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1.Find Which Process is Using a Port

netstat -ano | findstr :port_number(5432)

Purpose:

note: here 5432 port is user , you can used any port 

This command checks if any process on your Windows machine is listening on port 5532 — which is the port you're trying to use for PostgreSQL.

Breakdown:

What You’re Looking For:

If PostgreSQL is listening on port 5432, you’ll see output like:

  TCP    127.0.0.1:5532       0.0.0.0:0              LISTENING       1234

The last column (1234) is the PID (Process ID) of the process using the port.

How to Check What’s Listening (e.g., PostgreSQL)

If a process is listening on port 5432, note the PID in the last column.

Then run

tasklist /FI "PID eq 1234"

(Replace 1234 with the actual PID.)

This will tell you which program is using that port.

Here are several useful Windows terminal commands and functionalities you can explore:

1. List All Listening Ports

netstat -an | findstr LISTENING

Shows all ports your system is listening on.

2.Kill a Process by PID (Be careful!)

taskkill /PID 1234 /F

Forcefully stops the process using PID 1234. Useful if something is blocking the port.

3. Check if PostgreSQL is Running (in Services)

sc query | findstr postgre

Shows if PostgreSQL service is installed and its status.

Or Open:

services.msc

5. Find PostgreSQL Configuration Path

If PostgreSQL is installed but you don’t know where the config files are:

where psql

Then go to the bin folder, and check the path above it — typically:

C:\Program Files\PostgreSQL\<version>\data

Files to look for:

• postgresql.conf – contains the port setting.
• pg_hba.conf – contains the access control rules.

How to Add a New Remote Origin in Git and Push Code

If you already have a Git project locally and want to add a new remote origin (i.e., a new Git repository, like on GitHub/GitLab/Bitbucket), here’s how you can do it:

1. Check existing remotes

git remote -v

This will show something like:

origin  [email protected]:username/old-repo.git (fetch)
origin  [email protected]:username/old-repo.git (push)

2. Add a new remote

You can add a new remote with a different name:

git remote add new-origin https://github.com/username/new-repo.git

or if you prefer SSH:

git remote add new-origin [email protected]:username/new-repo.git

3. Verify the new remote

git remote -v

Now you should see both:

4. Push to the new remote

If you want to push your current branch (say main or master) to the new repo:

git push new-origin main

• The main here is the name of your local branch (the branch you’re currently working on).
• Git will push this local main branch to the remote repo (new-origin), creating a branch called main there too (if it doesn’t already exist).

So to clarify:

• If your current branch is main, then this command pushes it to the new remote as main.
• If your current branch is dev (for example), then you should run:

• git push new-origin dev

You want to push your local dev branch into the master branch of the new remote (new-origin).

git push new-origin dev:master

Explanation:

• dev ? your local branch (the source).
• master ? the branch name on the remote (the destination).
• new-origin ? the remote repository you added.

So this says:
Take my local dev branch and push it into the master branch on new-origin.

If you want to set it as the default upstream:

git push -u new-origin main

Know more about upstream

What does upstream mean?

In Git, the upstream branch is the remote branch that your local branch is “tracking.”

• When you set an upstream, your local branch knows:
  • Where to push changes (git push without extra arguments).
  • Where to pull changes from (git pull without extra arguments).

Example without upstream

Suppose you’re on main and you type:

git push

Git might complain:

fatal: The current branch main has no upstream branch.

Because it doesn’t know which remote branch it should push to.

Example with upstream

Now, if you run:

git push -u origin main

• origin : remote repo
• main : branch on the remote

This sets origin/main as the upstream branch for your local main.

From now on:

• git push : pushes to origin/main automatically.
• git pull : pulls from origin/main automatically.
• git status : shows if your local main is ahead/behind origin/main.

Think of upstream like setting a default shipping address in an online store:

• Once set, you don’t need to type the address each time.
• Without it, you must enter the address every single order.

