davfs2/FAQ

davfs2 1.2.2 2008-01-24
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# Copyright (C) 2006, 2007, 2008 Werner Baumann

# Copying and distribution of this file, with or without modification, are
# permitted in any medium without royalty.


FREQUENTLY ASKED QUESTIONS

Q: What are these files with size 0 and date of 1970-01-01?
A: WebDAV allows to lock files that do not exist, to protect the name
   while you are preparing a file for upload. These "locked-null-resources"
   will show as files with size 0. This is OK as long as the locks are
   released some day.

Q: But the size-0-files don't disappear. How can I get rid of them?
Q: Some files cannot be accessed because they are locked. But I know for
   sure that nobody uses them.
A: It can happen that locks are not released:
   - An WebDAV client may crash.
   - The network connection may get down before the locks are released.
   - ...
   How davfs2 tries to handle this:
   - It sets a timeout for locks, when they should be released automatically.
   - It sends a lock-owner property, so it can identify its own locks.
   - Whenever it discovers that a file is locked, it tries to discover whether
     it owns the lock. In this case it will reuse the lock and then release it.
   But not all servers will support this.
   Sometimes, only the administrator of the server may be able to free stale
   locks. It would be a good idea if the server implements an administrative
   timeout for locks, because it is impossible to make sure that all clients
   will always release locks properly.

Q: When I try to save may backups to the WebDAV Server, davfs2 creates another
   copy on disk, so I run out of disk space. Why does davfs2 do this?
A: davfs2 will always create a local copy of all files moved between the local
   computer and the server. There are several reasons for this:
   - The coda kernel file system needs this. It will only read and write to
     local copies.
   - davfs2 is not able to do incremental uploads. So davfs2 needs to get the
     whole file from the application before it can send it to the server.
   davfs2 really is not a replacement for network file systems like nfs.

Q: When I unmount a davfs2 file system, umount blocks and it sometimes takes
   hours before it returns.
A: This is intentionally. umount should not return before all cached data is
   saved to the media. The time needed depends on the amount of data and the
   transfer rate. It is almost unnoticeable for a hard disk, some minutes for
   a floppy, and for davfs2 it varies with the quality of the connection.
   Note: You should always unmount davfs2 file systems before you shut down
         your system. On shut down mount.davfs will usually be killed
         regardless of the time needed to save data. 

Q: Displaying large directories with nautilus or konqueror is very, very slow.
   Is there a way to speed this up?
A: Reason is that this programs open every file in a directory to evaluate the
   file type. mount.davfs has to download them all. Even if the files are
   cached, it will have to ask the server whether there is a new version.
   You may try the configuration option 'gui_optimize'. This will not help when
   you visit the directory for the first time, but when the files are already
   in the cache it will reduce response time.

O: When I mount a resource form Microsoft IIS, I can create new files, but when
   I try to open them I get an error saying 'File does not exist'. This does not
   happen when the file is named something.txt or something.doc, but it happens
   for instance with files named something.odt.
A: Microsoft IIS only serves files with extensions and MIME-types that are
   registered with IIS (or Windows). But when files are created it does not apply
   this restriction. So you can create a new file with e.g. OpenOffice.org and
   when you try to open it again, IIS will tell it can't find it. But it really
   exists in the servers file system.
   By default, only extensions used by Microsoft are registered (because you do
   not want to use file formats that are not owned by Microsoft.). To change
   this you have to register all file extensions you want to use. You may also
   register a wildcard extension.
   - Open the microsoft management console for IIS.
   - Select the WebDAV folder within IIS you want to use.
   - Right click and choose: Properties->HTTP-headers->MIME-types->new
   - Edit '*' as extension and 'application/octet-stream' as MIME-type.
   - Apply the changes.
   - Select your IIS (the server as a whole, not just the WebDAV folder).
   - From the menu choose actions->all tasks->save configuration on disk
   - Restart IIS.
   Please Note:
   I had to retranslate the names of menu items from Microsoft's German. So the
   exact naming in English might be different.