Day 15 submission

2026/day-01/learning-plan.md

@@ -0,0 +1,2 @@
+in simple understanding devops means complete end to end process desigining and deploying applications.consists of two words dev +ops 
+dev means development in which code ,plan and features are included but in operations (ops) the code si deployed on servers where continous monitoring happens

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

@@ -0,0 +1,15 @@
+* process states
+1 running- means the process is currently in execution 
+2 sleep -process waiting for its execution
+3 stopped - proces is paused by user or other 
+4 zombie - hwne process is terminianted but in process table and wiating for exit
+5 dead - when process is completely terminated and nt present in process table
+* 5 commands that i will use daily
+cd - to navigate between dir
+mkdir - create a new dir
+vim - for text editor
+touch - for creating new file
+man - for description
+pwd - to check current working directory
+systemctl - to know logs of system
+

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

@@ -0,0 +1,30 @@
+* Basic commands
+cd - to navigate between dir
+mv - to move or rename file
+cp -copy file
+pwd - current directory
+ls - lsit all files
+ls -a - list hidden files
+ls -l - list the permissions of file
+mkdir - make dir
+touch - create file
+whoami - display user name
+cat - edit file
+* adding user or group
+useradd - add user in environment
+useradd -m - add suer in home dir also
+groupadd - add new group
+usermod - to modify the permissions
+chown - change owership
+chgrp - change group ownership
+ssh-keygen = genrate new keys
+su - to with users
+* file permissions
+chmod - change permissions
+* to know about systems
+systemctl - to manage service on linux like start,stop,restart,reload
+
+* network commands
+ipcongig - to check all ip address
+ping - send ICMP requests
+dig - Dns lookups in nslookups

2026/day-04/linux-practice.md

@@ -0,0 +1,15 @@
+Process checks
+ps - snapshot of current process
+top - this provides dynamic view of running system
+pgrep - looks htrough the currently running process and lists the process IDs 
+    pgrep [options] pattern 
+
+Service checks
+systemctl - gives log for system and controls systemd
+systemctl list-units - units are a managed resource this command helps to check the acitve services,sockets,mounts
+
+Log checks 
+journalctl -u ssh - print logs of the specific service
+tail -n - 50 this shows the last 50 entries 
+
+Mini troubleshooting steps

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

@@ -0,0 +1,77 @@
+
+
+## Target Service
+ssh (OpenSSH Server)
+
+## Environment
+- Kernel: Linux 6.14.0-1018-aws (x86_64)
+- OS: Ubuntu 24.04.3 LTS (Noble Numbat)
+- System uptime low, clean boot state
+
+## Filesystem Sanity Check
+Commands:
+- mkdir /tmp/runbook-demo
+- cp /etc/hosts /tmp/runbook-demo/hosts-copy
+
+Observations:
+- Temporary directory created successfully
+- File copy succeeded with normal permissions
+- Filesystem is writable and healthy
+
+## CPU & Memory
+Commands:
+- top- this provide the list fo processes
+- free -h - this display the storage in human readable format
+
+Observations:
+- CPU is 99% idle, load average near zero
+- No high CPU processes observed
+- Memory usage is low with ~510MB available
+- No swap usage or memory pressure
+
+## Disk & IO
+Commands:
+- df -h- This display file system usage in 1000 powers
+- du -sh /var/log
+
+Observations:
+- Root filesystem only 36% utilized
+- /var/log size is ~35MB
+- No disk space or IO concerns
+
+## Network
+Commands:
+- ss -tulpn
+- ping -c 3 localhost
+
+Observations:
+- sshd listening on port 22 (IPv4 and IPv6)
+- Localhost connectivity is healthy
+- No packet loss or latency issues
+
+---
+
+## Logs Reviewed
+Commands:
+- journalctl -u ssh -n 50
+- tail -n 50 /var/log/auth.log
+
+Observations:
+- SSH service starts cleanly after reboot
+- Successful key-based logins observed
+- No authentication errors or service crashes
+- Log entries appear normal and expected
+
+---
+
+## Quick Findings
+- System resources are healthy
+- SSH service is stable and responsive
+- No indicators of CPU, memory, disk, or network issues
+- Logs show normal operational behavior
+
+---
+
+## If This Worsens (Next Steps)
+1. Restart ssh service gracefully using systemctl and monitor logs
+2. Investigate failed login attempts and review firewall or security group rules

