Nguyễn Khánk's Wiki

# SSH Notes

# Generate SSH key pair

ssh-keygen -t rsa -b 4096 -C "My SSH Key for Server Access"

This will generate a 4096-bit RSA key pair with the comment "My SSH Key for Server Access". The private key will be saved as ~/.ssh/id_rsa and the public key as ~/.ssh/id_rsa.pub.

  • -t rsa (default): type of key
  • -b 4096 (recommended): key size in bits
  • -C comment"
  • -f filename: By default, it's saved as id_rsa in the .ssh directory of home directory

# Connect remote server with alias

ssh server-dev-app

Configure your config at ~/.ssh/config with something like:

Host server-dev-app
    Hostname 13.xx.xx.xx
    User ubuntu
    Port 22
    IdentityFile ~/.ssh/{file-name}.pem

Note: make sure your .pem file is correct

# SSH Connection Flow

SSH Flow

# Local Port Forwarding

A typical scenario for this kind of port forwarding is when you're developing locally and need to connect to a database or service running on a remote server.

ssh -L 54321:127.0.0.1:5432 ubuntu@server-dev-app
  • -L: Local Port Forwarding

This command creates a tunnel that redirects traffic from a specific port (54321) on your local machine to a different port (5432) on the remote server (server-dev-app).

When you try to connect to localhost:54321 on your machine, the SSH connection will transparently route that traffic to the actual service running on port 5432 of the remote server.

# Copy files

scp ubuntu@server-dev-app:/var/log/logs ~/Downloads

Copy a directory named logs from /var/log on the server 192.168.1.10 to local Downloads directory

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