mirror of
https://github.com/StackExchange/dnscontrol.git
synced 2024-09-20 14:56:20 +08:00
142 lines
4.6 KiB
Markdown
142 lines
4.6 KiB
Markdown
# CLI variables
|
|
|
|
You can pass variables into your configuration from the command line using the `-v key=value` flag. There is also a mechanism called `CLI_DEFAULTS` which lets you easily set the defaults on variables that are otherwise controlled from the command line.
|
|
|
|
This gives you the opportunity to run different code when a value is passed.
|
|
|
|
## Passing variables
|
|
|
|
To pass a variable from CLI, just use the parameter `-v key=value` when using subcommands `preview` or `push`.
|
|
|
|
Example: `dnscontrol preview -v testKey=testValue`
|
|
|
|
This would set the variable with the name `testKey` and the value of `testValue` when processing `dnsconfig.js`
|
|
|
|
## Define defaults
|
|
|
|
The `CLI_DEFAULTS` feature is used to define default values for when a variable is not defined on the command line.
|
|
|
|
{% code title="dnsconfig.js" %}
|
|
```javascript
|
|
CLI_DEFAULTS({
|
|
"variableName": "defaultValue",
|
|
});
|
|
```
|
|
{% endcode %}
|
|
|
|
|
|
You need to define this defaults just once in your `dnsconfig.js`. It should be defined **before** using it.
|
|
|
|
_Please keep in mind that accessing an undefined variable is an error. If it is not set on the command line nor in `CLI_DEFAULTS`, accessing the variable will fail._
|
|
|
|
## Example 1: Different IPs for internal/external DNS
|
|
|
|
In this example we have a number of variables which need to be set differently when `view=internal`.
|
|
|
|
In this configuration:
|
|
|
|
* `dnscontrol push` would generate the external (default) view.
|
|
* `dnscontrol push -v view=internal` would generate the internal view.
|
|
|
|
{% code title="dnsconfig.js" %}
|
|
```javascript
|
|
// See https://docs.dnscontrol.org/advanced-features/cli-variables
|
|
CLI_DEFAULTS({
|
|
"view": "external",
|
|
});
|
|
if (view == "external") {
|
|
// BIND view: external (192.168.0.0/16 addresses)
|
|
var host01 = "192.168.0.16";
|
|
var host02 = "192.168.0.17";
|
|
} else {
|
|
// BIND view: internal (10.0.0.0/8 addresses)
|
|
var host01 = "10.0.0.16";
|
|
var host02 = "10.0.0.17";
|
|
}
|
|
|
|
/// ...much later...
|
|
|
|
D("example.com", REG_NAMECOM, DnsProvider(DNS_NAMECOM), DnsProvider(DNS_BIND),
|
|
A("sitea", host01, TTL(1800)),
|
|
A("siteb", host01, TTL(1800)),
|
|
A("sitec", host02, TTL(1800)),
|
|
A("sited", host02, TTL(1800)),
|
|
END);
|
|
```
|
|
{% endcode %}
|
|
|
|
|
|
## Example 2: Different DNS records
|
|
|
|
In this example different code is run when `emergency=true`. Normally
|
|
`server12` is an A record but in an emergency it is a CNAME.
|
|
|
|
In this configuration:
|
|
|
|
* `dnscontrol push` would generate the normal configuration.
|
|
* `dnscontrol push -v emergency=true` would generate the emergency configuration.
|
|
|
|
{% code title="dnsconfig.js" %}
|
|
```javascript
|
|
// See https://docs.dnscontrol.org/advanced-features/cli-variables
|
|
CLI_DEFAULTS({
|
|
"emergency": false,
|
|
});
|
|
|
|
// ...much later...
|
|
|
|
D("example.com", REG_EXAMPLE, DnsProvider(DNS_EXAMPLE),
|
|
A("www", "10.10.10.10"),
|
|
END);
|
|
|
|
if (emergency) {
|
|
// Emergency mode: Configure A/B/C using CNAMEs to our alternate site.
|
|
|
|
D_EXTEND("example.com",
|
|
CNAME("a", "a.othersite"),
|
|
CNAME("b", "b.othersite"),
|
|
CNAME("c", "c.othersite"),
|
|
END);
|
|
|
|
} else {
|
|
// Normal operation: Configure A/B/C using A records.
|
|
|
|
D_EXTEND("example.com",
|
|
A("a", "10.10.10.10"),
|
|
A("b", "10.10.10.11"),
|
|
A("c", "10.10.10.12"),
|
|
END);
|
|
|
|
}
|
|
```
|
|
{% endcode %}
|
|
|
|
|
|
#### ProTips
|
|
|
|
The cli variables functionality permits you to create very complex and
|
|
sophisticated configurations, but you shouldn't. Be nice to the next person
|
|
that edits the file, who may not be as expert as yourself.
|
|
|
|
While there is no limit to the number of variables that can be set on the
|
|
command line, doing so is annoying to the person using the tool. It is better
|
|
to set one variables which specifies a "mode". This mode is then used to
|
|
automatically set other variables. This way the user can determine the mode and
|
|
the code can determine what to do in that mode. This is less error-prone and
|
|
more testable.
|
|
|
|
In the first example, you'll see that one variable is used to set a mode which
|
|
then determines many other variables. This is done in one place, at the top of
|
|
the file. Everything related to this is isolated to one place, thus easier to
|
|
maintain. The rest of the file simply uses those variables.
|
|
|
|
In the second example, you'll see a boolean variable is set which selects which
|
|
code will run different code. While the conditional code is not isolated to the
|
|
top of the file, the conditional code is placed immediately after the domain.
|
|
|
|
In both examples, not setting any variables on the command line does something
|
|
reasonable. If someone accidentally runs `dnscontrol push` without any
|
|
variables, the behavior is correct (assuming we're not in emergency mode, which
|
|
is unlikely).
|
|
|