Linux network administrator questions

A pretty funny story - someone was offered a test of basic Linux questions for a junior network administrator position, and figured out that the best way to impress the future employer with good answers is to post the list on UbuntuForums. Good idea, right? That’s where all the Linux experts hang out. Unfortunately, that’s where the employer hung out as well:

It didn’t seem to me that I was asking too much for people to use mailing lists, forums, IRC whatever to compile the answers themselves. I actually expected to see some questions show up on forums but I didn’t expect someone to paste the entire thing and expect the forum users to do all the work that would qualify you for an interview. I think at this point you could save us all some time and not turn the answers back in, I already have the information I need on your answers.

Anyway, the list has been made public, so enjoy:

  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
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7 Comments on Linux network administrator questions

  1. Subha Pindiproli
    Posted 7/31/2008 at 3:31 pm | Permalink

    1.Give an example of set of shell commands that will give you the number of files in a directory ?
    Ans: ls | wc -w or ls -l | wc -l, and subtract 2 for ./ and ../

  2. Posted 8/3/2008 at 4:52 pm | Permalink

    the word “port” has dissapeared in last comment ;-) lsof -i :port

  3. Hitesh
    Posted 8/28/2008 at 1:49 am | Permalink

    lsof -i | grep “[tT][cC][pP]“

  4. asdf
    Posted 10/1/2008 at 2:49 pm | Permalink

    3. On a Red Hat Linux Variant how do you control whether a service starts when the system boots

    /etc/init.d/

    4. How do you tell the amount of free disk space left on a volume

    df
    or df -h for human readable format

    6. Give an example of a recursively copying a directory from one location to another.

    cp -R /home/asdf/source /home/asdf/target

    8. Give an example of a set of shell commands that will give you the number of “httpd” processes running on a Linux box.

    ps awx | grep httpd | wc -l

    11. What is the maximum length of CAT6

    100 meters (328 feet)

  5. abhishek
    Posted 10/24/2008 at 11:09 am | Permalink

    What’s the difference between TCP and UDP

    TCP - Connection Oriented

    UDP - Connection less

  6. Trilok
    Posted 11/30/2008 at 7:09 am | Permalink

    Give an example of a set of shell commands to tell how many times “bob” has logged on to the system this month

    #last | grep bob | wc -l

  7. nigam
    Posted 12/7/2008 at 7:14 am | Permalink

    5 )Give an example of a set of shell commands to tell how many times “bob” has logged on to the system this month

    Ans:last -u bob|wc -l

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