Improves documentation

 * Describes better available source tree sharing method (between
xds-agent and xds-server), and which to prefer depending on the
deployment setup.
 * Gives indication about how to pass RSYNC_TARGET and RSYNC_PREFIX
 env vars to the helloworld-native-application build process.
 * Swap chapter order (build before config)

Bug: SPEC-1993

Change-Id: Ie4c22f277a59b0405744d71b0fadff67c5d5d025
Signed-off-by: Sebastien Douheret <sebastien.douheret@iot.bzh>

1 files changed, 52 insertions, 0 deletions

diff --git a/docs/part-2/2_xds-agent/3_start.md b/docs/part-2/2_xds-agent/3_start.md
new file mode 100644
index 0000000..d750fac
--- /dev/null
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+# Start-up
+
+## Start-up based on systemd user service
+
+For **Linux** distro, XDS agent can be started as a user service by Systemd.
+
+```bash
+/usr/lib/systemd/user/xds-agent.service
+```
+
+Use well-known systemd commands to control `xds-agent.service` service.
+
+```bash
+# Status XDS agent:
+systemctl --user status xds-agent
+
+# Start XDS agent
+systemctl --user start xds-agent
+
+# Stop XDS agent
+systemctl --user stop xds-agent
+```
+
+Default settings are defined in  `/etc/default/xds-agent` file but these
+settings you can overwritten by `$HOME/.xds/agent/agent-config.json` file,
+see [Configuration chapter](./2_config.html) for more details.
+
+## Manual start-up
+
+On **Linux or MacOS**, simply execute `xds-agent` executable:
+
+```bash
+/opt/AGL/bin/xds-agent
+```
+
+On **Windows**, simply execute `xds-agent` executable (root path may change
+depending where you installed/unzipped xds-agent tarball):
+
+```batch
+C:\AGL\bin\xds-agent.exe
+```
+
+<!-- section-note -->
+**Note:**
+
+If need be, you can increase log level by setting option
+`--log <level>`, supported *level* are: panic, fatal, error, warn, info, debug.
+
+Invoke `xds-agent --help` to get more details about possible options that allow
+for example to change logging level or select a specific configuration file.
+
+<!-- end-section-note -->