02-linux-tasks.md

Research Linux Distributions

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• Compare and contrast features of RHEL, Fedora and Ubuntu.
• Compare the package managers used by RHEL, Fedora and Ubuntu.
• Discuss how system administration varies across different Linux distributions.
• Investigate the security features inherent to RHEL.

Setup Linux Environment

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Task 1: Installing a Linux Distribution

• Download a popular Linux distribution (like Ubuntu, Fedora, or CentOS) and install it in a virtual machine or a spare computer.
• Set up the root user and create a new non-root user for daily tasks.
• Update the system packages to their latest versions using the package manager (like apt, dnf, or yum).

Task 2: Configuring the Shell Environment

• Familiarize yourself with the command line interface.
• Customize the shell prompt to your liking using PS1 environment variable.
• Learn about environment variables and set some of your own.
• Learn about shell aliases and create some useful ones.

Task 3: Installing Additional Software

• Install software from the distribution's repositories using the package manager.
• Add a third-party repository and install software from it.
• Install software manually from a .deb or .rpm file.
• Install software manually from source code.

Task 4: Configuring Networking

• Configure the network settings using the command line (IP address, DNS servers, etc.).
• Test the network connectivity with commands like ping and traceroute.
• Set up SSH and connect to your machine remotely.

Task 5: Setting Up a Development Environment

• Install a text editor or IDE, like Vim, Emacs, Visual Studio Code, or JetBrains IDEs.
• Install build tools like gcc for C/C++, openjdk for Java, python for Python, etc.
• Write a small program and compile/run it.
• Install Git, clone a repository, and make some changes to it.

Understanding Linux Terminal

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Task 1: Navigating the Filesystem

• Use cd to change directories.
• Use ls to list directory contents.
• Use pwd to print the current working directory.
• Practice with absolute and relative paths.

Task 2: Managing Files and Directories

• Use cp to copy files and directories.
• Use mv to move or rename files and directories.
• Use rm to remove files and directories.
• Use touch to create new empty files.

Task 3: Working with File Content

• Use cat to display the content of files.
• Use less and more for paging through text files.
• Use head and tail to display the beginning or end of files.

Task 4: Redirection and Pipes

• Learn about standard input, standard output, and standard error.
• Use > and >> to redirect output to a file.
• Use < to redirect input from a file.
• Use | to pipe output from one command to another.

Task 5: Searching and Regular Expressions

• Use grep to search within text.
• Use find to search for files in the file system.
• Use | and grep together to filter command output.
• Learn about basic regular expressions and use them with grep.

Linux Storage

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Task 1: Exploring File Systems

• Use df to display file system disk space usage.
• Use du to estimate file and directory space usage.
• Understand the difference between hard and soft links (ln command).
• Explore different file systems (ext4, XFS, Btrfs etc).

Task 2: Disk Partitioning and Management

• Use fdisk to view and manage disk partitions.
• Format a partition with a file system of your choice.
• Mount and unmount file systems manually and by using /etc/fstab.

Task 3: Logical Volume Management

• Install and set up Logical Volume Manager (LVM).
• Create a logical volume, format it, and mount it.
• Extend a logical volume and resize the file system.
• Reduce a logical volume and resize the file system.

Task 4: Network File System

• Set up a NFS server.
• Configure a NFS client and mount a remote file system.
• Understand NFS permissions and squash options.

Task 5: Backup and Restore

• Use tar and gzip to create a backup of your files.
• Use rsync to sync files between different directories or systems.
• Restore your files from the tar backup.
• Explore other backup solutions like dd, dump, cpio, etc.

Linux File Permissions

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Task 1: Basic File Permissions

• Create a file and use the ls -l command to list the permissions.
• Change the permissions of the file using chmod command with symbolic (e.g., chmod u+x filename) and numerical (e.g., chmod 644 filename) modes.
• Explain the different permissions (read, write, execute) for user, group, and others.

Task 2: Understanding Directory Permissions

• Create a directory and list its permissions.
• Change the permissions of the directory and explain the impact on the files within.
• Explain the significance of execute permission on a directory.

Task 3: User and Group Management

• Create a new user and group using useradd and groupadd commands.
• Add the user to the group with usermod or gpasswd.
• Change the ownership of a file/directory with chown and chgrp.

Task 4: Setuid, Setgid, and Sticky Bit

• Create a file and set the Setuid and Setgid permissions.
• Run the file as a different user and observe the result.
• Create a directory and set the Sticky Bit. Explain its purpose.

