Useful commands to manage Desktop and Server in Linux - Part 2

Useful commands to manage Desktop and Server

Some useful commands which helps you to manage Desktop/Server more efficiently in Linux is illustrated in this article with examples.


> Command

It is used to delete the contents of the file without removing and creating the same file again.

[root@linuxhelp Desktop]# cat my.txt
[root@linuxhelp Desktop]# > my.txt
[root@linuxhelp Desktop]# cat my.txt

at Command

It is used to schedule a task or command to run at specified time.

[root@linuxhelp Desktop]# at 15:10
at> mkdir dir  
job 17 at 2016-03-30 15:10

du Command

It displays the output of the sub folders size within the current directory.

[root@linuxhelp Desktop]# du -h --max-depth=1  
4.0K    ./mydirc
428K    ./mhddfs-0.1.39
500K    .

For info about du command:



expr Command

It helps to do simple mathematical calculation in terminal.

[root@linuxhelp Desktop]# expr 5 + 5
[root@linuxhelp Desktop]# expr 5 – 2

look Command

It is used to check for words in dictionary.

[root@linuxhelp Desktop]# look ap

yes Command

It is used to display the specified content infinitely.

[root@linuxhelp Desktop]# yes "This is Linuxhelp Tutorial"
This is Linuxhelp Tutorial
This is Linuxhelp Tutorial
This is Linuxhelp Tutorial
This is Linuxhelp Tutorial
This is Linuxhelp Tutorial
. . .
. . . .
. . . . .
This is Linuxhelp Tutorial
This is Linuxhelp Tutorial

factor Command

It displays the factorial of a given number.

[root@linuxhelp Desktop]# factor 25
25: 5 5
[root@linuxhelp Desktop]# factor 27
27: 3 3 3

Using ping with audible output

It is used to check is whether the server is alive or not with audible output.

[root@linuxhelp Desktop]# ping -i 10 -a
PING ( 56(84) bytes of data.
64 bytes from ( icmp_seq=1 ttl=57 time=21.4 ms
64 bytes from ( icmp_seq=2 ttl=57 time=6.02 ms

For info about ping command:

tac Command

It prints the content of a text file in reverse order, i.e., from last line to first line.

[root@linuxhelp Desktop]# cat  my.txt
1. Linux
2. Windows
3. Mac
4. Android
[root@linuxhelp Desktop]# tac my.txt
4. Android
3. Mac
2. Windows
1. Linux

strace Command

strace Command is used display the full details of how the command is executed from the kernel.

[root@linuxhelp Desktop]# strace ls
execve("/bin/ls", ["ls"], [/* 45 vars */]) = 0
brk(0)                                  = 0x16c3000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f79fd614000
access("/etc/", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/", O_RDONLY)      = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=63821, ...}) = 0
mmap(NULL, 63821, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f79fd604000

disown -a && exit Command

It is used to run the jobs continuously in the background even after you closing the terminal session.

[root@linuxhelp Desktop]# top; disown -a && exit

getconf Command

It displays the machine architecture if it is 32 bit or 64 bit.

[root@linuxhelp Desktop]# getconf LONG_BIT

To display Date on the Terminal

Execute this command to see the date and time in the terminal.

[root@linuxhelp Desktop]# while sleep 1;do tput sc;tput cup 0 $(($(tput cols)-29));date;tput rc;done &

For info about date command:

Convert Command

It is used to to produce output in image format.

[root@linuxhelp Desktop]# tree | convert label:@- shot1.png
[root@linuxhelp Desktop]# display shot1.png

watch -t -n1 “date +%T|figlet”

To display animated digital clock

It shows the animated digital clock in the terminal.

[root@linuxhelp Desktop]# watch -t -n1 "date +%T|figlet"


To check DNS lookup utility by using host and dig Commands

[root@linuxhelp Desktop]# host has address has IPv6 address 2a03:2880:2130:cf24:face:b00c:0:25de mail is handled by 10

[root@linuxhelp Desktop]# dig
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.17.rc1.el6 <<>>
;; global options: +cmd
;; Got answer:
;; ->>HEADER<

For more info about dig command:

To view all of your system resources

[root@linuxhelp Desktop]# dstat




To displays all the shortcuts available for BASH shell using bind

[root@linuxhelp Desktop]# bind -p
"C-g": abort
"C-xC-g": abort
"eC-g": abort
"C-j": accept-line
"C-m": accept-line
. . .
. . . .
. . . . .
"C-y": yank
"e.": yank-last-arg
"e_": yank-last-arg
"ey": yank-pop

Alias Command

The command alias is usually a short name that the shell translates into another name or command. Aliases allow you to define new commands by substituting a string for the first token of a simple command. They are located in the ~/.bashrc (bash) or ~/.tcshrc (tcsh) start up files so that they are available to interactive sub shells.

