add systemd unit file

Update the spec file with the rpm macro to put the unit file
in the system-wide unit file directory based on:

    [root@1713bbf19a0b /]# rpmbuild --eval '%{_unitdir}'
    /usr/lib/systemd/system

Allow user to create a drop directory to specify options
via environment variables.

Resolves https://github.com/purpleidea/mgmt/issues/12.

README.md

@@ -25,6 +25,28 @@ If you have a well phrased question that might benefit others, consider asking i
 ## Examples:
 Please look in the [examples/](examples/) folder for more examples!
 
+## Systemd:
+See [`misc/mgmt.service`](misc/mgmt.service) for a sample systemd unit file.
+This unit file is part of the RPM.
+
+To specify your custom options for `mgmt` on a systemd distro:
+
+```bash
+sudo mkdir -p /etc/systemd/system/mgmt.service.d/
+
+cat > /etc/systemd/system/mgmt.service.d/env.conf <<EOF
+# Environment variables:
+MGMT_SEED_ENDPOINT=http://127.0.0.1:2379
+MGMT_CONVERGED_TIMEOUT=-1
+MGMT_MAX_RUNTIME=0
+
+# Other CLI options if necessary.
+#OPTS="--max-runtime=0"
+EOF
+
+sudo systemctl daemon-reload
+```
+
 ## Documentation:
 Please see: [DOCUMENTATION.md](DOCUMENTATION.md) or [PDF](https://pdfdoc-purpleidea.rhcloud.com/pdf/https://github.com/purpleidea/mgmt/blob/master/DOCUMENTATION.md).
 

TODO.md

@@ -40,7 +40,6 @@ Let us know if you're working on one of the items.
 ## Other
 - [ ] implement noop functionality [bug](https://github.com/purpleidea/mgmt/issues/21) [:heart:](https://github.com/purpleidea/mgmt/labels/mgmtlove)
 - [ ] better error/retry handling
-- [ ] mgmt systemd service file [bug](https://github.com/purpleidea/mgmt/issues/12) [:heart:](https://github.com/purpleidea/mgmt/labels/mgmtlove)
 - [ ] deb package target in Makefile
 - [ ] reproducible builds
 - [ ] add your suggestions!

misc/mgmt.service

@@ -0,0 +1,13 @@
+[Unit]
+Description=Run mgmt configuration management
+Documentation=https://github.com/purpleidea/mgmt/
+After=systemd-networkd.service
+Requires=systemd-networkd.service
+
+[Service]
+ExecStart=/usr/bin/mgmt run ${OPTS}
+RestartSec=5s
+Restart=always
+
+[Install]
+WantedBy=multi-user.target

spec.in

@@ -40,6 +40,8 @@ rm -rf %{buildroot}
 # _datadir is typically /usr/share/
 install -d -m 0755 %{buildroot}/%{_datadir}/__PROGRAM__/
 cp -a AUTHORS COPYING COPYRIGHT DOCUMENTATION.md README.md THANKS examples/ %{buildroot}/%{_datadir}/__PROGRAM__/
+mkdir -p %{buildroot}/%{_unitdir}/
+install -pm 0644 misc/__PROGRAM__.service %{buildroot}/%{_unitdir}/
 
 # install the binary
 mkdir -p %{buildroot}/%{_bindir}
@@ -58,6 +60,7 @@ install -m 0644 misc/example.conf %{buildroot}%{_sysconfdir}/__PROGRAM__/__PROGR
 %{_datadir}/__PROGRAM__/*
 %{_bindir}/__PROGRAM__
 %{_sysconfdir}/__PROGRAM__/*
+%{_unitdir}/__PROGRAM__.service
 
 # this changelog is auto-generated by git log
 %changelog