SSH Keys — macOS + GitHub + GitLab

Table of contents

1. 1. Generate SSH keys
2. 2. Add keys to the macOS keychain
3. 3. Configure ~/.ssh/config
4. 4. Add public keys to GitHub and GitLab
5. 5. Test connections
6. 6. Clone / set remote URLs
7. 7. Multiple accounts on the same host
8. 8. Troubleshooting

---

1. Generate SSH keys

Create separate keys for GitHub and GitLab (recommended for isolation).

# GitHub key
ssh-keygen -t ed25519 -C "cjrequena001+claudeai@gmail.com" -f ~/.ssh/id_ed25519_github

# GitLab key
ssh-keygen -t ed25519 -C "cjrequena001+claudeai@gmail.com" -f ~/.ssh/id_ed25519_gitlab

Use -t rsa -b 4096 if the remote requires RSA.

---

2. Add keys to the macOS keychain

ssh-add --apple-use-keychain ~/.ssh/id_ed25519_github
ssh-add --apple-use-keychain ~/.ssh/id_ed25519_gitlab

Verify loaded keys:

ssh-add -l

---

3. Configure ~/.ssh/config

# GitHub
Host github.com
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_ed25519_github
  AddKeysToAgent yes
  UseKeychain yes

# GitLab
Host gitlab.com
  HostName gitlab.com
  User git
  IdentityFile ~/.ssh/id_ed25519_gitlab
  AddKeysToAgent yes
  UseKeychain yes

Set correct permissions:

chmod 600 ~/.ssh/config

---

4. Add public keys to GitHub and GitLab

Copy each public key to the clipboard:

# GitHub
pbcopy < ~/.ssh/id_ed25519_github.pub

# GitLab
pbcopy < ~/.ssh/id_ed25519_gitlab.pub

GitHub: Settings → SSH and GPG keys → New SSH key → paste → Save

GitLab: Preferences → SSH Keys → Add new key → paste → Save

---

5. Test connections

ssh -T git@github.com
# Hi <username>! You've successfully authenticated...

ssh -T git@gitlab.com
# Welcome to GitLab, @<username>!

---

6. Clone / set remote URLs

SSH URLs use the git@ scheme — not https://.

# Clone
git clone git@github.com:user/repo.git
git clone git@gitlab.com:user/repo.git

# Update existing remote from HTTPS to SSH
git remote set-url origin git@github.com:user/repo.git
git remote set-url origin git@gitlab.com:user/repo.git

# Verify
git remote -v

---

7. Multiple accounts on the same host

To use two GitHub accounts, define aliases in ~/.ssh/config:

Host github-personal
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_ed25519_github_personal
  AddKeysToAgent yes
  UseKeychain yes

Host github-work
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_ed25519_github_work
  AddKeysToAgent yes
  UseKeychain yes

Clone using the alias:

git clone git@github-personal:user/repo.git
git clone git@github-work:org/repo.git

---

8. Troubleshooting

Problem	Fix
Permission denied (publickey)	Key not loaded — run ssh-add --apple-use-keychain ~/.ssh/id_ed25519_github
Key not persisting after reboot	Confirm UseKeychain yes and AddKeysToAgent yes are in ~/.ssh/config
Multiple keys, wrong one used	Check IdentityFile path in config; test with ssh -vT git@github.com
Bad owner or permissions on ~/.ssh/config	Run chmod 600 ~/.ssh/config

Verbose connection debug:

ssh -vT git@github.com
ssh -vT git@gitlab.com