modal.Volume

class Volume(modal.object.Object)

A writeable volume that can be used to share files between one or more Modal functions.

The contents of a volume is exposed as a filesystem. You can use it to share data between different functions, or to persist durable state across several instances of the same function.

Unlike a networked filesystem, you need to explicitly reload the volume to see changes made since it was mounted. Similarly, you need to explicitly commit any changes you make to the volume for the changes to become visible outside the current container.

Concurrent modification is supported, but concurrent modifications of the same files should be avoided! Last write wins in case of concurrent modification of the same file - any data the last writer didn’t have when committing changes will be lost!

As a result, volumes are typically not a good fit for use cases where you need to make concurrent modifications to the same file (nor is distributed file locking supported).

Volumes can only be reloaded if there are no open files for the volume - attempting to reload with open files will result in an error.

Usage

import modal

app = modal.App()
volume = modal.Volume.from_name("my-persisted-volume", create_if_missing=True)

@app.function(volumes={"/root/foo": volume})
def f():
    with open("/root/foo/bar.txt", "w") as f:
        f.write("hello")
    volume.commit()  # Persist changes

@app.function(volumes={"/root/foo": volume})
def g():
    volume.reload()  # Fetch latest changes
    with open("/root/foo/bar.txt", "r") as f:
        print(f.read())

hydrate

hydrate(self, client=None)

Synchronize the local object with its identity on the Modal server.

It is rarely necessary to call this method explicitly, as most operations will lazily hydrate when needed. The main use case is when you need to access object metadata, such as its ID.

Added in v0.72.39: This method replaces the deprecated .resolve() method.

objects

objects: VolumeManager

Namespace with methods for managing named Volume objects.

objects.create

create(self, name, *, version=None, allow_existing=False, environment_name=None,
    client=None)

Create a new named Volume in the workspace environment.

This does not return a local handle; use modal.Volume.from_name to look up the Volume after creation.

Added in v1.1.2.

Parameters

name str

Name for the new Volume.

version int | None

Optional VolumeFS backend version (1 or 2); experimental.

allow_existing bool

If True, do nothing when a Volume with this name already exists. (Default is False)

environment_name str | None

Environment to create in; defaults to the active environment.

client _Client | None

Modal client to use; defaults to Client.from_env() when omitted.

Usage

modal.Volume.objects.create("my-volume")

Volumes will be created in the active environment, or another one can be specified:

modal.Volume.objects.create("my-volume", environment_name="dev")

By default, an error is raised if the Volume already exists; allow_existing=True makes that case a no-op:

modal.Volume.objects.create("my-volume", allow_existing=True)

Note that this method does not return a local instance of the Volume. You can use modal.Volume.from_name to perform a lookup after creation.

objects.list

list(self, *, max_objects=None, created_before=None, environment_name="",
    client=None)

List named Volumes in the workspace environment as hydrated handles.

Results are ordered newest to oldest. By default, all matching Volumes are returned.

Added in v1.1.2.

Parameters

max_objects int | None

Maximum number of Volumes to return.

created_before datetime | str | None

Only include Volumes created before this time (datetime or ISO date string).

environment_name str

Environment to list from; defaults to the active environment. (Default is "")

client _Client | None

Modal client to use; defaults to Client.from_env() when omitted.

Returns

Hydrated Volume objects for each named Volume in the listing.

Usage

volumes = modal.Volume.objects.list()
print([v.name for v in volumes])

Volumes will be retrieved from the active environment, or another one can be specified:

dev_volumes = modal.Volume.objects.list(environment_name="dev")

By default, all named Volumes are returned, newest to oldest. It’s also possible to limit the number of results and to filter by creation date:

volumes = modal.Volume.objects.list(max_objects=10, created_before="2025-01-01")

objects.delete

delete(self, name, *, allow_missing=False, environment_name=None, client=None)

Delete a named Volume entirely (not individual files).

Deletion is irreversible and affects any Apps using this Volume.

Added in v1.1.2.

Parameters

name str

Name of the Volume to delete.

allow_missing bool

If True, do nothing when the Volume does not exist. (Default is False)

environment_name str | None

Environment to delete from; defaults to the active environment.

client _Client | None

Modal client to use; defaults to Client.from_env() when omitted.

Usage

await modal.Volume.objects.delete("my-volume")

Volumes will be deleted from the active environment, or another one can be specified:

await modal.Volume.objects.delete("my-volume", environment_name="dev")

name

name(self)

with_mount_options

with_mount_options(self, *, read_only=None, sub_path=None)

Configure options used when mounting this Volume.

Note that these options are not properties stored with the Volume itself - they can be individually configured for each Volume - container association.

Parameters

read_only bool | None

Set this to True to make the Volume read only from within containers.

sub_path str | PurePosixPath | None

Only mount this sub_path directory from the Volume. If the directory doesn't exist in the Volume, it will be created when the container starts up.

Returns

A Volume handle with the mount options applied.

Usage

To mount a volume in read-only mode:

import modal

volume = modal.Volume.from_name("my-volume")

@app.function(volumes={"/mnt": volume.with_mount_options(read_only=True)})
def f():
    return os.mkdir("/mnt/foo")  # not possible!

