SSH Key GitHub Setup - Complete Guide

# SSH Key Generation

# 1. Generate SSH Key Pair
ssh-keygen -t ed25519 -C "your-email@example.com"

# 2. Generate RSA Key (if ed25519 not supported)
ssh-keygen -t rsa -b 4096 -C "your-email@example.com"

# 3. Specify custom key name
ssh-keygen -t ed25519 -C "your-email@example.com" -f ~/.ssh/github_ed25519

# 4. Generate key with passphrase
ssh-keygen -t ed25519 -C "your-email@example.com" -N "your-passphrase"

# 5. Generate key without passphrase
ssh-keygen -t ed25519 -C "your-email@example.com" -N ""

# 6. List existing SSH keys
ls -la ~/.ssh/

# 7. View public key
cat ~/.ssh/id_ed25519.pub

# 8. View private key (be careful!)
cat ~/.ssh/id_ed25519

# 9. Test SSH key
ssh -T git@github.com

# 10. Add key to SSH agent
ssh-add ~/.ssh/id_ed25519

# GitHub SSH Configuration

# 1. Copy public key to clipboard
# macOS
pbcopy < ~/.ssh/id_ed25519.pub

# Linux
cat ~/.ssh/id_ed25519.pub | xclip -selection clipboard

# Windows (PowerShell)
Get-Content ~/.ssh/id_ed25519.pub | Set-Clipboard

# 2. Add key to GitHub
# Go to GitHub Settings > SSH and GPG keys
# Click "New SSH key"
# Paste public key
# Add descriptive title
# Click "Add SSH key"

# 3. Test GitHub connection
ssh -T git@github.com

# 4. Clone repository with SSH
git clone git@github.com:username/repository.git

# 5. Change remote URL to SSH
git remote set-url origin git@github.com:username/repository.git

# 6. Verify remote URL
git remote -v

# 7. Multiple SSH keys
# Create SSH config file
touch ~/.ssh/config

# Add configuration
Host github.com
    HostName github.com
    User git
    IdentityFile ~/.ssh/github_ed25519

# 8. Test specific key
ssh -T -i ~/.ssh/github_ed25519 git@github.com

# 9. SSH agent management
# Start SSH agent
eval "$(ssh-agent -s)"

# Add key to agent
ssh-add ~/.ssh/id_ed25519

# List keys in agent
ssh-add -l

# Remove key from agent
ssh-add -d ~/.ssh/id_ed25519

# 10. Remove all keys from agent
ssh-add -D

# SSH Configuration

# 1. SSH Config File
# ~/.ssh/config
Host github.com
    HostName github.com
    User git
    IdentityFile ~/.ssh/id_ed25519
    IdentitiesOnly yes
    AddKeysToAgent yes
    UseKeychain yes

# 2. Multiple GitHub Accounts
Host github-work
    HostName github.com
    User git
    IdentityFile ~/.ssh/github_work_ed25519

Host github-personal
    HostName github.com
    User git
    IdentityFile ~/.ssh/github_personal_ed25519

# 3. SSH Agent Configuration
# ~/.ssh/config
Host *
    AddKeysToAgent yes
    UseKeychain yes
    IdentitiesOnly yes

# 4. SSH Key Permissions
# Set correct permissions
chmod 700 ~/.ssh
chmod 600 ~/.ssh/id_ed25519
chmod 644 ~/.ssh/id_ed25519.pub
chmod 600 ~/.ssh/config

# 5. SSH Key Rotation
# Generate new key
ssh-keygen -t ed25519 -C "new-email@example.com" -f ~/.ssh/github_new

# Add new key to GitHub
# Remove old key from GitHub
# Update local configuration

# 6. SSH Key Backup
# Backup private key (encrypted)
gpg --symmetric --cipher-algo AES256 ~/.ssh/id_ed25519

# Backup public key
cp ~/.ssh/id_ed25519.pub ~/backup/

# 7. SSH Key Recovery
# Restore from backup
gpg --decrypt ~/.ssh/id_ed25519.gpg > ~/.ssh/id_ed25519

# Set permissions
chmod 600 ~/.ssh/id_ed25519

# 8. SSH Key Validation
# Validate key format
ssh-keygen -l -f ~/.ssh/id_ed25519.pub

# Check key fingerprint
ssh-keygen -l -E sha256 -f ~/.ssh/id_ed25519.pub

# 9. SSH Connection Debug
# Debug SSH connection
ssh -vT git@github.com

# Verbose output
ssh -vvT git@github.com

# 10. SSH Key Troubleshooting
# Check SSH agent
ssh-add -l

# Restart SSH agent
eval "$(ssh-agent -s)"

# Test connection
ssh -T git@github.com