day push till shell scripting

2026/day-01/learning-plan.md

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+# Plan for 90 days
+Linux basics -2 weeks
+Git/Github - 1 week
+Docker - 1 week

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

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+# Devops Commad and systemd
+A - Application/user<br>
+S - Shell (terminal where you access shell)<br>
+K -  Kernel<br>
+
+BIOS runs Hardware ---> GNU GRUB load linux kernel ---> ubuntu loading --> init process/systemd<br> 
+
+File System: / --root<br>
+             / > ls ---you get bin sbin called directories binaries and systembinaries<br>
+             /user/bin > ls --shows all the linux command<br>
+             /user/you dir name -- make directory inside home and work here<br>
+
+Everything start with process<br>
+Command: uname -r ----Gives version of op system Kernel                           free ---shows memory <br>
+         htop/top ---- all the process running                                    ip addr --gives ip address<br>
+         ps aux | grep ping ----SS of running process                             systemctl start nginx/docker/python/ssh <br>
+         ping XXXX.com ---gives all the ip of ping Api of website                 systemctl status docker/ssh<br>
+         man <Command> (ex. man ls)  ----manuel for all the command<br>
+         touch hello.txt --to make file<br>
+         mkdir ---to make directory<br>
+         ls -l --detail of file | ls cp in bin will show availablity<br>
+         cp -r file1(source) file2(destination) --copy folder/files<br>
+         mv file1(source) file2(destination) --rename/move files<br>
+         rmdir filename/ rm -r filename ---to remove directory(shift delete similar for rm command)<br>