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

@@ -0,0 +1,39 @@
+root@Asus:/mnt/c/users/# cd documents
+root@Asus:/mnt/c/users/documents# touch name.txt
+root@Asus:/mnt/c/users/documents# cat "hello my name is " > name.txt
+cat: 'hello my name is ': No such file or directory
+root@Asus:/mnt/c/users/documents# man cat
+root@Asus:/mnt/c/users/documents# man touch
+root@Asus:/mnt/c/users/documents# mv name.txt notes.txt
+root@Asus:/mnt/c/users/documents# echo "hello my name si :" > notes.txt
+root@Asus:/mnt/c/users/documents# echo "hi everyone" >> notes.txt
+root@Asus:/mnt/c/users/documents# echo "I am student of batch 10 " >> notes.txt
+root@Asus:/mnt/c/users/documents# cat notes.txt
+hello my name si :
+hi everyone
+I am student of batch 10
+root@Asus:/mnt/c/users/documents# head notes.txt
+hello my name si :
+hi everyone
+I am student of batch 10
+root@Asus:/mnt/c/users/documents# man head
+root@Asus:/mnt/c/users/documents# head -n 2 notes.txt
+hello my name si :
+hi everyone
+root@Asus:/mnt/c/users/documents# tail -n 2 notes.txt
+hi everyone
+I am student of batch 10
+root@Asus:/mnt/c/users/documents# tee "hello" >notes.txt
+hello
+my name is
+i am student of batch 10
+^C
+root@Asus:/mnt/c/users/documents# cat notes.txt
+hello
+my name is
+i am student of batch 10
+root@Asus:/mnt/c/users/documents# tee hello
+hello
+hello
+i am
+i am

2026/day-07/README.md

@@ -116,7 +116,7 @@ Write at least 4 commands in order.
 - Then check: What do the logs say?
 - Finally check: Is it enabled to start on boot?
 
-**Commands to explore:** `systemctl status myapp`, `systemctl is-enabled myapp`, `journalctl -u myapp -n 50`
+**Commands to explore:** `systemctl status myapp`, ` myapp`, `journalctl -u myapp -n 50`systemctl is-enabled
 
 **Resource:** Review Day 04 (Process and Services practice)
 

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

@@ -0,0 +1,51 @@
+### Part 1: Linux File System Hierarchy
+- '/' (root) - This contains the boot files of system 
+- '/home' - this conatisn file configurations and users
+- `/root' - This is subdirectory inside '/' which has full user access
+- 'etc' - this contains editable configurations files
+- '/var/log' - This contains the log of system
+- '/tmp' - these are created for short term uses and they got deleted when system reboots
+
+### Part 2: Scenario-Based Practice
+**Scenario 1: Service Not Starting** 
+Step 1: systemctl status
+Why: This will display the status 
+s
+Step 2: journalctl 
+why :this will display recent logs
+
+Step 3: systemctl start my-app
+Why: this will again start the application
+
+step 4: systemctl is-enabled
+why : to check is service is enabled
+
+**Scenario 2: High CPU Usage** 
+step 1: top
+why : this will display the top processes executing / htop has interactive display
+
+step 2: htop
+why : htop has interactive display where i can scroll also
+
+step 3 : ps aux --sort=-%cpu | head -10
+why : this will sort the process and then print first 10 processes
+
+**Scenario 3: Finding Service Logs** 
+step 1 : journalctl -u docker.io
+why : this will display the logs of docker
+
+step 2 :journalctl -u docker.service -n 50
+why : this will show last 50 lines
+
+step 3: journalctl -u docker.service -f
+why : this will show me the docker logs in real time
+
+**Scenario 4: File Permissions Issue** 
+step 1 : ls -l
+why : firstly check the permsission of file 
+
+Step 2 : chmod u+x file_name.sh
+why : then give execute perimission to user 
+
+step 3: ls-l
+why :rwxr--r-- this means owner got permission to execute

