1.jps命令，查看进程
[hadoop@hadoop003 ~]$ jps
2034 NameNode
2148 DataNode
2633 NodeManager
5129 Jps
2521 ResourceManager
2364 SecondaryNameNode
查看详细进程
[hadoop@hadoop003 ~]$ jps -l
2034 org.apache.hadoop.hdfs.server.namenode.NameNode
5170 sun.tools.jps.Jps
2148 org.apache.hadoop.hdfs.server.datanode.DataNode
2633 org.apache.hadoop.yarn.server.nodemanager.NodeManager
2521 org.apache.hadoop.yarn.server.resourcemanager.ResourceManager
2364 org.apache.hadoop.hdfs.server.namenode.SecondaryNameNode
查看某进程相关信息
[hadoop@hadoop003 ~]$ ps -el|grep 2148
0 S 515 2148 1 0 80 0 - 690720 futex_ ? 00:00:42 java
若有残留进程，则利用jps命令+ps命令，删除残留信息：
[hadoop@hadoop003 ~]$ rm -f 2148
2.hadoop和hdfs 文件系统命令
hdfs dfs等价于Hadoop fs
查看主目录下内容：
[hadoop@hadoop003 hadoop]$ bin/hdfs dfs -ls /
Found 3 items
drwxr-xr-x - hadoop supergroup 0 2018-05-23 12:27 /lizhigangdir001
drwx------ - hadoop supergroup 0 2018-05-17 12:33 /tmp
drwxr-xr-x - hadoop supergroup 0 2018-05-17 12:33 /user
创建目录：
[hadoop@hadoop003 hadoop]$ bin/hdfs dfs -mkdir -p /lizhignagdir001/001
新建文件并写入000000：
[hadoop@hadoop003 hadoop]$ echo "000000">lizhigang.log
将lizhigang.log上传到/lizhigangdir001/001/目录下：
[hadoop@hadoop003 hadoop]$ bin/hdfs dfs -put lizhigang.log /lizhigangdir001/001
查看/lizhigangdir001/001/lizhigang.log内容：
[hadoop@hadoop003 hadoop]$ bin/hdfs dfs -cat /lizhigangdir001/001/lizhigang.log
将/lizhigangdir001/001目录下lizhigang.log文件下载到/tmp/目录下：
[hadoop@hadoop003 hadoop]$ bin/hdfs dfs -get /lizhigangdir001/001/lizhigang.log /tmp/
将/lizhigangdir001/001目录下lizhigang.log文件下载到/tmp/目录下，并重命名为lizhigang1.log：
bin/hdfs dfs -get /lizhigangdir001/001/lizhigang.log /tmp/lizhigang1.log
[-moveFromLocal <localsrc> ... <dst>]上传
[-moveToLocal <src> <localdst>]下载
将/lizhigangdir001/001目录下lizhigang.log文件删除，此操作被删除文件放入回收站，一定时间内可恢复：
[hadoop@hadoop003 hadoop]$ bin/hdfs dfs -rm -f /lizhigangdir001/001/lizhigang.log
将/lizhigangdir001/001目录下lizhigang.log文件删除，此操作被删除文件不放入回收站，不可恢复：
[hadoop@hadoop003 hadoop]$ bin/hdfs dfs -rm -f -skipTrash /lizhigangdir001/001/lizhigang.log
3.hdfs dfsadmin
查看磁盘空间：
[hadoop@hadoop003 hadoop]$ bin/hdfs dfsadmin -report
Configured Capacity: 39900024832 (37.16 GB)
Present Capacity: 23986335744 (22.34 GB)
DFS Remaining: 23986073600 (22.34 GB)
DFS Used: 262144 (256 KB)
DFS Used%: 0.00%
Under replicated blocks: 0
Blocks with corrupt replicas: 0
Missing blocks: 0
Missing blocks (with replication factor 1): 0
Pending deletion blocks: 0
-------------------------------------------------
Live datanodes (1):
Name: 192.168.137.200:50010 (hadoop003)
Hostname: hadoop003
Decommission Status : Normal
Configured Capacity: 39900024832 (37.16 GB)
DFS Used: 262144 (256 KB)
Non DFS Used: 13886844928 (12.93 GB)
DFS Remaining: 23986073600 (22.34 GB)
DFS Used%: 0.00%
DFS Remaining%: 60.12%
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: Fri May 25 09:38:02 CST 2018
安全模式进入、退出、get、wait：
[hadoop@hadoop003 hadoop]$ bin/hdfs dfsadmin -safemode [ enter | leave | get | wait ]
4.hadoop fsck
检查整个文件系统的健康状况：
[hadoop@hadoop003 hadoop]$ bin/hadoop fsck /
DEPRECATED: Use of this script to execute hdfs command is deprecated.
