How to generate an SSH key - Rocketeers app

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How to generate an SSH key
==========================

### [\#Security](https://rocketeersapp.com/knowledge/security)

Here is how to generate an SSH key pair on Linux, macOS, or Windows and add the public key to a server, GitHub, or GitLab.

 Published by [Mark van Eijk](https://rocketeersapp.com/author/mark-van-eijk) on June 23, 2026 · 1 minute read

1. [Generate the key pair](#content-generate-the-key-pair)
2. [Where the files end up](#content-where-the-files-end-up)
3. [Add the key to the ssh-agent](#content-add-the-key-to-the-ssh-agent)
4. [Copy the public key to a server](#content-copy-the-public-key-to-a-server)
5. [Add the key to GitHub or GitLab](#content-add-the-key-to-github-or-gitlab)
6. [If the connection is rejected](#content-if-the-connection-is-rejected)

If you're not sure what an SSH key is or how it works, start with [what is an SSH key](/what-is-an-ssh-key). Otherwise, here's how to make one.

[\#](#content-generate-the-key-pair "Permalink")Generate the key pair
---------------------------------------------------------------------

Use `ssh-keygen` with the modern ed25519 algorithm. The comment (`-C`) is just a label to help you recognise the key later:

 ```
ssh-keygen -t ed25519 -C "you@example.com"

```

You'll be asked where to save the key (press Enter for the default `~/.ssh/id_ed25519`) and for an optional passphrase. A passphrase encrypts your private key on disk — recommended for laptops.

If you need to support older systems that don't speak ed25519, generate an RSA key instead:

 ```
ssh-keygen -t rsa -b 4096 -C "you@example.com"

```

[\#](#content-where-the-files-end-up "Permalink")Where the files end up
-----------------------------------------------------------------------

The command creates two files in `~/.ssh`:

- `id_ed25519` — your **private** key. Never share or copy this off your machine.
- `id_ed25519.pub` — your **public** key. This is the one you hand out.

[\#](#content-add-the-key-to-the-ssh-agent "Permalink")Add the key to the ssh-agent
-----------------------------------------------------------------------------------

The agent keeps your unlocked key in memory so you don't retype the passphrase every time:

 ```
eval "$(ssh-agent -s)"
ssh-add ~/.ssh/id_ed25519

```

[\#](#content-copy-the-public-key-to-a-server "Permalink")Copy the public key to a server
-----------------------------------------------------------------------------------------

The easiest way to install your public key on a server is `ssh-copy-id`:

 ```
ssh-copy-id user@your-server

```

This appends your public key to the server's `~/.ssh/authorized_keys`. From then on you can log in without a password:

 ```
ssh user@your-server

```

If `ssh-copy-id` isn't available, print the public key and paste it into `~/.ssh/authorized_keys` on the server yourself:

 ```
cat ~/.ssh/id_ed25519.pub

```

[\#](#content-add-the-key-to-github-or-gitlab "Permalink")Add the key to GitHub or GitLab
-----------------------------------------------------------------------------------------

Copy the public key to your clipboard, then paste it into **Settings → SSH and GPG keys** (GitHub) or **Preferences → SSH Keys** (GitLab):

 ```
# macOS
pbcopy