To mount only part of a Volume using sub_path:

import modal

volume = modal.Volume.from_name("my-volume")

@app.function(volumes={"/user_data": volume.with_mount_options(sub_path="/users/my_user")})
def f():
    return os.listdir("/user_data")  # lists data from /users/my_user

from_name

from_name(name, *, environment_name=None, create_if_missing=False, version=None,
    client=None)

Reference a Volume by name, optionally creating it on the server first.

Hydration is lazy: metadata is fetched from Modal the first time the handle is used.

Parameters

name str

Deployment name of the Volume.

environment_name str | None

Environment to resolve the name in; defaults to the active environment.

create_if_missing bool

If True, create the Volume when it does not already exist. (Default is False)

version "modal_proto.api_pb2.VolumeFsVersion.ValueType | None"

Optional VolumeFS backend version; must match an existing Volume when set.

client _Client | None

Modal client to use for loading; defaults to Client.from_env() when omitted.

Returns

A Volume handle (possibly not yet hydrated).

Usage

vol = modal.Volume.from_name("my-volume", create_if_missing=True)

app = modal.App()

@app.function(volumes={"/data": vol})
def f():
    pass

from_id

from_id(volume_id, client=None)

Construct a Volume from an id and look up the Volume metadata.

This is a lazy method that defers hydrating the local object with metadata from Modal servers until the first time it is actually used.

The ID of a Volume object can be accessed using .object_id.

Parameters

volume_id str

Volume object ID to attach to.

client _Client | None

Modal client to use for loading; defaults to Client.from_env() when omitted.

Returns

A Volume handle (possibly not yet hydrated).

Usage

@app.function()
def my_worker(volume_id: str):
    vol = modal.Volume.from_id(volume_id)
    for entry in vol.listdir("/"):
        print(entry.path)

with modal.Volume.ephemeral() as vol:
    my_worker.remote(vol.object_id)

ephemeral

ephemeral(cls, client=None, environment_name=None, version=None)

Create an anonymous Volume that exists for the duration of the context manager.

Parameters

client _Client | None

Modal client to use; defaults to Client.from_env() when omitted.

environment_name str | None

Environment for the ephemeral Volume; defaults to the active environment.

version "modal_proto.api_pb2.VolumeFsVersion.ValueType | None"

Optional VolumeFS backend version for the ephemeral Volume.

Usage

import modal

with modal.Volume.ephemeral() as vol:
    assert vol.listdir("/") == []

async with modal.Volume.ephemeral() as vol:
    assert await vol.listdir("/") == []

info

info(self)

Return information about the Volume object.

commit

commit(self)

Commit changes to a mounted volume.

If successful, the changes made are now persisted in durable storage and available to other containers accessing the volume.

reload

reload(self)

Make latest committed state of volume available in the running container.

Any uncommitted changes to the volume, such as new or modified files, may implicitly be committed when reloading.

Reloading will fail if there are open files for the volume.

iterdir

iterdir(self, path, *, recursive=True)

Iterate over all files in a directory in the volume.

Passing a directory path lists all files in the directory. For a file path, return only that file’s description. If recursive is set to True, list all files and folders under the path recursively.

listdir

listdir(self, path, *, recursive=False)

List all files under a path prefix in the modal.Volume.

read_file

read_file(self, path)

Read a file from the modal.Volume.

Note - this function is primarily intended to be used outside of a Modal App. For more information on downloading files from a Modal Volume, see the guide.

Parameters

path str

Path to the file inside the Volume.

Usage

vol = modal.Volume.from_name("my-modal-volume")
data = b""
for chunk in vol.read_file("1mb.csv"):
    data += chunk
print(len(data))  # == 1024 * 1024

remove_file

remove_file(self, path, recursive=False)

Remove a file or directory from a volume.

copy_files

copy_files(self, src_paths, dst_path, recursive=False)

Copy files within the volume from src_paths to dst_path. The semantics of the copy operation follow those of the UNIX cp command.

The src_paths parameter is a list. If you want to copy a single file, you should pass a list with a single element.

src_paths and dst_path should refer to the desired location inside the volume. You do not need to prepend the volume mount path.

Note that if the volume is already mounted on the Modal function, you should use normal filesystem operations like os.rename() and then commit() the volume. The copy_files() method is useful when you don’t have the volume mounted as a filesystem, e.g. when running a script on your local computer.

Parameters

src_paths Sequence[str]

Source paths inside the Volume (list of one or more paths).

dst_path str

Destination path inside the Volume (file or directory, following cp semantics).

recursive bool

Whether to copy directories recursively (V2 volumes only). (Default is False)

Usage

vol = modal.Volume.from_name("my-modal-volume")

vol.copy_files(["bar/example.txt"], "bar2")
vol.copy_files(["bar/example.txt"], "bar/example2.txt")

batch_upload

batch_upload(self, force=False)

Initiate a batched upload to a volume.

To allow overwriting existing files, set force to True (you cannot overwrite existing directories with uploaded files regardless).

Parameters

force bool

If True, allow overwriting existing files with uploads (not directories). (Default is False)

Usage

vol = modal.Volume.from_name("my-modal-volume")

with vol.batch_upload() as batch:
    batch.put_file("local-path.txt", "/remote-path.txt")
    batch.put_directory("/local/directory/", "/remote/directory")
    batch.put_file(io.BytesIO(b"some data"), "/foobar")

rename

rename(old_name, new_name, *, client=None, environment_name=None)