Merge pull request #1777 from deitch/document-container-mount-options

Add docs how to use mount options for special mounting containers
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Justin Cormack 2017-05-08 20:32:15 +01:00 committed by GitHub
commit da72655886

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@ -106,3 +106,35 @@ For more details see the [OCI specification](https://github.com/opencontainers/r
- `sysctl` sets a list of `sysctl` key value pairs that are set inside the container namespace.
Further OCI values will be added, as the list is not yet complete.
### Mount Options
When mounting filesystem paths into a container - whether as part of `onboot` or `services` - there are several options of which you need to be aware. Using them properly is necessary for your containers to function properly.
For most containers - e.g. nginx or even docker - these options are not needed. Simply doing the following will work fine:
```yml
binds:
- /var:/some/var/path
```
However, in some circumstances you will need additional options. These options are used primarily if you intend to make changes to mount points _from within your container_ that should be visible from outside the container, e.g., if you intend to mount an external disk from inside the container but have it be visible outside.
In order for new mounts from within a container to be propagated, you must set the following on the container:
1. `rootfsPropagation: shared`
2. The mount point into the container below which new mounts are to occur must be `rshared,rbind`. In practice, this is `/var` (or some subdir of `/var`), since that is the only true read-write area of the filesystem where you will mount things.
Thus, if you have a regular container that is only reading and writing, go ahead and do:
```yml
binds:
- /var:/some/var/path
```
On the other hand, if you have a container that will make new mounts that you wish to be visible outside the container, do:
```yml
binds:
- /var:/var:rshared,rbind
rootfsPropagation: shared
```