SSH Permission Denied (publickey) Error

SSH private keys must have strict permissions to be accepted.

# Fix private key permissions (Linux/macOS)
chmod 600 ~/.ssh/id_rsa
chmod 700 ~/.ssh
chmod 644 ~/.ssh/id_rsa.pub

# On Windows, check Properties → Security → Advanced
# The key should be readable only by the user

Register your SSH key with the SSH agent.

# Start ssh-agent
ssh-agent bash
# or
eval "$(ssh-agent -s)"

# Add your key
ssh-add ~/.ssh/id_rsa

# List added keys
ssh-add -l

# Test connection
ssh -T git@github.com

Copy your public key to the server's authorized_keys.

# Copy public key to server
ssh-copy-id user@server.com

# Or manually append to ~/.ssh/authorized_keys
cat ~/.ssh/id_rsa.pub | ssh user@server.com "cat >> ~/.ssh/authorized_keys"

# For GitHub: add key at https://github.com/settings/keys
# Test: ssh -T git@github.com
# Should say: "Hi username! You've successfully authenticated"

Use -i flag to specify a specific private key.

# Connect with specific key
ssh -i ~/.ssh/my-custom-key user@server.com

# Or configure in ~/.ssh/config
Host myserver
  HostName server.com
  User ubuntu
  IdentityFile ~/.ssh/my-custom-key