A mounted drive and duply are a good combination for backup data to a remote location. Duply allows for encrypted backups, and the encryption also helps to prevent bit rot. A remote drive is useful for keeping cloud-based servers free of extraneous data, which is especially useful when paying per GB per month for storage.

My problem started after I upgraded Ubuntu. Apparently, I used a the default configuration for davfs2 instead of my custom configuration, which caused a few errors. But I also learned a few things:

To use, you must have an appropriately sized cache and disable file locking in the davfs2 config.

To set this up, edit the config: sudo nano /etc/davfs2/davfs2.conf

Add these two lines anywhere (preferably under the commented out section or at the bottom):

use_locks 0
cache_size 100
  • File locking should be disabled for Box, as it is not compatible. Files can be written to on the server while they are being uploaded to Box, and vice versa, but your timed sync/backup strategy should prevent this.
  • is limited to files of around 50 MB, and duply defaults to 25 MB, so a cache of 100 MB is certainly safely over the limits.
If a mounted drive cannot be written to, the davfs2 cache will grow (very large).

In my case, it was up to around 9 GB. Check to see what’s going on with journal ctl: sudo journalctl -b | grep mount or something like journalctl -u davfs2 --since today. You might see a message like open files exceed max cache size. Then check the configuration of davfs2 to increase the cache size and see if locking is enabled, as detailed above.

The davfs2 cache can be deleted safely if a drive is unmounted.

Unmount using umount /LOCATION/NAME

If a drive is busy, it can’t be unmounted. You can force an unmount (with chance of data corruption) using umount -f or umount -l, but it’s better to identify and kill the processes using the drive:

  1. lsof | grep '/dev/sda1' (change /dev/sda1 to the mounted drive name)
  2. pkill target_process (kills busy proc. by name | kill PID | killall target_process)
  3. umount /dev/sda1

How do you set up a duply and backup? I think I wrote about it before, but if not, here are some links: 1, 2
Other resources: 1, 2 , 3, 4, 5



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Cloud storage is immensely useful for data security and accessibility purposes. Most tech enthusiasts recognize that WebDAV is one of the best (default) solutions for creating mappings to online storage. In fact, this website is backed up to DropBox and through mapped WebDAV connections.

How can WebDAV be used with OneDrive?

One solution is through using the OneDrive user link. TechAttend has a tutorial for standard accounts, but there are updated tutorials here. Basically, open OneDrive in the web for a URL containing the customer ID. Map the folder with customer ID as a drive, then input the username and password when required, and if using two-factor authentication, generate an app password instead of the standard user password. There is a script to do this here.

Another solution is less secure, but can also be used with Google Drive. CarotDAV is a portable tool that stores user logins in unencrypted XML, but does allow users to map drives to the CarotDAV server, which maps to a single letter. It is automatic and easy to use.

WebDAV solutions, however, are slow and inaccurate, so don’t depend on them for everything!