pull request accepted

2026/day-01/learning-plan.md

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+# Learning Plan
+
+---
+
+**What is your understanding of DevOps & Cloud Engineering?**
+
+**A:-** DevOps is a methodology that combines cultural philosophies, practices & tools.
+→ It's a combination of Development & Operations.
+
+---
+
+**Why you are starting learning DevOps & cloud?**
+
+**A:-**
+- To get the first job.
+- To start my career, make my career.
+
+---
+
+**Where do you want to reach?**
+
+**A:-** DevOps Engineer Level.
+
+---
+
+**How you will stay consistent every single day?**
+
+**A:-**
+- After Fajr: **2 hours/1** on weekdays
+- **4 to 6 hours** on weekends.
+
+---
+
+**Current Level:** Student.
+
+---
+
+### 3 Clear Goals:
+
+1. Containerize a project.
+2. Automate testing & deployment.
+3. Deploy to a cloud (AWS / Azure).
+
+---
+
+### 3-Core-DevOps Skills:
+
+1. Linux administration & Bash scripting.
+2. Containerization (Docker).
+3. CI/CD pipelines (or) Kubernetes.
+
+---
+
+### Weekly Time Budget
+
+- **Weekdays:** 1.5 to 2 hours
+- **Weekends:** 3 – 6 hours
+
+> *(Incl's: making of notes, understanding concepts by watching lectures – Doing practice & Building stuff)*

2026/day-02/linux-architecture-notes.md

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+# Day 02 – Linux Architecture, Processes, and systemd
+
+## Core Components of Linux
+* **Kernel:** It’s an intermediary between the hardware and the software which manages the hardware resources for the software.
+* **User Space:** It’s a layer where all the applications and the users exist. The users cannot directly access the hardware from here.
+* **Init / systemd:** (Stands for "system daemon"). When the Linux system boots up, it first loads the kernel. The kernel then starts this very first process to manage everything else. It is always assigned **PID 1**.
+
+## Processes
+A **process** is any program that is currently in execution. Every running process is assigned a unique identifier called a **PID** (Process ID).
+
+### Types of Process States:
+* **Running:** The process is active and executing.
+* **Sleeping:** The process is currently waiting for something to happen.
+* **Stopped:** The process is stopped or suspended.
+* **Zombie:** The process has finished executing and is dead, but it still has a record in the system.
+
+## 5 Daily Commands (Processes & systemd)
+* `top`: Shows a live dashboard of running processes.
+* `ps`: Takes a snapshot of active processes.
+* `kill`: Stops a process using its PID.
+* `systemctl`: Manages systemd background services.
+* `journalctl`: Views system logs for debugging.

2026/day-03/linux-commands-cheatsheet.md

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+# Day 03 – Linux Commands Cheatsheet
+
+## 📁 File System & Navigation
+* `pwd` - Prints the absolute path of the current working directory.
+* `cd` - Changes the current directory.
+* `cd ..` - Moves you up one directory level.
+* `ls` - Lists files and folders in the current directory.
+* `ls -l` - Lists files with detailed information (permissions, size, owner, timestamp).
+* `ls -a` - Lists all files in a directory, including hidden ones (files starting with a dot).
+* `mkdir` - Creates a new directory (folder).
+* `touch` - Creates a new empty file or updates the timestamp of an existing one.
+* `vim` - Opens the Vim command-line text editor to view or edit files.
+* `cat` - Displays the entire contents of a file directly in the terminal.
+* `echo` - Prints text or variables to the terminal screen.
+* `>` - Redirects command output into a file (overwriting the file's current contents).
+
+## ⚙️ Process & System Management
+* `top` - Displays a live, constantly updating dashboard of running processes and system resources.
+* `systemctl` - Manages systemd background services (start, stop, restart, enable).
+* `free -h` - Shows available and used system memory (RAM) in a human-readable format.
+* `df -h` - Displays the available and used disk space on your file systems.
+* `uptime` - Shows how long the system has been running without a reboot.
+* `sudo` - Allows you to execute commands with administrative (root) privileges.
+* `sudo apt-get update` - Refreshes the local list of available package updates from the repositories.
+* `sudo apt-get upgrade` - Installs the newest versions of all packages currently installed on the system.
+
+## 🌐 Networking Troubleshooting
+* `ping` - Tests network connectivity to a specific IP address or domain name.
+* `dig` - Queries DNS servers to find information about domain names (like resolving a domain to an IP).
+* `ip addr` - Displays your machine's active network interfaces and their assigned IP addresses.
+
+## 🛠️ General Utilities
+* `clear` - Clears the terminal screen for a cleaner workspace.
+* `whoami` - Displays the username of the currently logged-in user.
+* `date` - Shows the current system date and time.
+* `man` - Opens the official manual page for any given command (e.g., `man ls`).

