Overview of cloud storage systems

Each cloud storage system is slightly different. Rclone attempts to provide a unified interface to them, but some underlying differences show through.

Features

Here is an overview of the major features of each cloud storage system.

Name Hash ModTime Case Insensitive Duplicate Files MIME Type
1Fichier Whirlpool No No Yes R
Amazon Drive MD5 No Yes No R
Amazon S3 MD5 Yes No No R/W
Backblaze B2 SHA1 Yes No No R/W
Box SHA1 Yes Yes No -
Citrix ShareFile MD5 Yes Yes No -
Dropbox DBHASH † Yes Yes No -
FTP - No No No -
Google Cloud Storage MD5 Yes No No R/W
Google Drive MD5 Yes No Yes R/W
Google Photos - No No Yes R
HTTP - No No No R
Hubic MD5 Yes No No R/W
Jottacloud MD5 Yes Yes No R/W
Koofr MD5 No Yes No -
Mail.ru Cloud Mailru ‡‡‡ Yes Yes No -
Mega - No No Yes -
Memory MD5 Yes No No -
Microsoft Azure Blob Storage MD5 Yes No No R/W
Microsoft OneDrive SHA1 ‡‡ Yes Yes No R
OpenDrive MD5 Yes Yes No -
Openstack Swift MD5 Yes No No R/W
pCloud MD5, SHA1 Yes No No W
premiumize.me - No Yes No R
put.io CRC-32 Yes No Yes R
QingStor MD5 No No No R/W
SFTP MD5, SHA1 ‡ Yes Depends No -
SugarSync - No No No -
WebDAV MD5, SHA1 †† Yes ††† Depends No -
Yandex Disk MD5 Yes No No R/W
The local filesystem All Yes Depends No -

Hash

The cloud storage system supports various hash types of the objects. The hashes are used when transferring data as an integrity check and can be specifically used with the --checksum flag in syncs and in the check command.

To use the verify checksums when transferring between cloud storage systems they must support a common hash type.

† Note that Dropbox supports its own custom hash. This is an SHA256 sum of all the 4MB block SHA256s.

‡ SFTP supports checksums if the same login has shell access and md5sum or sha1sum as well as echo are in the remote’s PATH.

†† WebDAV supports hashes when used with Owncloud and Nextcloud only.

††† WebDAV supports modtimes when used with Owncloud and Nextcloud only.

‡‡ Microsoft OneDrive Personal supports SHA1 hashes, whereas OneDrive for business and SharePoint server support Microsoft’s own QuickXorHash.

‡‡‡ Mail.ru uses its own modified SHA1 hash

ModTime

The cloud storage system supports setting modification times on objects. If it does then this enables a using the modification times as part of the sync. If not then only the size will be checked by default, though the MD5SUM can be checked with the --checksum flag.

All cloud storage systems support some kind of date on the object and these will be set when transferring from the cloud storage system.

Case Insensitive

If a cloud storage systems is case sensitive then it is possible to have two files which differ only in case, eg file.txt and FILE.txt. If a cloud storage system is case insensitive then that isn’t possible.

This can cause problems when syncing between a case insensitive system and a case sensitive system. The symptom of this is that no matter how many times you run the sync it never completes fully.

The local filesystem and SFTP may or may not be case sensitive depending on OS.

  • Windows - usually case insensitive, though case is preserved
  • OSX - usually case insensitive, though it is possible to format case sensitive
  • Linux - usually case sensitive, but there are case insensitive file systems (eg FAT formatted USB keys)

Most of the time this doesn’t cause any problems as people tend to avoid files whose name differs only by case even on case sensitive systems.

Duplicate files

If a cloud storage system allows duplicate files then it can have two objects with the same name.

This confuses rclone greatly when syncing - use the rclone dedupe command to rename or remove duplicates.

Restricted filenames

Some cloud storage systems might have restrictions on the characters that are usable in file or directory names. When rclone detects such a name during a file upload, it will transparently replace the restricted characters with similar looking Unicode characters.

This process is designed to avoid ambiguous file names as much as possible and allow to move files between many cloud storage systems transparently.

The name shown by rclone to the user or during log output will only contain a minimal set of replaced characters to ensure correct formatting and not necessarily the actual name used on the cloud storage.

This transformation is reversed when downloading a file or parsing rclone arguments. For example, when uploading a file named my file?.txt to Onedrive will be displayed as my file?.txt on the console, but stored as my file?.txt (the ? gets replaced by the similar looking character) to Onedrive. The reverse transformation allows to read a fileunusual/name.txt from Google Drive, by passing the name unusual/name.txt (the / needs to be replaced by the similar looking character) on the command line.

