mag37 / ssh_key-setup.md

Setting up a keypair and adding it to remote server:

Generate keypair (will be asked where to save if no -f, default is fine):

ssh-keygen -t ed25519 -f ~/.ssh/filename -C "<comment/email>"

Copy public key to remote server:

# 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:

ssh-keygen -p -f ~/.ssh/filename

Troubleshoot:

# 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:

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:

ssh tankbox
# or
ssh hypebox