There are many linux commands which help you in many ways
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#ifconfig :-
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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 :-
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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
5 CLOSE_WAIT
2 CLOSING
31 ESTABLISHED
11 FIN_WAIT1
49 FIN_WAIT2
8 LAST_ACK
2 LISTEN
27 SYN_RECV
608 TIME_WAIT
#nslookup :-
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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 :-
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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:-
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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 :-
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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
server# uptime
23:54:25 up 11 days, 19:19, 2 users, load average: 14.73, 10.45, 9.63
wall :-
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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/suhail" --> the message will appear to every one logged in the server
#w,who,whoami ,who am i :-
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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 :-
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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 :-
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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/suhail/ /home/backup/ --> this will send all updated file from /home/suhail/ directory to /home/backup directory .
rsync --rsh='ssh -p22' -aur root@192.168.0.1:/home/suhail/images/ /home/suhail/images/ --> this command will get all files from different machine to current machine .
with ssh key
server # rsync -avzrp -e "ssh -i /root/.ssh/id.suhail" /home/suhail/public_html/* root@122.12.122.12:/home/suhail/public_html/
#lsof :-
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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/suhail/suhail.log --> will show open statistics for specific file /home/suhail/suhail.log
lsof +D /home/suhail/ --> will show files open under directory /home/suhail/
lsof -u root --> will show files opened by user root .
lsof -p 5 --> will specify opened file by specific process .i.e process id 5.
#find :-
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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 :-
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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 :-
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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:-
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this command will remove the alias created .like:-
unalias pp --> now pp will no longer be any alias .
#df :-
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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 :-
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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:-
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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 .
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