ssh public key authentication

## keys erzeugen
$ ssh-keygen -t rsa   # erzeugt RSA key für Protokol 2
$ ssh-keygen -t dsa   # erzeugt DSA key für Protokol 2

## public keys auf remote site kopieren
$ ssh-copy-id -i ~/.ssh/id_rsa.pub user@remote-system
$ ssh-copy-id -i ~/.ssh/id_dsa.pub user@remote-system
## ... alternativ ohne ssh-copy-id
$ cat ~/.ssh/*.pub | ssh user@remote-system 'umask 077; cat >>.ssh/authorized_keys'

### Anmeldung nur mit key (nur root):
    # /etc/ssh/sshd_config
    ...
    PermitRootLogin without-password
    ...
### Anmeldung nur mit key (alle user):
    # /etc/ssh/sshd_config
    ...
    PasswordAuthentication no
    ChallengeResponseAuthentication no
    UsePAM yes

## Centos 6 hat in der minimal installation kein scp
yum whatprovides "*/scp"         # in welchem Paket steckt scp?
yum install openssh-clients      # scp installieren

## There is a bug in CentOS 6 / SELinux that results in all client presented certificates to be ignored when SELinux is set to Enforcing. To fix this simply:
restorecon -R -v /root/.ssh