Task 5: Access Control Lists (ACLs)

• Use the getfacl and setfacl commands to view and modify ACLs on a file/directory.
• Discuss when and why you would want to use ACLs instead of traditional permissions.

Linux Security

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Task 1: Configuring Firewalls

• Install and enable a firewall tool like UFW or Firewalld.
• Create and apply rules to allow and deny certain types of traffic.
• Test the firewall's efficacy using tools like nmap or telnet.

Task 2: Understanding SELinux

• Learn about SELinux modes (Enforcing, Permissive, Disabled) and contexts.
• Use commands such as sestatus, getenforce, and setenforce.
• Practice changing the SELinux context for a file or process.

Task 3: User Rights Management

• Learn about sudo and the /etc/sudoers file.
• Add and remove users from the sudo group.
• Test the effect of these changes.

Task 4: Understanding SSH Key-Based Authentication

• Generate a pair of SSH keys and copy your public key to another machine.
• Attempt to SSH into the machine using key-based authentication.
• Disable password-based SSH authentication and attempt to SSH into the machine.

Task 5: System Hardening

• Explore system hardening guides and select measures applicable to your environment.
• Implement chosen hardening measures.
• Use a tool like Lynis or OpenSCAP to audit the security of your system.

Linux Networking

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Task 1: Hostname and Network Configuration

• Use commands such as ip, ip, ss, hostname and nslookup to view network configuration and system hostname.
• Change the IP address and hostname of your machine.
• Test the changes using ping, nslookup or hostname -f.

Task 2: Understanding Network Services

• Install and configure a network service, such as a web server or FTP server.
• Connect to the service from another machine.
• Troubleshoot any connection issues that arise.

Task 3: Using iptables

• Learn about the structure of iptables rules.
• Create iptables rules to allow, deny, or redirect traffic.
• Use iptables -L to list your current rules.

Task 4: Using netcat

• Use netcat to create a simple server and client on different machines.
• Send a message from the client to the server.
• Reverse the roles and send a message from the server to the client.

Task 5: Understanding DNS

• Use nslookup or dig to query the DNS records for a domain.
• Change your machine's DNS servers and test the effect.
• If possible, set up a local DNS server and configure another machine to use it.

Task 6: Managing Hostname

• Understand the role and importance of the system hostname.
• Learn the difference between static and transient hostnames.
• Change the system hostname using the hostnamectl command.
• Verify the changes by displaying the system hostname.
• Understand how changing the hostname can impact the applications and services running on the system.

Web Servers and Databases

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Task 1: Install and Configure a Web Server

• Install Apache or Nginx using package management tools like apt or yum.
• Understand and modify the main configuration files.
• Create a virtual host/domain.

Task 2: Host a Website

• Create a simple HTML webpage.
• Serve the webpage through the web server.
• Access the webpage from a different machine.

Task 3: Secure the Web Server

• Configure firewall rules to allow/deny traffic to the web server.
• Enable HTTPS using Let's Encrypt.

Task 4: Analyzing Server Logs

• Understand the structure and contents of server logs.
• Use grep, awk, and cut to analyze logs and find specific entries.

Database Tasks

Task 5: Install and Configure a Database

• Install MySQL or PostgreSQL using package management tools.
• Understand and modify the main configuration files.
• Secure the database installation.

Task 6: Create and Manage a Database

• Create a database and a table.
• Insert, update, and delete data.
• Perform basic SQL queries to retrieve data.

Task 7: Backup and Restore a Database

• Create a backup of the database using mysqldump or pg_dump.
• Restore the database from a backup.

Task 8: Monitor Database Performance

• Understand the basic performance metrics for databases.
• Use tools like top, iostat, and vmstat to monitor system resources utilized by the database.
• Use database-specific tools (like EXPLAIN in SQL) to analyze query performance.

Load Balancers and Reverse Proxy

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Task 1: Understand Load Balancing Concepts

• Learn about the purpose and benefits of load balancing.
• Understand different load balancing algorithms (Round Robin, Least Connections, etc.).

Task 2: Set Up a Load Balancer

• Install and configure HAProxy or Nginx as a load balancer.
• Create a couple of web servers and configure the load balancer to distribute traffic between them.

Task 3: Monitor and Troubleshoot the Load Balancer

• Learn to interpret the stats page in HAProxy or the nginx -s command output in Nginx.
• Troubleshoot common issues (e.g., backend server down, high latency).

Task 4: Understand Reverse Proxy Concepts

• Understand the purpose of a reverse proxy and how it differs from a forward proxy.

Task 5: Set Up a Reverse Proxy

• Configure Nginx or Apache as a reverse proxy server for a web application.
• Test access to the web application through the reverse proxy.

