docker · Docker
The message
Conflict. The container name "/api" is already in use by container
What it means
The name you passed with --name is already taken by another container. Names are unique across stopped containers as well as running ones, so usually a container that died yesterday still holds it — invisible in docker ps and visible only in docker ps -a. docker rm -f api frees the name, and it also destroys that container's writable layer along with it (named volumes survive). For a container you only need once, starting it with docker run --rm avoids the situation entirely.
The fix
docker rm -f api- Printed by
- docker
- Docker
- 12
Docker errors only become readable once you place them in a layer — the client failing to reach the daemon, the registry refusing you, a RUN failing during the build, and a container dying the instant it starts are four different problems — and for the build and run layers the line itself is not the reason: the reason is in the output of the command that was running inside, while the cost of each fix differs by layer too.
Reading an error message
- Read from the first line down. The lower you go the more it is about the tool’s internals; the cause is usually at the top.
- If there is a file and a line number, start there — not the top stack frame, but the topmost line that names a file you wrote.
- Search the message verbatim, but strip your own paths and variable names first; those are what stop the search from matching.
- The same condition is worded differently across tool versions. If results look wrong, add the version number to the query.
- Before pasting a fix, check what it throws away. Some of these cannot be undone.
Common questions
Q. What does “Conflict. The container name "/api" is already in use by container” mean?
The name you passed with --name is already taken by another container. Names are unique across stopped containers as well as running ones, so usually a container that died yesterday still holds it — invisible in docker ps and visible only in docker ps -a. docker rm -f api frees the name, and it also destroys that container's writable layer along with it (named volumes survive). For a container you only need once, starting it with docker run --rm avoids the situation entirely.
Q. How do I fix it?
docker rm -f api — before running it, check the explanation above for what this command discards.
Q. Which tool prints this?
docker. It sits under Docker, and the message runs to 11 words.