Basic UNIX commands

How to findout background processes from OS:  
$ ps -ef|grep ora_|grep SID


–To find out files size more than 5MB
find . -size +5000 -exec ls -ltr {} \;

– To **Remove** files size more than 5MB
find . -size +5000k -exec rm -rf {} \;

–To find out files older than 30days
find . -mtime +30 -exec ls -ltr {} \;

–To find **Remove** files older than 30days
find . -mtime +30 -exec rm -rf {} \;

-To find users list, user id in a server
awk -F':' '{ print $1 " uid="$3}'  /etc/passwd
awk -F: '$0=$1 " uid="$3' /etc/passwd

How would you change all occurrences of a value using VI?

Use :%s/<old>/<new>/g

Explain iostat, vmstat and netstat.
Iostat reports on terminal, disk and tape I/O activity.
Vmstat reports on virtual memory statistics for processes, disk, tape and CPU activity.
Netstat reports on the contents of network data structures.

What is stored in oratab file?
it's being used to list the databases and software versions installed on a server

Give the command to display space usage on the UNIX file system.
df -kh
df -h
df -lh

Explain the read, write, and execute permissions on a UNIX directory.
Read allows you to see and list the directory contents.
Write allows you to create, edit and delete files and subdirectories in the directory.
Execute gives you the previous read/write permissions plus allows you to change into the directory and execute programs or shells from the directory.

How do you list the files in an UNIX directory while also showing hidden files?
ls -ltra

How do you execute a UNIX command in the background?
Use the "&"

How do you kill a process in Unix?
kill -9 process_id