Improve documentation of reproducibility of /etc/resolv.conf and /etc/hostname

Closes: #26

mmdebstrap

@@ -6763,7 +6763,25 @@ Performs cleanup tasks, unless B<--skip=cleanup> is used:
 
 =item * Remove all files that were put into the chroot for setup purposes, like F</etc/apt/apt.conf.d/00mmdebstrap>, the temporary apt config and the qemu-user-static binary. This can be disabled using B<--skip=cleanup/mmdebstrap>.
 
-=item * Remove all files that make the result unreproducible, like apt and dpkg logs and caches or F</etc/machine-id> and F</var/lib/dbus/machine-id>. This can be disabled using B<--skip=cleanup/reproducible>
+=item * Remove files that make the result unreproducible and write "uninitialized" to /etc/machine-id if it exists. This can be disabled using B<--skip=cleanup/reproducible>. Note that this will not remove files that make the result unreproducible on machines with differing F</etc/resolv.conf> or F</etc/hostname>. Use a B<--customize-hook> to make those two files reproducible across multiple hosts. See section C<SOURCE_DATE_EPOCH> for more information. The following files will be removed:
+
+=over 4
+
+=item * F</var/log/dpkg.log>
+
+=item * F</var/log/apt/history.log>
+
+=item * F</var/log/apt/term.log>
+
+=item * F</var/log/alternatives.log>
+
+=item * F</var/cache/ldconfig/aux-cache>
+
+=item * F</var/log/apt/eipp.log.xz>
+
+=item * F</var/lib/dbus/machine-id>
+
+=back
 
 =item * Remove everything in F</tmp> inside the chroot. This can be disabled using B<--skip=cleanup/tmp>.
 
@@ -6978,8 +6996,21 @@ As a docker/podman replacement:
 
 =item C<SOURCE_DATE_EPOCH>
 
-By setting C<SOURCE_DATE_EPOCH> the result will be reproducible over multiple
-runs with the same options and mirror content.
+By setting C<SOURCE_DATE_EPOCH> the result will be reproducible across multiple
+runs with the same options and mirror content. Note that for debootstrap
+compatibility, B<mmdebstrap> will copy the host's F</etc/resolv.conf> and
+F</etc/hostname> into the chroot. This means that the B<mmdebstrap> output will
+differ if it is run on machines with differing F</etc/resolv.conf> and
+F</etc/hostname> contents. To make the result reproducible across different
+hosts, you need to manually either delete both files from the output:
+
+    $ mmdebstrap --customize-hook='rm "$1"/etc/resolv.conf' \
+                 --customize-hook='rm "$1"/etc/hostname' ...
+
+or fill them with reproducible content:
+
+    $ mmdebstrap --customize-hook='echo nameserver X > "$1"/etc/resolv.conf' \
+                 --customize-hook='echo host > "$1"/etc/hostname' ...
 
 =item C<TMPDIR>