---
title: "graylog2() destination options"
url: "https://axoflow.com/docs/axosyslog-core/4.28/chapter-destinations/configuring-destinations-graylog/reference-destination-graylog/"
last_modified: "2026-05-08T10:45:29+02:00"
---

> For the complete documentation index, see [llms.txt](https://axoflow.com/docs/axosyslog-core/4.28/llms.txt).

# graylog2() destination options

The `graylog2()` destination has the following options:

## ca-dir()

|  |  |
| --- | --- |
| Accepted values: | Directory name |
| Default: | none |

*Description:* The name of a directory that contains a set of trusted CA certificates in PEM format. The CA certificate files have to be named after the 32-bit hash of the subject’s name. This naming can be created using the c_rehash utility in openssl. For an example, see [Configuring TLS server authentication on the AxoSyslog clients](https://axoflow.com/docs/axosyslog-core/4.28/chapter-encrypted-transport-tls/tls-serverauth/procedure-configuring-tls-client/index.md). The AxoSyslog application uses the CA certificates in this directory to validate the certificate of the peer.

This option can be used together with the optional `ca-file()` option.

## ca-file()

|  |  |
| --- | --- |
| Accepted values: | File name |
| Default: | empty |

*Description:* Optional. The name of a file that contains a set of trusted CA certificates in PEM format. The AxoSyslog application uses the CA certificates in this file to validate the certificate of the peer.

Example format in configuration:

```shell
ca-file("/etc/pki/tls/certs/ca-bundle.crt")
```

> **Note:**
> The `ca-file()` option can be used together with the `ca-dir()` option, and it is relevant when `peer-verify()` is set to other than `no` or `optional-untrusted`.

## hook-commands()

*Description:* This option makes it possible to execute external programs when the relevant driver is initialized or torn down. The `hook-commands()` can be used with all source and destination drivers with the exception of the `usertty()` and `internal()` drivers.

> **Note:**
> The AxoSyslog application must be able to start and restart the external program, and have the necessary permissions to do so. For example, if your host is running AppArmor or SELinux, you might have to modify your AppArmor or SELinux configuration to enable AxoSyslog to execute external applications.

### Using `hook-commands()` when AxoSyslog starts or stops

To execute an external program when AxoSyslog starts or stops, use the following options:

#### `startup()`

| Type: | string |
| --- | --- |
| Default: | N/A |

*Description:* Defines the external program that is executed as AxoSyslog starts.

#### `shutdown()`

| Type: | string |
| --- | --- |
| Default: | N/A |

*Description:* Defines the external program that is executed as AxoSyslog stops.

### Using the hook-commands() when AxoSyslog reloads

To execute an external program when the AxoSyslog configuration is initiated or torn down, for example, on startup/shutdown or during a AxoSyslog reload, use the following options:

#### `setup()`

| Type: | string |
| --- | --- |
| Default: | N/A |

*Description:* Defines an external program that is executed when the AxoSyslog configuration is initiated, for example, on startup or during a AxoSyslog reload.

#### `teardown()`

| Type: | string |
| --- | --- |
| Default: | N/A |

*Description:* Defines an external program that is executed when the AxoSyslog configuration is stopped or torn down, for example, on shutdown or during a AxoSyslog reload.

### Example: Using hook-commands() with a network source

In the following example, the `hook-commands()` is used with the `network()` driver and it opens an [iptables](https://en.wikipedia.org/wiki/Iptables "https://en.wikipedia.org/wiki/Iptables") port automatically as AxoSyslog is started/stopped.

The assumption in this example is that the `LOGCHAIN` chain is part of a larger ruleset that routes traffic to it. Whenever the AxoSyslog created rule is there, packets can flow, otherwise the port is closed.

```shell
source {
    network(transport(udp)
    hook-commands(
          startup("iptables -I LOGCHAIN 1 -p udp --dport 514 -j ACCEPT")
          shutdown("iptables -D LOGCHAIN 1")
        )
     );
};
```

## tls()

|  |  |
| --- | --- |
| Type: | tls options |
| Default: | n/a |

*Description:* This option sets various options related to TLS encryption, for example, key/certificate files and trusted CA locations. TLS can be used only with tcp-based transport protocols. For details, see [TLS options](https://axoflow.com/docs/axosyslog-core/4.28/chapter-encrypted-transport-tls/tlsoptions/index.md).

## transport()

|  |  |
| --- | --- |
| Type: | udp, tcp, or tls |
| Default: | tcp |

*Description:* Specifies the protocol used to send messages to the destination server.

If you use the `udp` transport, AxoSyslog automatically sends multicast packets if a multicast destination address is specified. The `tcp` transport does not support multicasting.

Last modified May 8, 2026: [Renames hook-commands snippet (473feff3)](https://github.com/axoflow/axosyslog-core-docs/commit/473feff317cce35465fb8e527d1c4a7f46486b0a)