Show detailed upstream config

git rev-parse --abbrev-ref --symbolic-full-name @{u}

This prints the full name of the upstream branch your current branch is tracking, e.g.:

origin/main

If no upstream is set

You’ll get an error like:

fatal: no upstream configured for branch 'main'

In that case, you can set it with:

git push -u origin main

After this, whenever you want to push to the new repo, just run:

git push new-origin

You Can Also Change the remote URL

Instead of adding a new remote_name, just update the existing origin:

git remote set-url origin https://github.com/username/new-repo.git

This will set the remote-url of mention git repo to origin basically it update teh remote-url

OR with (SSH)

git remote set-url origin [email protected]:username/new-repo.git

How to Install Cisco VPN AnyConnect Client in Linux, Ubuntu

1.Install the dependencies bu running the below commands

sudo apt update

sudo apt-get install  libpango-1.0-0 libcanberra-gtk-module

2. visit the site https://vpn.nic.in/  , 

• move to software menu 

• click on VPN client for Linux 64-bit

• it will download the anyconnect-linux-64-5.1.8.122-k9.tar.gz file

3.Extract the downloaded file

4.Move to the VPN directory and run the below command

sudo ./vpn_install.sh

wget

wget is a command-line utility used to download files from the internet in Linux, macOS, or Windows (via WSL or Cygwin). It’s very common for downloading .deb packages, scripts, or any file over HTTP, HTTPS, or FTP.

1.Basic usage

wget <URL>

Example:

wget http://example.com/file.txt

This will download file.txt to the current directory.

2.Download and save with a custom name:

wget -O newname.txt http://example.com/file.txt

-O specifies the filename you want.

3.Resume interrupted downloads:

wget -c http://example.com/largefile.zip

-c continues downloading if it was stopped.

4.Download in background:

wget -b http://example.com/largefile.zip

This lets the download continue in the background.

5.Recursive downloads (download entire websites):

wget -r http://example.com

Example:

wget http://mirrors.kernel.org/ubuntu/pool/universe/p/pangox-compat/libpangox-1.0-0_0.0.2-2_amd64.deb

This command downloads the old libpangox package directly to your system so you can install it with dpkg.

dpkg

dpkg is the low-level package management tool for Debian-based systems (like Ubuntu). It is used to install, remove, and manage .deb packages directly. Think of it as the underlying engine behind apt and apt-get.

Debian Package

It’s essentially the Debian package management tool used to install, remove, and manage .deb files on Debian-based systems like Ubuntu.

• dpkg handles the low-level operations on packages.
• Tools like apt and apt-get are high-level frontends that use dpkg under the hood to manage packages and dependencies.

1.Install a package:

sudo dpkg -i package_name.deb

-i stands for install.

This installs the .deb file you downloaded with wget.

2.Remove a package:

sudo dpkg -r package_name

Removes the package but leaves configuration files.

sudo dpkg --purge package_name

Removes package + configuration files completely.

3.List installed packages:

dpkg -l

Shows all packages installed on your system.

4.Check package details:

dpkg -s package_name

• Displays info like version, description, dependencies, and status.

5.List files installed by a package:

dpkg -L package_name
dpkg -l | grep zip

Useful to see where files are installed.

6.Check dependencies:

dpkg -I package_name.deb

• Lists info about a .deb file without installing it.

If dpkg fails due to missing dependencies, run:

sudo apt-get install -f

This fixes missing dependencies automatically.

Difference Between dpkg and apt

Ctrl + Shift + P  (for crome browser)

Install zip and download zip file

1.install zip (if not installed)

sudo apt update
sudo apt install zip

2.Zip the folder

Suppose your folder is named my_folder and you want the zip file to be my_folder.zip:

zip -r my_folder.zip my_folder

• -r recursively includes all files and subfolders inside my_folder.
• my_folder.zip ? the output zip file.
• my_folder ? the folder you want to compress.

