Pushing Logs with a Forwarder - Syslog-ng 3.12.1+ (Linux) – Articles

Learn how to send Logs from your Linux instance to Logs Data Platform.

Do you have a server, a Raspberry Pi, a cloud instance, or something else running on Linux and you want to follow your Logs, the easy way? Have you never installed a log collector and you're new to Graylog? Then this tutorial is for you!

Requirements

a Linux-based instance (server, VPS, Cloud instance, Raspberry Pi, etc.). Command lines will be for DEBIAN 12 in this tutorial
a root access to this instance
an activated Logs Data Platform account
at least one Stream and its token

Instructions

Why?

On Linux, logs are generated automatically for a variety of actions such as excessive resource usage, file downloads, login attempts, network failure, and many more. However, logs can be difficult to read without proper tools. With this platform, you can sort logs and create useful (or fancy) dashboards.

What are logs?

Here are some example logs from an OVHcloud Public Cloud instance on Debian 12:

 Jan 27 12:21:15 server syslog-ng[29512]: syslog-ng starting up; version='3.8.1'
 Jan 27 12:21:15 server syslog-ng[29512]: Syslog connection established; fd='10', server='AF_INET(51.38.195.65:6514)', local='AF_INET(0.0.0.0:0)'
 Jan 29 15:32:23 server sshd[9563]: Received disconnect from 211.110.82.180: 11: Bye Bye [preauth]
 Jan 29 18:39:24 server sshd[29694]: Failed password for root from 59.45.79.51 port 39827 ssh2

Configure your Account

The first thing to do is to configure your Logs Data Platform account: create your user!

Install and configure a log collector

So let's assume you have your Linux. This tutorial DOES NOT fully cover how to configure other flavors of syslog or other operating systems. Please refer to their own documentation to know how to set up a source, a filter, and an external destination for the logs. You can still read this entire document to have a grasp on how the configuration is built. However, this configuration should work on any syslog-ng version above 3.12.1.

We will install a log collector. What is it? It's a tool that collects logs from any source, processes them, and delivers them to various destinations, like the Logs Data Platform.

In this section we will install Syslog-ng:

Log in your Linux
Install syslog-ng and the last certificates
Check that your syslog-ng version is above 3.12.1 (use syslog-ng --version to confirm it).

$ debian@server:~$ sudo apt-get install syslog-ng ca-certificates

Once it's done we will configure it to deliver logs to the platform
Create a new syslog-ng configuration file ldp.conf with a text editor (here we use nano for example)

$ debian@server:~$ sudo nano /etc/syslog-ng/conf.d/ldp.conf

Copy-paste this configuration. Don't forget to replace the variables with your stream write token and with your Logs Data Platform cluster address.

rewrite ovh-token {
    # This will add X-OVH-TOKEN as custom structured data specified by the RFC 5424.
    # change <YOUR X-OVH-TOKEN VALUE> by the value of your X-OVH-TOKEN.
    set("<YOUR X-OVH-TOKEN VALUE>", value(".SDATA.token@29084.X-OVH-TOKEN"));
};

destination ovhPaaSLogs {
    # Change <YOUR LDP CLUSTER> by your Logs Data Platform cluster address.
    # The address can be found in your Logs Data Platform Manager
    # Your LDP Cluster address has the following form: <RegionX>.logs.ovh.com
    network("<YOUR LDP CLUSTER>"
        port(6514)
        transport("tls")
        flags(syslog-protocol)
        ts_format("iso")
        frac-digits(6)
        tls(peer-verify("required-trusted") ca_dir("/etc/ssl/certs/"))
        keep-alive(yes)
        so_keepalive(yes)
    );
};

## you can use this destination for debugging purposes
#destination debugfile {
#    file("/var/log/debugpaaslogs.log"
#      flags(syslog-protocol)
#    );
#};

log { source(s_src); rewrite(ovh-token); destination(ovhPaaSLogs); };
#log { source(s_src); rewrite(ovh-token); destination(debugfile); };

NOTE: If you push your syslog-ng logs to one of your dedicated data gathering tools, you will need to perform an extra step.

Copy the data-gathering tools certificate from the manager Home page in SSL Configuration section, and paste it in file "/usr/local/share/ca-certificates/ldp.pem"
Ensure the permission on this file is 644

$ debian@server:~$ sudo chmod 644 /usr/share/ca-certificates/ldp.pem

Import this certificate to your system's trusted CA repository

$ debian@server:~$ sudo update-ca-certificates

Let's review this configuration.

REWRITE: this will set your X-OVH-TOKEN as an RFC 5424 structured data. You can retrieve your stream write token by going to Stream page in the OVHcloud Control Panel and select Copy the write token from the desired stream.

DESTINATION: This is where we will deliver logs in nearly real time. Here, we have two destinations: The first is the remote endpoint in Logs Data Platform, the second one is a local file for debugging purposes only. You can find your Logs Data Platform cluster address by going to Home page in the OVHcloud Control Panel in access point configuration. For debugging purposes, you can uncomment the "debugfile" section to check if the whole pipeline is working properly. It will write to the local file destination. Since local file writing might consume a lot of I/O resources, we recommend not using this debugging output in production.

LOG: This directive specifies the whole pipeline: "s_src" => "ovh-token" => "ovhPaasLogs".

Save the file, close nano and restart syslog-ng.

$ debian@server:~$ sudo systemctl restart syslog-ng.service

Let's play with Graylog Dashboards

Let's recap: you have a Linux instance and it's sending logs locally and remotely, thanks to the syslog-ng log collector. We send two types of flows: internal() and system().

The last step is to create a dashboard displaying the results. Connect to the Logs Data Platform manager and ensure you that you have a Stream and that the token in the syslog configuration file is OK. Ensure that you have a Dashboard created.

Access Graylog, click the Streams tab, and select your stream.

operate_LDP_ingest_syslog-ngLinux01*.png

In the top-left corner, chose ..last 1 day as your range, then click on the green button 🔍 to search.

operate_LDP_ingest_syslog-ngLinux02*.png

On the top right corner of the histogram, click the more options ▼ icon and select Copy to Dashboard.

operate_LDP_ingest_syslog-ngLinux03*.png

Choose the dashboard you want to add to, then click Select.

operate_LDP_ingest_syslog-ngLinux04*.png

To change the format of your widget to a pie chart, in the top right corner of the histogram, click the more options ▼ icon and select Edit.

operate_LDP_ingest_syslog-ngLinux05*.png

On the next screen, under VISUALIZATION TYPE select Pie Chart and then click Save.

operate_LDP_ingest_syslog-ngLinux06*.png

The best feature is the ability to mix criteria, based on what is important to you. For example, facility:auth AND level:6. Why not create an alert on this condition?

Go further

For more information and tutorials, please see our other Logs Data Platform support guides or explore the guides for other OVHcloud products and services.

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