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

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+# Process Management
+systemd is the 1st process<br>
+systemctl status nginx/docker --to check status of process<br>
+systemctl start nginx/docker --- To start any process<br>
+systemctl stop nginx/docker ---  To Stop any process<br>
+journalctl -u nginx/docker ---- to show all logs of an individual process<br>
+
+# User Management
+whoami  ---- shoes which user is active<br>
+sudo adduser xxx --- Adds user and made directory automatically <br>
+sudo passwd xxx --- set up password for login<br>
+su xxx --- command to enter inside user giving password (opens black bash)<br>
+which bash --- which bash currently am i using (usually coloured) gives path<br>
+sudo useradd -m yyy -s usr/bin/bash --- to make bash similar to **older coloured style** and using -m (Simialr to windows switching)<br>
+cd / > cd home --- ls -l gives list of all users<br>
+cat /etc/group --- shows all the user group<br>
+sudo addgroup ggg ---making group for user<br>
+sudo gpasswd -a xxx ggg   ---adding user inside group. here xxx is added in group ggg along **with permission** gets added<br>
+sudo gpasswd -d xxx ggg   ---To remove the user from that group and revoke their permissions. Restart with newgrp current user<br>
+sudo usermod -aG docker ubuntu ---Adding an Ubuntu User to the docker Group to **avoid sudo** and have permissions<br>
+sudo chown ggg filename.txt ---change the individual owner of the file from ubuntu to other user only valid for individual<br>
+sudo chgrp xxx filename.txt --change group owner can be done with chown (:) as well<br>
+# File System
+Read (cat)<br>
+Write (vim/nano)<br>
+Execute (shell/ ./)<br>
+mkdir -p devops  -----makes directory **with path** without error even if it exists do not throw error<br>
+vim hello.txt > Insert i > write content > Esc > :wq(save and quit)/:q!(exit without saving)<br>
+newgrp ubuntu --- changes current active primary group to the group named ubuntu for your current terminal session<br>
+-rwxrwxrwx --read write execute for **owner group others** in sets of 3<br>
+chmod 777 ---giving all permission / chmod 400 ----giving only read permission<br>
+
+# Volume Mounting
+lsblk ---volume/disk all attached to the server shows block with various partition<br>
+xvda ---extended version is written in form **/dev/xvda**<br>
+df -h ---free disk space in disk and shows mount point<br>
+Attach and Mount are 2 different thing. /dev/xvda shows attachment to system<br>
+Instance attached to volume is called attaching. Binding volume to a location is called mounting.<br>
+EBS(Elastic block store to  to create ssd) ---go to EBS in aws and create multiple volumes.<br>
+select volume > Actions > Attach volume to the corrosponding instances(select correct device name) > Check through lsblk<br>
+To make volume of EBS into useable volume convert into Physical Volume<br>
+Logical volume size can be incraesed or decreased according to the usage<br>
+
+            LVM(Logical Volume Manager)
+       ------------Logical Volume-----------------------
+       --------        ---------             ----------
+       | 10GB  |       |  6GB   |            |         |
+       ---------       ----------            -----------
+           |                |                      |
+           |                |                      |
+      ------------------------------------------------------
+      |               Volume Group                          |
+      |                                                     |
+      -------------------------------------------------------
+           |                 |                      |
+           |                 |                      |
+        --------        ---------             ----------
+        |  10G  |       |  12G   |            | 11 GB   |
+        ---------       ----------            -----------
+        --------------Physical volume-------------------
+
+# Logical Volume Manager (LVM)
+Sudo lvm ---become a root user initially. Its a tool to manage LVM having commands for mounting<br>
+pvcreate /dev/xvdf /dev/xvdg /dev/xvdh ----create physical volume for 3 ebs volume available in aws<br>
+pvs ---- shows the physical volume details<br>
+
+vgcreate  tws_vg  /dev/xvdf  /dev/xvdg ---To create Volume group using 2 physical volume earlier made. initail is the vg nam and then from the source path to be combined<br>
+vgs ----shows list of all the volume from group craeted where PV is phy. vol. and LV is Logical vol.<br>
+
+lvcreate -L 10G -n tws_lv tws_vg --- to create logical volume from the volumegroup<br>
+lvs --- shows list of all the volume of group created<br>
+
+pvdisplay ---- to display physical volume details<br>
+vgdisplay ----- to display volume group details<br>
+lvdisplay ---- to displaylogical volume details<br>
+
+# How to mount volumes 
+Go to root always<br>
+mkdir /mnt/tws_lv_mount --- create a temproary directory which creates a location where volume is mounted<br>
+mkfs.ext4 /dev/tws_vg/tws_lv  ---to format the path and create space and make file system<br>
+mount /dev/tws_vg/tws_lv /mnt/tws_lv_mount --mount the logical volume to specified location craeted before to bind the path<br>
+umount /mnt/tws_lv_mount ---to unmount the volume directory<br>
+Now you can use the path to craete directory and work here  /mnt/tws_lv_mount<br>
+
+# Directly mount physical volume to disk mount
+No need to go to room <br>
+mkdir /mnt/tws_disk_mount ----this is to create space for disk mount directly from phy. vol.<br>
+mkfs -t ext4  /dev/xvdh ----file system to mount disk store<br>
+mount /dev/xvdh  /mnt/tws_disk_mount --- mounting disk to the destination<br>
+df -h --to check all the disk mounted<br>
+
+# Dynamic storage management with EBS(AWS)
+Adding extra storage to Logical Volume<br>
+lvm > lvextend -L +5G -n /dev/tws_vg/tws_lv <br>

