The "docker container run" command has two options that allow you to mount local files and directories into your containers:

-v, --volume list                      Bind mount a volume
    --mount mount                      Attach a filesystem mount to the container

The first option is to use Docker volumes, a special type of data storage managed by Docker that allows us to manage the files and directories used by containers

Create a test volume:

$ docker volume create volume1

volume1

Let's check the created volume:

$ docker volume ls --format json | jq

{
  "Availability": "N/A",
  "Driver": "local",
  "Group": "N/A",
  "Labels": "",
  "Links": "N/A",
  "Mountpoint": "/var/lib/docker/volumes/volume1/_data",
  "Name": "volume1",
  "Scope": "local",
  "Size": "N/A",
  "Status": "N/A"
}

$ docker volume inspect volume1 --format json | jq

[
  {
    "CreatedAt": "2024-06-18T23:55:27Z",
    "Driver": "local",
    "Labels": null,
    "Mountpoint": "/var/lib/docker/volumes/volume1/_data",
    "Name": "volume1",
    "Options": null,
    "Scope": "local"
  }
]

Let's use the created volume:

$ docker container run --rm --volume volume1:/cvdata ubuntu:latest \
/bin/bash -c "echo 'hello docker volumes' > /cvdata/file1.txt; cat /cvdata/file1.txt"

hello docker volumes

The second option is to bind mount a directory and a file from the Docker host.

Let's bind mount a directory and a file using the -v (--volume) option:

$ touch ./dockerhostfile.txt
$ sudo chown root:root ./dockerhostfile.txt

$ docker container run --rm \
--volume /usr/local/bin:/tmp/ulb:ro \
--volume ./dockerhostfile.txt:/tmp/containerfile.txt \
ubuntu:latest \
/bin/bash -c "ls -1 /tmp/ulb | wc -l; echo 'test' > /tmp/containerfile.txt"

Notes:

• We are mounting a directory (/usr/local/bin) and a file (./dockerhostfile.txt) from the Docker host into the container.
  
• The files/directories from the source (docker host) and the target (container) are separated by the colon character (:).
  
• The ro flag indicates that the source directory is mounted using the read-only mode (otherwise mounted read-write by default: rw).
  
• The source file (docker host) needs to be created in advance (otherwise it will be mounted as a directory).
  
• The user that run the container (in this example root) should have write access if needed.
  
• If the directories don't exist, they will be automatically created if no permission issues.
  
• The created directories will be owned by the user that run the container.
  

The third option is to use the --mount option to mount a directory and a file from the Docker host.

Let's do the same with the --mount option:

$ docker container run --rm \
--mount type=bind,source=/usr/local/bin,target=/tmp/ulb,readonly \
--mount type=bind,source=./dockerhostfile.txt,target=/tmp/containerfile.txt \
ubuntu:latest \
/bin/bash -c "ls -1 /tmp/ulb | wc -l; echo 'test' > /tmp/containerfile.txt"

The same notes discussed above apply to the --mount option, with the following exceptions:

• The files/directories from the source (docker host) and the target (container) are separated by the comma character (,).
  
• To indicate a read only mount, we need to use the flag readonly (otherwise mounted read-write by default).
  
• The flag source is used for the source file/directory in the Docker host.
  
• The flag target is used for the target file/directory in the container.
  

The command "docker container run" provides the option --tmpfs to mount a temporary filesystem.
The data of a tmpfs filesystem is stored in RAM and lost when the container is stopped.

Let's check the default "/tmp" folder:

$ docker container run --rm ubuntu:latest /bin/bash -c "df -h /tmp"

Filesystem      Size  Used Avail Use% Mounted on
overlay         507G  5.3G 451G   1% /

By default the /tmp folder is mounted as the root filesystem. This can be an issue if the container's root filesystem is mounted read only (option --read-only).

Let's use the the option --tmpfs:

$ docker container run --rm --tmpfs /tmp ubuntu:latest /bin/bash -c "df -h /tmp"

Filesystem      Size  Used Avail Use% Mounted on
tmpfs           7.8G     0  7.8G   0% /tmp

We can use the --mount option to mount a tmpfs filesystem and set it size:

$ docker container run --rm --mount type=tmpfs,destination=/tmp,tmpfs-size=1G ubuntu:latest /bin/bash -c "df -h /tmp"

Filesystem      Size  Used Avail Use% Mounted on
tmpfs           1.0G     0  1.0G   0% /tmp