chmod during build, chown with check

build/root/install.sh

@@ -54,13 +54,29 @@ done
 # convert comma separated string of install paths to space separated, required for chmod/chown processing
 install_paths=$(echo "${install_paths}" | tr ',' ' ')
 
+# set permissions for container during build - Do NOT double quote variable for install_paths otherwise this will wrap space separated paths as a single string
+chmod -R 775 ${install_paths}
+
 # create file with contents of here doc, note EOF is NOT quoted to allow us to expand current variable 'install_paths'
 # we use escaping to prevent variable expansion for PUID and PGID, as we want these expanded at runtime of init.sh
-# note - do NOT double quote variable for install_paths otherwise this will wrap space separated paths as a single string
 cat <<EOF > /tmp/permissions_heredoc
-# set permissions inside container
-chown -R "\${PUID}":"\${PGID}" ${install_paths}
-chmod -R 775 ${install_paths}
+
+# get previous puid/pgid (if first run then will be empty string)
+previous_puid=$(cat "/tmp/puid" 2>/dev/null)
+previous_pgid=$(cat "/tmp/pgid" 2>/dev/null)
+
+# if first run (no puid or pgid files in /tmp) or the PUID or PGID env vars are different 
+# from the previous run then re-apply chown with current PUID and PGID values.
+if [[ ! -f "/tmp/puid" || ! -f "/tmp/pgid" || "\${previous_puid}" != "\${PUID}" || "\${previous_pgid}" != "\${PGID}" ]]; then
+
+	# set permissions inside container - Do NOT double quote variable for install_paths otherwise this will wrap space separated paths as a single string
+	chown -R "\${PUID}":"\${PGID}" ${install_paths}
+
+fi
+
+# write out current PUID and PGID to files in /tmp (used to compare on next run)
+echo "\${PUID}" > /tmp/puid
+echo "\${PGID}" > /tmp/pgid
 
 EOF