Improve configuration docs with common changes and start/stop/restart directions (#10415)

* Finish new common config doc, delete old one

* Small tweak to blockquote

* Add new files

* Fix broken links

* Fix one more broken link

* Copyedits and improvements

* Fix broken link

* Re-add common config doc

* service -> systemctl

* Reverse systemctl order

* Add mention of .conf files in health.d

* Add mention of minimum global update every

4 files changed, 377 insertions, 27 deletions

diff --git a/docs/configure/common-changes.md b/docs/configure/common-changes.md
new file mode 100644
index 0000000000..79faae9876
--- /dev/null
+++ b/docs/configure/common-changes.md
@@ -0,0 +1,204 @@
+<!--
+title: "Common configuration changes"
+description: "See the most popular configuration changes to make to the Netdata Agent, including longer metrics retention, reduce sampling, and more."
+custom_edit_url: https://github.com/netdata/netdata/edit/master/docs/configure/common-changes.md
+-->
+
+# Common configuration changes
+
+The Netdata Agent requires no configuration upon installation to collect thousands of per-second metrics from most
+systems, containers, and applications, but there are hundreds of settings to tweak if you want to exercise more control
+over your monitoring platform.
+
+This document assumes familiarity with using [`edit-config`](/docs/configure/nodes.md) from the Netdata config
+directory.
+
+## Change dashboards and visualizations
+
+The Netdata Agent's [local dashboard](/web/gui/README.md), accessible at `http://NODE:19999` is highly configurable. If
+you use Netdata Cloud for [infrastructure monitoring](/docs/quickstart/infrastructure.md), you will see many of these
+changes reflected in those visualizations due to the way Netdata Cloud proxies metric data and metadata to your browser.
+
+### Increase the long-term metrics retention period
+
+Increase the values for the `page cache size` and `dbengine multihost disk space` settings in the [`[global]`
+section](/daemon/config/README.md#global-section-options) of `netdata.conf`.
+
+```conf
+[global]
+    page cache size = 128   # 128 MiB of memory for metrics storage
+    dbengine multihost disk space = 4096   # 4GiB of disk space for metrics storage
+```
+
+Read our doc on [increasing long-term metrics storage](/docs/store/change-metrics-storage.md) for details, including a
+[calculator](/docs/store/change-metrics-storage.md#calculate-the-system-resources-RAM-disk-space-needed-to-store-metrics)
+to help you determine the exact settings for your desired retention period.
+
+### Reduce the data collection frequency
+
+Change `update every` in the [`[global]` section](/daemon/config/README.md#global-section-options) of `netdata.conf` so
+that it is greater than `1`. An `update every` of `5` means the Netdata Agent enforces a _minimum_ collection frequency
+of 5 seconds.
+
+```conf
+[global]
+    update every = 5
+```
+
+Every collector and plugin has its own `update every` setting, which you can also change in the `go.d.conf`,
+`python.d.conf`, `node.d.conf`, or `charts.d.conf` files, or in individual collector configuration files. If the `update
+every` for an individual collector is less than the global, the Netdata Agent uses the global setting. See the [enable
+or configure a collector](/docs/collect/enable-configure.md) doc for details.
+
+### Disable a collector or plugin
+
+Turn off entire plugins in the [`[plugins]` section](/daemon/config/README.md#plugins-section-options) of
+`netdata.conf`.
+
+To disable specific collectors, open `go.d.conf`, `python.d.conf`, `node.d.conf`, or `charts.d.conf` and find the line
