KodeKloud Notes

In this tutorial, you’ll learn how to manage Docker’s logging drivers—check the default, switch the daemon-wide setting, apply advanced options, and override the driver for individual containers.

1. Check the Default Logging Driver

Docker uses the json-file driver by default, storing container logs as JSON on the host.

# Verify the current logging driver
docker system info | grep -i "logging driver"
# Output: Logging Driver: json-file

Note

The json-file driver is the standard Docker logging backend. It’s easy to parse and works out of the box.

2. Create and Inspect a Test Container

Run an Ubuntu container to see its inherited log configuration:

# Start a detached Ubuntu container
docker container run -itd --name test-container ubuntu

Inspect its log settings:

docker container inspect test-container \
  --format='{{json .HostConfig.LogConfig}}'
# Output:
# {
#   "Type": "json-file",
#   "Config": {}
# }

3. Supported Logging Drivers

Docker supports multiple logging backends for different use cases. You can find the full list in the official docs:
Configure containers → Logging

The image shows a section of the Docker documentation webpage, specifically listing and describing various logging drivers available for Docker containers.

Driver	Use Case
json-file	Local JSON logs, simple parsing
syslog	Centralized logging to syslog daemon
journald	Integration with systemd’s journal
fluentd	Forward logs to a Fluentd collector
awslogs	Ship logs to Amazon CloudWatch Logs
splunk	Send logs to a Splunk HTTP Event Collector (HEC)
…	And others (gcplogs, logentries, etc.)

4. Change the Default Driver to Syslog

To switch the daemon-wide driver to syslog, edit /etc/docker/daemon.json:

Warning

Modifying daemon.json requires restarting the Docker daemon. Existing containers will continue using their current driver until recreated.

Stop Docker:
```
sudo systemctl stop docker
```
Update /etc/docker/daemon.json:
```
{
  "log-driver": "syslog"
}
```
Restart Docker:
```
sudo systemctl start docker
```

Verify:

docker system info | grep -i "logging driver"
# Output: Logging Driver: syslog

5. Advanced Logging Options

You can fine-tune log behavior with log-opts. For example, to limit file size and rotation on json-file:

{
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "10m",
    "max-file": "3"
  },
  "labels": "production_status",
  "env": "os_customer"
}

Retrieve the current default driver in scripts:

docker info --format '{{.LoggingDriver}}'
# e.g., json-file

6. Override the Logging Driver per Container

Even when the daemon default is syslog, you can pick a different driver for a specific container:

docker container run -itd \
  --name logtest \
  --log-driver journald \
  ubuntu

Confirm the override:

docker container inspect logtest \
  --format='{{json .HostConfig.LogConfig}}'
# Output:
# {
#   "Type": "journald",
#   "Config": {}
# }

7. Conclusion

You’ve learned how to:

Check and view Docker’s default logging driver
Change the daemon-wide driver in /etc/docker/daemon.json
Apply advanced options like rotation and size limits
Override logging drivers for individual containers

Happy logging!

References

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