How its works in Docker Logging?

How its works in Docker Logging?
Techiio-author
Written by Nilima PaulFebruary 19, 2022
11 min read
Docker
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Techiio-author
Nilima Paul

Technology Security Analyst

In this article, We will discuss how its works in Docker Logging.

Introduction to Docker Logging:

Docker Logging assists with investigating mistakes connected with Docker. It is a system to investigate the issues that occurred in our Docker climate. For instance, assuming that Docker daemon or any compartment running on Docker isn't firing up as expected then we want to look at the logs to realize what is causing the issue. Docker has two degrees of logging one is at the Docker daemon level and another is at the compartment level.

How does Logging work in Docker:

Docker has numerous instruments to log data from running compartments and administrations. We say these system logging drivers. There is a default logging driver, currently designed for every Docker daemon that is utilized by compartments if we don't arrange it to utilize any unique driver. There are additionally logging driver modules other than worked in logging drivers that we can carry out to expand and modify Docker's logging capacities.

We want to refresh the 'daemon.json' record to expressly arrange the default logging driver to some other logging driver, the 'daemon.json' document is situated in/and so on/docker/on Linux has or c:\programdata\docker\config\ on windows server has. We can set choices in the daemon.json document as JSON objects with the key 'log-picks' assuming that the logging driver permits doing as such. We utilize the 'docker log' order to check the logs produced by any compartment.

1. Docker logging at daemon level:

Daemon-level docker logging is used to fix issues and errors that are generated by the Docker daemon itself.

There are four levels of logging available at the daemon level.

  • Debug: It provides every possible information generated by the Docker daemon process.
  • Info: It provides all types of information and errors generated by the Docker daemon process.
  • Error: It provides all the errors generated by the daemon process.
  • Fatal: It only provides details about all the fatal errors generated by the daemon process.

We can enable Docker daemon logging by command or editing the ‘daemon.json’ file. We need to stop the Docker process in either case.

Let’s do it by the command first. So first we need to stop the Docker daemon process using the below command:

sudo service docker stop

Or

sudo systemctl stop docker

Then we need to start the Docker daemon process with the option ‘-I'd and specify the level of the logging. For example, debug, info, etc.

Code:

docker -l debug &

Code:

docker -l  info &

Explanation: In the over two depictions, we can see when we indicated the 'troubleshoot' choice, we got all the data including investigating data anyway when we determined the 'information' choice, there is no 'investigate' sign in it, just a blunder, cautioning, and information.

We can likewise alter the daemon.json record situated at/and so forth/docker to change the default daemon logging level.

We add "investigate": valid in the daemon.json record as displayed underneath and begin the Docker daemon process.

Code:

cat /etc/docker/daemon.json

Below is the snapshot before enabling debug level daemon logging and the default logging level is set to ‘info’ as there is debug log showing in the below snapshot.

Code:

docker

And below is the snapshot after enabling the debug level daemon logging by editing the ‘daemon.json’ file and there is debug log in the snapshot however we are using the same command as above again.

Code:

docker

2. Docker logging at container level:

Compartment level Docker logging is utilized to investigate blunders and issues connected with holders or administrations. For instance, getting a blunder while beginning a holder or compartment ceaselessly crashing or caught in loopback, and so on The default logging driver for holder level logging is 'JSON-record'. We can again design the 'daemon.json' record to change the default setting. We can set the worth of 'log-driver' to the name of the logging driver and indicate the log choices utilizing the 'log-selects' vital assuming different logging choices are accessible for that driver.

We utilize the 'docker information' order to realize the default logging driver for holders as underneath.

Code:

docker info

Explanation:In the above depiction, we see that 'JSON-record' is set as the default logging driver. It gives insights regarding modules too, for example, AWS logs, fund, Syslog, and so on

How about we change the default logging driver to 'Syslog' and set some log choices also in the 'daemon.json' record.

Code:

sudo cat /etc/docker/daemon.json

Explanation: In the above model, the default logging driver has been set to 'Syslog' with choices like tag, names, and env that are plain as day. We want to restart the docker to apply these changes. First halted the docker daemon and afterward began it once more. Assuming we check presently utilizing the 'docker information' order, we can see the default logging driver has been changed to 'syslog'Syslog

Code:

sudo systemctl stop docker
sudo systemctl start docker
docker info

We can also configure the logging driver per container. We can do this by passing the ‘–log-driver’ flag while starting the container. It bypasses the default logging driver configured in the ‘daemon.json’ file.

Example:

Code:

docker run -d --log-driver Syslog alpine

Explanation: In the above model, began a high holder and designed the compartment to utilize 'Syslog' as the logging driver. To check which logging driver is utilized by a holder, we investigate the compartment as displayed in the preview and look down and view it as the "HostConfig" key and search for the "LogConfig" type and here, it is 'Syslog'.

We can check the logs created by the holders utilizing 'docker log'.

Syntax:

docker log <container_id or container_name>

Example:

Code:

docker run -d MySQL
docker log 4b0ee

Explanation: In the above depiction, a holder has been made with default logging driver and if we check the logs of the compartment it shows us blunders and presently we can comprehend the reason why the compartment neglected to begin as it requires any of the variables to be passed while running this holder. So logging assists with investigating the issues.

Conclusion:

Docker logging is extremely valuable and important to get what's going on behind the scene. Assuming we utilize different logging drivers we want devices to peruse those logs as Docker logs can't peruse logs produced by any remaining logging drivers. There are other modules accessible anyway we want to design those appropriately in the 'daemon.json' document and we can get the accessible choices from the authority site of those module suppliers.

Docker
Docker Logging
DevOps
Containers
Docker swarm
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