Add cleanup instructions

bgp-contd/README.md

@@ -350,3 +350,9 @@ Using other resources on the internet you should be able to find out what all of
 Within a single AS, it's really important to have a single policy, so that all routers are on the same page about where to send traffic. You cannot have two border routers, which independently from each other determine that the other one should be used as exit point to a specific external peer. They would pingpong all traffic between them until the IP packet TTL expires and then drop the traffic, resulting in a big black hole and a bunch of overloaded internal connections. So, yes, this can get quite complex quickly if you start to make customizations.
 
 Remember that we started this tutorial with an example network in which traffic between `AS65000` and `AS65010` was already using the two paths between them in an asymmetric way. Because the setup of both networks is so similar and mirrored, the fact that traffic back and forth flows asymmetrically is actually thanks to the last rule: "Prefer the route with the lowest value of router ID of the advertising router.". After initially setting up the example, I had to swap `R10` and `R11` again to get this behaviour. :-)
+
+# Cleaning up
+
+Make sure you preserve the configs that you wrote if you want to have a look at them later. Then, we can stop and remove everything:
+
+    for router in 0 1 2 10 11 12 20; do lxc-stop -n R$router; lxc-destroy -n R$router; sleep 2; done

bgp-intro/README.md

@@ -536,3 +536,10 @@ It might have occurred to you that the iBGP BIRD configuration specifies the loc
  * Look around on the internet and read other blogs and tutorials about OSPF and BGP and see if they're much more easy to understand having a frame of reference which was set by following this tutorial.
 
 In the next tutorial, [BGP Part II](/bgp-contd/README.md), I'll show more interesting topologies of different networks connecting together using BGP than just two networks with one eBGP connection. By doing so, we'll quickly discover and understand how the actual huge Internet is organized.
+
+# Cleaning up
+
+Before starting the next tutorial, we need to get rid of all our container stuff, since the names starting with R and H will be reused. Make sure you preserve the configs that you wrote if you want to have a look at them later. Then, we can stop and remove everything:
+
+    for router in 0 1 3 10 11 12; do lxc-stop -n R$router; lxc-destroy -n R$router; sleep 2; done
+    for host in 6 7 19 34; do lxc-stop -n H$host; lxc-destroy -n H$host; sleep 2; done

birdhouse-intro/README.md

@@ -111,4 +111,19 @@ To finish this tutorial:
 
 That's basically it. As you can see, when you get the hang of this, it's instantly also getting extremely boring to do the configuration every time. For later tutorials, I'll make sure all files that make up the starting point of the configuration are available to simply copy into the newly cloned containers.
 
+# Cleanup!
+
+Oh, wait, before we move on, let's introduce the cleaning up step...
+
+When working through the next pages of the tutorial, we'll often create a bunch of containers by cloning the birdbase container. Before starting the next tutorial, you want to clean them up, since container names might be reused.
+
+For now, we can stop and remove them like this:
+
+    lxcbird:/var/lib/lxc 0-# lxc-stop -n sparrow
+    lxcbird:/var/lib/lxc 0-# lxc-stop -n weaver
+    lxcbird:/var/lib/lxc 0-# lxc-destroy -n sparrow
+    lxcbird:/var/lib/lxc 0-# lxc-destroy -n weaver
+
+(N.B. With Debian Buster and btrfs, I currently get a lot of error like `lxc-destroy: sparrow: storage/btrfs.c: get_btrfs_subvol_path: 103 Failed to append name - rootfs<66>x`, it seems it actually in the end can remove everything, so I'm ignoring those for now.)
+
 Next up: [Meanwhile at the Birdhouse Factory...](/birdhouse-vlans-vpn/README.md)

ospf-intro/README.md

@@ -385,4 +385,11 @@ Another thing you can play with is rolling out IPv6 on this little network that
 
 After completing this tutorial, I also encourage you to start reading the other "An Introduction to OSPF" like pages on the internet, since they should be a lot easier to understand while having seen it work for real! Have fun.
 
+# Cleaning up
+
+Before starting the next tutorial, we need to get rid of all our container stuff, since the names starting with R and H will be reused. Make sure you preserve the configs that you wrote if you want to have a look at them later. Then, we can stop and remove everything:
+
+    for router in 1 2 5 6; do lxc-stop -n R$router; lxc-destroy -n R$router; sleep 2; done
+    for host in 12 10 8 5; do lxc-stop -n H$host; lxc-destroy -n H$host; sleep 2; done
+
 Next: [An introduction to BGP](/bgp-intro/README.md)