3. Verify the zip file

ls -lh my_folder.zip

This shows the zip file size and confirms it exists.

4. Downloading (if you’re on a remote server)

If your Linux terminal is on a remote server and you want to download to your local machine:

• Using scp (from your local machine):

• scp username@remote_server:/path/to/my_folder.zip /local/path/

• Using wget or curl (if served via HTTP) is another option.

• wget -O my_file.zip http://example.com/path/to/file.zip

• curl -O http://example.com/path/to/file.zip

• -O keeps the original file name.
• To save with a specific name:

• curl -o my_file.zip http://example.com/path/to/file.zip

If the server requires authentication:

wget --user=username --password=password http://example.com/file.zip
curl -u username:password -O http://example.com/file.zip

You can resume interrupted downloads with -c in wget:

wget -c http://example.com/file.zip

How to unzip

1.Using unzip command (you might need to install it first):

sudo apt update
sudo apt install unzip   # if not already installed

2.Unzip a file:

unzip filename.zip

This will extract the contents into the current directory.

3.Unzip to a specific folder

unzip filename.zip -d /path/to/destination/

4.List contents without extracting:

unzip -l filename.zip

Isssue while downloading the mysqlclinet in python

pip install mysqlclient

if  it shown issues

Exception: Can not find valid pkg-config name.
Specify MYSQLCLIENT_CFLAGS and MYSQLCLIENT_LDFLAGS env vars manually

means that the system dependencies for MySQL development are missing. The mysqlclient Python package needs MySQL headers and client libraries to build.

sudo apt update
sudo apt install python3-dev default-libmysqlclient-dev build-essential pkg-config

• python3-dev ? headers for Python (needed to compile C extensions)
• default-libmysqlclient-dev ? MySQL client libraries and headers
• build-essential ? compiler tools
• pkg-config ? helps find the libraries

Install web version of pgadmin

Run pgAdmin4 in a browser (web mode)

If you want it lightweight, you can install the web version instead:

sudo apt install pgadmin4-web -y

Then configure and start:

sudo /usr/pgadmin4/bin/setup-web.sh

It will ask you to set an admin email/password.
Then you can open pgAdmin4 in your browser:

http://127.0.0.1:5050

Hit the command to start the pgadmin server 

pgadmin4

In pgAdmin4, server connections (not the actual databases, just the saved connection details) are stored in a SQLite DB called pgadmin4.db.

SSH Key

1. Check if you already have an SSH key

On your local machine, run:

ls -al ~/.ssh

If you see files like id_rsa & id_rsa.pub (or id_ed25519 & id_ed25519.pub), you already have a key pair.

2. Generate an SSH key (if you don’t have one)

ssh-keygen -t ed25519 -C "[email protected]"

ed25519

• Modern, secure, and fast.
• Uses smaller keys but is very strong.
• Default choice for most cases today.
• Not supported on very old systems (rare).

you can used rsa as well like:

ssh-keygen -t rsa -b 4096 -C "[email protected]"

• Widely supported and compatible with almost every system.
• -b 4096 sets the key length (longer = more secure; 4096 is recommended).
• Larger key size than ed25519, so slightly slower for encryption.

Press Enter for defaults. This will create:

• ~/.ssh/id_ed25519 (private key – keep it safe!)
• ~/.ssh/id_ed25519.pub (public key – to share with the server)

3. Copy your public key to the server

ssh-copy-id [email protected]

If ssh-copy-id is not available, do it manually:

cat ~/.ssh/id_ed25519.pub

Copy the output and then (if you have console/other access to the server), add it to:

/home/dev/.ssh/authorized_keys

4. Retry SSH

ssh username@ip_address

5. If password login is required but disabled

The server might have disabled password login in /etc/ssh/sshd_config with:

PasswordAuthentication no

In that case, you’ll need server/console access to either:

• Add your key to authorized_keys, or
• Enable password login temporarily.