---
name: "rbd-nbd"
section: "8"
platform: "linux"
package: "rbd-nbd"
version: "18.2.7+ds-1+deb13u1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/rbd-nbd"
---

# rbd-nbd(8)

map rbd images to nbd device

## NAME

rbd-nbd - map rbd images to nbd device

## SYNOPSIS

```
rbd-nbd [-c conf] [--read-only] [--device nbd device] [--snap-id snap-id] [--nbds_max limit] [--max_part limit] [--exclusive] [--notrim] [--encryption-format format] [--encryption-passphrase-file passphrase-file] [--io-timeout seconds] [--reattach-timeout seconds] map image-spec | snap-spec
rbd-nbd unmap nbd device | image-spec | snap-spec
rbd-nbd list-mapped
rbd-nbd attach --device nbd device image-spec | snap-spec
rbd-nbd detach nbd device | image-spec | snap-spec
```

## DESCRIPTION

**rbd-nbd** is a client for RADOS block device (rbd) images like rbd kernel module. It will map a rbd image to a nbd (Network Block Device) device, allowing access it as regular local block device.

## OPTIONS

- **-c ceph.conf**

  Use *ceph.conf* configuration file instead of the default **/etc/ceph/ceph.conf** to determine monitor addresses during startup.

- **--read-only**

  Map read-only.

- **--nbds\_max \*limit\***

  Override the parameter nbds\_max of NBD kernel module when modprobe, used to limit the count of nbd device.

- **--max\_part \*limit\***

  Override for module param max\_part.

- **--exclusive**

  Forbid writes by other clients.

- **--notrim**

  Turn off trim/discard.

- **--encryption-format**

  Image encryption format. Possible values: *luks*, *luks1*, *luks2*

- **--encryption-passphrase-file**

  Path of file containing a passphrase for unlocking image encryption.

- **--io-timeout \*seconds\***

  Override device timeout. Linux kernel will default to a 30 second request timeout. Allow the user to optionally specify an alternate timeout.

- **--reattach-timeout \*seconds\***

  Specify timeout for the kernel to wait for a new rbd-nbd process is attached after the old process is detached. The default is 30 second.

- **--snap-id \*snapid\***

  Specify a snapshot to map/unmap/attach/detach by ID instead of by name.

## IMAGE AND SNAP SPECS

```
image-spec is [pool-name]/image-name
snap-spec  is [pool-name]/image-name@snap-name
```

The default for *pool-name* is "rbd".  If an image name contains a slash character ('/'), *pool-name* is required.

## AVAILABILITY

**rbd-nbd** is part of Ceph, a massively scalable, open-source, distributed storage system. Please refer to the Ceph documentation at *https://docs.ceph.com/* for more information.

## SEE ALSO

[*rbd*(8)](/rbd/8.md)

## COPYRIGHT

2010-2014, Inktank Storage, Inc. and contributors. Licensed under Creative Commons Attribution Share Alike 3.0 (CC-BY-SA-3.0)