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

@@ -0,0 +1,37 @@
+## Commands Used
+step 1: connecting with instance using ssh 
+command : ssh -i "keyname"ubuntu@"public_dns"
+
+step 2: update ubunut
+command : sudo apt update
+
+step 3: install nginx
+command : sudo apt install nginx
+
+step 4 :then to confirm if its starting
+command : systemctl status nginx
+
+step 5: check server logs
+command : journalctl -u nginx
+
+step 6: chekc nginx logs 
+
+command : var/log/nginx 
+this gives me two files
+access.log 
+error.log
+
+step 7: then copy the nginx logs and saev into a new file into home directory
+cp access.log ~/nginx-log.txt
+
+step 8 : then i download this using scp in my local machine
+scp -i "keyname"ubuntu@"instanceip":"file_path" .
+scp -secure copy it gets downloaded form remote server to local machine and . is used for current folder
+
+## Challenges Faced
+i got challanges during cp as i got confused between home directory then i see the linux hirarchy and then i faced challenges in scp as i am running this on instance as then i search about this command and run on my windows termianl
+
+## What I Learned
+i get used to ssh and got easy in connecting instance to my server
+i learn about the scp command
+i learn about creating inbound rules to check service on web 

2026/day-08/nginx-logs.txt

@@ -0,0 +1,4 @@
+115.70.62.21 - - [10/Feb/2026:10:32:37 +0000] "GET / HTTP/1.1" 200 409 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/144.0.0.0 Safari/537.36"
+115.70.62.21 - - [10/Feb/2026:10:32:37 +0000] "GET /favicon.ico HTTP/1.1" 404 196 "http://16.26.213.32/" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/144.0.0.0 Safari/537.36"
+146.190.26.148 - - [10/Feb/2026:10:33:08 +0000] "GET / HTTP/1.1" 200 409 "-" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/142.0.0.0 Safari/537.36"
+146.190.26.148 - - [10/Feb/2026:10:33:09 +0000] "GET /favicon.ico HTTP/1.1" 404 196 "http://16.26.213.32/" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/142.0.0.0 Safari/537.36"

2026/day-09/README.md

@@ -121,7 +121,7 @@ Create `day-09-user-management.md`:
 **User can't access directory?**
 - Check group: `groups username`
 - Check permissions: `ls -ld /path`
-
+cd 
 ---
 
 ## Submission

2026/day-09/day-09-user-management.md

@@ -0,0 +1,30 @@
+# Day 09 Challenge
+## Users & Groups Created
+- Users: tokyo, berlin, professor, nairobi
+- Groups: developers, admins, project-team
+
+## Group Assignments
+tokyo:x:1001:
+berlin:x:1002:
+professor:x:1003:
+developers:x:1004:tokyo,berlin
+admins:x:1005:berlin,professor
+nairobai:x:1006:
+project-team:x:1007:nairobai,tokyo
+
+## Directories Created
+drwxrwsr-x 2 root developers   4096 Feb 11 10:43 dev-project
+drwxrwxr-x 2 root project-team 4096 Feb 11 10:51 team-workspace
+
+## Commands Used
+useradd -m : for creating users in home also
+addgroup : for creating group
+usermod -aG : for adding user to group
+mkdir - for creating directory
+chown :group_name directory : for changing ownership of group only 
+chmod 775 directory 
+
+## What I Learned
+i learned about creating groups and users
+i learned about giving permissions and adding users to the groups
+i learned about changing ownerships and groups 

