diff --git a/docs/reference/commandline/create.md b/docs/reference/commandline/create.md index 844b7228a8..3540f6789c 100644 --- a/docs/reference/commandline/create.md +++ b/docs/reference/commandline/create.md @@ -233,3 +233,26 @@ daemon is running on Windows server, or `hyperv` if running on Windows client. | `hyperv` | Hyper-V hypervisor partition-based isolation. | Specifying the `--isolation` flag without a value is the same as setting `--isolation="default"`. + +### Dealing with dynamically created devices (--device-cgroup-rule) + +Devices available to a container are assigned at creation time. The +assigned devices will both be added to the cgroup.allow file and +created into the container once it is run. This poses a problem when +a new device needs to be added to running container. + +One of the solution is to add a more permissive rule to a container +allowing it access to a wider range of devices. For example, supposing +our container needs access to a character device with major `42` and +any number of minor number (added as new devices appear), the +following rule would be added: + +``` +docker create --device-cgroup-rule='c 42:* rmw' -name my-container my-image +``` + +Then, a user could ask `udev` to execute a script that would `docker exec my-container mknod newDevX c 42 ` +the required device when it is added. + +NOTE: initially present devices still need to be explicitely added to +the create/run command