Sudo Command Details

sudo -l -U a762311 Output : User a762311 may run the following commands on MACLB390804

vi commands

Here is the complete **HTML version** of the `vi` commands guide with examples: ```html

📝 vi Editor Commands with Examples

🔹 Starting vi

vi filename

This opens filename in vi. If it doesn't exist, vi will create it when saved.

📖 Modes in vi

• Normal Mode: Default mode for navigation and commands.
• Insert Mode: For editing text.
• Command Mode: For file operations (triggered by :).

✍️ Insert Mode Commands

Command	Description
i	Insert before cursor
I	Insert at beginning of line
a	Append after cursor
A	Append at end of line
o	Open new line below
O	Open new line above
Esc	Exit insert mode

🧪 Example:

Press i → type your text → press Esc to exit insert mode.

📂 File Commands (Command Mode)

Command	Description
:w	Save the file
:q	Quit vi
:wq	Save and quit
:q!	Quit without saving
:w new.txt	Save content to new.txt

🔍 Navigation Commands

Command	Description
h	Move left
l	Move right
j	Move down
k	Move up
0	Beginning of line
$	End of line
G	End of file
gg	Start of file
:n	Go to line number n
Ctrl+d	Scroll down half page
Ctrl+u	Scroll up half page

✂️ Editing Commands

Command	Description
x	Delete character under cursor
dd	Delete current line
yy	Copy (yank) current line
p	Paste below
P	Paste above
u	Undo last change
Ctrl+r	Redo
r<char>	Replace character under cursor
R	Enter replace mode

🔍 Search and Replace

Command	Description
/word	Search forward for "word"
?word	Search backward for "word"
n	Repeat last search
:%s/old/new/g	Replace all "old" with "new"
:5,10s/foo/bar/g	Replace from line 5 to 10

✅ Practical Example

$ vi demo.txt

Then inside vi:

1. Press i and type:

Hello World
This is a test file.

2. Press Esc
3. Type :wq to save and quit

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jobs command

Here is the combined HTML version of both responses: the explanation of the `jobs` command and the step-by-step example. ```html

Unix jobs Command - Usage Guide

🔧 What Is a "Job" in Unix?

A job refers to a command or process started from a shell. Jobs can be:

• Foreground: Active and attached to the terminal.
• Background: Running behind the scenes.
• Stopped: Suspended with Ctrl+Z.

📘 Usage of jobs Command

jobs

This displays all jobs started from the current shell, including their ID, state, and command.

📋 Example Output

$ sleep 100 &
[1] 12345
$ jobs
[1]+  Running                 sleep 100 &

⌨️ Related Job Control Commands

Command	Description
&	Run a command in the background
Ctrl+Z	Pause (suspend) a foreground job
fg	Resume job in foreground
bg	Resume job in background
kill %1	Kill job with ID 1
jobs -l	Show job PID
jobs -p	Show job all processes

✅ When It's Useful

• Managing long-running processes during an active shell session
• Suspending/resuming tasks without killing them
• Debugging shell-based automation or accidental background tasks

🧪 Step-by-Step Example: Managing Jobs

🔹 Step 1: Start a Long-Running Command

$ sleep 300

🔹 Step 2: Suspend with Ctrl + Z

^Z
[1]+  Stopped                 sleep 300

🔹 Step 3: Check Jobs

$ jobs
[1]+  Stopped                 sleep 300

🔹 Step 4: Resume in Background

$ bg %1
[1]+ sleep 300 &

🔹 Step 5: Bring Back to Foreground

$ fg %1
sleep 300

🔹 Step 6: Kill the Job

$ jobs
[1]+  Running                 sleep 300 &

$ kill %1

$ jobs
[1]+  Terminated              sleep 300

✅ Summary

• & to run in background
• Ctrl+Z to pause
• bg / fg to resume
• kill to terminate

``` You can save this as `jobs-command.html` and open it in any web browser. Want me to include downloadable links or CSS framework enhancements?

Unix Top Command

Here's the above explanation in clean, semantic HTML format: ```html

Unix top Command - Usage Guide

🔍 What top Shows

When you run top, it displays:

1. System Summary

• uptime: How long the system has been running.
• users: Number of logged-in users.
• load average: 1, 5, and 15 minute load.
• Tasks: Total, running, sleeping processes, etc.
• CPU usage:
  • %us: user processes
  • %sy: system/kernel processes
  • %id: idle time
  • %wa: I/O wait
  • %hi: hardware interrupts
  • %si: software interrupts
  • %st: steal time (VMs)
• Memory and Swap: Total, used, free, buffers, etc.

2. Process List

Displays information per process:

• PID: Process ID
• USER: Owner
• %CPU: CPU usage
• %MEM: Memory usage
• TIME+: Total CPU time used
• COMMAND: Command name

🛠️ Common Day-to-Day Usage in Production

• Find High CPU Usage: Use P to sort by CPU usage.
• Check Memory Leaks: Use M to sort by memory usage.
• Identify Stuck or Zombie Processes: Look for state Z.
• Check Load Averages: High load may indicate system stress.
• Check I/O Wait: High %wa indicates disk bottlenecks.
• Kill a Misbehaving Process: Use k and enter PID.

🧠 Useful Keybindings in top

Key	Action
P	Sort by CPU usage
M	Sort by memory usage
k	Kill a process (enter PID)
R	Renice a process
c	Toggle full command display
1	Show all CPU cores
h	Help
q	Quit

🧪 Pro Tips

• Use top -u <username> to filter by user.
• Use top -p <PID> to monitor a specific process.
• Use htop for a more visual alternative (if installed).

