Provide systemd unit file in .deb and .rpm packages (#4478)

Closes #2287.

Co-authored-by: Alexander Tobi Fashakin <fashakinalexander@gmail.com>
Co-authored-by: Alexey Palazhchenko <alexey.palazhchenko@ferretdb.io>

build/ferretdb.service

@@ -0,0 +1,17 @@
+[Unit]
+Description=FerretDB Database
+Documentation=https://docs.ferretdb.io/
+Wants=network-online.target
+After=network-online.target
+
+[Service]
+ExecStart=/usr/bin/ferretdb
+Restart=on-failure
+
+# Configure the FerretDB service with `systemctl edit ferretdb`.
+# For more configuration options check https://docs.ferretdb.io/configuration/flags/
+
+Environment="FERRETDB_POSTGRESQL_URL=postgres://127.0.0.1:5432/ferretdb"
+
+[Install]
+WantedBy=multi-user.target

build/nfpm.yml

@@ -20,3 +20,5 @@ contents:
   - src: tmp/build/linux_${DIR_ARCH}/ferretdb
     dst: /usr/bin/ferretdb
     expand: true
+  - src: build/ferretdb.service
+    dst: /etc/systemd/system/ferretdb.service

website/docs/quickstart-guide/deb.md

@@ -29,8 +29,8 @@ sudo apt update
 sudo apt install -y postgresql
 ```
 
-Currently, our `.deb` package does not provide a SystemD unit for starting FerretDB automatically.
-You have to do it manually by running `ferretdb` binary with the [correct flags](../configuration/flags.md).
+The `.deb` package ships with the systemd unit for starting FerretDB automatically.
+For more information about its configuration, please take a look at [systemd configuration guide](./systemd.md).
 
 Find out more about:
 

website/docs/quickstart-guide/go.md

@@ -1,5 +1,5 @@
 ---
-sidebar_position: 6
+sidebar_position: 7
 ---
 
 # Go

website/docs/quickstart-guide/macos.md

@@ -1,5 +1,5 @@
 ---
-sidebar_position: 4
+sidebar_position: 5
 ---
 
 # macOS

website/docs/quickstart-guide/rpm.md

@@ -28,8 +28,8 @@ To install PostgreSQL, run the following commands:
 sudo yum install -y postgresql
 ```
 
-Currently, our `.rpm` package does not provide a SystemD unit for starting FerretDB automatically.
-You have to do it manually by running `ferretdb` binary with the [correct flags](../configuration/flags.md).
+The `.rpm` package ships with the systemd unit for starting FerretDB automatically.
+For more information about its configuration, please take a look at [systemd configuration guide](./systemd.md).
 
 Find out more about:
 

website/docs/quickstart-guide/systemd.md

@@ -0,0 +1,43 @@
+---
+sidebar_position: 4
+---
+
+# Systemd Unit
+
+:::note
+This feature is still experimental.
+If you encounter any problem, please [join our community](/#community) to report it.
+:::
+
+With both DEB and RPM package we ship the systemd unit, to start FerretDB automatically.
+If FerretDB is not installed yet, please refer to the [`.deb`](https://docs.ferretdb.io/quickstart-guide/deb/) or [`.rpm`](https://docs.ferretdb.io/quickstart-guide/rpm/) installation pages.
+
+The unit file provides some basic environment variables as an example.
+They should be overwritten with the proper [configuration](../configuration/flags.md).
+
+```systemd
+[Service]
+ExecStart=/usr/bin/ferretdb
+Restart=on-failure
+
+# Configure the FerretDB service with `systemctl edit ferretdb`.
+# For more configuration options check https://docs.ferretdb.io/configuration/flags/
+
+Environment="FERRETDB_POSTGRESQL_URL=postgres://127.0.0.1:5432/ferretdb"
+```
+
+You can modify them by using `systemctl edit ferretdb` command.
+This'll open a text editor that'll allow you to override the systemd options of choice.
+For example, if we want to use SQLite backend instead of PostgreSQL, we could write something like:
+
+```systemd
+### Editing /etc/systemd/system/ferretdb.service.d/override.conf
+### Anything between here and the comment below will become the new contents of the file
+
+[Service]
+Environment="FERRETDB_SQLITE_URL=file:/var/lib/ferretdb/data/"
+Environment="FERRETDB_HANDLER=sqlite"
+
+### Lines below this comment will be discarded
+...
+```

website/docs/quickstart-guide/windows.md

@@ -1,5 +1,5 @@
 ---
-sidebar_position: 5
+sidebar_position: 6
 ---
 
 # Windows

website/docusaurus.config.js

@@ -152,7 +152,7 @@ const config = {
       prism: {
         theme: themes.github,
         darkTheme: themes.dracula,
-        additionalLanguages: ['go', 'sql', 'json', 'json5'],
+        additionalLanguages: ['go', 'sql', 'json', 'json5', 'systemd'],
       },
       mermaid: {
         theme: {light: 'default', dark: 'dark'},