+for that specific module. Uncomment the line and change its value to `no`.
+
+## Modify alarms and notifications
+
+Netdata's health monitoring watchdog uses hundreds of preconfigured health entities, with intelligent thresholds, to
+generate warning and critical alarms for most production systems and their applications without configuration. However,
+each alarm and notification method is completely customizable.
+
+### Add a new alarm
+
+To create a new alarm configuration file, initiate an empty file, with a filename that ends in `.conf`, in the
+`health.d/` directory. The Netdata Agent loads any valid alarm configuration file ending in `.conf` in that directory.
+Next, edit the new file with `edit-config`. For example, with a file called `ram-usage.conf`.
+
+```bash
+sudo touch health.d/ram-usage.conf
+sudo ./edit-config health.d/ram-usage.conf
+```
+
+Or, append your new alarm to an existing file by editing a relevant existing file in the `health.d/` directory.
+
+Read more about [configuring alarms](/docs/monitor/configure-alarms.md) to get started, and see the [health monitoring
+reference](/health/REFERENCE.md) for a full listing of options available in health entities.
+
+### Configure a specific alarm
+
+Tweak existing alarms by editing files in the `health.d/` directory. For example, edit `health.d/cpu.conf` to change how
+the Agent responds to anomalies related to CPU utilization.
+
+To see which configuration file you need to edit to configure a specific alarm, [view your active
+alarms](/docs/monitor/view-active-alarms.md) in Netdata Cloud or the local Agent dashboard and look for the **source**
+line. For example, it might read `source  4@/usr/lib/netdata/conf.d/health.d/cpu.conf`. Because the source path contains
+`health.d/cpu.conf`, you now you that you should run `sudo edit-config health.d/cpu.conf` to configure that alarm.
+
+### Disable a specific alarm
+
+Open the configuration file for that alarm and set the `to` line to `silent`.
+
+### Turn of all alarms and notifications
+
+Set `enabled` to `no` in the [`[health]` section](/daemon/config/README.md#health-section-options) section of
+`netdata.conf`.
+
+### Enable alarm notifications
+
+Open `health_alarm_notify.conf` for editing. First, read the [enabling
+notifications](/docs/monitor/enable-notifications.md#netdata-agent) doc for an example of the process using Slack, then
+click on the link to your preferred notification method to find documentation for that specific endpoint.
+
+## Improve node security
+
+While the Netdata Agent is both [open and secure by design](https://www.netdata.cloud/blog/netdata-agent-dashboard/), we
+recommend every user take some action to administer and secure their nodes.
+
+Learn more about a few of the following changes in the [node security doc](/docs/configure/secure-nodes.md).
+
+### Disable the local Agent dashboard (`http://NODE:19999`)
+
+If you use Netdata Cloud to visualize metrics, stream metrics to a parent node, or otherwise don't need the local Agent
+dashboard, disabling it reduces the Agent's resource utilization and improves security.
+
+Change the `mode` setting to `none` in the [`[web]` section](/web/server/README.md#configuration) of `netdata.conf`.
+
+```conf
+[web]
+    mode = none
+```
+
+### Use access lists to restrict access to specific assets
+
+Allow access from only specific IP addresses, ranges of IP addresses, or hostnames using [access
+lists](/web/server/README.md#access-lists) and [simple patterns](/libnetdata/simple_pattern/README.md).
+
+See a quickstart to access lists in the [node security
+doc](/docs/configure/secure-nodes.md#restrict-access-to-the-local-dashboard).
+
