adds ssh config info

modules/qualifying/learning_ssh.md

@@ -260,6 +260,65 @@ I'll let you figure it out by yourself but if you're stuck have a look at [this]
 
 ## Standard usage
 
+The basic usage of ssh is what you've been doing up until now, logging into remote machines.
+Now that you know how to add keys for automated logins, it's time to learn a few handy tricks.
+The first one is a bit basic but handy non the less.
+You can add a command to execute after the `ssh $USER@$HOST` so it becomes as follows.
+In this particular case it shows me information about the mounted partitions.
+
+```
+➜  ~ git:(master) ✗ ssh waldek@172.30.4.19 df -h
+Filesystem      Size  Used Avail Use% Mounted on
+udev             16G     0   16G   0% /dev
+tmpfs           3.2G  347M  2.8G  11% /run
+/dev/sda1       219G   99G  109G  48% /
+tmpfs            16G   16K   16G   1% /dev/shm
+tmpfs           5.0M     0  5.0M   0% /run/lock
+tmpfs            16G     0   16G   0% /sys/fs/cgroup
+tank            386G  128K  386G   1% /usr/share/zpool
+tank/set1       573G  187G  386G  33% /usr/share/zpool/set1
+tank/set2       386G  128K  386G   1% /usr/share/zpool/set2
+tank/set3       100M  128K  100M   1% /usr/share/zpool/set3
+tmpfs           3.2G     0  3.2G   0% /run/user/1000
+➜  ~ git:(master) ✗
+```
+
+A second nice thing to know about is the `~/.ssh/config` file.
+In this file you can add shortcut's to hosts you often contact.
+As an example I would like to add a shortcut to my matrix server.
+
+```
+➜  ~ git:(master) ✗ ssh matrixserver
+ssh: Could not resolve hostname matrixserver: No address associated with hostname
+```
+
+To create the shortcut I append the following to my `~/.ssh/config` file.
+
+```
+Host matrixserver
+	Hostname 172.30.4.19
+	Port 22
+	User waldek
+	IdentityFile ~/.ssh/id_rsa
+```
+
+I can now log in as follows.
+
+```
+➜  ~ git:(master) ✗ ssh matrixserver
+Linux debian 4.19.0-16-amd64 #1 SMP Debian 4.19.181-1 (2021-03-19) x86_64
+
+The programs included with the Debian GNU/Linux system are free software;
+the exact distribution terms for each program are described in the
+individual files in /usr/share/doc/*/copyright.
+
+Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
+permitted by applicable law.
+You have new mail.
+Last login: Tue Jul 13 14:12:18 2021 from 172.30.40.99
+➜  ~ 
+```
+
 ## Tweaking the sshd configuration file
 
 All server configuration is done in the `/etc/ssh/sshd_config` file.
@@ -283,6 +342,10 @@ Protocol
              “2,1” is identical to “1,2”.
 ```
 
+### Some classic security enhancements
+
+### Tunneling and X forward
+
 ## Tunnels
 
 ## SFTP