Unix, Linux, DevOps , Cloud computing and BigData Knowledge-Base


3 Commands to operate on File fields

1.  cut Command ‘cut’ writes to standard output selected parts of each line of each input file, or standard input if no files are given or for a file name of ‘-‘. Synopsis: cut OPTION… [FILE]… In the table which follows, the BYTE-LIST, CHARACTER-LIST, and FIELD-LIST...


Working with kpartx Command in Red Hat Enterprise Linux

This tool, derived from util-linux’ partx, reads partition tables on specified device and create device maps over partitions segments detected. It is called from hotplug upon device maps creation and deletion. kpartx [-a | -d | -l] [-v] wholedisk Usage Example To mount all the partitions...


Working with mdadm Command in RHEL7

Introduction RAID devices are virtual devices created from two or more real block devices. This allows multiple devices (typically disk drives or partitions thereof) to be combined into a single device to hold (for example) a single filesystem. Some RAID levels include redundancy and so can...


Working with dracut in RHEL7

Introduction dracut – low-level tool for generating an initramfs image Create an initramfs for the kernel with the version . If is omitted, then the version of the actual running kernel is used. If is omitted or empty, then the default location /boot/initramfs-.img is used.


Working with Parted – Linux Partition tool

1. Introduction to Partitioning Parted is  a  program to manipulate disk partitions. It supports multiple partition table formats, including MS-DOS and GPT.  It is useful for creating space for new operating systems, reorganising disk usage, and copying data to new hard disks.


‘tail’: Output the last part of files

‘tail’ prints the last part (10 lines by default) of each FILE; it reads from standard input if no files are given or when given a FILE of ‘-‘. Synopsis: tail [OPTION]… [FILE]… If more than one FILE is specified, ‘tail’ prints a one-line header consisting...


‘fold’: Wrap input lines to fit in specified width

‘fold’ writes each FILE (‘-‘ means standard input), or standard input if none are given, to standard output, breaking long lines.  Synopsis:      fold [OPTION]… [FILE]… By default, ‘fold’ breaks lines wider than 80 columns.  The output is split into as many lines as necessary. ‘fold’...


‘numfmt’: Reformat numbers

‘numfmt’ reads numbers in various representations and reformats them as requested.  The most common usage is converting numbers to/from _human_representation (e.g.  ‘4G’ ==> ‘4,000,000,000’).      numfmt [OPTION]… [NUMBER]    ‘numfmt’ converts each NUMBER on the command-line according to the specified options (see below).  If no NUMBERs...

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