Linux Network admin interview Questions

1. Give an example of set of shell commands that will give you the number of files in a directory
2. How do you tell what process has a TCP port open in Linux
3. On a Red Hat Linux Variant how do you control whether a service starts when the system boots
4. How do you tell the amount of free disk space left on a volume
5. Give an example of a set of shell commands to tell how many times “bob” has logged on to the system this month
6. Give an example of a recursively copying a directory from one location to another.
7. How do you modify the IP and Net mask of a system running a Red Hat Variant of Linux
8. Give an example of a set of shell commands that will give you the number of “httpd” processes running on a Linux box.
9. On CentOS or Fedora based system using the package management application, how do you tell what package provided the file “libnss_ldap.so”
10. What is the difference between VTP client, server, and transparent
11. What is the maximum length of CAT6
12. How does one set up a layer two link to share VLANs
13. How does one implement redundant links at Layer 2
14. What is the difference between a hub, switch, and a router? What are the security advantages of switch vs. hub?
15. Show an example of using telnet to learn the headers of an http server.
16. In what OSI layer does PPP exist
17. What’s the difference between TCP and UDP
18. Given a DNS server that has just started (with an empty cache) and host contacting this DNS server (using it’s OS setting) to learn an address for google.com, list the steps the DNS server will take to learn it with IP addresses (each step will have multiple possible IP addresses – you need choose only one per step).
19. Why are layer 2 loops bad, and what protocol was designed to prevent them
20. Given a radius server at 10.0.0.2 and a shared key of ‘abc123′ show the IOS commands necessary to authenticate switch users against the radius server, while still allowing the use of local username / password pairs

Command to find all of the files which have been accessed within the last 30 days in linux

Command to find all of the files which have been accessed within the last 30 days in linux
find / -type f -atime -30 > December.files
This command will find all the files under root, which is ‘/’, with file type is file. ‘-atime -30′ will give all the files accessed less than 30 days ago. And the output will put into a file call December.files.

for what daemon is responsible for in linux?

For what daemon is responsible for in linux?

Question: what daemon is responsible for in linux?
Ans: syslogd

The syslogd daemon is responsible for tracking  system information and saving it to specified log files.
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what is kernal upgradation

What is kernal upgradation?

kernel updation is a process of to upgrade the kernel file with a new or latest version of kernel & use of them as a default kernel.or we can say as 

Kernel updation is upgrading kernel version. To update kernel either you can enroll yourself to the official website of red hat or you can simply download the latest kernel version and then running rpm -u kernel version. But this method is not recommended, it is better to install the new kernel and let the older version of it remain untouched so that you can revert back the changes.
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What is LILO in Linux

What is LILO in linux?

Question :What is LILO in linux?
Answer :LILO stands for Linux boot loader. It will load the MBR, master boot record, into the memory, and tell the system which partition and hard drive to boot from.

Boot process:
When LILO loads itself, it displays the name LIO where each word specifies some actions
If it displays nothing then it does not load any part of LILO.
L: This is the first stage of the bootloader that has been loaded. If the process stops here it denotes that there were problems in the second stage. This may occur due to some incorrect disk parameter specified in the configuration file of lilo or some media problems also.
LI: It indicates that the second stage boot loader has been loaded and could not be executed. It can occur due to problems similar to L.
LIL: At this stage, the second stage boot loader has been completed in its execution. If it fails, this stage indicates that there were media problems or map file specified in the configuration file has some problems.
LIL?: This means that the second stage boot loader loaded at an incorrect address.
LIL-: This indicates that the descriptor table is corrupted.
LILO: All parts are successfully loaded.

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What is a Daemon?

What is a Daemon?

Question :What is a Daemon?
Answer :A daemon is a process that detaches itself from the terminal and runs, disconnected, in the background, waiting for requests and responding to them. It can also be defined as the background process that does not belong to a terminal session. Many system functions are commonly performed by daemons, including the sendmail daemon, which handles mail, and the NNTP daemon, which handles USENET news. Many other daemons may exist. Some of the most common daemons are: • init: Takes over the basic running of the system when the kernel has finished the boot process. • inetd: Responsible for starting network services that do not have their own stand-alone daemons. For example, inetd usually takes care of incoming rlogin, telnet, and ftp connections. • cron: Responsible for running repetitive tasks on a regular schedule.

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What is 'ps' command for?How would you kill a process?

What is 'ps' command for?How would you kill a process?

Question1 :What is 'ps' command for?
Answer :The ps command prints the process status for some or all of the running processes. The information given are the process identification number (PID),the amount of time that the process has taken to execute so far etc.

Question 2:How would you kill a process?
Answer :The kill command takes the PID as one argument; this identifies which process to terminate. The PID of a process can be got using 'ps' command. -9 is the option given

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