Category Archives: Basic UNIX

Generate Public and Private Keys using PuTTYgen

Start the PuTTYgen utility, by double-clicking on its .exe file

For Type of key to generate, select RSA. In the Number of bits in a generated key field, specify either 2048 or 4096 (increasing the bits makes it harder to crack the key by brute-force methods). Click the Generate button.

Putty Gen1

Move your mouse pointer around in the blank area of the Key section, below the progress bar (to generate some randomness) until the progress bar is full.

Putty Gen2

A private/ public key pair has now been generated, Click the Save public and private keys. If you lose your keys and have disabled username/password logins, you will no longer be able to log in server.

Putty Gen3

Thank you !!



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


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.