1. Write command to list all the links from a
directory?
In this UNIX command
interview questions interviewer is generally checking whether user knows basic
use of "ls" "grep" and regular expression etc
You can write command like:
ls -lrt | grep "^l"
2. Create a read-only file in your home directory?
This is a simple UNIX command
interview questions where you need to create a file and change its parameter to
read-only by using chmod command you can also change your umask to create read
only file.
touch file
chmod 400 file
3. How will you find which operating system your
system is running on in UNIX?
By using command "uname
-a" in UNIX
4. How will you run a process in background? How will
you bring that into foreground and how will you kill that process?
For running a process in
background use "&" in command line. For bringing it back in
foreground use command "fg jobid" and for getting job id you use
command "jobs", for killing that process find PID and use kill -9 PID
command. This is indeed a good Unix Command interview questions because many of
programmer not familiar with background process in UNIX.
5. How do you know if a remote host is alive or not?
You can check these by using
either ping or telnet command in UNIX. This question is most asked in various
Unix command Interview because its most basic networking test anybody wants to
do it.
6. How do you see command line history in UNIX?
Very useful indeed, use
history command along with grep command in unix to find any relevant
command you have already executed. Purpose of this Unix Command Interview
Questions is probably to check how familiar candidate is from available tools
in UNIX operation system.
7. How do you copy file from one host to other?
Many options but you can say
by using "scp" command. You can also use rsync command to answer this
UNIX interview question or even sftp would be ok.
8. How do you find which process is taking how much
CPU?
By using "top"
command in UNIX, there could be multiple follow-up UNIX command interview
questions based upon response of this because “TOP” command has various
interactive options to sort result based upon various parameter.
9. How do you check how much space left in current
drive?
By using "df"
command in UNIX. For example "df -h ." will list how full your
current drive is. This is part of anyone day to day activity so I think this
Unix Interview question will be to check anyone who claims to working in UNIX
but not really working on it.
10. What is the difference between Swapping and
Paging?
Swapping:
Whole process is moved from
the swap device to the main memory for execution. Process size must be less
than or equal to the available main memory. It is easier to implementation and
overhead to the system. Swapping systems does not handle the memory more
flexibly as compared to the paging systems.
Paging:
Only the required memory
pages are moved to main memory from the swap device for execution. Process size
does not matter. Gives the concept of the virtual memory. It provides greater
flexibility in mapping the virtual address space into the physical memory of
the machine. Allows more number of processes to fit in the main memory
simultaneously. Allows the greater process size than the available physical memory.
Demand paging systems handle the memory more flexibly.
Intermediate UNIX Interview Questions Answers
1. What is difference between ps -ef and ps -auxwww?
This is indeed a good Unix
Interview Command Question and I have faced this issue while ago where one
culprit process was not visible by execute ps –ef command and we are wondering
which process is holding the file.
ps -ef will omit process with
very long command line while ps -auxwww will list those process as well.
2. How do you find how many cpu are in your system and
there details?
By looking into file
/etc/cpuinfo for example you can use below command:
cat /proc/cpuinfo
4. What is Zombie process in UNIX? How do you find
Zombie process in UNIX?
When a program forks and the
child finishes before the parent, the kernel still keeps some of its
information about the child in case the parent might need it - for example, the
parent may need to check the child's exit status. To be able to get this
information, the parent calls 'wait()'; In the interval between the child
terminating and the parent calling 'wait()', the child is said to be a 'zombie'
(If you do 'ps', the child will have a 'Z' in its status field to indicate
this.)
Zombie : The process is dead
but have not been removed from the process table.
5. What is "chmod" command? What do you
understand by this line “r-- -w- --x?
6. There is a file some where
in your system which contains word "UnixCommandInterviewQuestions” How
will find that file in Unix?
7. In a file word UNIX is appearing many times? How
will you count number?
grep -c "Unix"
filename
8. How do you set environment variable which will be
accessible form sub shell?
By using export
for example export count=1 will be available on all sub shell.
9. How do you check if a particular process is
listening on a particular port on remote host?
By using telnet command for
example “telnet hostname port”, if it able to successfully connect then some
process is listening on that port. To read more about telnet read networking
command in UNIX
10. How do you find whether your system is 32 bit or
64 bit ?
Either by using "uname
-a" command or by using "arch" command.
Advanced UNIX Interview Questions and Answers
1. How do you find which processes are using a
particular file?
By using lsof command in
UNIX. It wills list down PID of all the process which is using a particular
file.
2. How do you find which remote hosts are connecting
to your host on a particular port say 10123?
By using netstat command
execute netstat -a | grep "port" and it will list the entire host
which is connected to this host on port 10123.
3. What is ephemeral port in UNIX?
Ephemeral ports are port used
by Operating system for client sockets. There is a specific range on which OS
can open any port specified by ephemeral port range.
4. If one process is inserting data into your MySQL
database? How will you check how many rows inserted into every second?
Purpose of this Unix Command
Interview is asking about "watch" command in UNIX which is repeatedly
execute command provided with specified delay.
5. There is a file Unix_Test.txt which contains words
Unix, how will you replace all Unix to UNIX?
You can answer this Unix
Command Interview question by using SED command in UNIX for example you can
execute sed s/Unix/UNIX/g fileName.
6. You have a tab separated file which contains Name,
Address and Phone Number, list down all Phone Number without there name and
Addresses?
To answer this Unix Command
Interview question you can either you AWK or CUT command here. CUT use tab as default
separator so you can use
cut -f3 filename.
7. Your application home directory is full? How will
you find which directory is taking how much space?
By using disk usage (DU)
command in Unix for example du –sh . | grep G will list down all the
directory which has GIGS in Size.
8. How do you find for how many days your Server is
up?
By using uptime command in
UNIX
9. You have an IP address in your network how will you
find hostname and vice versa?
This is a standard UNIX
command interview question asked by everybody and I guess everybody knows its
answer as well. By using nslookup command in UNIX