Default restricted characters

The table below shows the characters that are replaced by default.

When a replacement character is found in a filename, this character will be escaped with the character to avoid ambiguous file names. (e.g. a file named ␀.txt would shown as ‛␀.txt)

Each cloud storage backend can use a different set of characters, which will be specified in the documentation for each backend.

Character Value Replacement
NUL 0x00
SOH 0x01
STX 0x02
ETX 0x03
EOT 0x04
ENQ 0x05
ACK 0x06
BEL 0x07
BS 0x08
HT 0x09
LF 0x0A
VT 0x0B
FF 0x0C
CR 0x0D
SO 0x0E
SI 0x0F
DLE 0x10
DC1 0x11
DC2 0x12
DC3 0x13
DC4 0x14
NAK 0x15
SYN 0x16
ETB 0x17
CAN 0x18
EM 0x19
SUB 0x1A
ESC 0x1B
FS 0x1C
GS 0x1D
RS 0x1E
US 0x1F
/ 0x2F
DEL 0x7F

The default encoding will also encode these file names as they are problematic with many cloud storage systems.

File name Replacement
.
.. ..

Invalid UTF-8 bytes

Some backends only support a sequence of well formed UTF-8 bytes as file or directory names.

In this case all invalid UTF-8 bytes will be replaced with a quoted representation of the byte value to allow uploading a file to such a backend. For example, the invalid byte 0xFE will be encoded as ‛FE.

A common source of invalid UTF-8 bytes are local filesystems, that store names in a different encoding than UTF-8 or UTF-16, like latin1. See the local filenames section for details.

Encoding option

Most backends have an encoding options, specified as a flag --backend-encoding where backend is the name of the backend, or as a config parameter encoding (you’ll need to select the Advanced config in rclone config to see it).

This will have default value which encodes and decodes characters in such a way as to preserve the maximum number of characters (see above).

However this can be incorrect in some scenarios, for example if you have a Windows file system with characters such as and that you want to remain as those characters on the remote rather than being translated to * and ?.

The --backend-encoding flags allow you to change that. You can disable the encoding completely with --backend-encoding None or set encoding = None in the config file.

Encoding takes a comma separated list of encodings. You can see the list of all available characters by passing an invalid value to this flag, eg --local-encoding "help" and rclone help flags encoding will show you the defaults for the backends.

Encoding Characters
Asterisk *
BackQuote `
BackSlash \
Colon :
CrLf CR 0x0D, LF 0x0A
Ctl All control characters 0x00-0x1F
Del DEL 0x7F
Dollar $
Dot .
DoubleQuote "
Hash #
InvalidUtf8 An invalid UTF-8 character (eg latin1)
LeftCrLfHtVt CR 0x0D, LF 0x0A,HT 0x09, VT 0x0B on the left of a string
LeftPeriod . on the left of a string
LeftSpace SPACE on the left of a string
LeftTilde ~ on the left of a string
LtGt <, >
None No characters are encoded
Percent %
Pipe |
Question ?
RightCrLfHtVt CR 0x0D, LF 0x0A, HT 0x09, VT 0x0B on the right of a string
RightPeriod . on the right of a string
RightSpace SPACE on the right of a string
SingleQuote '
Slash /

To take a specific example, the FTP backend’s default encoding is

--ftp-encoding "Slash,Del,Ctl,RightSpace,Dot"

However, let’s say the FTP server is running on Windows and can’t have any of the invalid Windows characters in file names. You are backing up Linux servers to this FTP server which do have those characters in file names. So you would add the Windows set which are

Slash,LtGt,DoubleQuote,Colon,Question,Asterisk,Pipe,BackSlash,Ctl,RightSpace,RightPeriod,InvalidUtf8,Dot

to the existing ones, giving:

Slash,LtGt,DoubleQuote,Colon,Question,Asterisk,Pipe,BackSlash,Ctl,RightSpace,RightPeriod,InvalidUtf8,Dot,Del,RightSpace

This can be specified using the --ftp-encoding flag or using an encoding parameter in the config file.

Or let’s say you have a Windows server but you want to preserve and , you would then have this as the encoding (the Windows encoding minus Asterisk and Question).

Slash,LtGt,DoubleQuote,Colon,Pipe,BackSlash,Ctl,RightSpace,RightPeriod,InvalidUtf8,Dot

This can be specified using the --local-encoding flag or using an encoding parameter in the config file.

MIME Type

MIME types (also known as media types) classify types of documents using a simple text classification, eg text/html or application/pdf.

