Adding command references

Doc/Sdi/Hetzner/gettingStarted.xml

 <?xml version="1.0" encoding="UTF-8"?>
-<chapter version="5.1" xml:id="sdi_hetzner"
+<chapter annotations="slide" version="5.1" xml:id="sdi_hetzner"
          xmlns="http://docbook.org/ns/docbook"
          xmlns:xlink="http://www.w3.org/1999/xlink"
          xmlns:xila="http://www.w3.org/2001/XInclude/local-attributes"
@@ -18,14 +18,53 @@
     <figure xml:id="sdi_hetzner_getstarted_createSshKeyPair">
       <title>Create an <command>ssh</command> key pair</title>
 
-      <screen>sdiuser@martin-pc-dachboden:~$ ssh-keygen  -t ed25519
+      <screen>sdiuser@martin-pc-dachboden:~$ <command
+          xlink:href="https://linux.die.net/man/1/ssh-keygen">ssh-keygen</command> -t ed25519 <co
+          linkends="sdi_hetzner_getstarted_createSshKeyPair-1"
+          xml:id="sdi_hetzner_getstarted_createSshKeyPair-1-co"/>
 Generating public/private ed25519 key pair.
 Enter file in which to save the key (/home/sdiuser/.ssh/id_ed25519): 
 Created directory '/home/sdiuser/.ssh'.
-Enter passphrase (empty for no passphrase): 
+Enter passphrase (empty for no passphrase): <co
+          linkends="sdi_hetzner_getstarted_createSshKeyPair-2"
+          xml:id="sdi_hetzner_getstarted_createSshKeyPair-2-co"/>
 Enter same passphrase again: 
-Your identification has been saved in /home/sdiuser/.ssh/id_ed25519
-Your public key has been saved in /home/sdiuser/.ssh/id_ed25519.pub</screen>
+Your identification has been saved in /home/sdiuser/.ssh/id_ed25519 <co
+          linkends="sdi_hetzner_getstarted_createSshKeyPair-3"
+          xml:id="sdi_hetzner_getstarted_createSshKeyPair-3-co"/>
+Your public key has been saved in /home/sdiuser/.ssh/id_ed25519.pub <co
+          linkends="sdi_hetzner_getstarted_createSshKeyPair-4"
+          xml:id="sdi_hetzner_getstarted_createSshKeyPair-4-co"/></screen>
+
+      <calloutlist>
+        <callout arearefs="sdi_hetzner_getstarted_createSshKeyPair-1-co"
+                 xml:id="sdi_hetzner_getstarted_createSshKeyPair-1">
+          <para>Create an elliptic rather than default <abbrev>RSA</abbrev>
+          type key.</para>
+        </callout>
+
+        <callout arearefs="sdi_hetzner_getstarted_createSshKeyPair-2-co"
+                 xml:id="sdi_hetzner_getstarted_createSshKeyPair-2">
+          <para>Security aware folks will choose a decent passphrase
+          protecting the private key being generated.</para>
+        </callout>
+
+        <callout arearefs="sdi_hetzner_getstarted_createSshKeyPair-3-co"
+                 xml:id="sdi_hetzner_getstarted_createSshKeyPair-3">
+          <para>The generated private key.</para>
+        </callout>
+
+        <callout arearefs="sdi_hetzner_getstarted_createSshKeyPair-4-co"
+                 xml:id="sdi_hetzner_getstarted_createSshKeyPair-4">
+          <para>The generated public key.</para>
+
+          <note>
+            <para>Different implementations like e.g. <command
+            xlink:href="https://www.putty.org">putty</command> may use
+            different key storage formats.</para>
+          </note>
+        </callout>
+      </calloutlist>
     </figure>
 
     <figure xml:id="sdi_hetzner_getstarted_hetznerSignUp">
@@ -70,7 +109,10 @@ Your public key has been saved in /home/sdiuser/.ssh/id_ed25519.pub</screen>
         <tr>
           <td valign="top"><orderedlist>
               <listitem>
-                <para>Create a default firewall</para>
+                <para>Create a default firewall allowing <command
+                xlink:href="https://linux.die.net/man/8/ping">ping</command>
+                and <command
+                xlink:href="https://linux.die.net/man/1/ssh">ssh</command></para>
               </listitem>
 
               <listitem>
@@ -78,11 +120,15 @@ Your public key has been saved in /home/sdiuser/.ssh/id_ed25519.pub</screen>
               </listitem>
 
               <listitem>
-                <para>Shared vCPU / x86 / CX11</para>
+                <para>Shared vCPU / x86 / CX11 (<link
+                xlink:href="https://www.hetzner.com/cloud/#pricing">the
+                cheapest</link>)</para>
               </listitem>
 
               <listitem>
-                <para>Add <command>ssh</command> public key</para>
+                <para>Add your personal <command>ssh</command> public key from
+                <xref
+                linkend="sdi_hetzner_getstarted_createSshKeyPair"/></para>
               </listitem>
             </orderedlist></td>
 
@@ -92,7 +138,8 @@ Your public key has been saved in /home/sdiuser/.ssh/id_ed25519.pub</screen>
               </listitem>
 
               <listitem>
-                <para>Note the Networking / Public IPv4 address for later
+                <para>Note the <guimenuitem>Networking</guimenuitem> /
+                <guisubmenu>Public IPv4</guisubmenu> address for later
                 reference</para>
               </listitem>
 
@@ -109,7 +156,12 @@ Your public key has been saved in /home/sdiuser/.ssh/id_ed25519.pub</screen>
 
       <itemizedlist>
         <listitem>
-          <para>Ping your server</para>
+          <para>Ping your server:</para>
+
+          <note>
+            <para>The IP 91.107.232.156 serves just as a sample value
+            irrespective of your individual actual server IP.</para>
+          </note>
 
           <screen>sdiuser:~$ ping 91.107.232.156
 PING 91.107.232.156 (91.107.232.156) 56(84) bytes of data.
@@ -118,7 +170,7 @@ PING 91.107.232.156 (91.107.232.156) 56(84) bytes of data.
         </listitem>
 
         <listitem>
-          <para>Login via <command>ssh</command></para>
+          <para>Login via <command>ssh</command>:</para>
 
           <screen>ssh root@91.107.232.156</screen>
         </listitem>
@@ -126,7 +178,7 @@ PING 91.107.232.156 (91.107.232.156) 56(84) bytes of data.
     </figure>
 
     <figure xml:id="sdi_hetzner_getstarted_updateServer">
-      <title>Update and reboot </title>
+      <title>Update and reboot</title>
 
       <orderedlist>
         <listitem>