``` You can save this as an `.html` file and open it in any browser. Want me to include a live example or a downloadable template?

Windows Find a PID of a Process Running on a Port

 netstat -aon | findstr :<port>

  TCP    0.0.0.0:8080      0.0.0.0:0      LISTENING       1234

TO kill it 

taskkill /PID 1234 /F

SSH Like A Pro

Hey Mate! Welcome to another blog. Here we will discuss about SSH automation.

Tired of manually typing long SSH commands every time? Want to auto-complete your SSH like a pro? Well, you’re in the right place!

Ever find yourself typing out long SSH commands, only to realize you’ve misspelled the hostname? Or worse — forgotten the exact host? 😫 If you’re tired of manually looking up hostnames, it’s time to level up your SSH game with auto-completion using ~/.ssh/config! 🚀

With just a bit of setup, you can:
✅ Auto-complete SSH hostnames with Tab

✅ Avoid remembering long hostnames

✅ Save time and effort while connecting

✅SSH UI for Login

Let’s dive in and make SSH work for you, not against you! 😎

1️⃣ Without Use SSH Auto-Completion?

The Problem

Without SSH auto-completion, you might find yourself doing things like:

ssh 192.168.1.104 -i ~/.ssh/id_rsa -p 2222 -J jumpserver

That’s a lot of typing, and let’s be real — you’re going to mess it up at some point.

How to Access Windows Server via SSH: A Complete Guide

Step-by-step guide for How to Install Open SSH on Windows Machine

systemweakness.com

Solution:

🛠 Create or Edit Your ~/.ssh/config File

Run this command to open (or create) your SSH config file:

nano ~/.ssh/config

Now, add your SSH hosts in this format:

Host my-server
    HostName 192.168.1.104
    User myuser
    IdentityFile ~/.ssh/id_rsa
    Port 2222
    ProxyJump jumpserver
Host my-webserver
    HostName 10.0.0.5
    User ubuntu
    IdentityFile ~/.ssh/webserver_key
Host jumpserver
    HostName 10.11.0.5
    User ubuntu
    IdentityFile ~/.ssh/webserver_key

Seamless SSH Access: Automating Linux Connectivity via Windows Jump Servers

Effortless SSH Access: Automating Multi-Hop Logins in Linux

medium.com

The real problem is here:

But wait if you have 50+ hostname, how can you remember for all the hostnames ? it’s pretty annoying right.

How It feel like, if you can complete with “TAB” while type SSHhostnames ?

Like linux navigation 😋😋

Let’s do SSH Auto Completion…

🛠 2 : Enable Auto-Completion in Bash

Now, let’s make sure your terminal can auto-complete SSH hostnames:

complete -W "$(grep "Host" ~/.ssh/config | grep -vE "HostName|Hostname|no" | awk '{print $2}' | sed -E "/\*/d")" ssh

💡 Tip: Add this line to ~/.bashrc or ~/.zshrc to make it permanent:

echo 'complete -W "$(grep "Host" ~/.ssh/config | grep -vE "HostName|Hostname|no" | awk '{print $2}' | sed -E "/\*/d")"' ssh >> ~/.bashrc
source ~/.bashrc

3. Testing SSH Auto-Completion:

Now, try typing:

ssh my<tab>
# output
my-server my-webserver

Your terminal should auto-complete to myserver. 🎉

Ultimate SSH Mastery: Unlock Advanced Secure Shell Techniques with Real-World Examples

From basic commands to advanced. learn how to securely manage remote servers like a pro

aws.plainenglish.io

4. Let’s Connect via SSH UI:

But wait, yes you heard right it’s SSH UI.

Execute the below script, and you navigate and log in the hosts.

