Linux Commands For Devops

What is Linux?

Linux, an open-source and network created operating system for PCs, centralized servers, cell phones, and installed gadgets. It has endured on pretty much every significant PC platform including ARM, x86, and so on, one of the most generally maintained operating systems. The framework of Linux is like UNIX yet it has developed to function on a wide assortment of equipment from telephones to supercomputers. Each Linux-based OS includes the Linux Kernel that oversees hardware assets, and a bunch of software  bundles which constitute the remaining part of the operating system.

How is Linux popular?

Linux can be said as an important operating system compared to the rest of the operating systems. It is a free, open source software and secure operating system. We don't have to pay to use it like Windows. The codes used can be edited by the public. 

Linux Commands for DevOps

1.sudo 

This command operates only that command by root/ superuser privileges.

Syntax:

$ sudo

$ sudo

sudo useradd - To add a new user

sudo passwd - Creating a password for the new user

sudo groupadd - To add a new group

sudo userdel - To delete the user

sudo groupdel - To delete the  group

sudo usermod -g - To add a user to a primary group

2.Is

This command indexes all the contents in the present working directory.

Syntax: 

$ ls

ls - By mentioning the path after ls, the content in that path will be shown

ls –a - Using ‘a’ flag, indexes all the hidden contents in the particular directory

ls –l - Using ‘l’ flag, indexes all the contents with its permissions, owner settings, and time

stamp (long format)

3.Sort

This command sorts the outcomes of a search either numerically or alphabetically. It also sorts file contents, files, and directories.

Syntax:

$ sort {filename}

sort -f - the flag does case insensitive sorting 

sort -r - the flag returns the results in reverse order

sort -n - the flag returns the results as per numerical order

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4.Grep

This command searches for a particular string/ word in a text file. It is similar to “Ctrl+F” but operated through a CLI.

Syntax:

$ grep {filename}

grep -n - Returns the matching strings along with their line number

grep -i - Returns the results for case insensitive strings

grep -c - Returns the number of lines in which the results matched the search string

grep -v - Returns the result of lines not matching the search string

5.Tail

It is corresponding to head command. The tail command prints the last N number of information of the given info. Of course, it prints the last 10 lines of the predefined documents. In the event that you provide more than one file name, at that point information from each document goes before by its record name. 

Syntax:

tail [OPTION]... [FILE]...

tail -n 3 state.txt or tail -3 state.txt => -n for no. of lines

tail +25 state.txt

-c num: Prints the last ‘num’ bytes from the file specified.

6.Cat

This command could read, alter or concatenate text files. It also shows file contents.

Syntax:

$ cat {filename}

cat -n - It adds line numbers to all lines

cat -b - It adds line numbers to non-blank lines

cat -s - It squeezes blank lines into one line

cat –E - It shows $ at the end of line

7.Chmod

The command is utilized to alter the access authorizations of files and directories.

Syntax:

chmod {filename}

4 – read permission

2 – write permission

1 – execute permission

0 – no permission

8.Chown

Various clients in the operating system have proprietorship and authorization to guarantee that the records are secure and put limitations on who can alter the contents of the documents. In Linux, there exist various clients who utilize the framework:

• Every client has a few properties related to them, for example, a client ID and a home registry. We could add clients into a team to make the way toward dealing with clients in a simple manner. 
• A group can have at least zero clients. A predetermined client is related with a default group. It can likewise be an individual from different teams on the system also.

The chown command is utilized to aalter the file Owner or group. 

Syntax:

chown [OPTION]… [OWNER][:[GROUP]] FILE…

chown [OPTION]… –reference=RFILE FILE…

Example: To change owner of the file:

chown owner_name file_name

chown master file1.txt

Here, master is another user in the system. Consider that if you are user named user1 and you require to alter ownership to root (where your current directory is user1). You can use “sudo” before the syntax.

sudo chown root file1.txt

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9.Id

This command is utilized to discover client and group names and numeric IDs of the current client or some other client in the server. It is helpful to discover the accompanying data as shown below: 

• Client name and genuine user id. 
• Discover the particular Users UID. 
• Display  the UID and all groups related with a client. 
• Listing out all the groups a client has a place with. 
• Show security setting of the current client.

Syntax:

id [OPTION]… [USER]

Options:

-g: Print only the effective group id.

-G: Print all Group IDs.

-r: Prints real ID instead of numbers.

-n: Prints name instead of a number.

-u: Prints only the effective user ID.

–help: show help messages and exit.

–version: show the version information and exit.

10.Ifconfig

ifconfig(interface configuration) command is utilized to design the kernel occupant network interfaces. It is utilized at the boot time to organize the interfaces as required. From that point onward, it is typically utilized when required during investigating or when you need framework tuning. It is also utilized to allot the IP address and netmask to an interface or to empower or cripple a given interface.

Syntax:

ifconfig [...OPTIONS] [INTERFACE]

Syntax: ifconfig -a

-a : It is used to show all the interfaces accessible, even if they are down.

