Warning: can't write entry into mtab (SFTP as an alternative?)

NethServer Version: 7.9
Module: Backup/WebDav

I created a backup job to a Cloud Server (Strato HiDrive) and get this error mail.

Subject: Cron <root@ns-srv01> /sbin/e-smith/backup-data-wrapper fullbak2strato

/sbin/mount.davfs: Warning: can't write entry into mtab, but will mount the file system anyway at /etc/e-smith/events/actions/mount-webdav line 76.

What’s going on there?

Sincerely, Marko


full log
Backup: fullbak2strato
Backup started at 2021-11-25 03:05:01
Pre backup scripts status: SUCCESS
/sbin/mount.davfs: Warning: can't write entry into mtab, but will mount the file system anyway  at /etc/e-smith/events/actions/mount-webdav line 76.
--------------[ Backup Statistics ]--------------
StartTime 1637805923.58 (Thu Nov 25 03:05:23 2021)
EndTime 1637806002.03 (Thu Nov 25 03:06:42 2021)
ElapsedTime 78.45 (1 minute 18.45 seconds)
SourceFiles 144319
SourceFileSize 44122708701 (41.1 GB)
NewFiles 199
NewFileSize 57130779 (54.5 MB)
DeletedFiles 40
ChangedFiles 229
ChangedFileSize 672043305 (641 MB)
ChangedDeltaSize 0 (0 bytes)
DeltaEntries 468
RawDeltaSize 80489592 (76.8 MB)
TotalDestinationSizeChange 71046764 (67.8 MB)
Errors 0

Local and Remote metadata are synchronized, no sync needed.
Last full backup date: Wed Nov 24 18:19:18 2021
No old backup sets found, nothing deleted.
Action 'backup-data-duplicity fullbak2strato': SUCCESS
Post backup scripts status: SUCCESS
Backup status: SUCCESS
Backup ended at 2021-11-25 03:06:51
Time elapsed: 0 hours, 1 minutes, 50 seconds

Disk Usage:
      Size       Used  Available     Use%
  25.43 GB   12.72 GB   12.72 GB      50%

Maybe Strato HiDrive has similar issues than pCloud have for WebDAV?

And now i see that i should whip myself for posting screenshot in italian.

Full disclosure: with Box.com Webdav works flawleslly. With pCloud sometimes the source come validated, but backup quite never works.

Hi @pike
I only switched to Strato because I have the same problem with pCloud as you.
Even with the help of the pCloud support there it is not solvable, they simply claim - we have no issue, all systems work fine.

WebDAV with Strato woks fine (apart from this error message, I do not see any effects. The backup is saved well), but I’m reluctant to use WebDAV, I’d much rather use SFTP. However, SFTP does not come up, although a connection with a smp,en ftp client works.

@pagaille had comparible issues and wrote

But I can’t interpret what “Nethserver’s backup module expects the target server to be smart and will not work with dumb, basic, passive, restricted, pure (S)FTP servers” means to confront Stratos Support with concrete requirements in their SFTP server.

Box.com isn’t an alternative.

Edit.: sorry, I just realize that I have moved from the WebDAV problem to the SFTP problem.

I’ve some 50GB free accounts on box.com since ages, exploiting some “promotions” launched when iOS was not having box.net app. The service could be suitable for the size and speed, but price is not that interesting.

I’ve also nudged cubbit.io for adding WebDAV access for the service. Hope that someone will nudge them soon for implement the protocol on their nice infrastructure.

May be related to this issue: Sftp chroot is needed?

And I can’t judge if that would really be the solution I should apply

Sorry, I just realize that I have moved from the WebDAV problem to the SFTP problem. It seems a bit confusing

I mean that NS tries to log in the server through SSH and launch some shell commands before going to SFTP. That implies that the storage is “smart” and allows that, which is not the case for most storage offers I believe.

1 Like

…and with your suggestion SFTP chroot howto you can work around the problem and still use such servers?
I believe not, because I have to use credentials from the remote server.

Nope : that howto was server side (NS side), to lock a distant SFTP user into a home folder. Here the problem is storage side, which doesn’t offer features or rights that the NS client expects.


The warning is nothing to be concerned about. If a newer version of davfs2 package makes its way into CentOS it will be resolved. More info at:


FWIW, current version of davfs2 installed on a fully updated NethServer davfs2-1.4.7-6.el7.x86_64

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it seems that centos7 has to be updated since 2020

You might try a newer version of davfs2, e.g. 1.5.6. It will be able to handle situations where /etc/mtab is a symbolic link to a kernel file system and not writable.

Maybe is the “usual” management of CentOS: only patches/updates, not “upgrades”.

On CentOS 8 you have 1.5.6 but not on CentOS 7 (which is more or less like this since I coded the webDAV support for backups).

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Maybe another webdav provider? I use stack from transip (transip.nl/stack). Unfortunately their website in currently only available in Dutch, but with Goole translate it should be possible to get the idea of what it is and does.
I use it with WebDav for over 4 years now as backup location for my NethServer based VPS’s
ps: when you have an account, you can change the interface into English…

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Dutch isn’t an issue :blush: I’m Belgian :blush:

Good pointer I will have a look !

IDK which people loves more beer among these two…

That looks good, I will book it. I live 50 km from the Dutch border, in the Ruhrgebiet.

Thank you, Marko

Thank for the hint…can you point me, please? Perhaps I’m blind