+set -eE -o pipefail
+trap 'echo "$0:$LINENO:error: \"$BASH_COMMAND\" returned $?" >&2' ERR
+
+[[ $EUID == 0 ]] || exec sudo -E "${BASH_SOURCE[0]}" "$@"
+
+dest=/root/.ssh
+
+# leftover
+if [[ -L $dest ]]; then
+ rm $dest
+fi
+mkdir -p $dest
+chmod 700 $dest
+
+user=$(id -un)
+if [[ $SUDO_USER ]]; then
+ user=$SUDO_USER
+fi
+
+user_ssh_dir=$(eval echo ~$user)/.ssh
+if [[ ! -s $user_ssh_dir/authorized_keys ]]; then
+ echo missing $user_ssh_dir/authorized_keys. bad sign. bailing >&2
+ exit 1
+fi
+
+# remove broken links, or else rsync has error about them.
+find $user_ssh_dir -xtype l -exec rm '{}' \;
+# -t times, so it won't rewrite the file every time,
+# -L resolve links
+rsync -rtL --delete $user_ssh_dir/ $dest
+chown -R root:root /root/.ssh
+
+
+d=/etc/initramfs-tools
+if [[ -e $d ]] && ! diff -q /root/.ssh/authorized_keys $d/root/.ssh/authorized_keys &>/dev/null; then
+ mkdir -p $d/root/.ssh /etc/dropbear-initramfs
+ chmod 700 $d/root $d/root/.ssh
+ cp -p /root/.ssh/authorized_keys $d/root/.ssh/authorized_keys
+ cp -p /root/.ssh/authorized_keys /etc/dropbear-initramfs
+ update-initramfs -u -k all