Docker: ENTRYPOINT vs. CMD

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ENTRYPOINT is the process run when the container starts (PID 1).

CMD is the argument for the entrypoint.

When you run the container without arguments, this will execute ENTRYPOINT + CMD:

# ENTRYPOINT ["ls"]
# CMD ["-l"]
docker run alpine	# This will run "ls -h"

Shell
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# ENTRYPOINT ["ls"]
# CMD ["-l"]
docker run alpine   # This will run "ls -h"

When you run the container with arguments, this will execute ENTRYPOINT + arguments:

# ENTRYPOINT ["ls"]
# CMD ["-h"]
docker run alpine -alh	# This will run "ls -alh"

Shell
 
# ENTRYPOINT ["ls"]
# CMD ["-h"]
docker run alpine -alh  # This will run "ls -alh"

When you want to override the entrypoint use the –entrypoint flag:

# ENTRYPOINT ["ls"]
# CMD ["-h"]
docker run --entrypoint ps alpine	# This will run "ps -h"

Shell
 
# ENTRYPOINT ["ls"]
# CMD ["-h"]
docker run --entrypoint ps alpine   # This will run "ps -h"

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