1.   ls -lrt | grep "^1"

Used for command to list all the links from a directory


2.   # touch file
     # chmod 400 file

Used to Create a read-only file in your home directory

3.   uname -a 
     used for finding which operating system your system is running on in UNIX

4.    killing a process find PID and use kill -9 PID command

5.  For bringing a process back in foreground use command "fg jobid" and for getting job id you use command      jobs

6. By using "top" command in UNIX you will find which process is taking how much CPU

7. By using "df" command in UNIX. For example "df -h ." will list how full your current drive is