Write support¶
Version 2.0 introduced write support in Disk Decipher.
Storage provider¶
Write support is currently supported for local and linked disks. The NFS remote storage provider is also write-enabled.
Version 3.13.3 adds initial write support to the WebDAV remote storage provider.
To support write operations on a remote disk, Disk Decipher needs to be able to submit partial update operations to the WebDAV server. Unfortunately there is no official standard for partial updates in the WebDAV RFCs, but there are two common implementations:
- Apache mod_dav, which uses the PUT method combined with a Content-Range header (note that this conflicts with RFC 7231 section 4.3.4)
- SabreDav, which uses the PATCH method combined with a X-Update-Range header
Please let me know if you know other WebDAV implementations providing partial update support.
Limitations¶
The initial WebDAV write support has the following limitations:
- Synchronous writes (persistent write cache support will be added to improve performance)
- Secure network connection required (no manual trust)
- The disk image is not locked on the WebDAV server while mounted
These restrictions will be relaxed in future updates.
Disk format¶
Write support is supported for all disk formats supported by Disk Decipher (VeraCrypt, TrueCrypt, FreeOTFE and LUKS). All cipher combinations are supported.
File system¶
Write support is available for all supported filesystems. More details are listed on the Filesystems overview.
Multi-device access¶
When it comes to simultaneous mounts from multiple devices, caution is essential.
In short: Disk Decipher does not implement cross-device locking for shared disk images. While it uses Apple’s platform-provided coordination mechanisms during read and write operations—helping avoid conflicts when accessed by multiple apps on the same device—this coordination doesn't extend across network-mounted volumes like SMB or NFS.
Here’s what to keep in mind:
- Writing to the same image from more than one device can easily result in data corruption. Filesystem-level caching makes this inherently risky—even if devices alternate access.
- Read-only mounting is safe. You can safely access the same image from multiple devices, as long as you enable the read-only toggle on all of them. This prevents background journaling or metadata writes that could still cause corruption.
Never mount the same disk image in write mode on multiple devices at once.