fix: use ln -sf instead of update-alternatives --set

update-alternatives fails because iptables-nft isn't registered
as an alternative key (only iptables-legacy was registered by
the official Dockerfile). Direct symlink override works.

vpn/Dockerfile

@@ -2,8 +2,8 @@
 # Fixes crash-loop when host kernel lacks legacy iptable_nat module.
 FROM ghcr.io/wg-easy/wg-easy:latest
 
-# The upstream image defaults to iptables-legacy via update-alternatives.
+# The upstream image registers only iptables-legacy with update-alternatives.
-# Switch iptables to the nftables backend (already provided by the 'iptables'
+# iptables-nft binary exists but isn't registered as an alternative.
-# package on Alpine 3.18+). No apk add needed — iptables-nft is built-in.
+# Override the alternatives-managed symlinks directly.
-RUN update-alternatives --set iptables /usr/sbin/iptables-nft && \
+RUN ln -sf /usr/sbin/iptables-nft /usr/sbin/iptables && \
-    update-alternatives --set ip6tables /usr/sbin/ip6tables-nft
+    ln -sf /usr/sbin/ip6tables-nft /usr/sbin/ip6tables