Instead use the hdfs command for it.
Connecting to namenode via http://hadoop003:50070/fsck?ugi=hadoop&path=%2F
FSCK started by hadoop (auth:SIMPLE) from /192.168.137.200 for path / at Fri May 25 09:45:02 CST 2018
...Status: HEALTHY
Total size: 194589 B
Total dirs: 13
Total files: 3
Total symlinks: 0
Total blocks (validated): 3 (avg. block size 64863 B)
Minimally replicated blocks: 3 (100.0 %)
Over-replicated blocks: 0 (0.0 %)
Under-replicated blocks: 0 (0.0 %)
Mis-replicated blocks: 0 (0.0 %)
Default replication factor: 1
Average block replication: 1.0
Corrupt blocks: 0
Missing replicas: 0 (0.0 %)
Number of data-nodes: 1
Number of racks: 1
FSCK ended at Fri May 25 09:45:02 CST 2018 in 7 milliseconds
The filesystem under path '/' is HEALTHY
打印出hadoop的环境变量：
[hadoop@hadoop003 hadoop]$ bin/hadoop classpath
/opt/software/hadoop-2.8.1/etc/hadoop:/opt/software/hadoop-2.8.1/share/hadoop/common/lib/*:/opt/software/hadoop-2.8.1/share/hadoop/common/*:/opt/software/hadoop-2.8.1/share/hadoop/hdfs:/opt/software/hadoop-2.8.1/share/hadoop/hdfs/lib/*:/opt/software/hadoop-2.8.1/share/hadoop/hdfs/*:/opt/software/hadoop-2.8.1/share/hadoop/yarn/lib/*:/opt/software/hadoop-2.8.1/share/hadoop/yarn/*:/opt/software/hadoop-2.8.1/share/hadoop/mapreduce/lib/*:/opt/software/hadoop-2.8.1/share/hadoop/mapreduce/*:/contrib/capacity-scheduler/*.jar
5.start-blancer.sh
1.多台机器的磁盘存储分布不均匀？
解决方案：
1.1 不加新机器，原机器的磁盘分布不均匀：
[hadoop@rzdatahadoop002 ~]$ hdfs dfsadmin -setBalancerBandwidth 52428800
Balancer bandwidth is set to 52428800
[hadoop@rzdatahadoop002 ~]$
[hadoop@rzdatahadoop002 sbin]$ ./start-balancer.sh
等价
[hadoop@rzdatahadoop002 sbin]$ hdfs balancer
Apache Hadoop集群环境: shell脚本每晚业务低谷时调度
CDH集群环境: 忽略
http://blog.itpub.net/30089851/viewspace-2052138/
1.2 加新机器，原机器的磁盘比如450G(500G)，现在的新机器磁盘规格是5T，在业务低谷时，先将多台新机器加入到HDFS，做DN；然后选一台的DN下架掉，等待hdfs自我修复块，恢复3份（网络和io最高的，也是最有风险性的）
2.一台机器的多个磁盘分布不均匀？
2.1.无论加不加磁盘，且多块磁盘的分布不均匀
https://hadoop.apache.org/docs/r3.0.0-alpha2/hadoop-project-dist/hadoop-hdfs/HDFSDiskbalancer.html
hdfs diskbalancer -plan node1.mycluster.com
hdfs diskbalancer -execute /system/diskbalancer/nodename.plan.json
Apache Hadoop3.x
CDH5.12+
