<p>By a "local volume" I assume you mean a block device directly attached to the host, such as a "normal" internal disk. </p>

<p>The standard way to run multiple Docker, containers now is Kubernetes, since the demise of Docker Swarm. My reference here is the Kubernetes <a href="https://kubernetes.io/docs/concepts/storage/persistent-volumes/#persistent-volumes" rel="nofollow noreferrer">documentation for Persistent Volumes</a> specifically the table on Access Modes, and the column for <em>ReadWriteMany</em>. A local volume would be a <em>HostPath</em> which is <em>not</em> supported for this use case. However if you were using iSCSI it would support <em>ReadOnlyMany</em>, and if you used NFS you could get <em>ReadWriteMany</em>. </p>

CC BY-SA 4.0
2019-03-04T00:37:20.440Z
Searching for the demise of swarm I can only find articles that say that Swarm isn’t demised it is simply that Docker EE will also support k8s. Do you have an official link that says otherwise?
simbo1905
CC BY-SA 4.0
2019-03-02T15:15:34.847Z
2019-03-02T15:15:34.847Z
Gaius
<p>According to <a href="https://stackoverflow.com/a/42855234/2363712">that StackOverflow answer</a>:</p>

<blockquote>
  <p>Yes you can add same location as a volume to many docker containers.</p>
</blockquote>

<p>But I read the <a href="https://docs.docker.com/storage/volumes/" rel="nofollow noreferrer">Docker Volume documention</a> and I can't find where it is said a <em>local</em> volume can safely be shared between several containers on the same host. Could someone point me to an official statement regarding that? </p>

CC BY-SA 4.0
2019-02-26T15:39:17.840Z
It is the same as sharing the same directory between multiple process. /var/log is usually written into by multiple process in a system.
Tensibai
CC BY-SA 4.0
2019-02-26T18:06:53.057Z
Well, what confuses me @Tensibai is volumes are _mounted_ several times. Given the way the Linux kernel handles mounts, it isn't a problem to mount the same device at different locations. But is this just a happy consequence of that, or a supported feature guaranteed to work the same on non-Linux Docker platforms (ie, with Windows Native containers)?
Sylvain Leroux
CC BY-SA 4.0
2019-02-27T07:37:51.117Z
Technically, they are only mounted once in each container, and at the end of the day, that's not a real mount, that's more a hole in the name spaces where a process in namespace A is allowed to access filesystem in 'host' namespace
Tensibai
CC BY-SA 4.0
2019-02-27T09:48:41.213Z
Define "safe". Will it work? Yes. Will you get problems if multiple containers read/write the same set of files? Yes.
Raphael
<docker><volume>
Where is it said I can safely the same local volume to multiple docker containers?
Sylvain Leroux
# Where is it said I can safely the same local volume to multiple docker containers?

(Asked by: username_0 on 2019-02-26)

According to [that StackOverflow answer](https://stackoverflow.com/a/42855234/2363712):

> Yes you can add same location as a volume to many docker containers.

But I read the [Docker Volume documention](https://docs.docker.com/storage/volumes/) and I can't find where it is said a *local* volume can safely be shared between several containers on the same host. Could someone point me to an official statement regarding that?

**Tags:** docker, volume

> **Comments:**
> **username_1**: It is the same as sharing the same directory between multiple process. /var/log is usually written into by multiple process in a system.  
> **username_0**: Well, what confuses me @username_1 is volumes are _mounted_ several times. Given the way the Linux kernel handles mounts, it isn't a problem to mount the same device at different locations. But is this just a happy consequence of that, or a supported feature guaranteed to work the same on non-Linux Docker platforms (ie, with Windows Native containers)?  
> **username_1**: Technically, they are only mounted once in each container, and at the end of the day, that's not a real mount, that's more a hole in the name spaces where a process in namespace A is allowed to access filesystem in 'host' namespace  
> **username_2**: Define "safe". Will it work? Yes. Will you get problems if multiple containers read/write the same set of files? Yes.  

---

## 1 answers

### Answer by username_3 on 2019-03-02. Score: 1

By a "local volume" I assume you mean a block device directly attached to the host, such as a "normal" internal disk.

The standard way to run multiple Docker, containers now is Kubernetes, since the demise of Docker Swarm. My reference here is the Kubernetes [documentation for Persistent Volumes](https://kubernetes.io/docs/concepts/storage/persistent-volumes/#persistent-volumes) specifically the table on Access Modes, and the column for *ReadWriteMany*. A local volume would be a *HostPath* which is *not* supported for this use case. However if you were using iSCSI it would support *ReadOnlyMany*, and if you used NFS you could get *ReadWriteMany*.

> **Comments:**
> **username_4**: Searching for the demise of swarm I can only find articles that say that Swarm isn’t demised it is simply that Docker EE will also support k8s. Do you have an official link that says otherwise?  

---

