Fix and update minor issues in the README

README.md

@@ -22,13 +22,17 @@ For this you will first need to install `vmdb2`. As of July 2018, this
 repository still ships vmdb2, but will probably be deprecated in the
 future. You can choose:
 
-- `vmdb2` is available as a package for Testing and Unstable. If your
+<!-- - `vmdb2` is available as a package for Testing and Unstable. If your -->
-  Debian system is either, quite probably installing it systemwide is
+<!--   Debian system is either, quite probably installing it systemwide is -->
-  the easiest and most recommended way.
+<!--   the easiest and most recommended way. -->
+- `vmdb2` is available as a package for Debian Testing and
+  Unstable. However, we require at least [one
+  feature](http://git.liw.fi/vmdb2/commit/?id=474cd53826fda5a571cca8b5dda7cf949291dd62)
+  that has not been included in any of the releases uploaded to
+  Debian.
 
-- If you are using Debian stable (stretch) or for some reason prefer
+  Therefore, `vmdb2` is presented as a submodule in this
-  not to install the package, `vmdb2` is presented as a submodule in
+  project. First install the
-  this project. First install the
   [requirements](http://git.liw.fi/vmdb2/tree/README) of `vmdb2`:
 
 	```shell
@@ -53,8 +57,9 @@ want to use:
 - Testing is, however, constantly changing. You might want to choose a
   specific point in its history to build with. To do this, locate the
   line with `qemu-debootstrap: buster` in `raspi3.yaml`. Change
-  `mirror: http://deb.debian.org/debian` to `mirror:
+  `mirror: http://deb.debian.org/debian` to a known-good point in
-  http://snapshot.debian.org/archive/debian/20171007T213914Z/`. 
+  time. One such point can be `mirror:
+  https://snapshot.debian.org/archive/debian/20181204T164956Z/ `.
     - Due to a
       [missing feature](https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=763419)
       on snapshots, to make the build work, you have to disable an
@@ -63,15 +68,7 @@ want to use:
       Acquire::Check-Valid-Until=false`
 
 Once you have edited raspi3.yaml, you can generate the image by
-issuing the following. If you are using the systemwide `vmdb2`:
+issuing the following:
-
-```shell
-umask 022
-sudo env -i LC_CTYPE=C.UTF-8 PATH="/usr/sbin:/sbin:$PATH" \
-    vmdb2 --output raspi3.img raspi3.yaml --log raspi3.log
-```
-
-Or, if you are using it from the submodule in this repository
 
 ```shell
 umask 022
@@ -83,7 +80,10 @@ sudo env -i LC_CTYPE=C.UTF-8 PATH="/usr/sbin:/sbin:$PATH" \
 
 Plug an SD card which you would like to entirely overwrite into your SD card reader.
 
-Assuming your SD card reader provides the device `/dev/sdb`, copy the image onto the SD card:
+Assuming your SD card reader provides the device `/dev/sdb`
+(**Beware** If you choose the wrong device, you might overwrite
+important parts of your system.  Double check it's the correct
+device!), copy the image onto the SD card:
 
 ```shell
 sudo dd if=raspi3.img of=/dev/sdb bs=64k oflag=dsync status=progress
@@ -91,7 +91,9 @@ sudo dd if=raspi3.img of=/dev/sdb bs=64k oflag=dsync status=progress
 
 Then, plug the SD card into the Raspberry Pi 3 and power it up.
 
-The image uses the hostname `rpi3`, so assuming your local network correctly resolves hostnames communicated via DHCP, you can log into your Raspberry Pi 3 once it booted:
+The image uses the hostname `rpi3`, so assuming your local network
+correctly resolves hostnames communicated via DHCP, you can log into
+your Raspberry Pi 3 once it booted:
 
 ```shell
 ssh root@rpi3