Basic Commands

Frequently used commands

uname à  to verify OS

uname-r à version info of OS

clear  à to clear the screen

hostname à to know the host name

who à who logged into the box

uptime à when server was up

last -6 reboot à last 6 reboots

last –n reboot à last n reboots

pwd à present working directory

ls –ltr à long list

su àswitch to root user

id àto know a/c
ps  -ef =shows all the running processes
ps –ef  | grep java =shows all the java processes
ps –ef  | grep http  =shows webserves running
grep =search
telnet  hostname of database  port number =to check whether database server is running or not
iostat =disk utilization
vmstat =memory utilization
netstat =ipadress,
hostname =gives current system name
uptime=will show how long the system has been up and also shows cpu load number of users logged in
tar  -cvf<filename to be zipped><path of folder to be zipped>
tar  -xvf<zipped folder name>< path of the folder to which it should be unzipped>
init  0=shut down the system
init  6= to restart  or reboot the system
kill  -3 pid=generate thread dump
kill  -9 pid =kill procees id
tail filename=displays last 10 lines of the file
tail -100f systemout.log=displays last 100lines of systemout.log
head file name=displays first 10line of the file
ls –l=list all the files in the current directory
cat filename=opens the file in read only format
cat>filename=create the file and add data
cat>>filename=to append/update data to the file
touch filename=create file
rm filename=remove file
rm *=removes all the filein the present directory
top =cpu utilization
topas(in aix)=cpu utilization
du –sm =displays disk space utilized in MB
du –sg=displays disk space utilized in GB
du –sk=displays disk space utilized in KB
touch filename1 filename2 ……..=to create multiple files at atime
grep “  E “ systemout.log=search for E error in system out log
grep “ E “ systemout.log | more=displays pageby page(press space for next page)
prtconf=gives complete info about physical machine
prtconf | grep  “mem”=gives memory information about physical information
cmp file1 file2=compares two files
cp= coppy file
scp= secure shell command to copy file
comm file1 file2= check similarity in two file
diff file1 file2= differentiate one from other

fgrep=to search multiple strings/words at atime
chmode àto modify permissions

chown à to change the ownership

chown user1:user1 <filename>

              userid     groupid

grep à pattern search

grep –i <pattern name> <file name>

tar  à archiving utility

tar –xvf <location> <location to be copied>

ping à to check the remote host

telnet à remote server name

df àdisk free

du à disk usage

ps àprocess info

lsof àall processes info

head àfirst lines

tail àlast lines

diff àdifference

ifconfig  -aàip address

netstat àto get port numbers

netstat  -an | grep <port>àto get the process id

. àcurrent working directory

/ àentire root directory

Vi Editor Commands

vi à to open vi editor

vi <file name> à to open the file in vi editor

i àinserting ---right click

esc àto come back to normal command

shift:wq! àexit with saving

shift:q! àexit without saving

Cursor movements in Vi Editor

j àdown, k àup, l àright, h àleft, w àforward right one word,

b àbackward one word, e àwords last letter moves to end of the word,

H àhead top of the screen, M àmiddle of the screen,

L àlast line of the screen

x àremove char

u àundo previous change

X àremove one char left side

dw àremove char end of the word – right side

dd àdeletes all the current line

D àdeletes current line to end

a àcursor will go to insert mode – right side

i àcursor will go to insert mode – left side

yw àcopy the word to buffer

p àbring back after cursor

P àbring back before cursor

yy àcopy whole line to buffor

U àcomplete undo

u àprevious change

r àto replace char

R àit will go to insert mode

o àcreates blank line below the cursor and it will go to insert mode

O àcreates blank line above the cursor and it will go to insert mode.