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https://issues.apache.org/jira/browse/MESOS-9319?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16667915#comment-16667915
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James Peach commented on MESOS-9319:
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Retitling, based on a sightly expanded scope from review feedback. Rather than
just building /dev in the Linux filesystem isolator, we are going to build the
whole root filesystem.
| [r/69086|https://reviews.apache.org/r/69086] | Moved container root
construction to the isolators. |
| [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. |
> 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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