-[1] Please notice that lenny is an unsupported release within Debian nowadays.
-grml-debootstrap can handle the release but you really should not use lenny
-anymore unless you really know what you are doing. Choose Debian 8.0 (jessie) or
-something newer instead.
+[1] Please notice that releases like lenny, squeeze, wheezy, jessie, stretch and buster are unsupported releases within Debian nowadays.
+grml-debootstrap can handle the releases but you really should not use them
+anymore unless you really know what you are doing.
+Choose the current Debian stable version instead.
+See https://wiki.debian.org/DebianReleases for the list of supported releases.
+
+Notice that you need to specify a specific mirror providing old releases, the default (http://deb.debian.org/debian) doesn't provide them any longer.
+Set the mirror to e.g. http://archive.debian.org/debian/ if you don't have your own Debian mirror.
+
+Older releases might also fail to install when running on top of recent kernel versions,
+throwing segfaults during debootstrap. This can be identified by the following messages inside kernel log (check with 'dmesg'):
+
+ dpkg[...] vsyscall attempted with vsyscall=none ip:[...]
+ dpkg[...]: segfault at [...]