[root@linuxhelp Desktop]#alias c='clear'
[root@linuxhelp Desktop]#c
[root@linuxhelp Desktop]#alias 1='mkdir'
[root@linuxhelp Desktop]#1 myfolder
[root@linuxhelp Desktop]#ls
dir                                                                     mydir
download                                                                mydirc
download~                                                               myfolder
f1.txt                                                                  my.txt
gnome-screenshot.desktop                                                part2.odt
[root@linuxhelp Desktop]# unalias c
[root@linuxhelp Desktop]#unalias 1

w command

The w command displays the information about the users currently logged into the machine, and their processes.

[root@linuxhelp Desktop]# w
19:05:13 up  1:24,  2 users,  load average: 0.04, 0.08, 0.07
USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU  WHAT
root     tty1     :0               17:41     1:24m  1:33   1:33  /usr/bin/Xorg :0 -nr -verbose -audit
root     pts/0    :0.0             19:04     0.00s  0.03s  0.02s w

ddate command

The ddate command prints the date in Discordant date format. It is used to convert Gregorian date into the Discordian date format and print this on the standard output.

[root@linuxhelp Desktop]# ddate
Today is Boomtime, the 19th day of Discord in the YOLD 3182

To check the information of the operating system

It prints distribution-specific information. If it is not installed apt or yum from package.

[root@linuxhelp Desktop]# lsb_release –a
LSB Version:    :base-4.0-amd64:base-4.0-noarch:core-4.0-amd64:core-4.0-noarch:graphics-4.0-amd64:graphics-4.0-noarch:printing-4.0-amd64:printing-4.0-noarch
Distributor ID:    CentOS
Description:    CentOS release 6.4 (Final)
Release:    6.4
Codename:    Final

-a displays all the available information like version, id, description, release and codename.

nc command

The nc command stands for Netcat. It is used for debugging and investigating the networking utilities, typically by creating and utilizing raw TCP/IP connections. It is used to check if port 80 is open or not.

[root@linuxhelp Desktop]# nc -zv localhost 22
Connection to localhost 22 port [tcp/ssh] succeeded!

[root@linuxhelp Desktop]# nc -zv localhost 80
nc: connect to localhost port 80 (tcp) failed: Connection refused
nc: connect to localhost port 80 (tcp) failed: Connection refused

curl command

It displays the the ‘Geographical Location‘ of the IP address, provided.

[root@linuxhelp Desktop]# curl
  "ip": "",
  "hostname": "",
  "city": "New Delhi",
  "region": "National Capital Territory of Delhi",
  "country": "IN",
  "loc": "28.6000,77.2000",
  "org": "AS9498 BHARTI Airtel Ltd."

find . -user root

It displays the files with respect to the specified user owned files.

[root@linuxhelp Desktop]# find . -user user1
./System Config 03.02.15.docx
./ifconfig command in linux.odt
./System Config new.docx
./Ping modified.docx

For more info about find command:

lsof command

It displays the name of process and service using a specific port.

[root@linuxhelp Desktop]# lsof -iTCP:22 -sTCP:LISTEN
sshd    1727 root    3u  IPv4  10747      0t0  TCP *:ssh (LISTEN)
sshd    1727 root    4u  IPv6  10749      0t0  TCP *:ssh (LISTEN)

For more info about lsof command:

Find the file or directory with specific memory size

The below command used to list the files in the current directory above the specified size recursively.

[root@linuxhelp Desktop]# find -size +50M

pdftk Command

pdftk command is used to merge the multiple PDF file into one PDF file. Before executing this command you should install the pdftk package by using yum for CentOS / RHEL

[root@linuxhelp Downloads]# pdftk file1.pdf file2.pdf cat output merge.pdf
[root@linuxhelp Downloads]# ls
file1.pdf  file2.pdf  merge.pdf  ShellIntro.pdf
After executed the above command now open that merge file and check the status.

To displays the processes and threads of a user

The ps command display the processes and threads of the user. Options L list threads and “-F” for Full Format Listing.

[root@linuxhelp Desktop]# ps -LF -u root
root         1     0     1  0    1  4838  1348   0 17:47 ?        00:00:01 /sbin
root         2     0     2  0    1     0     0   0 17:47 ?        00:00:00 [kth]
root         3     2     3  0    1     0     0   0 17:47 ?        00:00:00 [mig]
root         4     2     4  0    1     0     0   0 17:47 ?        00:00:00 [kso]
root         5     2     5  0    1     0     0   0 17:47 ?        00:00:00 [mig]
root         6     2     6  0    1     0     0   0 17:47 ?        00:00:00 [wat]
root         7     2     7  0    1     0     0   0 17:47 ?        00:00:01 [eve]
root         8     2     8  0    1     0     0   0 17:47 ?        00:00:00 [cgr]
root         9     2     9  0    1     0     0   0 17:47 ?        00:00:00 [khe]

For more info about ps command:

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Tags: Basic Commands
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