+### Stop sending anonymous statistics to Google Analytics
+
+Create a file called `.opt-out-from-anonymous-statistics` inside of your Netdata config directory to immediately stop
+the statistics script.
+
+```bash
+sudo touch .opt-out-from-anonymous-statistics
+```
+
+Learn more about [why we collect anonymous statistics](/docs/anonymous-statistics.md).
+
+### Change the IP address/port Netdata listens to
+
+Change the `default port` setting in the `[web]` section to a port other than `19999`.
+
+```conf
+[web]
+   default port = 39999
+```
+
+Use the `bind to` setting to the ports other assets, such as the [running `netdata.conf`
+configuration](/docs/configure/nodes.md#see-an-agents-running-configuration), API, or streaming requests listen to.
+
+## Reduce resource usage
+
+Read our [performance optimization guide](/docs/guides/configure/performance.md) for a long list of specific changes
+that can reduce the Netdata Agent's CPU/memory footprint and IO requirements.
+
+## Organize nodes with host labels
+
+Beginning with v1.20, Netdata accepts user-defined **host labels**. These labels are sent during streaming, exporting,
+and as metadata to Netdata Cloud, and help you organize the metrics coming from complex infrastructure. Host labels are
+defined in the section `[host labels]`. 
+
+For a quick introduction, read the [host label guide](/docs/guides/using-host-labels.md).
+
+The following restrictions apply to host label names: 
+ 
+-   Names cannot start with `_`, but it can be present in other parts of the name.
+-   Names only accept alphabet letters, numbers, dots, and dashes.
+
+The policy for values is more flexible, but you can not use exclamation marks (`!`), whitespaces (` `), single quotes
+(`'`), double quotes (`"`), or asterisks (`*`), because they are used to compare label values in health alarms and
+templates.
+
+## What's next?
+
+If you haven't already, learn how to [secure your nodes](/docs/configure/secure-nodes.md).
+
+As mentioned at the top, there are plenty of other 
+
+You can also take what you've learned about node configuration to tweak the Agent's behavior or enable new features:
+
+- [Enable new collectors](/docs/collect/enable-configure.md) or tweak their behavior.
+- [Configure existing health alarms](/docs/monitor/configure-alarms.md) or create new ones.
+- [Enable notifications](/docs/monitor/enable-notifications.md) to receive updates about the health of your
+  infrastructure.
+- Change [the long-term metrics retention period](/docs/store/change-metrics-storage.md) using the database engine.
+
+### Related reference documentation
+
+- [Netdata Agent · Daemon](/health/README.md)
+- [Netdata Agent · Daemon configuration](/daemon/config/README.md)
+- [Netdata Agent · Web server](/web/server/README.md)
+- [Netdata Agent · Local Agent dashboard](/web/gui/README.md)
+- [Netdata Agent · Health monitoring](/health/REFERENCE.md)
+- [Netdata Agent · Notifications](/health/notifications/README.md)
+- [Netdata Agent · Simple patterns](/libnetdata/simple_pattern/README.md)
+
+[![analytics](https://www.google-analytics.com/collect?v=1&aip=1&t=pageview&_s=1&ds=github&dr=https%3A%2F%2Fgithub.com%2Fnetdata%2Fnetdata&dl=https%3A%2F%2Fmy-netdata.io%2Fgithub%2Fdocs%2Fconfigure%2Fcommon-changes&_u=MAC~&cid=5792dfd7-8dc4-476b-af31-da2fdb9f93d2&tid=UA-64295674-3)](<>)
diff --git a/docs/configure/nodes.md b/docs/configure/nodes.md
index 89aa760a69..2e4bef6408 100644
--- a/docs/configure/nodes.md
+++ b/docs/configure/nodes.md
@@ -14,7 +14,7 @@ For example, you might want to increase metrics retention, configure a collector
 setup, or secure the local dashboard by restricting it to only connections from `localhost`.
 
