# Setting up a keypair and adding it to remote server:

Generate keypair (will be asked where to save if no -f, default is fine):
```sh
ssh-keygen -t ed25519 -f ~/.ssh/filename -C "<comment/email>"
```

Copy public key to remote server:
```sh
# with ssh-copy-id tool:
ssh-copy-id -i ~/.ssh/filename.pub USER@REMOTEHOST

# manually, permissions are required!
cat ~/.ssh/filename.pub | ssh USER@REMOTEHOST "mkdir -p ~/.ssh && chmod 700 ~/.ssh && cat >> ~/.ssh/authorized_keys && chmod 600 ~/.ssh/authorized_keys"
```

Change passphrase of a file:
```sh
ssh-keygen -p -f ~/.ssh/filename
```

Troubleshoot:
```sh
# on the client:
ssh -vvv -i ~/.ssh/filename.pub USER@REMOTEHOST

# on the remote:
sudo journalctl -t sshd -n 100
```

# Setting up a ssh-config for multiple keys / servers

In `~/.ssh/config` add something like:
```ini
Host tankbox
    HostName 10.0.0.9
    User storage
    IdentityFile ~/.ssh/tankbox
    Port 2323

Host hypebox
    HostName 10.0.0.8
    User controller
    IdentityFile ~/.ssh/hypebox
    Port 22
```
And now instead of specifying key+user+port every time, you'd just:
```sh
ssh tankbox
# or
ssh hypebox
```