diff --git a/readme.md b/readme.md
index 0fa11f1..a42983a 100644
--- a/readme.md
+++ b/readme.md
@@ -45,6 +45,7 @@ from various contexts of CA, CI and OCI / OS.
 | SPCD_BRANCH_STAGING | Staging deployment branch | dev                             |
 | SPCD_BRANCH_FEATURE | Feature deployment branch | f                               |
 | SPCD_CA_n           | Numbered CA certificates  |                                 |
+| SPCD_CMD_SUM        | Command to check sums     | sha512sum                       |
 | SPCD_DNS_n          | Numbered name servers     | 9.9.9.9                         |
 | SPCD_GIT_MAIN       | Main Git repository       | spcd                            |
 | SPCD_GIT_ROOT       | Root Git repository       | rwx                             |
@@ -87,11 +88,16 @@ from various contexts of CA, CI and OCI / OS.
 * relay environment module name
 * write tests
 
-### .py
+### sh
 
-* detect ssh private key type
-* implement project repository cloning
-* install
+* support
+  * arch python virtual environment
+  * opensuse operating system
+
+### sh → py
+
+* check file & variable sums
+* install system packages
   * epel
     * plantuml
     * shellcheck
@@ -99,10 +105,17 @@ from various contexts of CA, CI and OCI / OS.
   * openssh
   * rsync
   * shfmt
+* python virtual environment
+  * install system package
+  * configure pip
+  * venv
+    * create
+    * activate
+
+### py
+
+* detect ssh private key type
+* implement project repository cloning
 * lint
   * .py
   * .sh
-
-### .sh
-
-* support opensuse
diff --git a/spcd.sh b/spcd.sh
index a48ff51..7557cd7 100644
--- a/spcd.sh
+++ b/spcd.sh
@@ -4,6 +4,7 @@
 [ -n "${SPCD_BRANCH_RELEASE}" ] || SPCD_BRANCH_RELEASE="main"
 [ -n "${SPCD_BRANCH_STAGING}" ] || SPCD_BRANCH_STAGING="dev"
 [ -n "${SPCD_BRANCH_FEATURE}" ] || SPCD_BRANCH_FEATURE="f"
+[ -n "${SPCD_CMD_SUM}" ] || SPCD_CMD_SUM="sha512sum"
 [ -n "${SPCD_DNS_1}" ] || SPCD_DNS_1="9.9.9.9"
 [ -n "${SPCD_GIT_MAIN}" ] || SPCD_GIT_MAIN="spcd"
 [ -n "${SPCD_GIT_ROOT}" ] || SPCD_GIT_ROOT="rwx"
@@ -32,7 +33,6 @@ spcd_main() {
     spcd_install_git
     spcd_install_python
     spcd_install_python_modules
-    # TODO move to Python
     spcd_install_packages
     spcd_write_python_module
     spcd_switch_to_python
@@ -605,6 +605,28 @@ spcd_install_python() {
     spcd_install_package "${SPCD_PYTHON_PACKAGE}"
     spcd_split
     spcd_ln_python "${SPCD_PYTHON_COMMAND}"
+    # venv
+    spcd_step "Install Python virtual environment"
+    case "${SPCD_OS_ID}" in
+    "${SPCD_OS_DEBIAN}" | "${SPCD_OS_UBUNTU}")
+        spcd_install_package "python3-venv"
+        ;;
+    "${SPCD_OS_ARCH}")
+        echo "Not supported!"
+        exit 255
+        ;;
+    *) ;;
+    esac
+    spcd_split
+    spcd_write "/etc/pip.conf" "\
+[global]
+index-url = ${SPCD_URL_PYTHON}
+"
+    spcd_split
+    "${SPCD_PYTHON_ALIAS}" -m "venv" "${SPCD_PYTHON_VENV}"
+    spcd_split
+    export PATH="${SPCD_PYTHON_VENV_BINARIES}:${PATH}"
+    export VIRTUAL_ENV="${SPCD_PYTHON_VENV}"
 }
 
 spcd_install_python_modules() {
@@ -639,13 +661,13 @@ ${spcd_ipm__target}"
         spcd_ipm__script="${spcd_ipm__root}/${spcd_ipm__name}/spcd.sh"
         if [ -f "${spcd_ipm__script}" ]; then
             spcd_split
-            spcd_ipm__check="${spcd_ipm__root}/check.sha512sum"
-            sha512sum "${spcd_ipm__script}" >"${spcd_ipm__check}"
+            spcd_ipm__check="${spcd_ipm__root}/check.${SPCD_CMD_SUM}"
+            "${SPCD_CMD_SUM}" "${spcd_ipm__script}" >"${spcd_ipm__check}"
             printf "%s" "${SPCD}" >"${spcd_ipm__script}"
             ls -l "${spcd_ipm__script}"
             dos2unix "${spcd_ipm__script}"
             ls -l "${spcd_ipm__script}"
-            sha512sum -c "${spcd_ipm__check}" || spcd_error_ci "SPCD"
+            "${SPCD_CMD_SUM}" -c "${spcd_ipm__check}" || spcd_error_ci "SPCD"
         fi
     done
     spcd_split
@@ -654,7 +676,6 @@ ${spcd_ipm__target}"
     spcd_rm "${spcd_ipm__root}"
 }
 
-# TODO move to Python
 spcd_install_packages() {
     # epel
     spcd_step "Install EPEL"
@@ -704,28 +725,6 @@ spcd_install_packages() {
     "${SPCD_PM_PACMAN}") spcd_install_package "openssh" ;;
     *) ;;
     esac
-    # venv
-    spcd_step "Install Python virtual environment"
-    case "${SPCD_OS_ID}" in
-    "${SPCD_OS_DEBIAN}" | "${SPCD_OS_UBUNTU}")
-        spcd_install_package "python3-venv"
-        ;;
-    "${SPCD_OS_ARCH}")
-        # FIXME arch
-        exit 255
-        ;;
-    *) ;;
-    esac
-    spcd_split
-    spcd_write "/etc/pip.conf" "\
-[global]
-index-url = ${SPCD_URL_PYTHON}
-"
-    spcd_split
-    "${SPCD_PYTHON_ALIAS}" -m "venv" "${SPCD_PYTHON_VENV}"
-    spcd_split
-    export PATH="${SPCD_PYTHON_VENV_BINARIES}:${PATH}"
-    export VIRTUAL_ENV="${SPCD_PYTHON_VENV}"
 }
 
 spcd_write_python_module() {