 Whatever the reason, Netdata users should know how to configure individual nodes to act decisively if an incident,
-anomaly, or change in infrastructure affects how their Agents should peform.
+anomaly, or change in infrastructure affects how their Agents should perform.
 
 ## The Netdata config directory
 
@@ -31,20 +31,36 @@ scripts from inside that directory.
 
 ## Netdata's configuration files
 
-Upon installation, the Netdata config directory contains a few files and directories.
-
--   `netdata.conf` is the main configuration file. This is where you'll find most configuration options. This doc won't
-    go into exhaustive detail about each setting. You can read descriptions for each in the [daemon config
-    doc](/daemon/config/README.md).
--   `orig` is a symbolic link to the directory `/usr/lib/netdata/conf.d`, which contains stock configuration files.
-    Stock versions are copied into the config directory when opened with `edit-config`. _Do not edit the files in
-    `/usr/lib/netdata/conf.d`, as they are overwritten by updates to the Netdata Agent._
--   `edit-config` is a shell script used for [editing configuration files](#use-edit-config-to-edit-netdataconf).
--   `go.d/`, `python.d/`, `charts.d/`, `node.d`/, and `custom-plugins.d/`, which are directories for each of Netdata's
-    [orchestrators](/collectors/plugins.d/README.md). These directories can each contain additional `.conf` files for
-    configuring specific collectors.
-
-## Use `edit-config` to edit `netdata.conf`
+Upon installation, the Netdata config directory contains a few files and directories. It's okay if you don't see all
+these files in your own Netdata config directory, as the next section describes how to edit any that might not already
+exist.
+
+- `netdata.conf` is the main configuration file. This is where you'll find most configuration options. Read descriptions
+  for each in the [daemon config](/daemon/config/README.md) doc.
+- `edit-config` is a shell script used for [editing configuration files](#use-edit-config-to-edit-configuration-files).
+- Various configuration files ending in `.conf` for [configuring plugins or
+  collectors](/docs/collect/enable-configure.md#enable-a-collector-or-its-orchestrator) behave. Examples: `go.d.conf`,
+  `python.d.conf`, and `ebpf.conf`.
+- Various directories ending in `.d`, which contain other configuration files, each ending in `.conf`, for [configuring
+  specific collectors](/docs/collect/enable-configure.md#configure-a-collector).
+- `apps_groups.conf` is a configuration file for changing how applications/processes are grouped when viewing the
+  **Application** charts from [`apps.plugin`](/collectors/apps.plugin/README.md) or
+  [`ebpf.plugin`](/collectors/ebpf.plugin/README.md).
+- `health.d/` is a directory that contains [health configuration files](/docs/monitor/configure-alarms.md).
+- `health_alarm_notify.conf` enables and configures [alarm notifications](/docs/monitor/enable-notifications.md).
+- `statsd.d/` is a directory for configuring Netdata's [statsd collector](/collectors/statsd.plugin/README.md).
+- `stream.conf` configures [parent-child streaming](/streaming/README.md) between separate nodes running the Agent.
+- `.environment` is a hidden file that describes the environment in which the Netdata Agent is installed, including the
+  `PATH` and any installation options. Useful for [reinstalling](/packaging/installer/REINSTALL.md) or
+  [uninstalling](/packaging/installer/UNINSTALL.md) the Agent.
+
+The Netdata config directory also contains one symlink:
+
+- `orig` is a symbolic link to the directory `/usr/lib/netdata/conf.d`, which contains stock configuration files. Stock
+  versions are copied into the config directory when opened with `edit-config`. _Do not edit the files in
+  `/usr/lib/netdata/conf.d`, as they are overwritten by updates to the Netdata Agent._
+
+## Use `edit-config` to edit configuration files
 
 The **recommended way to easily and safely edit Netdata's configuration** is with the `edit-config` script. This script
 opens existing Netdata configuration files using your system's `$EDITOR`. If the file doesn't yet exist in your config
@@ -79,11 +95,11 @@ To edit `netdata.conf`, run `./edit-config netdata.conf`. You may need to elevat
 method for `edit-config` to write into the config directory. Use your `$EDITOR`, make your changes, and save the file.
 
 > `edit-config` uses the `EDITOR` environment variable on your system to edit the file. On many systems, that is
-> defaulted to `vim` or `nano`. To change this variable for the current session (it will revert to the default when you
-> reboot), export a new value: `export EDITOR=nano`. Or, [make the change
-> permanent](https://stackoverflow.com/questions/13046624/how-to-permanently-export-a-variable-in-linux).
+> defaulted to `vim` or `nano`. Use `export EDITOR=` to change this temporarily, or edit your shell configuration file
+> to change to permanently.
 
-After you make your changes, you need to restart the Agent with `service netdata restart`.
+After you make your changes, you need to [restart the Agent](/docs/configure/start-stop-restart.md) with `sudo systemctl
+restart netdata` or the appropriate method for your system.
 
 Here's an example of editing the node's hostname, which appears in both the local dashboard and in Netdata Cloud.
 
@@ -103,13 +119,36 @@ You can edit any Netdata configuration file using `edit-config`. A few examples:
 
 The documentation for each of Netdata's components explains which file(s) to edit to achieve the desired behavior.
 
+## See an Agent's running configuration
+
+On start, the Netdata Agent daemon attempts to load `netdata.conf`. If that file is missing, incomplete, or contains
+invalid settings, the daemon attempts to run sane defaults instead. In other words, the state of `netdata.conf` on your
+filesystem may be different from the state of the Netdata Agent itself.
+
+To see the _running configuration_, navigate to `http://NODE:19999/netdata.conf` in your browser, replacing `NODE` with
+the IP address or hostname of your node. The file displayed here is exactly the settings running live in the Netdata
+Agent.
+
+If you're having issues with configuring the Agent, apply the running configuration to `netdata.conf` by downloading the
+file to the Netdata config directory. Use `sudo` to elevate privileges.
+
+```bash
+wget -O /etc/netdata/netdata.conf http://localhost:19999/netdata.conf
+# or
+curl -o /etc/netdata/netdata.conf http://NODE:19999/netdata.conf
+```
+
 ## What's next?
 
