Linux or, less frequently used, is a Unix-like and mostly POSIX-compliant computer operating system assembled under the model of free and open-source software development and distribution. The defining component of Linux is the Linux kernel, an operating system kernel first released on 5 October 1991 by Linus Torvalds. The Free Software Foundation uses the name GNU/Linux to describe the operating system, which has led to some controversy.
In this post discuss Most Useable advensed Linux commands for linux operating system user which helps in many ways . If you are not
linux administrator then these commands can help you in many ways .
Following commands are very important .
- ifconfig
- netsat
- nslookup
- who
- w
- who am i
- whoami
- uptime
- wall
- top
- rsync
- lsof
- find
- whereis
- alias
- unalias
- df
- su
- diff
- traceroute
- iostat
- mpstat
- iftop
ifconfig :-
this command is used to setup network details . Also we can see ip
address of the system . there are many uses of this command . complete
usage of this command can be seen use command "man ifconfig " .
some uses of that commands are :-
ifconfig -a --> will show all details of networks
ifconfig eth0 --> will show details of fist ethernet network
ifconfig eth0 down --> will take first ethernet down or shutdown ethernet first
ifconfig eth0 up --> just opposite to the down command . it will start firsth ethernet
ifconfig eth0 172.18.100.4 netmask 255.255.255.255 --> will set system ip to 172.18.100.4 and netmast to 255.255.255.255
netstat :-
netstat is very important command to use on servers . it shows details
about all port activities . which port are working and how many
connections on the ports at any time . complete usage of this command
can be seen using command "man netstat" .
Some uses of this commands are :-
netstat -a --> will show all port activities
netstat -at --> will show all TCP port activities
netstat -au --> will show all UDP port activities
netstat -l --> ports which are listening
netstat -tl --> TCP ports which are listening
netstat -s --> statistics for all ports
netstat -st --> statistics for alls TCP ports only
netstat -n --> will show hosts in numeric form i.e. in ip address forms
netstat -c --> continuously
use many commands combinations to get your desired results . like :-
netstat -atn | grep ":8080 " --> it will show connections on only 8080 port
also
netstat -tan | grep ':80 ' | awk '{print $6}' | sort | uniq -c
2 CLOSE_WAIT
140 CLOSING
13371 ESTABLISHED
1884 FIN_WAIT1
116 FIN_WAIT2
110 LAST_ACK
1 LISTEN
367 SYN_RECV
2168 TIME_WAIT
nslookup :-
this command is used to see dns entries of any domain or ip . like
nslookup pkonline.in --> it wil show details about pkonline.in , its ip and max available info
nslookup 1.1.1.1 --> will show details about this ip address
nslookup pkonline.in 2.2.2.2 --> will show details of pkonline.in from dns 2.2.2.2
traceroute :-
this command is used to trace route between your system to destination . use :-
traceroute google.com --> will show all nodes of connectivity between your system and google.com servers .
iostat :-
this command is used to get all input and output statistics over all
hard disks. to install this command in system use "yum install sysstat "
.uses :-
iostat --> will show average of input and output operation on every disk partition .
iostat 2 --> will show continuously current io statistics .
mpstat:-
mpstat shows output stats of every processor available .
mpstat ,
mpstat -P all --> will how all processors statistics .
mpstat -P 0 --> will show just first processor output statistics .
uptime :-
it will show uptime of your server . that means from how much time your
server is running . This will reset after restart of server . to use it
just write uptime in shell and hit enter
wall :-
this command is used to send a message to all shells of that system .
Suppose many people are logged in on that server . If any one want to
convey any message to all people then use wall .like :-
wall "dont delete anyfile from directory /home/parveen" --> the message will appear to every one logged in the server
w,who,whoami ,who am i :-
these three commands will provide you details about how many user are logged in the system and from how much time .
w --> will show details of all logged in users .
who -- > similar to w but show less details .
whoami --> will show you your username .
who am i --> will show you more details about your login .
top :-
top is most basic and mostly used command . it can provide complete
overview of your system . This will show CPU usage , RAM usage , load on
system ,which process is using maximum system .etc .
htop :-
slightly modified version of top command . It show use individually of every CPU .
rsync :-
this command is used to make two directoris in sync with each other .
This can be used over two different systems or on the same system itself
.
rsynch -uar /home/parveen/ /home/backup/ --> this will send all updated file from /home/parveen/ directory to /home/backup directory .
rsync --rsh='ssh -p22' -aur root@192.168.0.1:/home/parveen/images/ /home/parveen/images/ --> this command will get all files from different machine to current machine .
lsof :-
it will provide list of open files . there are many uses of this command . like :-
lsof --> list all opened files on the system
lsof /home/parveen/parveen.log --> will show open statistics for specific file
/home/parveen/parveen.log
lsof +D /home/parveen/ --> will show files open under directory /home/parveen/
lsof -u root --> will show files opened by user root .
lsof -p 10 --> will specify opened file by specific process .i.e process id 10 .
find :-
this command is used to search any file in the system .this can be used like that :-
find /home/ -name abc.txt --> this command will try to search file abc.txt under directory /home/ .
find / -name abc.txt --> this command will find abc.txt in the whole system .
find . -name abc.txt --> this command will find abc.txt in the current directory .
whereis :-
this command will search the location of commands . like:-
whereis cp --> will show the location of cp command . This may also search is binary files .
alias :-
this command is used to create aliasing for any command. this command is helping to create shortcuts of commands .like :-
alias pp="ls -lhtr" --> after this if you run pp command this it will show results equivalent to ls -lhtr
unalias:-
this command will remove the alias created .like:-
unalias pp --> now pp will no longer be any alias .
df :-
this command is used to show storage usage of all hard disk partitions . like :-
df -k --> this will show all partitions witgh there usage and free memory available in bits.
df -kh --> this will show size in MB KB and GB format .
du :-
this command is used to show disk usage by directories and files . this can be used in maby ways .
du --> will show directories which are using some space that means files which are non empty .
du -a --> this comamnd will show all files . also will show empty files
du -ah --> will show memory in human readle form like KB MB GB .
du -s --> will show summarised memory .
du -sh * --> will show memory taken by all files and directory at your current location with human readable form .
diff:-
this command is used to find difference between two files . for comparison of two files this is well structured command .
diff file1 file2 --> will print differences between this two files .
