Fix how we are handling system services in RPM packages. (#14781)

* Drop non-systemd init code in RPM spec file.

All of our currently supported RPM-based platforms are systemd-based, so
this is functionally dead code.

* Fix how we handle systemd service installation.

- Rely on the platform-provided macros, instead of doing our own thing.
  These do the right thing in 99.99% of cases, and behave how we
  actually need them to.
- Don’t depend on systemd at runtime. The macros handle this correctly,
  and nothing we actually do _needs_ systemd at runtime.
- Actually follow packaging guidelines for upgrades. In particular, only
  restart the agent if it’s already running (instead of unconditionally),
  and don’t enable it if it’s disabled.
- Just put the macro invocations down in the actual scriptlets, instead
  of using complicated nested macro definitions to compute things ahead
  of time. This makes the code _much_ easier to understand.

* Add a systemd preset file so the service is enabled by default.

3 files changed, 13 insertions, 3 deletions

diff --git a/system/Makefile.am b/system/Makefile.am
index 747c6d4e43..13466639d5 100644
--- a/system/Makefile.am
+++ b/system/Makefile.am
@@ -113,6 +113,7 @@ nodist_libsyssystemd_DATA = \
 
 dist_libsyssystemd_DATA = \
     systemd/netdata-updater.timer \
+    systemd/50-netdata.preset
     $(NULL)
 
 dist_noinst_DATA = \
diff --git a/system/install-service.sh.in b/system/install-service.sh.in
index 9a37528c54..a885a8618c 100755
--- a/system/install-service.sh.in
+++ b/system/install-service.sh.in
@@ -237,6 +237,8 @@ get_systemd_service_dir() {
 
 install_systemd_service() {
   SRCFILE="${SVC_SOURCE}/systemd/netdata.service"
+  PRESET_FILE="${SVC_SOURCE}/systemd/50-netdata.preset"
+  SVCDIR="$(get_systemd_service_dir)"
 
   if [ "$(systemctl --version | head -n 1 | cut -f 2 -d ' ')" -le 235 ]; then
     SRCFILE="${SVC_SOURCE}/systemd/netdata.service.v235"
@@ -255,18 +257,24 @@ install_systemd_service() {
   fi
 
   info "Installing systemd service..."
-  if ! install -p -m 0644 -o 0 -g 0 "${SRCFILE}" "$(get_systemd_service_dir)/netdata.service"; then
+  if ! install -p -m 0644 -o 0 -g 0 "${SRCFILE}" "${SVCDIR}/netdata.service"; then
     error "Failed to install systemd service file."
     exit 4
   fi
 
+  if [ -f "${PRESET_FILE}" ]; then
+    if ! install -p -m 0644 -o 0 -g 0 "${PRESET_FILE}" "${SVCDIR}-preset/50-netdata.preset"; then
+      warning "Failed to install netdata preset file."
+    fi
+  fi
+
   if [ "$(check_systemd)" = "YES" ]; then
     if ! systemctl daemon-reload; then
-        warning "Failed to reload systemd unit files."
+      warning "Failed to reload systemd unit files."
     fi
 
     if ! systemctl "${ENABLE}" netdata; then
-        warning "Failed to ${ENABLE} Netdata service."
+      warning "Failed to ${ENABLE} Netdata service."
     fi
   fi
 }
diff --git a/system/systemd/50-netdata.preset b/system/systemd/50-netdata.preset
new file mode 100644
index 0000000000..fe4e5a1977
--- /dev/null
+++ b/system/systemd/50-netdata.preset
@@ -0,0 +1 @@
+enable netdata.service