standard cron

Dockerfile

@@ -68,6 +68,7 @@ ENV PS1="$(whoami)@$(hostname):$(pwd)\\$ " \
 RUN \
   echo "**** install base packages ****" && \
   dnf -y --setopt=install_weak_deps=False --best install \
+    busybox \
     ca-certificates \
     coreutils \
     curl \

Dockerfile.aarch64

@@ -68,6 +68,7 @@ ENV PS1="$(whoami)@$(hostname):$(pwd)\\$ " \
 RUN \
   echo "**** install base packages ****" && \
   dnf -y --setopt=install_weak_deps=False --best install \
+    busybox \
     ca-certificates \
     coreutils \
     curl \

root/etc/s6-overlay/s6-rc.d/init-crontab-config/run

@@ -0,0 +1,26 @@
+#!/usr/bin/with-contenv bash
+# shellcheck shell=bash
+
+for cron_user in abc root; do
+    if [[ -f "/defaults/crontabs/${cron_user}" ]]; then
+        # make folders
+        mkdir -p \
+            /config/crontabs
+
+        # if crontabs do not exist in config
+        if [[ ! -f "/config/crontabs/${cron_user}" ]]; then
+            # copy crontab from system
+            if crontab -l -u "${cron_user}" >/dev/null; then
+                crontab -l -u "${cron_user}" >"/config/crontabs/${cron_user}"
+            fi
+
+            # if crontabs still do not exist in config (were not copied from system)
+            # copy crontab from image defaults (using -n, do not overwrite an existing file)
+            cp -n "/defaults/crontabs/${cron_user}" /config/crontabs/
+        fi
+
+        # set permissions and import user crontabs
+        lsiown "${cron_user}":"${cron_user}" "/config/crontabs/${cron_user}"
+        crontab -u "${cron_user}" "/config/crontabs/${cron_user}"
+    fi
+done

root/etc/s6-overlay/s6-rc.d/init-crontab-config/type

@@ -0,0 +1 @@
+oneshot

root/etc/s6-overlay/s6-rc.d/init-crontab-config/up

@@ -0,0 +1 @@
+/etc/s6-overlay/s6-rc.d/init-crontab-config/run

root/etc/s6-overlay/s6-rc.d/svc-cron/run

@@ -0,0 +1,15 @@
+#!/usr/bin/with-contenv bash
+# shellcheck shell=bash
+
+if builtin command -v crontab >/dev/null && [[ -n "$(crontab -l -u abc)" || -n "$(crontab -l -u root)" ]]; then
+    if builtin command -v busybox >/dev/null && [[ $(busybox) =~ [[:space:]](crond)([,]|$) ]]; then
+        exec busybox crond -f -S -l 5
+    elif [[ -f /usr/bin/apt ]] && [[ -f /usr/sbin/cron ]]; then
+        exec /usr/sbin/cron -f -L 5
+    else
+        echo "**** cron not found ****"
+        sleep infinity
+    fi
+else
+    sleep infinity
+fi

root/etc/s6-overlay/s6-rc.d/svc-cron/type

@@ -0,0 +1 @@
+longrun