2026/day-04/linux-practice.md

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+# Day 04 - Linux Practice: Processes and Services
+
+**Target Service Inspected:** `cron` (Task Scheduler)
+
+## Process Checks
+Checking for active processes running on my local WSL environment.
+
+**1. Command:** `ps aux | grep cron`
+```text
+root         151  0.0  0.0   4464  2816 ?        Ss   05:35   0:00 /usr/sbin/cron -f -P
+huzefa      2147  0.0  0.0   4120  2304 pts/0    S+   06:41   0:00 grep --color=auto cron
+```
+**2. Command:** `top -n 1 -b | head -n 15`
+```text
+top - 06:41:23 up  1:05,  1 user,  load average: 0.00, 0.00, 0.00
+Tasks:  24 total,   1 running,  23 sleeping,   0 stopped,   0 zombie
+%Cpu(s):  0.0 us,  0.0 sy,  0.0 ni, 98.8 id,  0.6 wa,  0.0 hi,  0.6 si,  0.0 st
+MiB Mem :   7776.2 total,   7205.6 free,    521.6 used,    204.9 buff/cache
+MiB Swap:   2048.0 total,   2048.0 free,      0.0 used.   7254.6 avail Mem
+
+    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
+      1 root      20   0   24148  14464  10880 S   0.0   0.2   0:01.38 systemd
+      2 root      20   0    3072   1664   1664 S   0.0   0.0   0:00.01 init-sy+
+     10 root      20   0    3072   1792   1792 S   0.0   0.0   0:00.00 init
+     53 root      19  -1   50396  15744  14720 S   0.0   0.2   0:00.40 systemd+
+     92 systemd+  20   0   22400  13952  11520 S   0.0   0.2   0:00.14 systemd+
+    101 root      20   0   35324  11648   8832 S   0.0   0.1   0:01.29 systemd+
+    151 root      20   0    4464   2816   2688 S   0.0   0.0   0:00.02 cron
+    157 message+  20   0    8796   4864   4480 S   0.0   0.1   0:00.12 dbus-da+
+```
+**1. Command:** `systemctl status cron`
+```text
+    ● cron.service - Regular background program processing daemon
+     Loaded: loaded (/usr/lib/systemd/system/cron.service; enabled; preset: enabled)
+     Active: active (running) since Fri 2026-07-31 05:11:51 UTC; 1h 29min ago
+ Invocation: 439aa67cae1f495399add4c0b4c264f4
+       Docs: man:cron(8)
+   Main PID: 151 (cron)
+      Tasks: 1 (limit: 9319)
+     Memory: 508K (peak: 4.5M)
+        CPU: 158ms
+     CGroup: /system.slice/cron.service
+             └─151 /usr/sbin/cron -f -P
+
+Jul 31 05:11:51 huzefa cron[151]: (CRON) INFO (Running @reboot jobs)
+Jul 31 05:17:01 huzefa CRON[564]: pam_unix(cron:session): session opened for user root(uid=0) by root(uid=0)
+Jul 31 05:17:01 huzefa CRON[566]: (root) CMD (cd / && run-parts --report /etc/cron.hourly)
+Jul 31 05:17:01 huzefa CRON[564]: pam_unix(cron:session): session closed for user root
+Jul 31 06:17:01 huzefa CRON[795]: pam_unix(cron:session): session opened for user root(uid=0) by root(uid=0)
+Jul 31 06:17:01 huzefa CRON[797]: (root) CMD (cd / && run-parts --report /etc/cron.hourly)
+Jul 31 06:17:01 huzefa CRON[795]: pam_unix(cron:session): session closed for user root
+Jul 31 06:25:01 huzefa CRON[811]: pam_unix(cron:session): session opened for user root(uid=0) by root(uid=0)
+Jul 31 06:25:01 huzefa CRON[813]: (root) CMD (test -x /usr/sbin/anacron || { cd / && run-parts --report /etc/cron.daily>
+Jul 31 06:25:01 huzefa CRON[811]: pam_unix(cron:session): session closed for user root
+```
+**2. Command:** `systemctl list-units --type=service --state=running`
+```text 
+UNIT                        LOAD   ACTIVE SUB     DESCRIPTION
+  console-getty.service       loaded active running Console Getty
+  cron.service                loaded active running Regular background program processing daemon
+  dbus.service                loaded active running D-Bus System Message Bus
+  getty@tty1.service          loaded active running Getty on tty1
+  polkit.service              loaded active running Authorization Manager
+  rsyslog.service             loaded active running System Logging Service
+  systemd-journald.service    loaded active running Journal Service
+  systemd-logind.service      loaded active running User Login Management
+  systemd-resolved.service    loaded active running Network Name Resolution
