diff --git a/spcd/bootstrap.sh b/spcd/bootstrap.sh
index a9708b5..e9f6c6b 100644
--- a/spcd/bootstrap.sh
+++ b/spcd/bootstrap.sh
@@ -620,6 +620,8 @@ spcd_step__environment_defaults() {
     [ -n "${SPCD_REF_STAGING}" ] || SPCD_REF_STAGING="dev"
 
     [ -n "${SPCD_URL_ALMA}" ] ||
+        # /almalinux/$releasever/…
+        # /vault/$releasever/…
         SPCD_URL_ALMA="https://repo.almalinux.org"
     [ -n "${SPCD_URL_ALPINE}" ] ||
         SPCD_URL_ALPINE="https://dl-cdn.alpinelinux.org/alpine"
@@ -630,12 +632,16 @@ spcd_step__environment_defaults() {
     [ -n "${SPCD_URL_EPEL}" ] ||
         SPCD_URL_EPEL="https://dl.fedoraproject.org"
     [ -n "${SPCD_URL_FEDORA}" ] ||
+        # /releases/$releasever/Everything/…
+        # /updates/$releasever/Everything/…
+        # /updates/testing/$releasever/Everything/…
         SPCD_URL_FEDORA="https://rpmfind.net/linux/fedora/linux"
     [ -n "${SPCD_URL_OPENSUSE}" ] ||
         SPCD_URL_OPENSUSE="https://download.opensuse.org"
     [ -n "${SPCD_URL_PYTHON}" ] ||
         SPCD_URL_PYTHON="https://pypi.org/simple"
     [ -n "${SPCD_URL_ROCKY}" ] ||
+        # /$contentdir/$releasever/…
         SPCD_URL_ROCKY="https://dl.rockylinux.org"
     [ -n "${SPCD_URL_UBUNTU}" ] ||
         SPCD_URL_UBUNTU="https://ubuntu.mirrors.ovh.net/ubuntu"
@@ -852,6 +858,7 @@ deb ${SPCD_URL_DEBIAN}-security ${SPCD_OS_VERSION}-security main
                 "rocky-extras"
             ;;
         "8")
+            # not Rocky-Media
             set -- \
                 "Rocky-AppStream" \
                 "Rocky-BaseOS" \