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Linux commands to check the disk utilization, size of directory or file

  • Command to check the disk utilization
df -h

The ‘-h’ option will provide the utilization in human readable format.

  • Command to check the size of a directory
du -sh <directory name>
  • Command to check the size of a file
du -sh <file name>
  • Command to check the size of files in a directory

Go inside the directory and execute the following command

du -sh *

 

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Utility to get the complete details of a Linux system

This is a small shell script that captures almost all the necessary details of a linux system. I tested this script in CentOS and Redhat operating systems. You can access this script directly from github.

Programmatic Data Upload to Amazon S3

S3 is a service provided by Amazon for storing data. The full form is Simple Storage Service. S3 is a very useful service for less price. Data can be uploaded to and downloaded from S3 very easily using some tools as well as program. Here I am explaining  a sample program for uploading file to S3 using a python program.

Files can be uploaded to S3 in two approaches. One is the normal upload and another is the multipart upload. Normal upload sends the file serially and is not suitable for large files. It will take more time. For large files, multipart upload is the best option. It will upload the file by dividing it into chunks and sends it in parallel and collects it in S3.

This program is using the normal approach for sending the files to S3. Here I used the boto library for uploading the files.

Linux Filesystem colour codes

When we fire ls –all in linux cli, files may be listed in different colours  

The color code of the files is as follows:

Blue: Directory file

White: Normal file

Green: Executable file

Yellow: Device file

Magenta: Picture file

Cyan: link file

Red: Compressed file

File Symbol

-(Hyphen) = Normal file

d=directory

l=link file

b=Block device file

c=character device file

Hadoop FS Shell Commands

FS Shell

FS shell means FileSystem shell. The file system may be hdfs or the local file system(linux file system.

For HDFS the scheme is hdfs,

Eg: hdfs://namenodehost:<port>/user/test

For the local filesystem the scheme is file.

Eg: file:///testfile

If no schema is specified, the default scheme specified in the configuration is used. By default it is hdfs.

Majority of the commands in FS shell behave like corresponding Unix commands. Differences are described with each of the commands.

cat

Usage: hadoop fs -cat URI [URI …]

Copies source paths to stdout.

Example:

  • hadoop fs -cat hdfs://nn1.example.com/file1 hdfs://nn2.example.com/file2
  • hadoop fs -cat file:///file3 /user/hadoop/file4

Exit Code:
Returns 0 on success and -1 on error.

chgrp

Usage: hadoop fs -chgrp [-R] GROUP URI [URI …]

Change group association of files. With -R, make the change recursively through the directory structure. The user must be the owner of files, or else a super-user. Additional information is in the HDFS Admin Guide: Permissions.

chmod

Usage: hadoop fs -chmod [-R] <MODE[,MODE]… | OCTALMODE> URI [URI …]

Change the permissions of files. With -R, make the change recursively through the directory structure. The user must be the owner of the file, or else a super-user. Additional information is in the HDFS Admin Guide: Permissions.

chown

Usage: hadoop fs -chown [-R] [OWNER][:[GROUP]] URI [URI ]

Change the owner of files. With -R, make the change recursively through the directory structure. The user must be a super-user. Additional information is in the HDFS Admin Guide: Permissions.

copyFromLocal

Usage: hadoop fs -copyFromLocal <localsrc> URI

Similar to put command, except that the source is restricted to a local file reference.

copyToLocal

Usage: hadoop fs -copyToLocal [-ignorecrc] [-crc] URI <localdst>

Similar to get command, except that the destination is restricted to a local file reference.

count

Usage: hadoop fs -count [-q] <paths>

Count the number of directories, files and bytes under the paths that match the specified file pattern. The output columns are:
DIR_COUNT, FILE_COUNT, CONTENT_SIZE FILE_NAME.

The output columns with -q are:
QUOTA, REMAINING_QUATA, SPACE_QUOTA, REMAINING_SPACE_QUOTA, DIR_COUNT, FILE_COUNT, CONTENT_SIZE, FILE_NAME.

Example:

  • hadoop fs -count hdfs://nn1.example.com/file1 hdfs://nn2.example.com/file2
  • hadoop fs -count -q hdfs://nn1.example.com/file1

Exit Code:

Returns 0 on success and -1 on error.

cp

Usage: hadoop fs -cp URI [URI …] <dest>

Copy files from source to destination. This command allows multiple sources as well in which case the destination must be a directory.
Example:

  • hadoop fs -cp /user/hadoop/file1 /user/hadoop/file2
  • hadoop fs -cp /user/hadoop/file1 /user/hadoop/file2 /user/hadoop/dir

Exit Code:

Returns 0 on success and -1 on error.

du

Usage: hadoop fs -du URI [URI …]

Displays aggregate length of files contained in the directory or the length of a file in case its just a file.
Example:
hadoop fs -du /user/hadoop/dir1 /user/hadoop/file1 hdfs://nn.example.com/user/hadoop/dir1
Exit Code:
Returns 0 on success and -1 on error.

dus

Usage: hadoop fs -dus <args>

Displays a summary of file lengths.

expunge

Usage: hadoop fs -expunge

Empty the Trash. Refer to HDFS Architecture for more information on Trash feature.

get

Usage: hadoop fs -get [-ignorecrc] [-crc] <src> <localdst>

Copy files to the local file system. Files that fail the CRC check may be copied with the -ignorecrc option. Files and CRCs may be copied using the -crc option.

