Only protect two kernels, not last installed one

The kernel autoremoval algorithm was written to accomodate
for Ubuntu's boot partition sizing, which was written to
accomodate 3 kernels - 2 installed ones + a new one being
unpacked.

It seems that when the algorithm was designed, it was overlooked
that it actually kept 3 kernels.

LP: #1968154

4 files changed, 6 insertions, 17 deletions

diff --git a/debian/apt.auto-removal.sh b/debian/apt.auto-removal.sh
deleted file mode 100644
index eef550a53..000000000
--- a/debian/apt.auto-removal.sh
+++ /dev/null
@@ -1,16 +0,0 @@
-#!/bin/sh
-set -e
-
-eval $(apt-config shell APT_CONF_D Dir::Etc::parts/d)
-test -n "${APT_CONF_D}" || APT_CONF_D="/etc/apt/apt.conf.d"
-config_file="${APT_CONF_D}/01autoremove-kernels"
-
-generateconfig() {
-	cat <<EOF
-// DO NOT EDIT! File autogenerated by $0
-APT::LastInstalledKernel "$1";
-EOF
-}
-generateconfig "$@" > "${config_file}.dpkg-new"
-mv -f "${config_file}.dpkg-new" "$config_file"
-chmod 444 "$config_file"
diff --git a/debian/apt.maintscript b/debian/apt.maintscript
index 296f83bd5..f37a9e27a 100644
--- a/debian/apt.maintscript
+++ b/debian/apt.maintscript
@@ -1,3 +1,4 @@
 rm_conffile /etc/apt/apt.conf.d/20changelog 1.2.4~
 # we use a systemd timer unit now
 rm_conffile /etc/cron.daily/apt 1.2.10~
+rm_conffile /etc/kernel/postinst.d/apt-auto-removal 2.4.5~
diff --git a/debian/apt.postinst b/debian/apt.postinst
index 837b46b7b..8a623f2fd 100755
--- a/debian/apt.postinst
+++ b/debian/apt.postinst
@@ -7,4 +7,9 @@ if [ "$1" = 'configure' ]; then
 	    --no-create-home --quiet _apt || true
 fi
 
+if [ "$1" = "configure" ] && [ -n "$2" ] && dpkg --compare-versions -- "$2" le-nl "2.4.5~"; then
+    rm -f /etc/apt/apt.conf.d/01autoremove-kernels
+fi
+
+
 #DEBHELPER#
diff --git a/debian/rules b/debian/rules
index 7997739fa..8a110f7a1 100755
--- a/debian/rules
+++ b/debian/rules
@@ -29,7 +29,6 @@ override_dh_install-arch:
 	dh_install -papt -Xmethods/curl -Xmethods/curl+https -Xmethods/curl+http
 	dh_install --remaining
 	install -m 644 debian/apt.conf.autoremove debian/apt/etc/apt/apt.conf.d/01autoremove
-	install -m 755 debian/apt.auto-removal.sh debian/apt/etc/kernel/postinst.d/apt-auto-removal
 
 override_dh_gencontrol:
 	dh_gencontrol -- -Vapt:keyring="$(shell ./vendor/getinfo keyring-package)"