[jira] [Commented] (MESOS-9319) Move root filesystem creation to the `filesystem/linux` isolator.

["James Peach (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MESOS-9319?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16699772#comment-16699772 ] 

James Peach commented on MESOS-9319:
------------------------------------

Updated patch series:

| [r/69211|https://reviews.apache.org/r/69211] | Improved the code comments for `getContainerDevicesPath`. |
| [r/69210|https://reviews.apache.org/r/69210] | Used the MS_SILENT mount flag to elide unwanted logging. |
| [r/69086|https://reviews.apache.org/r/69086] | Moved the container root construction to the isolators. |
| [r/69450|https://reviews.apache.org/r/69450] | Applied the `ContainerMountInfo` protobuf helper. |

> Move root filesystem creation to the `filesystem/linux` isolator.
> -----------------------------------------------------------------
>
>                 Key: MESOS-9319
>                 URL: https://issues.apache.org/jira/browse/MESOS-9319
>             Project: Mesos
>          Issue Type: Bug
>          Components: containerization
>            Reporter: James Peach
>            Assignee: James Peach
>            Priority: Major
>
> When using a custom user namespace isolator, the task fails at launch because opening devices fails with a EPERM error. This problem is described in [this systemd issue|https://github.com/systemd/systemd/pull/9483] and [this lxd|https://github.com/lxc/lxd/issues/4950] issue.
> The problem arises in the Mesos containerizer due to the order of operations:
> # Clone the containerizer with {{CLONE_NEWNS}}
> # Mount a tmpfs for the devices
> # mknod for the various device nodes
> Referring back to the lxc issue, because we do (1) before (2), the tmpfs on {{/dev}} is marked {{SB_I_NODEV}}. Due to the new 4.18 behavior, the mkdir in (3) now succeeds (see commit [55956b59df33|https://github.com/torvalds/linux/commit/55956b59df336f6738da916dbb520b6e37df9fbd]). Previously it would fail and we would fall back to bind mounting the device. However, even though we created the device, we can't actually open it due to the {{SB_I_NODEV}} flag on the tmpfs mount. It appears that the purpose of allowing mknod is to that containers can create overlayfs whiteouts.
> One approach to deal with this in the Mesos containerizer is to complete the device node cleanup that was begun in with the linux/devices isolator. This approach involves moving all the responsibility for creating devices back to the isolators. Then, at containerization time, we simply bind-mount the whole of /dev from the per-container staging area. Since the isolators create the devices in the host namespace and on the Mesos work directory, none of the conditions that trigger the failure would be invoked.
> The failure we observed with our tasks was a failure to open {{/dev/null}}, when redirecting it as standard input to a child process.



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