I have a folder name in HDFS Data# and I wanted replace it Data=
Is there a way to do it hdfs?
Assuming Data# is just short for the HDFS path of the folders a simple solution to achieve this would be to simply move your folder
hadoop fs -mv Data# Data=
If Data# is only the folder name you will need the full HDFS path as well and the command becomes something like:
hadoop fs -mv full/path/to/Data# full/path/to/Data=
where you will need to change full/path/to to the actual HDFS path.
In docker, I want to copy a file README.md from an existing directory /opt/ibm/labfiles to a new one /input/tmp. I try this
hdfs dfs -put /opt/ibm/labfiles/README.md input/tmp
to no effect, because there seems to be no /input folder in the root. So I try to create it:
hdfs dfs -mkdir /input
mkdir:'/input': File exists
However, when I ls, there is no input file or directory
How can I create a folder and copy the file? Thank you!!
Please try hdfs dfs -ls / if you want to see there is an input folder that exists in HDFS at the root.
You cannot cd into an HDFS directory
It's also worth mentioning that the leading slash is important. In other words,
This will try to put the file in HDFS at /user/<name>/input/tmp
hdfs dfs -put /opt/ibm/labfiles/README.md input/tmp
While this puts the file at the root of HDFS
hdfs dfs -put /opt/ibm/labfiles/README.md /input/tmp
My aim is to read all the files that starts with "trans" in a directory and convert them into a single file and load that single file into HDFS location
my source directory is /user/cloudera/inputfiles/
Assume that inside that above directory , there are lot of file , but i need all the files that start with "trans"
my destination directory is /user/cloudera/transfiles/
So i tried this command below
hadoop dfs - getmerge /user/cloudera/inputfiles/trans* /user/cloudera/transfiles/records.txt
but the above command is not working .
If i try the below command then it works
hadoop dfs - getmerge /user/cloudera/inputfiles /user/cloudera/transfiles/records.txt
Any suggestion on how do i merge some files from a hdfs location and store that merged single file in another hdfs location
Below is the usage of getmerge command:
Usage: hdfs dfs -getmerge <src> <localdst> [addnl]
Takes a source directory and a destination file as input and
concatenates files in src into the destination local file.
Optionally addnl can be set to enable adding a newline character at the
end of each file.
It expects directory as first parameter.
you can try cat command like this:
hadoop dfs -cat /user/cloudera/inputfiles/trans* > /<local_fs_dir>/records.txt
hadoop dfs -copyFromLocal /<local_fs_dir>/records.txt /user/cloudera/transfiles/records.txt
I am a beginner in hadoop. I have two doubts
1) how to access files stored in the hdfs? Is it same as using a FileReader in java.io and giving the local path or is it something else?
2) i have created a folder where i have copied the file to be stored in hdfs and the jar file of the mapreduce program. When I run the command in any directory
${HADOOP_HOME}/bin/hadoop dfs -ls
it just shows me all the files in the current dir. So does that mean all the files got added without me explicitly adding it?
Yes, it's pretty much the same. Read this post to read files from HDFS.
You should keep in mind that HDFS is different than your local file system. With hadoop dfs you access the HDFS, not the local file system. So, hadoop dfs -ls /path/in/HDFS shows you the contents of the /path/in/HDFS directory, not the local one. That's why it's the same, no matter where you run it from.
If you want to "upload" / "download" files to/from HDFS you should use the commads:
hadoop dfs -copyFromLocal /local/path /path/in/HDFS and
hadoop dfs -copyToLocal /path/in/HDFS /local/path, respectively.
How to copy file from HDFS to the local file system . There is no physical location of a file under the file , not even directory . how can i moved them to my local for further validations.i am tried through winscp .
bin/hadoop fs -get /hdfs/source/path /localfs/destination/path
bin/hadoop fs -copyToLocal /hdfs/source/path /localfs/destination/path
Point your web browser to HDFS WEBUI(namenode_machine:50070), browse to the file you intend to copy, scroll down the page and click on download the file.
In Hadoop 2.0,
hdfs dfs -copyToLocal <hdfs_input_file_path> <output_path>
where,
hdfs_input_file_path maybe obtained from http://<<name_node_ip>>:50070/explorer.html
output_path is the local path of the file, where the file is to be copied to.
you may also use get in place of copyToLocal.
In order to copy files from HDFS to the local file system the following command could be run:
hadoop dfs -copyToLocal <input> <output>
<input>: the HDFS directory path (e.g /mydata) that you want to copy
<output>: the destination directory path (e.g. ~/Documents)
Update: Hadoop is deprecated in Hadoop 3
use hdfs dfs -copyToLocal <input> <output>
you can accomplish in both these ways.
1.hadoop fs -get <HDFS file path> <Local system directory path>
2.hadoop fs -copyToLocal <HDFS file path> <Local system directory path>
Ex:
My files are located in /sourcedata/mydata.txt
I want to copy file to Local file system in this path /user/ravi/mydata
hadoop fs -get /sourcedata/mydata.txt /user/ravi/mydata/
If your source "file" is split up among multiple files (maybe as the result of map-reduce) that live in the same directory tree, you can copy that to a local file with:
hadoop fs -getmerge /hdfs/source/dir_root/ local/destination
This worked for me on my VM instance of Ubuntu.
hdfs dfs -copyToLocal [hadoop directory] [local directory]
1.- Remember the name you gave to the file and instead of using hdfs dfs -put. Use 'get' instead. See below.
$hdfs dfs -get /output-fileFolderName-In-hdfs
if you are using docker you have to do the following steps:
copy the file from hdfs to namenode (hadoop fs -get output/part-r-00000 /out_text).
"/out_text" will be stored on the namenode.
copy the file from namenode to local disk by (docker cp namenode:/out_text output.txt)
output.txt will be there on your current working directory
bin/hadoop fs -put /localfs/destination/path /hdfs/source/path