadoop安全模式

• 安全模式是保证系统保密性，完整性及可使用性的一种机制，一定程度上可以防止系统里的资源遭到破坏，更改和泄露，使得整个系统持续，可靠的正常运行。
• Hadoop集群也有安全模式，在安全模式下可保证Hadoop集群中数据块的安全性。对Hadoop集群可以进行查看安全模式，解除和开启安全模式的操作，

查看namenode是否处于安全模式

[root@master ~]# hdfs dfsadmin -safemode get
Safe mode is OFF

进入安装模式

[root@master ~]# hdfs dfsadmin -safemode enter
Safe mode is ON

解除安全模式

[root@master ~]# hdfs dfsadmin -safemode leave
Safe mode is OFF

执行MapReduce任务

语法：

hadoop jar <jar包名称> <MapReduce程序类名> <输入路径> <输出路径>

示例：

[root@master ~]# hadoop jar wordcount.jar WordCount /user/hadoop/input /user/hadoop/output

启动集群

启动hadoop集群需要先启动NameNode和DataNode

start-dfs.sh
start-yarn.sh

停止集群

停止hadoop集群需要先停止YARN和HDFS

stop-dfs.sh
start-yarn.sh

官方文档

Hadoop文档 (apache.org)