2026/day-10/day-10-file-permissions.md

@@ -0,0 +1,30 @@
+# Day 10 Challenge
+
+## Files Created
+devops.txt
+notes.txt
+script.sh
+
+## Permission Changes
+before
+-rw-rw-r-- 1 ubuntu ubuntu  0 Feb 12 10:15 devops.txt
+-rw-rw-r-- 1 ubuntu ubuntu 60 Feb 12 10:16 notes.txt
+-rw-rw-r-- 1 ubuntu ubuntu 21 Feb 12 10:16 sript.sh
+
+after
+-r--r--r-- 1 ubuntu ubuntu  0 Feb 12 10:15 devops.txt
+-rw-r----- 1 ubuntu ubuntu 60 Feb 12 10:16 notes.txt
+-rwxrw-r-- 1 ubuntu ubuntu 21 Feb 12 10:16 script.sh
+
+## Commands Used
+touch
+cat
+chmod
+head 
+tail
+vim
+
+## What I Learned
+i learned about creating file
+editing file
+permissions of files 

2026/day-14/day-14-networking.md

@@ -0,0 +1,28 @@
+### OSI Model vs TCP/IP Stack
+The OSI (Open Systems Interconnection) model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven distinct layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application. Each layer serves a specific purpose and interacts with the layers directly above and below it.
+The TCP/IP (Transmission Control Protocol/Internet Protocol) stack, on the other hand, is a more practical and widely used model that consists of four layers: Link, Internet, Transport, and Application. The TCP/IP stack is designed to be simpler and more efficient for real-world networking.
+- **Link Layer**: Corresponds to the OSI's Physical and Data Link layers. It handles the physical transmission of data over a network and manages the hardware addressing (MAC addresses)and DNS resolution for local network communication.
+- **Internet Layer**: Corresponds to the OSI's Network layer. It is responsible for logical addressing (IP addresses) and routing of data packets across networks.
+- **Transport Layer**: Corresponds to the OSI's Transport layer. It manages end-to-end communication, error checking, and flow control. This is where TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) operate.
+- **Application Layer**: Corresponds to the OSI's Session, Presentation, and Application layers. It provides protocols for specific applications, such as HTTP/HTTPS for web traffic, DNS for domain name resolution, and FTP for file transfers.
+
+### Hands-on Checklist
+- **Identity:** `hostname -I` (or `ip addr show`) — shows th e IP address(es) assigned to the host.
+- **Reachability:** `ping <target>` — tests the reachability of a target host and measures the round-trip time for messages sent from the originating host to a destination computer.
+- **Path:** `traceroute <target>` (or `tracepath`) — displays the route and measures transit delays of packets across an IP network.
+- **Ports:** `ss -tulpn` (or `netstat -tulpn`) — lists all listening ports and the associated services.
+- **Name resolution:** `dig <domain>` or `nslookup <domain>` — queries DNS servers to resolve domain names to IP addresses.
+- **HTTP check:** `curl -I <http/https-url>` — retrieves the HTTP headers from the specified URL, showing the HTTP status code and other metadata.
+- **Connections snapshot:** `netstat -an | head` — provides a snapshot of current network connections, showing the state of each connection (e.g., ESTABLISHED, LISTENING).
+
+### Mini Task: Port Probe & Interpret
+i have tested on port no 80  its succesfull 
+(test.png)
+## Reflection (add to your markdown)
+- Which command gives you the fastest signal when something is broken?
+curl -I as it will shows me the HTTP status code and headers.
+- What layer (OSI/TCP-IP) would you inspect next if DNS fails? If HTTP 500 shows up?
+applica1tion layer for both cases, as DNS is part of the application layer in the TCP/IP stack, and HTTP 500 is an error code that indicates a server-side issue, which also falls under the application layer.
+- Two follow-up checks you’d run in a real incident.
+dns failure, I would check the DNS server configuration and logs to identify any issues. 
+Ports `ss -tulpn` to check if the DNS service is running and listening on the correct port (usually port 53).