Task 6: Secure the Reverse Proxy

• Enable HTTPS on the reverse proxy.
• Understand and configure basic access controls (e.g., IP whitelisting).

Task 7: Troubleshoot the Reverse Proxy

• Understand common issues (e.g., 502 Bad Gateway errors) and how to resolve them.
• Learn to read and interpret the reverse proxy logs.

Systemd Management

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Task 1: Understanding Systemd

• Understand the role of systemd in the Linux system.
• Explore the basic concepts related to systemd (units, targets, services, etc.).

Task 2: Working with Services

• Use systemctl to start, stop, restart, and check the status of services.
• Identify failed services and understand the reasons using systemctl and journalctl.

Task 3: Managing Systemd Units

• Understand the structure of a systemd unit file.
• Create a simple systemd service unit from scratch.
• Enable and disable systemd services to start at boot.

Task 4: Systemd Logs and Troubleshooting

• Use journalctl to read and filter systemd logs.
• Analyze log messages to troubleshoot systemd service issues.

Task 5: Advanced Systemd Management

• Learn about and use systemd timers as cron replacements.
• Understand and apply systemd resource controls and sandboxing features.
• Create a complex systemd service unit that manages a real-world application (like a web server or database).

Linux Troubleshooting

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Task 1: Investigating High Load

• Identify a high load on a system using tools like top, htop, or uptime.
• Determine which processes are causing the high load.
• Analyze the system logs (/var/log/syslog, /var/log/messages) to look for any error messages related to the problematic processes.

Task 2: Resolving Disk Space Issues

• Determine which directories are consuming the most disk space using the du command.
• Identify large, unnecessary files for deletion.
• Monitor disk usage over time to understand usage patterns.

Task 3: Troubleshooting Network Issues

• Use ping and traceroute to identify network connectivity issues.
• Use netstat or ss to identify which services are listening on which ports.
• Use tcpdump to capture and analyze network traffic.
• Troubleshoot DNS issues using tools like dig or nslookup.

Task 4: Investigating Memory Usage

• Identify high memory usage processes with top or htop.
• Understand the difference between virtual, shared, and resident memory.
• Monitor memory usage over time to spot leaks or excessive usage.

Task 5: Resolving Permission Issues

• Identify files with incorrect permissions using the find command.
• Correctly set file permissions and ownership with chmod and chown.
• Understand and apply the principle of least privilege.

Task 6: Analyzing System Performance

• Use sar to monitor system performance over time.
• Identify and analyze CPU, memory, and I/O bottlenecks.
• Troubleshoot slow boot time issues using systemd-analyze.

Task 7: Dealing with Failed Services

• Use systemctl to check the status of a failed service.
• Analyze logs of the failed service using journalctl.
• Identify and resolve common service failure issues (e.g., configuration errors, missing dependencies).

Control Groups & Namespaces Tasks

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Task 1: Exploring Control Groups (cgroups)

• Install cgroup utilities.
• Create a new cgroup and assign a process to it.
• Limit the CPU and memory usage of your cgroup.
• Monitor the resource usage of your cgroup.

Task 2: Playing with Namespaces

• Use unshare to create new namespaces and run processes inside them.
• Explore different types of namespaces (PID, NET, UTS, IPC, USER, MNT).
• Use nsenter to enter an existing namespace.

Task 3: Combining cgroups and namespaces

• Create a new cgroup and a new namespace.
• Run a process inside the new namespace and cgroup.
• Limit and monitor the resource usage of the process.

Task 4: Troubleshooting with cgroups and namespaces

• Diagnose a system performance issue using cgroup statistics.
• Use namespaces to isolate a problematic process and diagnose it.
• Understand how to use cgroups and namespaces for resource management and isolation.

eBPF Tasks

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Task 1: Learning Basics of eBPF

• Read up on the basics and understand the concept of eBPF.
• Explore the purpose and uses of eBPF.

Task 2: Setting Up eBPF

• Set up an environment that supports eBPF.
• Install BCC (BPF Compiler Collection).

Task 3: Exploring eBPF Tools

• Use different tools provided by BCC for system analysis.
• Understand how each tool works and what information it provides.

Task 4: Writing eBPF Programs

• Write a basic eBPF program that performs a simple task.
• Compile and load your eBPF program using BCC.
• Analyze the effect of your eBPF program on the system.

Task 5: Advanced eBPF

• Use eBPF to monitor network traffic.
• Use eBPF to trace system calls and kernel functions.
• Implement a complex use case using eBPF. For example, implementing a basic firewall.