+  systemd-udevd.service       loaded active running Rule-based Manager for Device Events and Files
+  unattended-upgrades.service loaded active running Unattended Upgrades Shutdown
+  user@1000.service           loaded active running User Manager for UID 1000
+  wsl-pro.service             loaded active running Bridge to Ubuntu Pro agent on Windows
+
+Legend: LOAD   → Reflects whether the unit definition was properly loaded.
+        ACTIVE → The high-level unit activation state, i.e. generalization of SUB.
+        SUB    → The low-level unit activation state, values depend on unit type.
+
+13 loaded units listed.
+```
+**1. Command:** `journalctl -u cron -n 10 --no-pager`
+```text
+Jul 31 05:11:51 huzefa cron[151]: (CRON) INFO (Running @reboot jobs)
+Jul 31 05:17:01 huzefa CRON[564]: pam_unix(cron:session): session opened for user root(uid=0) by root(uid=0)
+Jul 31 05:17:01 huzefa CRON[566]: (root) CMD (cd / && run-parts --report /etc/cron.hourly)
+Jul 31 05:17:01 huzefa CRON[564]: pam_unix(cron:session): session closed for user root
+Jul 31 06:17:01 huzefa CRON[795]: pam_unix(cron:session): session opened for user root(uid=0) by root(uid=0)
+Jul 31 06:17:01 huzefa CRON[797]: (root) CMD (cd / && run-parts --report /etc/cron.hourly)
+Jul 31 06:17:01 huzefa CRON[795]: pam_unix(cron:session): session closed for user root
+Jul 31 06:25:01 huzefa CRON[811]: pam_unix(cron:session): session opened for user root(uid=0) by root(uid=0)
+Jul 31 06:25:01 huzefa CRON[813]: (root) CMD (test -x /usr/sbin/anacron || { cd / && run-parts --report /etc/cron.daily; })
+Jul 31 06:25:01 huzefa CRON[811]: pam_unix(cron:session): session closed for user root
+```
+**2. Command:** `sudo tail -n 15 /var/log/syslog`
+```text
+[sudo: authenticate] Password:
+2026-07-31T06:29:10.155625+00:00 huzefa systemd[379]: Reexecuting.
+2026-07-31T06:29:10.164178+00:00 huzefa systemd[1]: Received SIGRTMIN+25 from PID 2016 (kill).
+2026-07-31T06:29:10.169252+00:00 huzefa systemd[1]: Reexecuting.
+2026-07-31T06:29:10.243000+00:00 huzefa (generators)[2036]: '/run/systemd/user-generators/wsl-user-generator' is marked world-writable, which is a security risk as it is executed with privileges. Please remove world writability permission bits. Proceeding anyway.
+2026-07-31T06:29:12.026290+00:00 huzefa systemd[1]: apt-daily-upgrade.service: Deactivated successfully.
+2026-07-31T06:29:12.026583+00:00 huzefa systemd[1]: Finished apt-daily-upgrade.service - Daily apt upgrade and clean activities.
+2026-07-31T06:29:12.027129+00:00 huzefa systemd[1]: apt-daily-upgrade.service: Consumed 8.710s CPU time over 11.651s wall clock time, 329.5M memory peak.
+2026-07-31T06:34:18.944633+00:00 huzefa PackageKit: daemon quit
+2026-07-31T06:34:18.959207+00:00 huzefa systemd[1]: packagekit.service: Deactivated successfully.
+2026-07-31T06:37:54.415958+00:00 huzefa systemd[1]: wsl-pro.service: Scheduled restart job, restart counter is at 2.
+2026-07-31T06:37:54.425856+00:00 huzefa systemd[1]: Starting wsl-pro.service - Bridge to Ubuntu Pro agent on Windows...
+2026-07-31T06:37:54.613873+00:00 huzefa wsl-pro-service[2112]: #033[36mINFO#033[0m Starting WSL Pro Service version wsl-pro-service/0.1.19
+2026-07-31T06:37:54.786185+00:00 huzefa systemd[1]: Started wsl-pro.service - Bridge to Ubuntu Pro agent on Windows.
+2026-07-31T06:37:55.919062+00:00 huzefa wsl-pro-service[2112]: #033[33mWARNING#033[0m Daemon: could not connect to Windows Agent: could not get address: could not read agent port file "/mnt/c/Users/Huzef/.ubuntupro/.address": open /mnt/c/Users/Huzef/.ubuntupro/.address: no such file or directory
+2026-07-31T06:43:59.279978+00:00 huzefa wsl-pro-service[2112]: message repeated 11 times: [ #033[33mWARNING#033[0m Daemon: could not connect to Windows Agent: could not get address: could not read agent port file "/mnt/c/Users/Huzef/.ubuntupro/.address": open /mnt/c/Users/Huzef/.ubuntupro/.address: no such file or directory]
+```

