Linux interview questions

1)How to compile Apache?

2)Users come to you and they will be saying mail server is very slow, what are the necessary steps you will take to resolve this issue?

3)Which are the configuration files associate with DNS server and client?

4)Where you will provide ISP details for your network?

5)How you will configure Squid proxy?

6)How you will block pron sites using Squid proxy?

7)Give me details how to configure mail support for NAGIOS?

8)Can you use NAGIOS to send SMS? how to do that?

9)What is web-min?
A) Webmin is a web-based system configuration tool for OpenSolaris, Linux and other Unix-like systems.

10)How you will do kernel compilation? Explain each step?

11)What is the difference between SGID, SUID and sticky bit?

12)How to restrict users to set password with complexity ?

13)How do you monitor system performance?

14)Which are the configuration files of FTP server?

15)What are the different types of FTP servers?

16)What is the difference between active FTP and passive FTP?

17)How you will configure FTP in DMZ?

18)What is the use of htaccess file?

19)how do you configure website authentication for user logins?

20)Give me the steps to configure sendmail.

21)How to block particular network not to access my sendmail server?

22)How to send duplex/half duplex etc to the network card?

23)Can a web server have multiple ip add? if yes why? if no why?

24)How to configure multiple ip address for a web server?

25)What is the difference between VMWare and XEN?

26)Explain me the difference between ext2 and ext3

27)How do you configure route in Linux server?

28)How do you make routes permanent in Linux server?

29)Why you want to change your job?

30)What is an inode?

31)what is the difference between soft link and hard link?

32)How to get info about the files which are not accessed from last 30days?

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Linux:GUI troubleshooting

Linux server's can be accessed through GUI(Graphical User Interface) or CLI(Command Line Interface).

Some times User will face some issues when accessing GUI such as

• Blurred screen.
• System crashes when users try to access GUI.
• Only particular user will face an issue not able to access GUI.
• Resolution problems.

In order to resolve this issues we have to pin point the problem, check weather its a problem with the single user or all the users in the server not able to access the GUI

ISSUE1: If it is for a single user this GUI related problems will occur due to some space issue
So check these following things

1. Check weather his disk quota is exceeded or not(when ever GUI is started in Linux/Nix it require some temporary space which is used to store some temp files for the purpose of GUI running), so if there is no free space left for the user GUI will not start for that particular user.
2. Remove temporary files which are not in use for that particular user.

ISSUE2: If the GUI is not working for all the users then there is some configuration issues in xorg.conf file.

The best and simple way to resolve this issue is just take a backup of the existing file and regenerate the new config file

#mv /etc/X11/xorg.conf /etc/X11/xorg.conf.old

Regenerating new GUI configuration file

#system-config-display

this command will regenerate fresh GUI and it will ask you for new resolution too, so set the new resolution to your requirement.

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DNS Troubleshooting in Linux

Some basic DNS troubleshooting in Linux.

1. First collect the information which has created the problem by doing some investigation(such as logs, debug messages etc) .
   
2. Prepare your tools which is required for your troubleshooting.
3. Troubleshooting is nothing but considering so many issues that may cause the problem and working one by one to pin point the actual culprit which created the issue.
   
4. once issue is pin-pointed you have to work on that issue with the tools/commands/logs all other resources and have to resolve it.

Coming to troubleshooting DNS aka named services, here are the steps how we can resolve the DNS related issue:

I will take one scenario "suppose my client is unable to resolve host-names to IP address"

Step1:Check the DNS server is configured on Client end or not

check in below file if name server is configured to proper DNS server or not
#vi /etc/resolv.conf

If the client is configured with proper DNS server follow to next step

Stpe2:Ping to DNS server ip address

#ping serveripadd

If pinging is happening proceed with the next step other wise click here to do network troubleshooting.

Step3:So pinging is happening... then there is a communication path between Server-client, so we have to check weather DNS server is running or not. Here nmap can be used to check what ports opened on server.

#nmap serveripadd

Example:

#nmap 125.22.73.23

this command will give you output what are the services running/ports opened on remote server, if DNS server is running and working fine means you can see DNS port(53) in the list of opened ports. If suppose server is not running/port blocked you can click here to troubleshoot in this way.

Step4:Now checking DNS server issue in deep

• Checking under whom the DNS server is register and its properties .
  

#whois example.com

• Checking what server is used to resolve and some basic info.

#nslookup www.example.com

• Checking who is resolving and what is resolving in details about DNS server.

#dig www.example.com

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