Diagnosing a Running Container

To do the same kind of diagnostics on a running container, you can either:

• attach to the container using the docker attach command.

• use the docker exec command to execute commands in the container and return the result to the command prompt using docker exec <container-id> command.

For example, you can call the exec command on the elasticsearch container using the first four characters of the container id, “bbd8,” to view the contents of a file using the Linux cat command.

Click here to view code image

docker exec bbd8 cat docker-entrypoint.sh

This will execute the command in the container and return the output, in this case the contents of the docker-entrypoint.sh file as shown in Figure 4.9.

FIGURE 4.9: Using Docker Exec to see the contents of a file in a running container