介绍：
- HDFS 文件系统提供了相当多的shell 操作命令，大大方便了程序员和系统管理人员查看、修改HDFS 上的文件。进一步，HDFS 的操作命令和Unix/Linux 的命令名称和格式相当一致，因而学习HDFS 命令的成本也大为缩小。
1.命令帮助
[hadoop@hadoop000 ~]$ hdfs dfs
Usage: hadoop fs [generic options]
[-appendToFile <localsrc> ... <dst>]
[-cat [-ignoreCrc] <src> ...]
[-checksum <src> ...]
[-chgrp [-R] GROUP PATH...]
[-chmod [-R] <MODE[,MODE]... | OCTALMODE> PATH...]
[-chown [-R] [OWNER][:[GROUP]] PATH...]
[-copyFromLocal [-f] [-p] [-l] [-d] <localsrc> ... <dst>]
[-copyToLocal [-f] [-p] [-ignoreCrc] [-crc] <src> ... <localdst>]
[-count [-q] [-h] [-v] [-t [<storage type>]] [-u] [-x] <path> ...]
[-cp [-f] [-p | -p[topax]] [-d] <src> ... <dst>]
[-createSnapshot <snapshotDir> [<snapshotName>]]
[-deleteSnapshot <snapshotDir> <snapshotName>]
[-df [-h] [<path> ...]]
[-du [-s] [-h] [-x] <path> ...]
[-expunge]
[-find <path> ... <expression> ...]
[-get [-f] [-p] [-ignoreCrc] [-crc] <src> ... <localdst>]
[-getfacl [-R] <path>]
[-getfattr [-R] {-n name | -d} [-e en] <path>]
[-getmerge [-nl] [-skip-empty-file] <src> <localdst>]
[-help [cmd ...]]
[-ls [-C] [-d] [-h] [-q] [-R] [-t] [-S] [-r] [-u] [<path> ...]]
[-mkdir [-p] <path> ...]
[-moveFromLocal <localsrc> ... <dst>]
[-moveToLocal <src> <localdst>]
[-mv <src> ... <dst>]
[-put [-f] [-p] [-l] [-d] <localsrc> ... <dst>]
[-renameSnapshot <snapshotDir> <oldName> <newName>]
[-rm [-f] [-r|-R] [-skipTrash] [-safely] <src> ...]
[-rmdir [--ignore-fail-on-non-empty] <dir> ...]
[-setfacl [-R] [{-b|-k} {-m|-x <acl_spec>} <path>]|[--set <acl_spec> <path>]]
[-setfattr {-n name [-v value] | -x name} <path>]
[-setrep [-R] [-w] <rep> <path> ...]
[-stat [format] <path> ...]
[-tail [-f] <file>]
[-test -[defsz] <path>]
[-text [-ignoreCrc] <src> ...]
[-touchz <path> ...]
[-truncate [-w] <length> <path> ...]
[-usage [cmd ...]]
# 注：hdfs dfs等同于hadoop fs
2.文件操作命令案例
hdfs dfs -copyFromLocal /local/data /hdfs/data：将本地文件上传到 hdfs 上（原路径只能是一个文件）
hdfs dfs -put /tmp/ /hdfs/ ：和 copyFromLocal 区别是，put 原路径可以是文件夹等
hadoop fs -ls / ：查看根目录文件
hadoop fs -ls /tmp/data：查看/tmp/data目录
hadoop fs -cat /tmp/a.txt ：查看 a.txt，与 -text 一样
hadoop fs -mkdir dir：创建目录dir
hadoop fs -get /aaa/jdk.tar.gz :等同于copyToLocal，就是从hdfs下载文件到本地
hadoop fs -df -h / :统计文件系统的可用空间信息
hadoop fs -cp /aaa/jdk.tar.gz /bbb/jdk.tar.gz.2 :从hdfs的一个路径拷贝hdfs的另一个路径
hadoop fs -mv /aaa/jdk.tar.gz / :在hdfs目录中移动文件
hadoop fs -du -s -h /aaa/* :统计文件夹的大小信息
hadoop fs -rm -r /aaa/bbb/ :删除文件或文件夹
hadoop fs -rmdir /aaa/bbb/ccc :删除目录
hadoop fs -tail /weblog/access_log.1 :显示一个文件的末尾
3.管理命令
# 命令帮助
[hadoop@hadoop000 ~]$ hdfs dfsadmin
Usage: hdfs dfsadmin
Note: Administrative commands can only be run as the HDFS superuser.
[-report [-live] [-dead] [-decommissioning]]
[-safemode <enter | leave | get | wait>]
[-saveNamespace]
[-rollEdits]
[-restoreFailedStorage true|false|check]
[-refreshNodes]
[-setQuota <quota> <dirname>...<dirname>]
[-clrQuota <dirname>...<dirname>]
[-setSpaceQuota <quota> [-storageType <storagetype>] <dirname>...<dirname>]
[-clrSpaceQuota [-storageType <storagetype>] <dirname>...<dirname>]
[-finalizeUpgrade]
[-rollingUpgrade [<query|prepare|finalize>]]
[-refreshServiceAcl]
[-refreshUserToGroupsMappings]
[-refreshSuperUserGroupsConfiguration]
[-refreshCallQueue]
[-refresh <host:ipc_port> <key> [arg1..argn]
[-reconfig <datanode|...> <host:ipc_port> <start|status|properties>]
[-printTopology]
[-refreshNamenodes datanode_host:ipc_port]
[-deleteBlockPool datanode_host:ipc_port blockpoolId [force]]
[-setBalancerBandwidth <bandwidth in bytes per second>]
[-getBalancerBandwidth <datanode_host:ipc_port>]
[-fetchImage <local directory>]
[-allowSnapshot <snapshotDir>]
[-disallowSnapshot <snapshotDir>]
[-shutdownDatanode <datanode_host:ipc_port> [upgrade]]
[-evictWriters <datanode_host:ipc_port>]
[-getDatanodeInfo <datanode_host:ipc_port>]
[-metasave filename]
[-triggerBlockReport [-incremental] <datanode_host:ipc_port>]
[-help [cmd]]
hdfs dfsadmin -report :显示所有dataNode
hdfs dfsadmin -safemode leave :离开安全模式