2026/day-04/linux-practice.md

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+Systemctl status ssh/docker  --- to see the curreent status of a single process<br>
+<img width="941" height="132" alt="image" src="https://github.com/user-attachments/assets/a753e730-bd4e-4edc-90e3-bb630f2359da" />
+
+sudo systemctl start  nginx/docker/ssh ----to stop the process <br>
+<img width="970" height="110" alt="image" src="https://github.com/user-attachments/assets/06be6f0b-e541-46d4-96ee-379b89a0044b" />
+
+sudo systemctl stop  nginx/docker/ssh ----to stop the process<br>
+<img width="971" height="157" alt="image" src="https://github.com/user-attachments/assets/eec3aa2d-1fea-4b8f-bb2f-2ac99a5aa238" />
+
+ping zeiss.com ---Sends icmp packets to the hosts<br>
+htop -- to see the running status of the process and track live running process<br>
+<img width="1022" height="522" alt="image" src="https://github.com/user-attachments/assets/107a7da9-5eb9-4448-bb0d-cb702a94fa55" />
+
+ps aux | grep zeiss --it create the screen shot of the process and grep filter the required process<br>
+kill -9 PID --force kill the running process<br>
+kill PID --kill the process<br>
+<img width="1086" height="205" alt="image" src="https://github.com/user-attachments/assets/1d504474-630b-401e-9678-a9134758541d" />
+
+systemctl list-units ----command displays all currently loaded and active \(systemd\) units (like services, sockets, and mount points) in memory.<br>
+systemctl list-units --state=failed<br>
+systemctl list-units --state=waiting<br>
+<img width="1342" height="187" alt="image" src="https://github.com/user-attachments/assets/2611afdc-3add-4d46-ae22-d1535ef20661" />
+
+journalctl -u docker/nginx/ssh --- to see all the log file of a sinle process<br>
+<img width="1447" height="92" alt="image" src="https://github.com/user-attachments/assets/59708455-c1e3-4761-9adc-7ceb5abc13f0" />
+
+head -n 5 <file name> --- this is to see first 5 line in log files or any files<br>
+<img width="1447" height="230" alt="image" src="https://github.com/user-attachments/assets/aa441a6c-cc10-4399-a00e-227c567e6d3d" />
+
+tail -n 5 <file name> --- this is to see last 5 line in log files or any files<br>
+<img width="1446" height="207" alt="image" src="https://github.com/user-attachments/assets/3b260983-9870-4fe7-9afc-c69db584635f" />
+
+# Process additional command
+pstree ubuntu --- Visualizes running processes in a hierarchical, parent-child tree structure<br>
+pgrep nginx  --- Searches for processes by name and returns their Process IDs (PIDs) <br>
+<img width="487" height="341" alt="image" src="https://github.com/user-attachments/assets/977cafe5-2d1d-4f4c-bf6c-aca0c5c3718c" />

