Running Knowledge

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Administrator and developer concepts to research and understand.

Having worked in a Linux sysadmin role for many years, I have seen a set of core capabilities and conceptual understandings that new hires should have. What follows is a running list of those items

  • Compare java, c, and python in the following areas: compilation, runtime/execution, and memory management.
  • What are the three common network types assignable to virtual machine network adapters? Explain the differences between each type.
  • If you don't have the ‘jar’ command available on your system, how else can you look at the contents of a ‘.jar’ file?
  • Name a build system for a project's source code.
  • Name some IDE's for Python, Java, and C++.
  • What considerations should you note when writing a piece of code? (HINT: Has nothing to do with your love of <insert your favorite language> here.)
  • Write a bash command that will find all files ending in ‘.log’, and print out their file type.
  • You are asked to create a CentOS system that will be used in production for running some remotely accessible service. Only you and the developer will be accessing the system from remote network connections. What version of the CentOS installer do you use? How many packages were installed with this option? Compare that to another option that could have been chosen? Discuss the one choice over the other.

  • You are trying to figure out why no one can remotely connect to the web service running on your CentOS system. You run the netstat command and have the following output: 

    Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 127.0.0.1:1313          0.0.0.0:*               LISTEN      61819/hugo

    • What netstat options would you use to get a similar output?
    • What information in that output helps you troubleshoot the connection problem?

  • Using firewall-cmd, list all current rules for the default zone.

  • Using firewall-cmd, create a runtime only rule that allows TCP connections on port 1313 on the default zone.

  • Using firewall-cmd, create a permanent rule that allows TCP connections on port 1313 on the default zone.

  • Using ‘firewall-cmd’ make all runtime rules permanent on the default zone.

  • What command-line tool would you use to dump network traffic from an interface?

  • Write an example of using that network dump command to capture 3 TCP packets of a connection to port 1313 involving the host 10.0.0.1 written to the file ‘3pkts1313.pcap’

  • Describe the difference between an iptables’ table and chain