Week 1 of My DevOps Journey: Linux Fundamentals, SSH, and More

📌 The Topics I Learned

This week, I focused on understanding Linux, its fundamental commands, and system management. My learning was guided by the YouTube video: Linux for DevOps Engineers | Beginner to Advanced. Here’s a breakdown of the topics I covered:

• How the Internet Works & What are Servers?

• Linux OS Overview & Setting Up a Linux Server

• Basic Linux Commands for DevOps Engineers

• Advanced Linux Commands

• Users and Groups Management

• File Management in Linux

• File Transfer Commands

• Linux Networking Commands

• Pro Linux Commands (AWK, GREP, FIND, SED)

• Linux Volume Management

• LVM (Logical Volume Manager) in Linux

🚧 Challenges I Faced

During my learning process, I encountered a few hurdles:

1️⃣ Setting Up SSH (Without AWS EC2 Instance)

• Issue: Configuring SSH on my local Linux system instead of an AWS instance was tricky. Initially, I faced errors like "Unit ssh.service could not be found" and "Connection refused" when trying to connect.

• Solution:

  Commands on the system I wanted to connect to:

    whoami
  

  Output: root

    ifconfig
  

  Output: Displays network interfaces and their IP addresses.

    hostname -I
  

  Output: 172.30.108.140 (Example IP Address)

    sudo systemctl status ssh
  

  Output: Unit ssh.service could not be found. (SSH not installed)

    systemctl list-units --type=service | grep ssh
  

  Output: No output (SSH service not found)

    dpkg -l | grep openssh
  

  Output:

    ii  openssh-client                       1:8.9p1-3ubuntu0.11                     amd64        secure shell (SSH) client, for secure access to remote machines
    ii  openssh-server                       1:8.9p1-3ubuntu0.11                     amd64        secure shell (SSH) server, for secure access from remote machines
    ii  openssh-sftp-server                  1:8.9p1-3ubuntu0.11                     amd64        secure shell (SSH) sftp server module, for SFTP access from remote machines
  

    sudo apt update
    sudo apt install openssh-server -y
  

  Output: Installs OpenSSH server.

    sudo systemctl enable --now ssh
  

  Output: SSH service starts successfully.

    dpkg -l | grep openssh
  

  Output:

    ii  openssh-client                       1:8.9p1-3ubuntu0.11                     amd64        secure shell (SSH) client, for secure access to remote machines
    ii  openssh-server                       1:8.9p1-3ubuntu0.11                     amd64        secure shell (SSH) server, for secure access from remote machines
    ii  openssh-sftp-server                  1:8.9p1-3ubuntu0.11                     amd64        secure shell (SSH) sftp server module, for SFTP access from remote machines
  

    ssh root@172.30.108.140
  

  Output: Successfully logs into the remote system.

  SSH Key Handling: I didn't need to specify -i path_to_private_key because my SSH client automatically used the default private key stored in ~/.ssh/id_ed25519.

  By default, SSH looks for private keys in:

    ~/.ssh/id_rsa
    ~/.ssh/id_ecdsa
    ~/.ssh/id_ed25519
    ~/.ssh/id_dsa (legacy)
  

  Since my system already had a private key (id_ed25519), SSH used it automatically when connecting to root@172.30.108.140. If I used a different key not stored in the default location, I have to specify it with:

    ssh -i /path/to/private_key root@172.30.108.140
  

2️⃣ Linux Volume Management (Without AWS)

• Issue: Practicing LVM without cloud resources like AWS was a challenge since many tutorials use EC2 instances.

• Solution: I manually created and managed LVM using google Drive:

    dd if=/dev/zero of="/mnt/g/disk1.img" bs=1M count=1024
    dd if=/dev/zero of="/mnt/g/disk2.img" bs=1M count=2048
    dd if=/dev/zero of="/mnt/g/disk3.img" bs=1M count=3072
  

  Output: Creates 1GB, 2GB, and 3GB disk images.

    sudo losetup -fP --show /mnt/g/disk1.img
    sudo losetup -fP --show /mnt/g/disk2.img
    sudo losetup -fP --show /mnt/g/disk3.img
  

  Output: Attaches the disk images as loop devices.

    lsblk
  

  Output:

    NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
    loop0    7:0    0     2G  0 loop  
    loop1    7:1    0     3G  0 loop  
    loop2    7:2    0     1G  0 loop  
    sda      8:0    0 388.4M  1 disk  
    sdb      8:16   0     2G  0 disk  [SWAP]
    sdc      8:32   0   256G  0 disk  
                                        /snap
                                        /mnt/wslg/distro
                                        /
  

Now I can follow the video.

3️⃣ Understanding Some Linux Commands

• Issue: Some commands like FIND, UMASK, KILL, FUSER, PS, VMSTAT explanations were not clear, requiring further research.

• Solution: I referred to official documentation and multiple sources to gain clarity and experimented with these commands on my system.

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This was my first week of DevOps learning, and I am excited to keep going!

I'm eager to hear about your experiences and insights! Have you embarked on a DevOps journey or faced similar challenges? What strategies or resources have you found helpful? Share your thoughts and tips in the comments below. Let's learn and grow together! 😊