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

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+# Environment Basic
+uname -a  --give details aboutabout the Linux kernel and hardware architecture (What it outputs: Kernel version, kernel build date, CPU architecture)<br>
+lsb_release -a (The Legacy Standard) --- prints all available Linux Standard Base (LSB) and **distribution-specific** version details<br>
+cat /etc/os-release (The Modern Standard) --- tells you about the specific **Linux distribution** (OS) and its version<br>
+<img width="1262" height="527" alt="image" src="https://github.com/user-attachments/assets/2ac70fb0-bec5-4c8d-abed-2fe8a4c174fe" />
+
+# filesystem sanity
+mkdir /tmp/runbook-demo  ---make directory<br>
+cp /etc/hosts /tmp/runbook-demo/hosts-copy && ls -l /tmp/runbook-demo --copy directory file from hosts to copy hosts and dispalys permission<br>
+<img width="1157" height="112" alt="image" src="https://github.com/user-attachments/assets/ef507f8c-4b97-4786-82d4-1069b710bf26" />
+
+# Troubleshooting
+systemctl status docker --- one target service/process to see the status<br>
+<img width="1047" height="116" alt="image" src="https://github.com/user-attachments/assets/597b3818-588f-419b-b3eb-691cc1c53e5c" />
+
+htop --to see the running process
+<img width="1338" height="126" alt="image" src="https://github.com/user-attachments/assets/cb02c30d-793a-490b-ac12-b44487bb3595" />
+<img width="1640" height="163" alt="image" src="https://github.com/user-attachments/assets/740b5135-7c23-4aff-891e-2646d713df01" />
+
+ # customized details of CPU / Memory <br>
+ps -o pid,pcpu,pmem,comm -p <pid> --- ps is process -o user-defined format pid - unique process id<br>
+            pcpu --- details about cpu                     pmem --- detail about memory<br>
+            comm ---  short executable command -p <pid>--- specific process ID<br>
+ free -h  --- shows free space in human redeable format. without -h it is in byte format<br>
+<img width="982" height="276" alt="image" src="https://github.com/user-attachments/assets/357d0c1c-e675-4a8d-bb26-aaa64ecf84b3" />
+
+# Disk / IO
+df -h --detail of file system mounted<br>
+du -sh /var/log --- calculates and displays the total disk space used by the /var/log folder in redeable format number<br>
+iostat --- Focuses heavily on storage drive performance and input/output (I/O) speeds and idle time<br>
+vmstat --- Focuses heavily on virtual memory, RAM, paging, processes, and CPU activity(Virtual Memory Statistics)<br>
+dstat --- Combines both tools into a single, Everything simultaneously—CPU, disk, network, and memory(Versatile Statistics)<br>
+<img width="1165" height="957" alt="image" src="https://github.com/user-attachments/assets/486b7db3-9bcb-450d-b4a8-50e4229b7eb8" />
+
+# Network
+ss -tulpn -- display all open and listening network ports<br>
+<img width="1241" height="227" alt="image" src="https://github.com/user-attachments/assets/0e9bdab3-aeb7-4836-a5e7-e7870b742d85" />
+
+netstat -tulpn  ---  displays same data but its old style <br>
+<img width="1162" height="163" alt="image" src="https://github.com/user-attachments/assets/2b8c9bee-d9ae-4202-a389-b53876e4099f" />
+
+ping zeiss.com --checks network connectivity at the system level using ICMP (Is the server powered on and reachable?)<br>
+curl -I  API     ---- checks application-layer web responses using HTTP(give full address) (Is the web application/API running and healthy?)<br>
+<img width="953" height="302" alt="image" src="https://github.com/user-attachments/assets/e850a2ef-eade-48a9-b0e8-d16666cd19a4" />
+
+# Logfile
+journalctl -u docker -n 5 ---shows the detail of any running process depending on number of lines asked (here 5 lines of docker)<br>
+tail -n 5 /var/log/syslog  --- last 5 lines of a particular log files <br>
+<img width="1451" height="348" alt="image" src="https://github.com/user-attachments/assets/4ef3ee13-4ab1-4129-a2cf-2988d1102e30" />
+
+# If this worsens(example Nginx)
+Nginx Troubleshooting ChecklistFollow this sequential checklist to diagnose, configure, and isolate web server failures<br>
+Phase 1: Initial Triage & VerificationVerify OS Environment: Run cat /etc/os-release to confirm the distribution baseline.<br>
+Test Network Reachability: Run ping <target-ip> to verify the physical server is online.<br>
+Inspect HTTP Headers: Run curl -I http://localhost to capture the exact status code (e.g., 502 Bad Gateway).<br>
+Audit Open Ports: Run sudo ss -tulpn to ensure Nginx is actively listening on ports 80/443.
+
+Phase 2: Elevate Verbosity (The "If This Worsens" Plan)<br>
+Open Configuration: Run sudo nano /etc/nginx/nginx.conf (Do not use cd).
+Enable Debug Logs: Locate the error_log directive and append debug to the end of the line:**nginxerror_log /var/log/nginx/error.log debug**<br>
+Test Layout Syntax: sudo nginx -t ---- to verify there are no missing semicolons or typos.<br>
+Apply Changes Safely: sudo systemctl reload nginx --- to load the settings without dropping user traffic.<br>
+Stream Live Errors: sudo tail -f /var/log/nginx/error.log --- to watch the debug output in real time.
+
+Phase 3: Advanced Diagnostics & RecoveryTrace System Calls: Run sudo strace -fp <PID> -e trace=network,file on a worker PID if the process hangs.Isolate and Restart: If the state corrupts, run sudo systemctl stop nginx, confirm ports are vacant with ss, then run sudo systemctl start nginx.
+
+

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

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+# Operation in files
+touch notes.txt ---- creates file with name notes <br>
+echo "Line 1" > notes.txt -----add content to the line and over write if anything written<br>
+echo "Line 2" >> notes.txt ----add content and append the content at the end it do not overwrite<br>
+echo "Line 3" | tee -a notes.txt ---display the content as well as append at last. If -a not there it will overwrite<br>
+cat notes.txt  ---displayes the overall output
+head -n 2 notes.txt ---diaplays firat 2 line<br>
+tail -n 2 notes.txt ---displays last 2 lines<br>
+<img width="1025" height="487" alt="image" src="https://github.com/user-attachments/assets/1c18571c-51a7-4e3c-be24-b2456154a91c" />
+
+# Negative scenarios of > and tee without -a will overwrite whole file
+echo "Line 1" > notes.txt -----add content to the line and over write if anything written<br>
+echo "Line 2" >> notes.txt ----add content and append the content at the end it do not overwrite<br>
+echo "Line 3" | tee notes.txt ---display the content as well as append at last. If -a not there it will overwrite<br>
+<img width="1032" height="227" alt="image" src="https://github.com/user-attachments/assets/25146a24-146f-4fa1-8b9a-535f993e8f3d" />