Pre-requisites:

apt install dialog

SSH-UI Script:

#!/bin/bash

# Extract hosts from SSH config
HOSTS=$(grep "Host" ~/.ssh/config | grep -vE "HostName|Hostname|no" | awk '{print $2}' | sort -h | sed -E "/\*/d")

# Build dialog menu options dynamically
MENU_OPTIONS=""
COUNT=1
declare -A HOST_MAP  # Map for storing numbered options

while read -r HOST; do
    MENU_OPTIONS+="$COUNT \"$HOST\" "
    HOST_MAP["$COUNT"]="$HOST"
    ((COUNT++))
done <<< "$HOSTS"

# Show dialog menu
MACHINE=$(dialog --menu "Welcome! Karthick-Dkk\nSelect Machine for Login:" 0 0 0 $MENU_OPTIONS 3>&1 1>&2 2>&3 3>&-)

clear

# If a valid selection was made, SSH into the selected host
if [[ -n "$MACHINE" ]]; then
    ssh "${HOST_MAP[$MACHINE]}"
    exit
else
    echo "No machine selected. Exiting..."
    exit 1
fi

Execute:

chmod +x 
./ssh-ui-script

SSH-UI

Add to system-level command: (Optional)

If tired of executing manually, we can make our life easier, will add system command for SSH-UI.

command: ui-ssh

# ln -s >location of script>  <command-name>
ln -s ssh-ui-script /usr/bin/ui-ssh

Once added you can use the below command to open the SSH-UI.

ui-ssh

Now you can select your SSH host from a menu instead of typing! 🖥️

How to Set Up SSH Login Menu with Dialog on Linux (Easy Guide!)

Automate SSH Logins with a Dialog Menu on Linux (Step-by-Step)

aws.plainenglish.io

️5. Bonus: Convert Salt Roster (/etc/salt/roster) to ~/.ssh/config (Automation)

If you manage many hosts using SaltStack, manually adding entries is a pain. Here’s a script to convert /etc/salt/roster to ~/.ssh/config automatically:

🔧 Roster to SSH Config Script

#!/bin/bash
ROSTER_FILE="/etc/salt/roster"
SSH_CONFIG="$HOME/.ssh/config"
# Backup existing SSH config
cp "$SSH_CONFIG" "$SSH_CONFIG.bak"
> "$SSH_CONFIG"
while read -r line; do
    [[ -z "$line" || "$line" =~ ^#.*$ ]] && continue  
    if [[ "$line" =~ ^[a-zA-Z0-9_-]+: ]]; then
        HOST_ALIAS="${line%:}"
    elif [[ "$line" =~ "host:" ]]; then
        HOST_IP=$(echo "$line" | awk '{print $2}')
    elif [[ "$line" =~ "user:" ]]; then
        SSH_USER=$(echo "$line" | awk '{print $2}')
    elif [[ "$line" =~ "port:" ]]; then
        SSH_PORT=$(echo "$line" | awk '{print $2}')
    elif [[ "$line" =~ "priv:" ]]; then
        SSH_KEY=$(echo "$line" | awk '{print $2}')
    elif [[ "$line" =~ "proxy:" ]]; then
        PROXY_JUMP=$(echo "$line" | awk '{print $2}')
    fi
    if [[ -n "$HOST_ALIAS" && -n "$HOST_IP" && -n "$SSH_USER" && -n "$SSH_KEY" ]]; then
        {
            echo "Host ${HOST_ALIAS}"
            echo "    HostName $HOST_IP"
            echo "    User $SSH_USER"
            echo "    Port ${SSH_PORT:-22}"
            echo "    IdentityFile $SSH_KEY"
            [[ -n "$PROXY_JUMP" ]] && echo "    ProxyJump $PROXY_JUMP"
            echo ""
        } >> "$SSH_CONFIG"
        unset HOST_ALIAS HOST_IP SSH_USER SSH_PORT SSH_KEY PROXY_JUMP  
    fi
done < "$ROSTER_FILE"
echo "SSH config updated!"

Salt-SSH Agentless Monitoring: No Minions, No Hassle — Just Pure SSH Magic!

How to Monitor Like a Pro Without Installing a Thing!-Salt-SSH Agentless

medium.com

Run It:

chmod +x roster_to_ssh_config.sh
sudo ./roster_to_ssh_config.sh

TL;DR — Quick Setup

1️⃣ Edit ~/.ssh/config and add your hosts
2️⃣ Enable auto-completion in Bash/Zsh
3️⃣ Use ssh <tab> to autocomplete hostnames
4️⃣ (Bonus) Convert /etc/salt/roster to ~/.ssh/config
5️⃣ (Bonus) SSH menu selection script

Enjoy your new and improved SSH workflow! 🎉

Seamless SSH Access: Automating Linux Connectivity via Windows Jump Servers

Effortless SSH Access: Automating Multi-Hop Logins in Linux

medium.com

Why This Rocks?

✅ Saves Time: No more typing long SSH commands
✅ Auto-Completion: Just press TAB and autocomplete!
✅ No More IP Headaches: Human-friendly SSH hostnames
✅ Portable & Reusable: Works across multiple machines

Final Thoughts:

🔹 Before: Manually typing long SSH commands 😩
🔹 After: Tab-completion, menu selection, and automation! 🚀

This setup saves time, reduces errors, and makes SSH easier. No more “What was that server’s IP again?” moments! 😂

If you found this useful, share it with your fellow sysadmins! 💡💻

Try it out and thank me later! 😉 Happy SSH-ing! 🚀🐧

Localhost

if ping localhost or 127.0.0.1 and getting response then that system is using IP4
if ::1 and getting response then that system is using IPV6