You add variables via Dashboard cogs menu > Templating. This opens up a list of variables and a `New` button to create a new variable.
### Basic variable options
Option | Description
------- | --------
*Name* | The name of the variable, this is the name you use when you refer to your variable in your metric queries. Must be unique and contain no white-spaces.
*Label* | The name of the dropdown for this variable.
*Query* | This variable type allows you to write a data source query that usually returns a list of metric names, tag values or keys. For example, a query that returns a list of server names, sensor ids or data centers.
*Interval* | This variable can represent time spans. Instead of hard-coding a group by time or date histogram interval, use a variable of this type.
*Datasource* | This type allows you to quickly change the data source for an entire Dashboard. Useful if you have multiple instances of a data source in for example different environments.
*Custom* | Define the variable options manually using a comma separated list.
*Constant* | Define a hidden constant. Useful for metric path prefixes for dashboards you want to share. During dashboard export, constant variables will be made into an import option.
*Ad hoc filters* | Very special kind of variable that only works with some data sources, InfluxDB & Elasticsearch currently. It allows you to add key/value filters that will automatically be added to all metric queries that use the specified data source.
*Refresh* | Controls when to update the variable option list (values in the dropdown). **On Dashboard Load** will slow down dashboard load as the variable query needs to be completed before dashboard can be initialized. Set this only to **On Time Range Change** if your variable options query contains a time range filter or is dependent on dashboard time range.
*Mulit-value* | If enabled, the variable will support the selection of multiple options at the same time.
*Include All option* | Add a special `All` option whose value includes all options.
*Custom all value* | By default the `All` value will include all options in combined expression. This can become very long and can have performance problems. Many times it can be better to specify a custom all value, like a wildcard regex. To make it possible to have custom regex, globs or lucene syntax in the **Custom all value** option it is never escaped so you will have to think avbout what is a valid value for your data source.
**Elasticsearch** uses lucene query syntax, so the same variable would, in this case, be formatted as `("host1" OR "host2" OR "host3")`. In this case every value
*Tags query* | Data source query that should return a list of tags
*Tag values query* | Data source query that should return a list of values for a specified tag key. Use `$tag` in the query to refer the currently selected tag.
Use the `Interval` type to create a variable that represents a time span (eg. `1m`,`1h`, `1d`). There is also a special `auto` option that will change depending on the current time range. You can specify how many times the current time range should be divided to calculate the current `auto` timespan.
This variable type is useful as a parameter to group by time (for InfluxDB), Date histogram interval (for Elasticsearch) or as a *summarize* function parameter (for Graphite).
Only make changes to the first panel (the original template). To have the changes take effect on all panels you need to trigger a dynamic dashboard re-build.
You can do this by either changing the variable value (that is the basis for the repeat) or reload the dashboard.