2026/day-07/day-07-linux-fs-and-scenarios.md

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+# Linux File System Hierarchy
+Symbol / --root consists of all folder. System starts from here<br>
+ / > ls -l ---you get bin sbin called directories binaries and system binaries<br>
+ /user/bin > ls --shows all the linux command<br>
+ /bin ---  Essential command binaries all the commands are either on bin and system command is in sbin<br>
+ /user/<your directory> -- make directory inside home and work here<br>
+ /opt --- Optional/third-party applications<br>
+
+  /var/log - **Log files** -- all log files and can open through vim<br>
+ <img width="550" height="232" alt="image" src="https://github.com/user-attachments/assets/96317d6a-93e9-4b40-a81f-1ba441353b4f" />
+
+du -sh /var/log/*  2>/dev/null -- du -sh --is disk space -sh flah is summerize and human readable the log file, *wildcard to trace all<br>
+                               -- 2>dev/null ---its a black hole where all eoor goes for example permission denied
+
+ Find the largest log file in /var/log. Use of log file scenario
+du -sh /var/log/*  2>/dev/null | sort -h | tail -n 5 --sort and gives result of last 5 files<br>
+<img width="692" height="132" alt="image" src="https://github.com/user-attachments/assets/f7ce3f71-7c07-4b96-912a-d0c6d0a6b0a6" />
+
+Negative scenarios --- this is without blackhole(**2>/dev/null**)<br>
+<img width="588" height="187" alt="image" src="https://github.com/user-attachments/assets/91c0cfa2-09f1-43a2-9b2c-dc3e88048604" />
+
+Look at a config file in /etc --shows which host is aasigned<br>
+cat /etc/hostname  ---displays the unique network name assigned to your Linux system<br>
+
+Check your home directory
+ls -la ~ ---list aal hidden file but ~ is used to access home directory from anywhere
+
+# Scenario 1
+  systemctl status myapp  ----Check the status of myapp<br>
+  systemctl is-enabled myapp  --is system enabled<br>
+  sudo journalid -u myapp -e --no-pager   --check the log file in chronological order<br>
+  sudo ss -tulpn -- Check other service (like Apache or Nginx) already grabbed the port myapp needs<br>
+
+ # Scenario 2
+ htop --to see memory usage
+ ps aux --sort=-pcpu | head -n 5 -- (-pcpu) arrange in decending and apply head or remove minus and apply tail<br>
+
+  # Scenario 3
+  systemctl status docker  ---status of docker <br>
+  journalctl -u docker -n 50 ---chek log file<br>
+  journalctl -u docker -f --follow log in real time<br>
+
+  # Scenario 4
+ ls -l home/user/backup.sh --to check the permission<br>
+ chmod a+x home/user/backup.sh --gives permission to execute to all<br>
+ ls -l home/user/backup.sh  --verify all cmd  has r-xr-xr-x permission<br>
+ (or) chmod 755 will work --based on number system but it has all the group<br>
+
+

2026/day-08/day-08-cloud-deployment.md

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+# Part 1: Launch Cloud Instance & SSH Access
+Step 1: Create a Cloud Instance<br>
+Step 2: Connect via SSH<br>
+
+# Part 2: Install Docker & Nginx
+ Step 1: Update System ---  sudo apt update<br>
+ Step 3: Install Nginx  --  sudo apt-get install nginx<br>
+ Verify Nginx is running: -- systemctl status nginx<br>
+
+ # Part 3: Security Group Configuration
+ http://51.21.160.162/
+ <img width="1227" height="377" alt="image" src="https://github.com/user-attachments/assets/27aa8f74-701c-4664-8ea4-ad1654737b36" />
+
+# Part 4: Extract Nginx Logs
+Step 1: View Nginx Logs --- cd /var/log/nginx<br>
+                            tail -f /var/log/nginx/access.log<br>
+Step 2: Save Logs to File(~ home) --- cp -r error.log ~/nginx.txt<br> 
+Step 3: Download Log File to Your Local Machine --- scp -i shell-scripting.pem ubuntu@51.21.160.162:~/nginx.txt .<br>