Nextcloud is not syncing some files: causes and solutions

Have you been managing your self-hosted cloud on Nextcloud for a while? Then you know it's one of the best platforms in its class. Of course, that doesn't mean file synchronization always works as expected. In this post, we'll talk about causes and solutions which are the reasons why Nextcloud does not sync some files.

Nextcloud is not syncing some files: causes and solutions

The client shows "Everything synced," but when you check the server or access it from another device, you discover that dozens of files never reached their destination. Why Nextcloud? It doesn't sync some files, but seems to have no problem with others.If it's any consolation, this irregular situation occurs in almost all distributed file systems.

In fact, there are reasons common to most platforms, such as the presence of characters not allowed in the file names. size restrictions File or disk space issues also affect other platforms, such as Synology DriveDropbox or Syncthing. Other times it has to do with security features specific to each service, such as Nextcloud's Pending File Lock.

Thinking specifically about Nextcloud, There have been reports of Linux and macOS user synchronization problemsThe first issues are related to operating system resource limitations, which prevented the synchronization of large volumes of files. On macOS, the problem is related to file synchronization. .DS_Store, automatically generated to store folder attributes.

Nextcloud is not syncing some files: common causes and solutions

One of the most frequent reasons why Nextcloud fails to sync some files is the use of incompatible names or characters between different operating systems. Thus, a valid filename in Linux or macOS may break the rules of the NTFS or FAT32 file systems in Windows. Keep the following in mind:

• Forbidden characters in Windows: \, /, :, *, ?, ", <, >, |.
• Names reserved: Files named CON, PRN, AUX, NUL, COM1, LPT1 (and variants).
• Periods or spaces at the endWindows deletes or rejects files that end with a space or a period (example: informe.pdf.).
• Invisible characters or emojisSome non-printable Unicode characters may cause another system to refuse to process the file.

Solution? Start by reviewing the list of errors in Activity – Synchronization errorsNext, rename the file in the source location, removing special characters, complex accents, or unnecessary spaces. If this happens to you often, consider installing the application. filenamepattern from the Nextcloud app catalog to block or warn about incompatible names.

Excessive size or server limits

While Nextcloud allows handling large files, each installation has limits set by the administratorIf a file exceeds the maximum size allowed by PHP, the web server, or the Nextcloud configuration, synchronization fails. What solution can you apply in this case?

Open the Nextcloud client preferences, go to General, and check if the option is enabled. "Ask before downloading folders larger than…"Also, make sure you have enough free space in your user account, if there is a limit. Another alternative is reduce file size that you want to synchronize by compressing it beforehand.

Nextcloud does not sync some files due to lock conflicts

Another common cause of synchronization failures is the server-side file lockingNextcloud uses this mechanism to prevent two users from modifying the same file simultaneously and corrupting the data. The problem occurs when the desktop client attempts to synchronize files that are open by other applications.

The typical case occurs with email files such as .pst from Outlook. When a file is open by an application, the Nextcloud client fails to sync it. And that's not all: The error blocks the synchronization of other files that are in the queue.Both local and remote files are not synchronized until the locked file is released.

In these cases, the best solution when Nextcloud fails to sync some files is to schedule the sync jobs for off-peak hoursFewer concurrent transfers mean fewer concurrent lock requests, and transient locks are released faster.

Operating system limitations: synchronization failures in Linux

It also happens that Nextcloud doesn't sync some files from the Linux desktop app. The problem is due to operating system resource limitations. synchronization of large volumes of filesAnd the key detail is that the app shows that everything is correct, with no errors or registration warnings.

But in reality, there are dozens or even hundreds of folders that aren't being synchronized. What solution can be applied in this particular case? Simple: increase the limits running ulimit -u 100000 && ulimit -n 100000 before restarting the client. Or it's even better to configure higher values ​​permanently in /etc/security/limits.conf.

The problem in macOS with VFS

Let's look at another case where Nextcloud doesn't sync some files, this time on macOS with Virtual File System (VFS). The problem begins with the message "Some files could not be synchronized," but without The app should specify which files are the culprits.During manual diagnostics, it was discovered that the client was attempting to synchronize macOS .DS_Store files.

It turns out that these files are automatically generated by the operating system to store folder attributes. They fail without warning, marking the entire synchronization as failed without even listing the cause. What can you do if this is your case? The solution is simple: add *.DS_Store to the list of ignored files en Settings – General – Edit ignored filesand force a resynchronization.

Nextcloud not syncing some files: Fixed!

When Nextcloud fails to sync some files, the problem is almost always due to invalid names, size limits, locks, permissions, conflicts, or exclusion settingsThe key is to systematically review each cause and apply the corresponding solution.

As a final recommendation, Don't forget to keep the application and server updated To avoid synchronization problems, with a little patience you can restore the service to normal and prevent your files from getting stuck or, worse, lost.