Use this structured cheatsheet to quickly verify your Git + SSH setup for GitHub, support multiple accounts (work + personal), and debug typical issues like wrong identity or HTTPS remotes asking for passwords.

1) Check your current setup

• Remotes

  • git remote -v — list repo remotes and see whether they are HTTPS or SSH.
  • git remote get-url origin — show the URL used by origin.

• SSH auth with GitHub

  • ssh -T git@github.com — verify which account is authenticated (it prints your username).
  • ssh -vT git@github.com — verbose output to see which key is being offered/used.

• Local keys

  • ssh-add -l — list keys loaded in the SSH agent.
  • ls -al ~/.ssh — list keys available on disk.

2) Generate keys for multiple accounts

Create one key per account and label them clearly:

ssh-keygen -t ed25519 -C "personal@email.com" -f ~/.ssh/id_ed25519_personal
ssh-keygen -t ed25519 -C "work@email.com" -f ~/.ssh/id_ed25519_work

ssh-add ~/.ssh/id_ed25519_personal
ssh-add ~/.ssh/id_ed25519_work

• Add the corresponding .pub files to GitHub → Settings → SSH and GPG keys.
• Optional: Keep keys password-protected and use your OS keychain/agent.

3) Configure ~/.ssh/config (host aliases)

This lets you pick the account per repo by using a host alias instead of github.com:

Host github-personal
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_ed25519_personal
  IdentitiesOnly yes

Host github-work
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_ed25519_work
  IdentitiesOnly yes

Now you can set a repo remote to either identity:

git remote set-url origin git@github-work:Org/repo.git
# or
git remote set-url origin git@github-personal:user/repo.git

4) Switch a repo between users (without recloning)

The effective identity for push/pull is decided by the remote URL host. Change the remote and you switch identities:

git remote -v
git remote set-url origin git@github-work:Org/repo.git
git remote -v

Confirm SSH auth with the chosen alias:

ssh -T git@github-work

5) Useful fixes and one-off overrides

• Force a specific key once (without editing ssh config):

GIT_SSH_COMMAND='ssh -i ~/.ssh/id_ed25519_work -o IdentitiesOnly=yes' git push

• Clear all keys from the agent (reload a clean set):

ssh-add -D
ssh-add ~/.ssh/id_ed25519_work

• Debug which key is selected:

ssh -vT git@github.com

• Ensure repo author identity (commit metadata):

git config user.name "Your Work Name"
git config user.email "you@work.com"

For a global default use git config --global ..., but prefer per-repo configs when juggling multiple identities.

6) Convert an HTTPS remote to SSH

If Git asks for a password or a token, your remote is likely HTTPS. Switch to SSH:

git remote -v
git remote set-url origin git@github.com:user/repo.git

If using aliases from ~/.ssh/config:

git remote set-url origin git@github-personal:user/repo.git

7) Common errors (and quick resolutions)

• Permission denied (publickey)

  • Key not added to GitHub, wrong key file, or agent missing the key.
  • Action: ssh-add -l, then ssh-add ~/.ssh/id_ed25519_*, confirm ssh -T git@github.com.

• Wrong account used

  • Remote still points to github.com (no alias), or alias maps to a different key.
  • Action: git remote get-url origin, switch to git@github-work:Org/repo.git or git@github-personal:user/repo.git.

• Asking for password

  • HTTPS remote instead of SSH.
  • Action: change to an SSH URL as in section 6.

• Connection refused / firewalled 22

  • Some networks block SSH port 22.
  • Action: try GitHub’s SSH over port 443 by adding to ~/.ssh/config:

Host github.com
  Hostname ssh.github.com
  Port 443
  User git

• Host key mismatch
  • Known hosts entry is stale (e.g., OS reinstall/migration).
  • Action: ssh-keygen -R github.com then reattempt the SSH command.

8) End-to-end sanity test

git remote -v
ssh -T git@github-personal    # or git@github-work
git fetch --all --prune
git switch -c test-ssh-setup
echo "test $(date)" >> ssh-setup-check.txt
git add -A && git commit -m "test: verify ssh setup works for pushes"
git push -u origin test-ssh-setup

Confirm the branch appears on GitHub, then clean up:

git switch -
git branch -D test-ssh-setup
git push origin :test-ssh-setup

9) Handy reference block (copy/paste)

# Inspect remotes and URLs
git remote -v
git remote get-url origin

# Switch remotes to specific identities
git remote set-url origin git@github-work:Org/repo.git
git remote set-url origin git@github-personal:user/repo.git

# Check SSH auth and keys
ssh -T git@github.com
ssh -vT git@github.com
ssh-add -l
ls -al ~/.ssh

# Manage keys
ssh-keygen -t ed25519 -C "you@work.com" -f ~/.ssh/id_ed25519_work
ssh-add ~/.ssh/id_ed25519_work
ssh-add -D

# One-off force with a specific key
GIT_SSH_COMMAND='ssh -i ~/.ssh/id_ed25519_work -o IdentitiesOnly=yes' git push

# Commit identity per repo
git config user.name "Your Work Name"
git config user.email "you@work.com"

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If you need a step-by-step for your exact setup (team vs. personal, or mixed CI/CD), drop the repo details and I’ll suggest the safest mapping strategy for your keys and remotes.