UNIX Interview Questions for Oracle DBAs

1) What’s the difference between soft link and hard link?

Ans:
A symbolic (soft) linked file and the targeted file can be located on the same or different file system while for a hard link they must be located on the same file system, because they share same inode number and an inode table is unique to a file system, both must be on the same file system.


2) How you will read a file from shell script?
Ans:
while read line
do
 echo $line
done < file_name


3) 3. What’s the use of umask?
ANS:
Will decide the default permissions for files.

4) What is crontab and what are the arguments?
Ans:
The entries have the following elements:
field             allowed values
-----             --------------
minute            0-59
hour                0-23
day of month   1-31
month             1-12
day of week     0-7 (both 0 and 7 are Sunday)
user                 Valid OS user
command         Valid command or script

? ? ? ? ? command
|  | |  | |_________day of the week (0-6, 0=Sunday)
|  | |  |___________month (1-12)
|  | |_____________day of the month (1-31)
|  |_______________hour (0-23)
|_________________minute (0-59)


5) How to find operating system (OS) version?
Ans:
uname –a

6)  How to find out the run level of the user?
Ans:
uname –r


7) How to delete 7 days old trace files?
Ans:
find ./trace –name *.trc –mtime +7 –exec rm {} \;

8) What is top command?
Ans:
top is a operating system command, it will display top processes which are taking high cpu and memory.


9) 8. How to get 10th line of a file (by using grep)?