# How to SSH into a server from Windows, macOS or Linux

To SSH into a server, open a terminal on your computer and type `ssh`, your user name, `@` and the server's address:

```
ssh myuser@203.0.113.10
```

This works in Windows 10 and 11, macOS and Linux. You don't need to install anything on most computers.

## What you need

- The server's IP address or name.
- A user name on that server.
- An SSH key that the server knows, or a password if the server allows them.

## Connect

1. Open a terminal. On Windows, use **PowerShell**. On macOS, use **Terminal**.
2. Type the command above, with your own user name and address.
3. The first time, SSH asks if you trust this server. Type `yes`.
4. You are in when you see the server's prompt. Type `exit` to leave.

## Make an SSH key

A key is safer than a password, and you don't have to type it each time. These commands work on all three systems:

```
ssh-keygen -t ed25519
```

Press Enter to save it in the normal place. You can add a passphrase, which protects the key if someone copies it.

This makes two files. The one ending in `.pub` is your **public key**, and it is safe to share. The other one is your
**private key**. Never share it or send it to anyone.

Show your public key so you can copy it:

| Your computer | Command |
|---|---|
| Windows (PowerShell) | `Get-Content $env:USERPROFILE\.ssh\id_ed25519.pub` |
| macOS or Linux | `cat ~/.ssh/id_ed25519.pub` |

To add the key to a server you can already log in to, put that one line at the end of `~/.ssh/authorized_keys` on the server.

## When it does not work

| What you see | What it means | What to do |
|---|---|---|
| `Permission denied (publickey)`, sometimes with more words in the brackets | The server doesn't accept your key for this user | Check the user name. Check that your public key is on the server |
| `Connection timed out` | Your computer can't reach the server | Check the address. Check that the server's firewall allows port 22 |
| `Connection refused` | The server answered, but SSH is not listening on that port | Check that SSH is running. Your server may use another port. Use `ssh -p 2222 myuser@203.0.113.10` to try one |
| `REMOTE HOST IDENTIFICATION HAS CHANGED` | The server's identity is not the one your computer remembers | This is normal if you just reinstalled the server. If you didn't, stop and find out why. Then run `ssh-keygen -R 203.0.113.10` |
| `UNPROTECTED PRIVATE KEY FILE` | Other people on your computer can read your key | On macOS or Linux, run `chmod 600 ~/.ssh/id_ed25519` |
| The key is on the server, but it still asks for a password | The server may be ignoring the key because of its file permissions | On the server, run `chmod 700 ~/.ssh` and `chmod 600 ~/.ssh/authorized_keys` |

## Restart SSH on the server

If you have another way in, such as a web terminal, you can check SSH there. Its name depends on the system:

| System | Check it | Restart it |
|---|---|---|
| Ubuntu or Debian | `sudo systemctl status ssh` | `sudo systemctl restart ssh` |
| Rocky Linux, AlmaLinux or RHEL | `sudo systemctl status sshd` | `sudo systemctl restart sshd` |

## Doing this on CortexHosting

1. Add your public key in **Settings**, under **SSH keys**. Press **Add an SSH key**.
2. Pick the key when you make a new server. For a server you already have, open it and go to **SSH keys**.
3. Connect with the user name `cortex`:

   ```
   ssh cortex@your-server-address
   ```

Logging in as root is switched off on servers we run. On a VPS, `cortex` can use `sudo` to do anything root can do. On a
Managed server, no account has `sudo`.

Don't have a key, or can't get in? Open your server and go to **Console**. It gives you a terminal in your browser.

CortexHosting is not open yet, so you can’t order a server today.
Last changed: 2026-11-02
Source: https://cortexhosting.dev/docs/ssh-into-a-server/