SYNCTHING-VERSIONING(7) Syncthing SYNCTHING-VERSIONING(7)

syncthing-versioning - Keep automatic backups of deleted files by other nodes

Syncthing supports archiving the old version of a file when it is deleted or replaced with a newer version from the cluster. This is called “file versioning” and uses one of the available versioning strategies described below. File versioning is configured per folder, on a per-device basis, and defaults to “no file versioning”, i.e. no old copies of files are kept.

NOTE:

Versioning applies to changes received from other devices. That is, if Alice has versioning turned on and Bob changes a file, the old version will be archived on Alice’s computer when that change is synced from Bob. If Alice changes a file locally on her own computer Syncthing will not and can not archive the old version.

The applicable configuration options for each versioning strategy are described below. For most of them it’s possible to specify where the versions are stored, with the default being the .stversions folder inside the shared folder path. If you set a custom version path, please ensure that it’s on the same partition or filesystem as the regular folder path, as moving files there may otherwise fail.

This versioning strategy emulates the common “trash can” approach. When a file is deleted or replaced due to a change on a remote device, it is moved to the trash can in the .stversions folder. If a file with the same name was already in the trash can it is replaced.

A configuration option is available to clean the trash can from files older than a specified number of days. If this is set to a positive number of days, files will be removed when they have been in the trash can that long. Setting this to zero prevents any files from being removed from the trash can automatically.

With “Simple File Versioning” files are moved to the .stversions folder when replaced or deleted on a remote device. In addition to the cleanoutDays option, this strategy also takes a value in an input titled “Keep Versions” which tells Syncthing how many old versions of the file it should keep. For example, if you set this value to 5, if a file is replaced 5 times on a remote device, you will see 5 time-stamped versions on that file in the .stversions folder on the other devices sharing the same folder.

With “Staggered File Versioning” files are also moved to the .stversions folder when replaced or deleted on a remote device (just like “Simple File Versioning”), however, versions are automatically deleted if they are older than the maximum age or exceed the number of files allowed in an interval.

The following intervals are used and they each have a maximum number of files that will be kept for each.

1 Hour
For the first hour, the oldest version in every 30-seconds interval is kept.
1 Day
For the first day, the oldest version in every hour is kept.
30 Days
For the first 30 days, the oldest version in every day is kept.
Until maximum age, the oldest version in every week is kept.
The maximum time to keep a version in days. For example, to keep replaced or deleted files in the .stversions folder for an entire year, use 365. If only for 10 days, use 10. Corresponds to the maxAge option. Note: Set to 0 to keep versions forever.

This means that there is only one version in each interval and as files age they will be deleted unless when the interval they are entering is empty. By keeping the oldest versions this versioning scheme preserves the file if it is overwritten.

For more info, check the unit test file https://github.com/syncthing/syncthing/blob/main/lib/versioner/staggered_test.go#L32 that shows which versions are deleted for a specific run.

This versioning strategy delegates the decision on what to do to an external command (e.g. a program or a command line script). Just prior to a file being replaced, the command will be executed. The file needs to be removed from the folder in the process, or otherwise Syncthing will report an error. The command can use the following templated arguments:

%FOLDER_PATH%
Path to the folder
%FILE_PATH%
Path to the file within the folder

Note that the former expands to the path of the actual Syncthing folder, and the latter to the path inside that folder. For instance, if you use the default Sync folder in Windows, and the full path to the file is C:\Users\User\Sync\Family photos\IMG_2021-03-01.jpg, then the %FOLDER_PATH% will be C:\Users\User\Sync, and the %FILE_PATH% will be Family photos\IMG_2021-03-01.jpg.

Let’s say I want to keep the latest version of each file as they are replaced or removed; essentially I want a “trash can”-like behavior. For this, I create the following script and store it as /Users/jb/bin/onlylatest.sh (i.e. the bin directory in my home directory):

#!/bin/sh
set -eu
# Where I want my versions stored
versionspath=~/.trashcan
# The parameters we get from Syncthing
folderpath="$1"
filepath="$2"
# First ensure the dir where we need to store the file exists
outpath=$(dirname "$versionspath/$filepath")
mkdir -p "$outpath"
# Then move the file there
mv -f "$folderpath/$filepath" "$versionspath/$filepath"

I must ensure that the script has execute permissions (chmod 755 onlylatest.sh), then configure Syncthing with command /Users/jb/bin/onlylatest.sh %FOLDER_PATH% %FILE_PATH%

Let’s assume I have a folder “default” in ~/Sync, and that within that folder there is a file docs/letter.txt that is being replaced or deleted. The script will be called as if I ran this from the command line:

$ /Users/jb/bin/onlylatest.sh /Users/jb/Sync docs/letter.txt

The script will then move the file in question to ~/.trashcan/docs/letter.txt, replacing any previous version of that letter that may already have been there.

On Windows we can use a batch script to perform the same “trash can”-like behavior as mentioned above. I created the following script and saved it as C:\Users\mfrnd\Scripts\onlylatest.bat.

