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Working with Files in CentOS

Knowing the different commands to look at and manipulate files is a required skill for new system administrators. This hands-on lab will allow you to use the different utilities for normal sysadmin work and learn through repetition. **Note:** After the lab starts up, please wait a minute or so to give the instance time to spin up before connecting via SSH.

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Lab Info
Level
Beginner
Last updated
Apr 06, 2025
Duration
15m

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Table of Contents
  1. Challenge

    Find Out How Many and What Type of CPUs Are on the System

    Note: After the lab starts up, please wait a minute or so to give the instance time to spin up before connecting via SSH.

    Once you ssh in, become root with:

    sudo -i
    

    We need to look at the CPUs on the system. That information is stored in /proc/cpuinfo.

    If we cat that file, we notice we only have one CPU so we can just use head -5 to get the relevant information.

    To do this, run:

    head -5 /proc/cpuinfo > /tmp/cpus
    

    If we had more than one CPU, we could use grep -A 4 processor /proc/cpuinfo to get information about all of them. The -A flag tells grep to print four lines after it matches, and we're looking for "processor", which is the first line of the /proc/cpuinfo file.

  2. Challenge

    Gather the Logs
    1. Get the format for today's date:

      tail /var/log/messages
      
    2. Copy and paste the date.

    3. Run the following, and output it to the terminal to make sure it looks right:

      grep "<DATE> " /var/log/messages
      
    4. Once we verify it looks right, run:

      grep "<DATE> " /var/log/messages > /tmp/logs
      
  3. Challenge

    Find Out How Many Users Are on the System

    Since /etc/passwd contains all the users on the system, we just need to count how many lines are in that file. Fortunately, the wc command will do that for us.

    Run:

    wc -l /etc/passwd > /tmp/usernum
    
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