-Take advantage of this newfound understanding of node configuration to [add security to your
-node](/docs/configure/secure-nodes.md). We have a few best practices based on how you use the Netdata Agent and Netdata
-Cloud.
+Learn more about [starting, stopping, or restarting](/docs/configure/start-stop-restart.md) the Netdata daemon to apply
+configuration changes.
+
+Apply some [common configuration changes](/docs/configure/common-changes.md) to quickly tweak the Agent's behavior.
 
-You can also take what you've learned about node configuration to tweak the Agent's behavior or enable new features:
+[Add security to your node](/docs/configure/secure-nodes.md) with what you've learned about the Netdata config directory
+and `edit-config`. We put together a few security best practices based on how you use the Netdata.
+
+You can also take what you've learned about node configuration to enable or enhance features:
 
 -   [Enable new collectors](/docs/collect/enable-configure.md) or tweak their behavior.
 -   [Configure existing health alarms](/docs/monitor/configure-alarms.md) or create new ones.
@@ -117,4 +156,10 @@ You can also take what you've learned about node configuration to tweak the Agen
     infrastructure.
 -   Change [the long-term metrics retention period](/docs/store/change-metrics-storage.md) using the database engine.
 
-[![analytics](https://www.google-analytics.com/collect?v=1&aip=1&t=pageview&_s=1&ds=github&dr=https%3A%2F%2Fgithub.com%2Fnetdata%2Fnetdata&dl=https%3A%2F%2Fmy-netdata.io%2Fgithub%2Fdocs%2Fconfigure%2Fnodesa&_u=MAC~&cid=5792dfd7-8dc4-476b-af31-da2fdb9f93d2&tid=UA-64295674-3)](<>)
+### Related reference documentation
+
+- [Netdata Agent · Daemon](/health/README.md)
+- [Netdata Agent · Health monitoring](/health/README.md)
+- [Netdata Agent · Notifications](/health/notifications/README.md)
+
+[![analytics](https://www.google-analytics.com/collect?v=1&aip=1&t=pageview&_s=1&ds=github&dr=https%3A%2F%2Fgithub.com%2Fnetdata%2Fnetdata&dl=https%3A%2F%2Fmy-netdata.io%2Fgithub%2Fdocs%2Fconfigure%2Fnodes&_u=MAC~&cid=5792dfd7-8dc4-476b-af31-da2fdb9f93d2&tid=UA-64295674-3)](<>)
diff --git a/docs/configure/secure-nodes.md b/docs/configure/secure-nodes.md
index e58102401d..704db35a33 100644
--- a/docs/configure/secure-nodes.md
+++ b/docs/configure/secure-nodes.md
@@ -50,8 +50,9 @@ static-threaded` setting, and change it to `none`.
     mode = none
 ```
 
-Save and close the editor, then restart your Agent using `service netdata restart`. If you try to visit the local
-dashboard to `http://NODE:19999` again, the connection will fail because that node no longer serves its local dashboard.
+Save and close the editor, then [restart your Agent](/docs/configure/start-stop-restart.md) using `sudo systemctl
+restart netdata`. If you try to visit the local dashboard to `http://NODE:19999` again, the connection will fail because
+that node no longer serves its local dashboard.
 
 > See the [configuration basics doc](/docs/configure/nodes.md) for details on how to find `netdata.conf` and use
 > `edit-config`.
@@ -112,7 +113,9 @@ We also have guides for [Apache](/docs/Running-behind-apache.md), [Lighttpd](/do
 
 ## What's next?
 
-If you haven't already, be sure to read about [Netdata's security design](/docs/netdata-security.md).
+Read about [Netdata's security design](/docs/netdata-security.md) and our [blog
+post](https://www.netdata.cloud/blog/netdata-agent-dashboard/) about why the local Agent dashboard is both open and
+secure by design.
 
 Next up, learn about [collectors](/docs/collect/how-collectors-work.md) to ensure you're gathering every essential
 metric about your node, its applications, and your infrastructure at large.
diff --git a/docs/configure/start-stop-restart.md b/docs/configure/start-stop-restart.md
new file mode 100644
index 0000000000..4967fff087
--- /dev/null
+++ b/docs/configure/start-stop-restart.md
@@ -0,0 +1,98 @@
+<!--
+title: "Start, stop, or restart the Netdata Agent"
