UNIX Useful Commands

1) Find whether OS is 64/32 Bit Kernel in UNIX.

uname -a

2) Find free physical memory in UNIX.

free -m

3) Find CPU details in UNIX.

cat /proc/cpuinfo

4) Find files modified within specific time.

find . -mtime -3 (modified less than 3days ago)

5) command used to alter file permissions.

chmod 777 abc.txt

6) Command used to reset the Ownership.

chown oracle:dba abc.txt

7) command used to set, or reset, the users login password.

Passwd username

8) Kill specific process in UNIX.

Kill -9 processid

9) Command used for display last given lines of a file.

tail -n alert_PROD.log

10) Command used for intall a rpm package.

rpm -ivh packagename.rpm

11) Command used to querry about any rpm package

rpm -q packagename

12) Command to Check the server up time

uptime

13) Command to check the file versions

strings -a <filename> |grep ‘$Header’

14) Command will keep ‘n’ number of days files and remove rest of file.

find . -mtime +n -exec rm  {} ; &

15) Basic commands for  vi editor

i   :- insert before cursor.

l   : insert begining of the line.

a  :- append after the cursor.

A  :- Append at the end of the line.

o :- insert a blank line below the cursor.

O :- insert a blank line above the cursor position.

h :- from current position one char towards left .

I :- from current position one char towards right.

j :- from current position one line towards down.

k :- from current position one line towards up.

Shift+g  :- go to end of the file.

Shift+:1 :- go to top of the file.

dd –> delete the ful line.

:q! —> closing the file without saving any changes.

:wq! –> save the changes and force close.

:w –> to save the changes without closing the file.

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