2026/day-05/linux-troubleshooting-runbook.md

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+# Day 05 - Linux Troubleshooting Drill: CPU, Memory, and Logs
+
+**Target service / process:** `cron`
+
+## Environment Basics
+**Commands:** `uname -a` and `cat /etc/os-release`
+```text
+Linux huzefa 6.6.87.2-microsoft-standard-WSL2 #1 SMP PREEMPT_DYNAMIC Thu Jun  5 18:30:46 UTC 2025 x86_64 GNU/Linux
+```
+
+**Command:** `mkdir -p /tmp/runbook-demo && cp /etc/hosts /tmp/runbook-demo/hosts-copy && ls -l /tmp/runbook-demo`
+
+```text
+total 4
+-rw-r--r-- 1 huzefa huzefa 409 Aug  1 07:52 hosts-copy
+```
+
+**Commands:** `free -h and ps -C cron -o pid,%cpu,%mem,cmd`
+
+```text
+               total        used        free      shared  buff/cache   available
+Mem:           7.6Gi       523Mi       6.9Gi       4.4Mi       351Mi       7.1Gi
+Swap:          2.0Gi          0B       2.0Gi
+
+ PID %CPU %MEM CMD
+    151  0.0  0.0 /usr/sbin/cron -f -P
+
+```
+
+**Command:** `df -h`
+
+```text 
+Filesystem      Size  Used Avail Use% Mounted on
+none            3.8G     0  3.8G   0% /usr/lib/modules/6.6.87.2-microsoft-standard-WSL2
+none            3.8G  4.0K  3.8G   1% /mnt/wsl
+drivers         294G  182G  113G  62% /usr/lib/wsl/drivers
+/dev/sdd       1007G  2.0G  954G   1% /
+none            3.8G  228K  3.8G   1% /mnt/wslg
+none            3.8G     0  3.8G   0% /usr/lib/wsl/lib
+rootfs          3.8G  2.7M  3.8G   1% /init
+none            3.8G  544K  3.8G   1% /run
+none            3.8G     0  3.8G   0% /run/lock
+none            3.8G     0  3.8G   0% /run/shm
+none            3.8G   76K  3.8G   1% /mnt/wslg/versions.txt
+none            3.8G   76K  3.8G   1% /mnt/wslg/doc
+C:\             294G  182G  113G  62% /mnt/c
+D:\             141G  2.2G  139G   2% /mnt/d
+E:\             245G   32G  213G  13% /mnt/e
+F:\             176G  277M  176G   1% /mnt/f
+G:\              99G  4.8G   94G   5% /mnt/g
+tmpfs           3.8G  4.0K  3.8G   1% /tmp
+none            1.0M     0  1.0M   0% /run/credentials/systemd-journald.service
+none            1.0M     0  1.0M   0% /run/credentials/systemd-resolved.service
+none            1.0M     0  1.0M   0% /run/credentials/getty@tty1.service
+none            1.0M     0  1.0M   0% /run/credentials/console-getty.service
+tmpfs           778M   12K  778M   1% /run/user/1000
+```
+
+**Command:** `ping -c 3 google.com`
+```text
+PING google.com (142.251.223.14) 56(84) bytes of data.
+64 bytes from lcmaaa-ao-in-f14.1e100.net (142.251.223.14): icmp_seq=1 ttl=117 time=20.3 ms
+64 bytes from lcmaaa-ao-in-f14.1e100.net (142.251.223.14): icmp_seq=2 ttl=117 time=17.4 ms
+64 bytes from lcmaaa-ao-in-f14.1e100.net (142.251.223.14): icmp_seq=3 ttl=117 time=18.1 ms
+
+--- google.com ping statistics ---
