#Docker logs manual#

This is easy to confirm, as the location is stored against each container under the “LogPath” JSON property when inspecting. There are occasions where the log file may not exist in the location you expected (such as when installing Docker via Snap on Linux). For now, we are only interested in the location on MacOS, which is under the path /var/lib/docker/containers/. You can view the different locations in the Docker documentation. Docker outputs these files to different locations based on the operating system and installation method. Docker supplies two ways for us to do this.įirst, let’s look at the file written to disk. Next, we need to check the logs for the container. ID and NAME values both must be unique as they are used to refer to containers when utilizing Docker. The NAME can be explicitly specified by the user when creating the container, or if omitted, Docker will automatically generate one. The ID is a unique identifier generated for each individual container. Running this command should display some information for all containers in a tabular format, including the container ID and NAME. The –a option tells Docker that you want to view all containers returned by the ps command, regardless of state. You can view this container with the following command: $ docker ps –aĬONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMESī53f3a24df95 hello-world '/hello' 12 minutes ago Exited (0) 12 minutes ago vibrant_dirac Since the Hello World image outputs a message when started and then stops again, the subsequent container will exist in a stopped state. Now that you have run that command, a single container should exist within Docker. You can see an example of the output of this command on Docker Hub. It is also a great way to verify that your Docker installation has been setup correctly. It simply outputs an informational message with some additional links to guide you to more resources to help you get started with Docker. This command creates a new container from a simple image hosted on Docker Hub called “Hello World”. Assuming you have Docker fully installed, run the following command in the terminal: $ docker run hello-world So, let’s start by looking at what Docker offers by default for logging.

#Docker logs manual#

Not to mention the fact that trawling through these files would be an arduous and manual task, prone to missing vital information, and complex to build automated alerts around. microservices) that may be hosted across many different servers (both physical and virtual), it becomes a very big problem to try to use these basic log outputs to diagnose any potential issues. This is fine in a scenario where there is one, or a few containers running on one machine, but in a world of applications being comprised of a collection of smaller components (i.e. The default configuration of Docker supplies a view of the logs emitted from containers (and the applications within) in two forms: the console or standard output (also known as stdout) and JSON-formatted files stored on the hard disk.ĭocker also exposes a remote API that allows users to run a command through the terminal to view the logs stored in these files. Please refer to the official Docker documentation for further details in these areas.īased on a vanilla installation of MacOS, the following other programs are needed to follow along with the tutorials in this article: It is possible to run through the same Docker commands using Windows or Linux as well, but some steps, commands or file locations may vary.

This article has been written for use on MacOS. We will go through the default logging approach, as well as look at some more advanced configurations that will make diagnosing issues in your Docker-hosted applications much easier going forward. This article provides an overview of managing and analyzing Docker logs and explores some of the complexities that may arise when looking through the log data.