Some cloud storage systems support reading (R) the MIME type of objects and some support writing (W) the MIME type of objects.

The MIME type can be important if you are serving files directly to HTTP from the storage system.

If you are copying from a remote which supports reading (R) to a remote which supports writing (W) then rclone will preserve the MIME types. Otherwise they will be guessed from the extension, or the remote itself may assign the MIME type.

Optional Features

All the remotes support a basic set of features, but there are some optional features supported by some remotes used to make some operations more efficient.

Name Purge Copy Move DirMove CleanUp ListR StreamUpload LinkSharing About EmptyDir
1Fichier No No No No No No No No No Yes
Amazon Drive Yes No Yes Yes No #575 No No No #2178 No Yes
Amazon S3 No Yes No No No Yes Yes No #2178 No No
Backblaze B2 No Yes No No Yes Yes Yes Yes No No
Box Yes Yes Yes Yes No #575 No Yes Yes No Yes
Citrix ShareFile Yes Yes Yes Yes No No Yes No No Yes
Dropbox Yes Yes Yes Yes No #575 No Yes Yes Yes Yes
FTP No No Yes Yes No No Yes No #2178 No Yes
Google Cloud Storage Yes Yes No No No Yes Yes No #2178 No No
Google Drive Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Google Photos No No No No No No No No No No
HTTP No No No No No No No No #2178 No Yes
Hubic Yes † Yes No No No Yes Yes No #2178 Yes No
Jottacloud Yes Yes Yes Yes No Yes No Yes Yes Yes
Mail.ru Cloud Yes Yes Yes Yes Yes No No Yes Yes Yes
Mega Yes No Yes Yes Yes No No No #2178 Yes Yes
Memory No Yes No No No Yes Yes No No No
Microsoft Azure Blob Storage Yes Yes No No No Yes No No #2178 No No
Microsoft OneDrive Yes Yes Yes Yes No #575 No No Yes Yes Yes
OpenDrive Yes Yes Yes Yes No No No No No Yes
Openstack Swift Yes † Yes No No No Yes Yes No #2178 Yes No
pCloud Yes Yes Yes Yes Yes No No No #2178 Yes Yes
premiumize.me Yes No Yes Yes No No No Yes Yes Yes
put.io Yes No Yes Yes Yes No Yes No #2178 Yes Yes
QingStor No Yes No No No Yes No No #2178 No No
SFTP No No Yes Yes No No Yes No #2178 Yes Yes
SugarSync Yes Yes Yes Yes No No Yes Yes No Yes
WebDAV Yes Yes Yes Yes No No Yes ‡ No #2178 Yes Yes
Yandex Disk Yes Yes Yes Yes Yes No Yes Yes Yes Yes
The local filesystem Yes No Yes Yes No No Yes No Yes Yes

Purge

This deletes a directory quicker than just deleting all the files in the directory.

† Note Swift and Hubic implement this in order to delete directory markers but they don’t actually have a quicker way of deleting files other than deleting them individually.

‡ StreamUpload is not supported with Nextcloud

Copy

Used when copying an object to and from the same remote. This known as a server side copy so you can copy a file without downloading it and uploading it again. It is used if you use rclone copy or rclone move if the remote doesn’t support Move directly.

If the server doesn’t support Copy directly then for copy operations the file is downloaded then re-uploaded.

Move

Used when moving/renaming an object on the same remote. This is known as a server side move of a file. This is used in rclone move if the server doesn’t support DirMove.

If the server isn’t capable of Move then rclone simulates it with Copy then delete. If the server doesn’t support Copy then rclone will download the file and re-upload it.

DirMove

This is used to implement rclone move to move a directory if possible. If it isn’t then it will use Move on each file (which falls back to Copy then download and upload - see Move section).

CleanUp

This is used for emptying the trash for a remote by rclone cleanup.

If the server can’t do CleanUp then rclone cleanup will return an error.

ListR

The remote supports a recursive list to list all the contents beneath a directory quickly. This enables the --fast-list flag to work. See the rclone docs for more details.

StreamUpload

Some remotes allow files to be uploaded without knowing the file size in advance. This allows certain operations to work without spooling the file to local disk first, e.g. rclone rcat.

LinkSharing

Sets the necessary permissions on a file or folder and prints a link that allows others to access them, even if they don’t have an account on the particular cloud provider.

About

This is used to fetch quota information from the remote, like bytes used/free/quota and bytes used in the trash.

This is also used to return the space used, available for rclone mount.

If the server can’t do About then rclone about will return an error.

EmptyDir

The remote supports empty directories. See Limitations for details. Most Object/Bucket based remotes do not support this.