Example:

  • hadoop fs -get /user/hadoop/file localfile
  • hadoop fs -get hdfs://nn.example.com/user/hadoop/file localfile

Exit Code:

Returns 0 on success and -1 on error.

getmerge

Usage: hadoop fs -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.

ls

Usage: hadoop fs -ls <args>

For a file returns stat on the file with the following format:
filename <number of replicas> filesize modification_date modification_time permissions userid groupid
For a directory it returns list of its direct children as in unix. A directory is listed as:
dirname <dir> modification_time modification_time permissions userid groupid
Example:
hadoop fs -ls /user/hadoop/file1 /user/hadoop/file2 hdfs://nn.example.com/user/hadoop/dir1 /nonexistentfile
Exit Code:
Returns 0 on success and -1 on error.

lsr

Usage: hadoop fs -lsr <args>
Recursive version of ls. Similar to Unix ls -R.

mkdir

Usage: hadoop fs -mkdir <paths>

Takes path uri’s as argument and creates directories. The behavior is much like unix mkdir -p creating parent directories along the path.

Example:

  • hadoop fs -mkdir /user/hadoop/dir1 /user/hadoop/dir2
  • hadoop fs -mkdir hdfs://nn1.example.com/user/hadoop/dir hdfs://nn2.example.com/user/hadoop/dir

Exit Code:

Returns 0 on success and -1 on error.

moveFromLocal

Usage: dfs -moveFromLocal <localsrc> <dst>

Similar to put command, except that the source localsrc is deleted after it’s copied.

moveToLocal

Usage: hadoop fs -moveToLocal [-crc] <src> <dst>

Displays a “Not implemented yet” message.

mv

Usage: hadoop fs -mv URI [URI …] <dest>

Moves files from source to destination. This command allows multiple sources as well in which case the destination needs to be a directory. Moving files across filesystems is not permitted.
Example:

  • hadoop fs -mv /user/hadoop/file1 /user/hadoop/file2
  • hadoop fs -mv hdfs://nn.example.com/file1 hdfs://nn.example.com/file2 hdfs://nn.example.com/file3 hdfs://nn.example.com/dir1

Exit Code:

Returns 0 on success and -1 on error.

put

Usage: hadoop fs -put <localsrc> … <dst>

Copy single src, or multiple srcs from local file system to the destination filesystem. Also reads input from stdin and writes to destination filesystem.

  • hadoop fs -put localfile /user/hadoop/hadoopfile
  • hadoop fs -put localfile1 localfile2 /user/hadoop/hadoopdir
  • hadoop fs -put localfile hdfs://nn.example.com/hadoop/hadoopfile
  • hadoop fs -put – hdfs://nn.example.com/hadoop/hadoopfile
    Reads the input from stdin.

Exit Code:

Returns 0 on success and -1 on error.

rm

Usage: hadoop fs -rm URI [URI …]

Delete files specified as args. Only deletes non empty directory and files. Refer to rmr for recursive deletes.
Example:

  • hadoop fs -rm hdfs://nn.example.com/file /user/hadoop/emptydir

Exit Code:

Returns 0 on success and -1 on error.

rmr

Usage: hadoop fs -rmr URI [URI …]

Recursive version of delete.
Example:

  • hadoop fs -rmr /user/hadoop/dir
  • hadoop fs -rmr hdfs://nn.example.com/user/hadoop/dir

Exit Code:

Returns 0 on success and -1 on error.

setrep

Usage: hadoop fs -setrep [-R] <path>

Changes the replication factor of a file. -R option is for recursively increasing the replication factor of files within a directory.

Example:

  • hadoop fs -setrep -w 3 -R /user/hadoop/dir1

Exit Code:

Returns 0 on success and -1 on error.

stat

Usage: hadoop fs -stat URI [URI …]

Returns the stat information on the path.

Example:

  • hadoop fs -stat path

Exit Code:
Returns 0 on success and -1 on error.

tail

Usage: hadoop fs -tail [-f] URI

Displays last kilobyte of the file to stdout. -f option can be used as in Unix.

Example:

  • hadoop fs -tail pathname

Exit Code:
Returns 0 on success and -1 on error.

test

Usage: hadoop fs -test -[ezd] URI

Options:
-e check to see if the file exists. Return 0 if true.
-z check to see if the file is zero length. Return 0 if true
-d check return 1 if the path is directory else return 0.

Example:

  • hadoop fs -test -e filename

text

Usage: hadoop fs -text <src>

Takes a source file and outputs the file in text format. The allowed formats are zip and TextRecordInputStream.

touchz

Usage: hadoop fs -touchz URI [URI …]

Create a file of zero length.

Example:

  • hadoop -touchz pathname

Exit Code:
Returns 0 on success and -1 on error.