Merge branch 'pr01' into 'master'

Praktikum 01 -01

See merge request !1

prak/pr01/README.md

+# PRAKTIKUMSBLATT 1
+
+## Solutions to exercises
+
+### Exercise (2b) 
+
+#### "Geben Sie den Inhalt Ihrer Konfiguratonsdatei /etc/netplan/00-installer-config.yaml an und interpretieren Sie diesen?"
+
+My netplan configuration file is as follows:
+
+```
+network:
+  ethernets:
+    ens18:
+      dhcp4: no
+      addresses:
+        - 2001:638:408:200:ff78::1/64
+      gateway6: 2001:638:408:200::1
+    ens19:
+      dhcp4: true
+  version: 2
+```
+
+We can see that there is two interfaces: 'ens18' which is configured with IPv6 address and its gateway (used for internet access), and 'ens19' which has DHCP for IPv4 enabled, and allows connectivity inside H-BRS Netzlab evironment
+
+### Exercise (3c)
+
+#### "Testen Sie den ssh-Zugriff über Public-Key-Authentifizierung. Wie haben Sie das gemacht?"
+
+Authentication by Public-Key is enabled by default in Ubuntu 22.04 (even on some previous versions). However if it is not working, we should edit the ssh config file in '/etc/ssh/sshd_config' and choosing "yes" for 'PubkeyAuthentication' option
+
+```
+#Port 22
+#AddressFamily any
+#ListenAddress 0.0.0.0
+#ListenAddress ::
+
+.
+.
+.
+
+PubkeyAuthentication yes
+.
+.
+.
+
+# Expect .ssh/authorized_keys2 to be disregarded by default in future.
+#AuthorizedKeysFile     .ssh/authorized_keys .ssh/authorized_keys2
+```
+
+### Exercise (3d)
+
+#### "Schalten Sie fuer openssh die Passwortauthentifizierung ab. Hierzu muessen Sie die Datei /etc/ssh/sshd_config anpassen. Welche Zeile bzw. Zeilen mussten Sie hierfuer aendern?"
+
+The following lines are modified:
+
+```
+ChallengeResponseAuthentication no
+PasswordAuthentication no´
+UsePAM no
+
+```
+
+### Exercise (3e)
+
+####Testen Sie, dass die Passwortauthentifizierung tatsaechlich abgeschaltet ist. Welche Fehlermeldung erhalten Sie bei einem Login-Versuch mit Passwort?
+
+There is an error regarding Public Key
+
+```
+ssh azurit2s@tazc.de
+Permission denied (publickey)
+```