+3 packets transmitted, 3 received, 0% packet loss, time 2003ms
+rtt min/avg/max/mdev = 17.449/18.631/20.299/1.212 ms
+```
+
+**Command:** `journalctl -u cron -n 10 --no-pager`
+```text
+Jul 31 14:17:01 huzefa CRON[2559]: pam_unix(cron:session): session opened for user root(uid=0) by root(uid=0)
+Jul 31 14:17:01 huzefa CRON[2561]: (root) CMD (cd / && run-parts --report /etc/cron.hourly)
+Jul 31 14:17:01 huzefa CRON[2559]: pam_unix(cron:session): session closed for user root
+Jul 31 16:17:01 huzefa CRON[2640]: pam_unix(cron:session): session opened for user root(uid=0) by root(uid=0)
+Jul 31 16:17:01 huzefa CRON[2640]: pam_unix(cron:session): session closed for user root
+Aug 01 06:52:01 huzefa CRON[2863]: pam_unix(cron:session): session opened for user root(uid=0) by root(uid=0)
+Aug 01 06:52:01 huzefa CRON[2865]: (root) CMD (test -x /usr/sbin/anacron || { cd / && run-parts --report /etc/cron.monthly; })
+Aug 01 06:52:01 huzefa CRON[2863]: pam_unix(cron:session): session closed for user root
+Aug 01 07:17:01 huzefa CRON[2955]: pam_unix(cron:session): session opened for user root(uid=0) by root(uid=0)
+Aug 01 07:17:01 huzefa CRON[2955]: pam_unix(cron:session): session closed for user root
+```
+```text
+If this worsens (next steps)
+If cron were to start failing or spiking the CPU, I would follow these 3 steps:[cite: 4]
+
+Restart Strategy: Attempt a graceful restart using sudo systemctl restart cron and immediately monitor systemctl status cron.
+
+Increase Log Verbosity: Check the master system logs (sudo tail -n 50 /var/log/syslog) for deeper, system-wide errors that might be affecting cron.
+
+Resource Isolation: Use top to verify if a specific rogue cron job (a scheduled script) is the actual culprit consuming the CPU, rather than the cron daemon itself.
+```

2026/day-06/file-io-practice.md

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+```text
+
+huzefa@huzefa:~$ touch notes.txt
+huzefa@huzefa:~$ ls
+notes.txt
+huzefa@huzefa:~$ echo "Line 1: Learning basic file creation." > notes.txt
+huzefa@huzefa:~$ echo "Line 2: This line is appended." >> notes.txt
+huzefa@huzefa:~$ cat notes.txt
+Line 1: Learning basic file creation.
+Line 2: This line is appended.
+huzefa@huzefa:~$ echo "Line 3: Writing and displaying at the same time." | tee -a notes.txt
+Line 3: Writing and displaying at the same time.
+huzefa@huzefa:~$ cat notes.txt
+Line 1: Learning basic file creation.
+Line 2: This line is appended.
+Line 3: Writing and displaying at the same time.
+huzefa@huzefa:~$ head -n 2 notes.txt
+Line 1: Learning basic file creation.
+Line 2: This line is appended.
+huzefa@huzefa:~$ tail -n 2 notes.txt
+Line 2: This line is appended.
+Line 3: Writing and displaying at the same time.
+```