Syntax: ifconfig -s

-s : Display a short list, instead of details.

11.Cut

Cut command is utilized for separating a part of a file utilizing segments and delimiters. If you need to list everything in a chosen section, utilize ‘- c’ with cut order. For instance, let's select the initial two columns from our demo1.txt document. 

cut -c1-2 demo1.txt

12.Sed

Sed is a text manager which can execute editing activities in a non-intuitive manner. The sed command gets its contribution from standard input or a document to play out the editing procedure on a record. It is an extremely ground-breaking utility and you could do a great deal of document controls utilizing sed. In the event that you need to supplant a text in a file via looking through it in a document, you can utilize the sed command with a substitute ‘s’ to look for the particular pattern and alter it.

To replace  “mikesh” in test.txt file to “Mukesh”, you can do as:

sed 's/mikesh/mukesh/' test.txt

13.dd

dd is a command-line utility for Unix and Unix-like operating systems whose main role is to change over and duplicate records.

• On Unix, gadget drivers for hardware, and exceptional gadget files, show up in the record system simply like typical files. 
• dd commands can also be read and/or write from/to these documents, given that capacity is executed in their individual drivers 
• Thus, dd can be utilized for undertakings like supporting the boot area of a hard drive, and getting a fixed measure of random information. 
• The dd program can likewise perform transformations on the information as it is replicated, including byte request trading and change to and from the EBCDIC and ASCII  text encodings.

14.History

history command is utilized to see the recently operated command. This component was not accessible in the Bourne shell. Slam and Korn uphold this element where each command executed is considered as an event and is related with an occasion number utilizing which they can be reviewed and altered whenever required. These commands are stored in a set of history records. In Bash shell history command shows the entire list of the commands.

Syntax:

$ history : To display the limited number of commands which are executed prior as follows:

$ history 10

15.Find

find command in UNIX is a command-line utility for strolling a file progressive system. It may very well be utilized to discover documents and indexes and perform the resulting procedure on them. It upholds searching by file, envelope, name, creation date, alteration date, proprietor and consents. By utilizing the '- executive' other UNIX commands could be operated on files or folders found.

Syntax :

$ find [where to start searching from]

[expression determines what to find] [-options] [what to find]

Options :

• -ok CMD : It operates the same as -exec except the user is prompted first.
• -inum N : It searches for files with inode number ‘N’.
• -links N : It searches for files with ‘N’ links.
• -exec CMD: The file being searched that meets the given criteria and returns 0 for as its exit status for accurate command execution.

16.Diff

diff command is utilized to discover the distinction between two files. It investigations the documents and prints the lines that are not comparative. Let’s state that we have two documents, test and test1. Syntax –  diff test.txt test1.txt

17.Free

In LINUX, there exists a command-line utility for this and that is free command that shows the aggregate sum of free space accessible alongside the measure of memory utilized and trade memory in the framework, and furthermore the buffers utilized by the kernel. 

Syntax:

$free [OPTION]

Options for free command

• -b, – -bytes :It shows the memory in bytes.
• -k, – -kilo :It shows the amount of memory in kilobytes(default).
• -m, – -mega :It shows the amount of memory in megabytes.
• -g, – -giga :It shows the amount of memory in gigabytes

18.tr

The tr command in UNIX is a command-line utility for translating  or erasing characters. It bolsters a scope of changes including capitalized to lowercase, pressing rehashing characters, erasing explicit characters and fundamental find and replace. It may be utilized with UNIX pipes to help more intricate interpretation. tr represents translate. 

Syntax:

$ tr [flag] SET1 [SET2]

Options

• -c : parallels the collection of characters in string.i.e., functions apply to characters not in the provided set.
• -d : delete the characters in the first set from the output.
• -s : replaces the repeated characters listed in the set1 having single events
• -t : truncates set1

19.telnet

Telnet aids to connect to a remote Linux computer and execute programs remotely and operate administration.

Syntax

• telnet hostname=”” or=””
• Example:
• telnet localhost

20.kill (Linux Command For DevOps)

kill command in Linux, is an underlying command that is utilized to end processes physically. This imparts a sign to a process that ends the process. In the event that the client doesn't indicate any sign that is to be sent alongside the kill command, at that point the default TERM signal is sent which ends the process.

kill -l :To show all the accessible signals you could utilize below command option:

Syntax:$kill -l

kill pid: To display how to utilize a PID using the kill command.

Syntax: $kill pid

Linux Commands For DevOps Final Conclusion:
Basic commands could upgrade your troubleshooting ability while deciding why your application works in a single advancement climate however maybe not in another. Learning a portion of these valuable commands can assist you in resolving problems with your application. With so numerous new tools and improvements, the designers and architects should get familiar with some essential Linux commands for DevOps. It will aid them sort out, investigate, and optimize their apps, when things turn out badly. By inventively executing these commands into your work measures, you can turn into a specialist Linux user.