Containerfile: cache dnf folder

Containerfile

@@ -1,9 +1,17 @@
 FROM quay.io/fedora/fedora-bootc:44
 
 # Install ZFS
-RUN dnf install -y kernel-devel-$(uname -r | awk -F'-' '{print $1}')
-RUN dnf install -y https://zfsonlinux.org/fedora/zfs-release-3-1$(rpm --eval "%{dist}").noarch.rpm
-RUN dnf install -y zfs
+# we want to keep ALL dnf downloaded packages in dnf cache,
+# this is not the default, hackily add it to the config,
+# assume there is not much in it. should be improved
+RUN echo 'keepcache=True' >> /etc/dnf/dnf.conf
+
+# deps
+RUN --mount=type=cache,target=/var/cache/libdnf5 <<EOF
+# dnf install -y kernel-devel-$(uname -r | awk -F'-' '{print $1}')
+dnf install -y https://zfsonlinux.org/fedora/zfs-release-3-1$(rpm --eval "%{dist}").noarch.rpm
+dnf install -y zfs
+EOF
 
 RUN useradd -m -d /var/home/backup -G wheel backup
 ARG PASSWORD