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gcapes merged 1 commit into from
Nov 17, 2025
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Explain checking github's public key on first connection #137

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19 changes: 16 additions & 3 deletions setup.md
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Expand Up @@ -25,7 +25,7 @@ Git is free and open-source software, available for all operating systems.

#### Installation on personal and unmanaged machines

[See here](https://git-scm.com/book/en/v2/Getting-Started-Installing-Git)
[See here](https://git-scm.com/book/en/v2/Getting-Started-Installing-Git)
for installation instructions for the major operating systems.

### SSH keys
Expand Down Expand Up @@ -62,7 +62,7 @@ id_ed25519 id_ed25519.pub
```
{: .output}

and you can skip to the next section
and you can skip to the next section
[(Add public ssh key to GitHub)](#add-public-ssh-key-to-github).

If you still need to set up ssh keys, you'll get a message like this:
Expand All @@ -80,7 +80,7 @@ $ ssh-keygen -t ed25519 -C "your_email@example.com"
{: .language-bash}

You *might* get an error from this if your system doesn't support
the ed25519 algorithm, in which case you can try
the ed25519 algorithm, in which case you can try
`$ ssh-keygen -t rsa -b 4096 -C "your_email@example.com"`

```
Expand Down Expand Up @@ -164,6 +164,19 @@ $ ssh -T git@github.com
```
{: .language-bash}

If this is the first time you have connected, you'll probably see a warning like this:

```output
The authenticity of host 'github.com (20.26.156.215)' can't be established.
ED25519 key fingerprint is SHA256:+DiY3wvvV6TuJJhbpZisF/zLDA0zPMSvHdkr4UvCOqU.
This key is not known by any other names.
Are you sure you want to continue connecting (yes/no/[fingerprint])?
```

This is asking you to verify github's public key to check you're connecting to the right thing.
Assuming it matches one of the [public keys](https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/githubs-ssh-key-fingerprints)
we can go ahead and type enter `yes`, which brings us to the confirmation.

```
Hi yourusername! You've successfully authenticated, but GitHub does not provide shell access.
```
Expand Down