Final answer:
A container exit code 143 indicates it received a SIGTERM signal, suggesting the process was instructed to shut down by the operating system or another application, often due to a 'docker stop' command.
Step-by-step explanation:
When a container exits with a status code of 143, it typically indicates that it received a SIGTERM signal. This signal is a generic termination signal sent by the operating system or by another application to indicate that the process should gracefully shutdown. In the context of containers (such as those managed by Docker), a SIGTERM can be sent when you issue a command to stop the container, like docker stop. The non-zero exit code 143 is a convention to signal that the process did not end on its own but was instead asked to terminate.
This termination process allows the container to perform any necessary cleanup operations before it shuts down, like closing open files, completing current transactions, etc. If the container process does not terminate within a grace period after receiving SIGTERM, it will receive a SIGKILL signal which forces it to end immediately, usually resulting in an exit code 137.