+description: "Manage the Netdata Agent daemon, load configuration changes, and troubleshoot stuck processes on systemd and non-systemd nodes."
+custom_edit_url: https://github.com/netdata/netdata/edit/master/docs/configure/start-stop-restart.md
+-->
+
+# Start, stop, or restart the Netdata Agent
+
+When you install the Netdata Agent, the [daemon](/daemon/README.md) is configured to start at boot and stop and
+restart/shutdown.
+
+You will most often need to _restart_ the Agent to load new or editing configuration files. [Health
+configuration](#reload-health-configuration) files are the only exception, as they can be reloaded without restarting
+the entire Agent.
+
+Stopping or restarting the Netdata Agent will cause gaps in stored metrics until the `netdata` process initiates
+collectors and the database engine.
+
+## Using `systemctl`, `service`, or `init.d`
+
+This is the recommended way to start, stop, or restart the Netdata daemon.
+
+- To **start** Netdata, run `sudo systemctl start netdata`.
+- To **stop** Netdata, run `sudo systemctl stop netdata`.
+- To **restart** Netdata, run `sudo systemctl restart netdata`.
+
+If the above commands fail, or you know that you're using a non-systemd system, try using the `service` command:
+
+- **service**: `sudo service netdata start`, `sudo service netdata stop`, `sudo service netdata restart`
+
+## Using `netdata`
+
+Use the `netdata` command, typically located at `/usr/sbin/netdata`, to start the Netdata daemon. 
+
+```bash
+sudo netdata
+```
+
+If you start the daemon this way, close it with `sudo killall netdata`.
+
+## Using `netdatacli`
+
+The Netdata Agent also comes with a [CLI tool](/cli/README.md) capable of performing shutdowns. Start the Agent back up
+using your preferred method listed above.
+
+```bash
+sudo netdatacli shutdown-agent
+```
+
+## Reload health configuration
+
+You do not need to restart the Netdata Agent between changes to health configuration files, such as specific health
+entities. Instead, use [`netdatacli`](#using-netdatacli) and the `reload-health` option to prevent gaps in metrics
+collection.
+
+```bash
+sudo netdatacli reload-health
+```
+
+If `netdatacli` doesn't work on your system, send a `SIGUSR2` signal to the daemon, which reloads health configuration
+without restarting the entire process.
+
+```bash
+killall -USR2 netdata
+```
+
+## Force stop stalled or unresponsive `netdata` processes
+
+In rare cases, the Netdata Agent may stall or not properly close sockets, preventing a new process from starting. In
+these cases, try the following three commands:
+
+```bash
+sudo systemctl stop netdata
+sudo killall netdata
+ps aux| grep netdata
+```
+
+The output of `ps aux` should show no `netdata` or associated processes running. You can now start the Netdata Agent
+again with `service netdata start`, or the appropriate method for your system.
+
+## What's next?
+
+Learn more about [securing the Netdata Agent](/docs/configure/secure-nodes.md).
+
+You can also use the restart/reload methods described above to enable new features:
+
+- [Enable new collectors](/docs/collect/enable-configure.md) or tweak their behavior.
+- [Configure existing health alarms](/docs/monitor/configure-alarms.md) or create new ones.
+- [Enable notifications](/docs/monitor/enable-notifications.md) to receive updates about the health of your
+  infrastructure.
+- Change [the long-term metrics retention period](/docs/store/change-metrics-storage.md) using the database engine.
+
+### Related reference documentation
+
+- [Netdata Agent · Daemon](/daemon/README.md)
+- [Netdata Agent · Netdata CLI](/cli/README.md)
+
+[![analytics](https://www.google-analytics.com/collect?v=1&aip=1&t=pageview&_s=1&ds=github&dr=https%3A%2F%2Fgithub.com%2Fnetdata%2Fnetdata&dl=https%3A%2F%2Fmy-netdata.io%2Fgithub%2Fdocs%2Fconfigure%2Fstart-stop-restart&_u=MAC~&cid=5792dfd7-8dc4-476b-af31-da2fdb9f93d2&tid=UA-64295674-3)](<>)