Docker: any way to list open sockets inside a running docker container?
DockerNetstatAlpineDocker Problem Overview
I would like to execute netstat inside a running docker container to see open TCP sockets and their statuses. But, on some of my docker containers, netstat is not available. Is there any way to get open sockets (and their statuses, and which IP addresses they are connected to if any) without using netstat, via some docker API? (BTW, my container uses docker-proxy - that is, not directly bridged)
I guess I could look at /proc file system directly, but at that point, I might as well docker cp netstat into the container and execute it. I was wondering if there was any facility that docker might provide for this.
Docker Solutions
Solution 1 - Docker
You can use the nsenter command to run a command on your host inside the network namespace of the Docker container. Just get the PID of your Docker container:
docker inspect -f '{{.State.Pid}}' container_name_or_id
For example, on my system:
$ docker inspect -f '{{.State.Pid}}' c70b53d98466
15652
And once you have the PID, use that as the argument to the target (-t) option of nsenter. For example, to run netstat inside the container network namespace:
$ sudo nsenter -t 15652 -n netstat
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN
Notice that this worked even though the container does not have netstat installed:
$ docker exec -it c70b53d98466 netstat
rpc error: code = 13 desc = invalid header field value "oci runtime error: exec failed: container_linux.go:247: starting container process caused \"exec: \\\"netstat\\\": executable file not found in $PATH\"\n"
(nsenter is part of the util-linux package)
Solution 2 - Docker
The two commands from @larsks answer merged into one-liner - no need to copy-paste the PID(s) (just replace container_name_or_id):
sudo nsenter -t $(docker inspect -f '{{.State.Pid}}' container_name_or_id) -n netstat
Solution 3 - Docker
If you have iproute2 package installed, you can use
sudo nsenter -t $(docker inspect -f '{{.State.Pid}}' container_name_or_id) -n ss
or
sudo nsenter -t $(docker inspect -f '{{.State.Pid}}' container_name_or_id) -n ss -ltu
It will show TCP and UDP
Solution 4 - Docker
If you want them all (all containers) try this.
$ for i in `docker ps -q` ; do sudo nsenter -t $(docker inspect -f '{{.State.Pid}}' $i) -n netstat ; done
Solution 5 - Docker
I tried the other solutions and it didn't work for me by my colleague gave me this solution. Thought I would mention it here for others like me and for me to refer to later lol.
docker exec -it [container name] bash
grep -v “rem_address” /proc/net/tcp
Solution 6 - Docker
docker inspect
- Look for "ExposedPorts" in "Config"
Solution 7 - Docker
> server:docker container ls
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
80acfa804b59 admirito/gsad:10 "docker-entrypoint.s…" 18 minutes ago Up 10 minutes 80/tcp gvmcontainers_gsad_1