HDFS file commands quick reference

Here's a quick reference of the most frequently used (and useful) HDFS (Hadoop Distributed File System) commands to manage files.

$HADOOP_HOME/bin/hadoop fs -ls /
Lists all of the files in the root HDFS directory.

$HADOOP_HOME/bin/hadoop fs -ls /rawdata/server01
Lists all of the files in the HDSF directory at the given path.

$HADOOP_HOME/bin/hadoop fs -mkdir /rawdata/
Creates a new directory in HDFS.

$HADOOP_HOME/bin/hadoop fs -put /home/user/importdir/*.txt /rawdata/
Copies files from a local directory to HDFS at the specified path. The destination directory should have been created preliminarily.

$HADOOP_HOME/bin/hadoop fs -get /rawdata/test01.txt
/home/user/importdir/
Copies files from HDFS back to the local filesystem.

$HADOOP_HOME/bin/hadoop fs -cp /rawdata/test01.txt /rawdatabackup/test01.txt
Copies files within HDFS.

$HADOOP_HOME/bin/hadoop fs -rm /rawdata/*.txt
Deletes files from a HDFS directory.

$HADOOP_HOME/bin/hadoop fs -rm -r /rawdata
Deletes a HDFS directory and all of its content.

$HADOOP_HOME/bin/hadoop fs -tail /rawdata/test01.txt
Prints the last kilobyte of a file to the standard output.

$HADOOP_HOME/bin/hadoop fs -df
Displays the free HDFS space.

$HADOOP_HOME/bin/hadoop fs -df -h
Displays the free HDFS space in human readable format.

Comments

Exporting InfluxDB data to a CVS file

Sometimes you would need to export a sample of the data from an InfluxDB table to a CSV file (for example to allow a data scientist to do some offline analysis using a tool like Jupyter, Zeppelin or Spark Notebook). It is possible to perform this operation through the influx command line client. This is the general syntax: sudo /usr/bin/influx -database '<database_name>' -host '<hostname>' -username '<username>' -password '<password>' -execute 'select_statement' -format '<format>' > <file_path>/<file_name>.csv where the format could be csv , json or column . Example: sudo /usr/bin/influx -database 'telegraf' -host 'localhost' -username 'admin' -password '123456789' -execute 'select * from mem' -format 'csv' > /home/googlielmo/influxdb-export/mem-export.csv

jOOQ: code generation in Eclipse

jOOQ allows code generation from a database schema through ANT tasks, Maven and shell command tools. But if you're working with Eclipse it's easier to create a new Run Configuration to perform this operation. First of all you have to write the usual XML configuration file for the code generation starting from the database: <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <configuration xmlns="http://www.jooq.org/xsd/jooq-codegen-2.0.4.xsd"> <jdbc> <driver>oracle.jdbc.driver.OracleDriver</driver> <url>jdbc:oracle:thin:@dbhost:1700:DBSID</url> <user>DB_FTRS</user> <password>password</password> </jdbc> <generator> <name>org.jooq.util.DefaultGenerator</name> <database> <name>org.jooq.util.oracle.OracleDatabase</name> ...

Turning Python Scripts into Working Web Apps Quickly with Streamlit

I just realized that I am using Streamlit since almost one year now, posted about in Twitter or LinkedIn several times, but never wrote a blog post about it before. Communication in Data Science and Machine Learning is the key. Being able to showcase work in progress and share results with the business makes the difference. Verbal and non-verbal communication skills are important. Having some tool that could support you in this kind of conversation with a mixed audience that couldn't have a technical background or would like to hear in terms of results and business value would be of great help. I found that Streamlit fits well this scenario. Streamlit is an Open Source (Apache License 2.0) Python framework that turns data or ML scripts into shareable web apps in minutes (no kidding). Python only: no front‑end experience required. To start with Streamlit, just install it through pip (it is available in Anaconda too): pip install streamlit and you are ready to execute the working de...

Googlielmo's blog

Search This Blog