@echo off
rem Enable UTF-8 encoding to deal with multilingual folder and file names
chcp 65001
rem We need command extensions for md to create intermediate folders in one go
setlocal enableextensions
rem Where I want my versions stored
set "versions_path=%USERPROFILE%\.trashcan"
rem The parameters we get from Syncthing, '~' removes quotes if any
set "folder_path=%~1"
set "file_path=%~2"
rem First ensure the dir where we need to store the file exists
for %%f in ("%versions_path%\%file_path%") do set "output_path=%%~dpf"
if not exist "%output_path%" md "%output_path%" || exit /b
rem Finally move the file, overwrite existing file if any
move /y "%folder_path%\%file_path%" "%versions_path%\%file_path%"

Finally, I set "C:\Users\mfrnd\Scripts\onlylatest.bat" "%FOLDER_PATH%" "%FILE_PATH%" as the command name in Syncthing.

We can use PowerShell to send files directly to the Recycle Bin, which mimics the behaviour of deleting them using the Windows Explorer. Firstly, create the following script and save it in your preferred location, e.g. C:\Users\User\Scripts\SendToRecycleBin.ps1.

# PowerShell has no native method to recycle files, so we use Visual
# Basic to perform the operation. If succeeded, we also include the
# recycled file in the Syncthing's DEBUG output.
Add-Type -AssemblyName Microsoft.VisualBasic
[Microsoft.VisualBasic.FileIO.FileSystem]::DeleteFile($args,'OnlyErrorDialogs','SendToRecycleBin')
if ($?) {
  Write-Output ("Recycled " + $args + ".")
}

Alternatively, the script can be expanded to send only deleted files to the Recycle Bin, and permanently delete modified ones, which makes it more consistent with how the Explorer works.

# PowerShell has no native method to recycle files, so we use Visual
# Basic to perform the operation.
Add-Type -AssemblyName Microsoft.VisualBasic
# We need to test if a Syncthing .tmp file exists. If it does, we assume
# a modification and delete the existing file. If if does not, we assume
# a deletion and recycle the current file. If succeeded, we also include
# the deleted/recycled file in the Syncthing's DEBUG output.
if (Test-Path -LiteralPath ((Split-Path -Path $args) + "\~syncthing~" + (Split-Path -Path $args -Leaf) + ".tmp")) {
  [Microsoft.VisualBasic.FileIO.FileSystem]::DeleteFile($args,'OnlyErrorDialogs','DeletePermanently')
  if ($?) {
    Write-Output ("Deleted " + $args + ".")
  }
} else {
  [Microsoft.VisualBasic.FileIO.FileSystem]::DeleteFile($args,'OnlyErrorDialogs','SendToRecycleBin')
  if ($?) {
    Write-Output ("Recycled " + $args + ".")
  }
}

Finally, we set the command name in Syncthing to powershell.exe -ExecutionPolicy Bypass -File "C:\Users\User\Scripts\SendToRecycleBin.ps1" "%FOLDER_PATH%\%FILE_PATH%".

The only caveat that you should be aware of is that if your Syncthing folder is located on a portable storage, such as a USB stick, or if you have the Recycle Bin disabled, then the script will end up deleting all files permanently.

The versioning settings are grouped into their own section of each folder in the configuration file. The following shows an example of such a section in the XML:

<folder id="...">
    <versioning type="simple">
        <cleanupIntervalS>3600</cleanupIntervalS>
        <fsPath></fsPath>
        <fsType>basic</fsType>
        <param key="cleanoutDays" val="0"></param>
        <param key="keep" val="5"></param>
    </versioning>
</folder>
Selects one of the versioning strategies: trashcan, simple, staggered, external or leave empty to disable versioning completely.
Overrides the path where old versions of files are stored and defaults to .stversions if left empty. An absolute or relative path can be specified. The latter is interpreted relative to the shared folder path, if the fsType is configured as basic. Ignored for the external versioning strategy.

This option used to be stored under the keys fsPath or versionsPath in the params element.

The internal file system implementation used to access this versions folder. Only applies if fsPath is also set non-empty, otherwise the filesystemType from the folder element is used instead. Refer to that option description for possible values. Ignored for the external versioning strategy.

This option used to be stored under the key fsType in the params element.

The interval, in seconds, for running cleanup in the versions folder. Zero to disable periodic cleaning. Limited to one year (31536000 seconds). Ignored for the external versioning strategy.

This option used to be stored under the key cleanInterval in the params element.

Each versioning strategy can have configuration parameters specific to its implementation under this element.
The number of days to keep files in the versions folder. Zero means to keep forever. Older elements encountered during cleanup are removed.
The number of old versions to keep, per file.
The maximum time to keep a version, in seconds. Zero means to keep forever.
External command to execute for storing a file version about to be replaced or deleted. If the path to the application contains spaces, it should be quoted.

The Syncthing Authors

2014-2019, The Syncthing Authors

May 8, 2024 v1.27.7