fix(lxc): auto-derive privileged from NFS fileSystems, not hostname list

Replace the hardcoded hostname check (docker, pxe-boot) with a check
on config.fileSystems: any lxc-* host whose NixOS config declares an
NFS fileSystem entry is automatically made privileged. The script
already reads proxmoxLXC.privileged dynamically via
flake_target_lxc_privileged, so no logic change is needed there —
only the comment is updated to describe the new derivation.

Result: lxc-docker and lxc-pxe-boot (the two with NFS mounts) evaluate
as privileged=true; lxc-nix-cache, lxc-minimal, lxc-server,
lxc-tailscale-router, lxc-tor-relay evaluate as privileged=false.
Any future lxc-* host that declares an NFS mount gets the correct
privilege level for free without a separate manual edit.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

modules/platforms/lxc.nix

@@ -63,25 +63,22 @@ in
     # back to decide `pct create`'s --unprivileged flag, so the two stay
     # in sync).
     #
-    # lxc-docker and lxc-pxe-boot are the exceptions: the kernel's NFS client
-    # doesn't set FS_USERNS_MOUNT, so mounting NFS from inside *any* non-init
-    # user namespace -- which is exactly what an unprivileged container's
-    # UID-mapped root runs in -- is rejected at the VFS layer with EPERM,
-    # no matter what Proxmox's own `mount=nfs;nfs4` container feature
-    # allows at the AppArmor layer (confirmed live: TCP to the NFS server
-    # succeeds, the server's export table matches the container's IP, and
-    # `mount.nfs: Operation not permitted` still fires immediately with no
-    # corresponding denial anywhere in the server's logs -- a kernel-level
-    # rejection, not a network or export-permission one). Keying off
-    # hostName rather than something build-type-specific because
-    # modules/build-types/{docker,pxe-boot}.nix are also composed for
-    # linode-docker/proxmox-docker/proxmox-pxe-boot, which don't import
-    # proxmox-lxc.nix at all -- setting this option there would break their
-    # eval with "option does not exist" regardless of any mkIf guard, since
-    # mkIf only makes a value conditional, not whether the option needs to
-    # exist somewhere.
-    privileged = config.networking.hostName == "docker"
-      || config.networking.hostName == "pxe-boot";
+    # Any lxc-* host with an NFS fileSystem must be privileged: the kernel's
+    # NFS client doesn't set FS_USERNS_MOUNT, so mounting NFS from inside
+    # *any* non-init user namespace -- which is exactly what an unprivileged
+    # container's UID-mapped root runs in -- is rejected at the VFS layer
+    # with EPERM, no matter what Proxmox's own `mount=nfs;nfs4` container
+    # feature allows at the AppArmor layer (confirmed live: TCP to the NFS
+    # server succeeds, the server's export table matches the container's IP,
+    # and `mount.nfs: Operation not permitted` still fires immediately with
+    # no corresponding denial anywhere in the server's logs -- a kernel-level
+    # rejection, not a network or export-permission one). Deriving this from
+    # fileSystems rather than a per-host override keeps it self-consistent:
+    # any new lxc-* host that declares an NFS mount automatically gets the
+    # privilege level it needs without a separate manual flag.
+    privileged = builtins.any
+      (fs: fs.fsType == "nfs" || fs.fsType == "nfs4")
+      (builtins.attrValues config.fileSystems);
   };
 
   boot.loader = {

scripts/proxmox/create-proxmox-resource.sh

@@ -867,17 +867,17 @@ if [[ "$type" == "lxc" ]]; then
   local_swap="${swap:-$memory}"
   # --unprivileged: read back from modules/platforms/lxc.nix's own
   # proxmoxLXC.privileged (via flake_target_lxc_privileged) rather than
-  # hardcoded, since that's no longer the same for every lxc-* target --
-  # lxc-docker sets it true so the container's NFS mounts work at all (the
-  # kernel's NFS client can't mount from inside any unprivileged
-  # container's user namespace, no matter what AppArmor allows -- see that
-  # option's own comment). The NixOS config inside the image bakes in
-  # cgroup/capability/mount expectations matching whichever value it was
-  # built with, so this must stay in sync with it -- `pct create`'s own
-  # CLI default for this flag is privileged (unlike the web UI, which
-  # defaults its checkbox the other way), so leaving it unset would create
-  # a privileged container running a NixOS config that assumes
-  # unprivileged for every target except lxc-docker, a real mismatch.
+  # hardcoded. lxc.nix derives this automatically: any lxc-* host whose
+  # config.fileSystems has an NFS entry gets privileged=true, because the
+  # kernel's NFS client (FS_USERNS_MOUNT not set) rejects NFS mounts from
+  # inside any non-init user namespace -- exactly what an unprivileged
+  # container's UID-mapped root lives in -- with EPERM at the VFS layer,
+  # regardless of AppArmor (see lxc.nix's own comment). The NixOS config
+  # bakes in cgroup/capability/mount expectations matching whichever value
+  # it was built with, so this must stay in sync -- `pct create`'s CLI
+  # default is privileged (unlike the web UI, which defaults the other
+  # way), so leaving it unset would create a privileged container running
+  # a NixOS config that assumes unprivileged, a real mismatch.
   privileged_eval="$(flake_target_lxc_privileged "$repo_root" "$flake_target")"
   unprivileged_flag=1
   [[ "$privileged_eval" == "true" ]] && unprivileged_flag=0