Secure remote shell access, key authentication, and file transfer
What is this?
SSH lets you control a remote computer securely, as if you're sitting in front of it.
Step 01
1# Ubuntu / Debian2sudo apt-get update3sudo apt-get install -y openssh-server4 5# RHEL / CentOS / Fedora6sudo dnf install -y openssh-server7 8# Enable and start9sudo systemctl enable sshd10sudo systemctl start sshdStep 02
1sudo cp /etc/ssh/sshd_config /etc/ssh/sshd_config.bak2sudo nano /etc/ssh/sshd_config3 4# Recommended settings:5# Port 226# PermitRootLogin no7# PasswordAuthentication yes8# PubkeyAuthentication yes9# AllowUsers youruser10 11sudo systemctl restart sshd12sudo sshd -t # test config1# On client — generate key2ssh-keygen -t ed25519 -C "you@example.com"3 4# Copy public key to server5ssh-copy-id user@server-ip6 7# Connect with key8ssh user@server-ip1# In /etc/ssh/sshd_config:2# PasswordAuthentication no3# ChallengeResponseAuthentication no4sudo systemctl restart sshdStep 03
1sudo systemctl status sshd2ssh -v user@localhost3ss -tlnp | grep :22Step 04
1# Copy to server2scp file.txt user@server:/home/user/3scp -r ./folder user@server:/home/user/4 5# SFTP session6sftp user@server7# put file.txt / get file.txt1eval "$(ssh-agent -s)"2ssh-add ~/.ssh/id_ed255193 4# Local port forward5ssh -L 8080:localhost:80 user@server6 7# Remote port forward8ssh -R 9090:localhost:3000 user@serverStep 05
SSH rejected your login — usually a key or password issue.
1# Check key permissions (must be 600)2chmod 600 ~/.ssh/id_ed255193chmod 700 ~/.ssh4 5# Verbose login to see why it failed6ssh -v user@server-ip7 8# Force password auth (if enabled on server)9ssh -o PreferredAuthentications=password user@server-ip1# On server — check SSH is running2sudo systemctl status sshd3sudo ufw allow 22/tcp4 5# Test port6nc -zv server-ip 22