Often there is a need to attach a shell to an already running Docker container. This is very useful, especially for debugging. This blog will explain how to attach a shell to an already running Docker container.
So, let’s say you run a Couchbase Docker container in detached mode:
| 1 2 3 4 | > docker run -d couchbase/server 02061ddf0a3d1b2806a1ee6e354f4064d9d2ff4d84d8c96c0273c8883917a92f |
Running the container gives you the complete container id, 02061ddf0a3d1b2806a1ee6e354f4064d9d2ff4d84d8c96c0273c8883917a92f in this case.
This can be verified as:
| 1 2 3 4 5 | > docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 02061ddf0a3d couchbase/server "/entrypoint.sh couch" 38 seconds ago Up 37 seconds 8091-8093/tcp, 11207/tcp, 11210-11211/tcp, 18091-18092/tcp clever_hypatia |
Or complete container id can be verified as:
| 1 2 3 4 5 | > docker ps --no-trunc CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 02061ddf0a3d1b2806a1ee6e354f4064d9d2ff4d84d8c96c0273c8883917a92f couchbase/server "/entrypoint.sh couchbase-server" About a minute ago Up 59 seconds 8091-8093/tcp, 11207/tcp, 11210-11211/tcp, 18091-18092/tcp clever_hypatia |
Attach Shell to Docker Container
Bash shell can be attached to an already running container using docker exec -it {CID} bash. The {CID} can be the complete container id, truncated container id, or even the first few digits of the container ids amongst all the currently running containers.
So, the following three commands are equivalent in our case:
Attach Using Complete Container Id
| 1 2 3 4 | > docker exec -it 02061ddf0a3d1b2806a1ee6e354f4064d9d2ff4d84d8c96c0273c8883917a92f bash root@02061ddf0a3d:/# |
Attach Using Truncated Container Id
| 1 2 3 4 | > docker exec -it 02061ddf0a3d bash root@02061ddf0a3d:/# |
Attach Using Unique Numbers From Container Id
| 1 2 3 4 | > docker exec -it 0 bash root@02061ddf0a3d:/# |
In this case, just specifying 0 would work because this is the only running container. If multiple containers are running that have 0 as the starting number, then the first few digits that make the container id unique are required.
Enjoy!
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