CODEWITHSUNDEEP
dockerhost
erikbstack
erikbstack

Reputation: 13254

Filesystems content of docker container on host

I've read quite a lot about how docker works using cgroups and namespaces. If that's correct the host should be able to see all the processes and filesystem tree that is used by the docker container. However I seem to be unable to figure it out.

Could someone show it with docker v1.12.6 and a running "nginx" container?

Optional: Is it possible to still access the files of already exited containers the same way?

PS, GraphDriver looks like this:

"GraphDriver" : {
  "Name" : "aufs",
  "Data" : null
},

Upvotes: 0

Views: 89

Answers (2)

thaJeztah
thaJeztah

Reputation: 29137

When running on the host that the docker daemon runs on, you can run (as root);

Start an nginx container

docker run -d nginx

View all processes that are running, hierarchically

ps auxf

which shows all processes, including the nginx container you just started;

root      3810  0.9  3.2 387460 67308 ?        Ssl  11:31   0:12 /usr/bin/dockerd -H fd://
root      3819  0.1  0.6 291624 14028 ?        Ssl  11:31   0:01  \_ docker-containerd -l unix:///var/run/docker/libcontainerd/docker-containerd.sock --metrics-interval=0 --start-timeout 2m --state-dir /var/run/docker/libcontainerd/containerd --shim docker-containerd-shim --runtime docker-runc
root      4241  0.0  0.3 143872  6652 ?        Sl   11:49   0:00      \_ docker-containerd-shim 1d3a6c65ac59e61c165d1f0119915a43e4d0387fd8432723f16b1ef2aa966522 /var/run/docker/libcontainerd/1d3a6c65ac59e61c165d1f0119915a43e4d0387fd8432723f16b1ef2aa966522 docker-runc
root      4277  0.0  0.2  31872  5280 ?        Ss   11:49   0:00          \_ nginx: master process nginx -g daemon off;
syslog    4304  0.0  0.1  32260  2904 ?        S    11:49   0:00              \_ nginx: worker process

container's filesystem

The storage location for container filesystems depend on the storage driver you're using. In your case the layers of images, and (writable) layers of containers are kept in /var/lib/docker/aufs. However, those files should not be messed with directly. You can use

  • docker cp to copy files from/to a container (even an exited container)
  • docker export to export the container's filesystem to a tar archive
  • docker commit a container to an image

Upvotes: 1

Girdhar Sojitra
Girdhar Sojitra

Reputation: 678

You can copy files from docker using docker cp command then you can access it.That will be simplest way to access files from exited container,too.

Upvotes: 1

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