sshfs/FAQ

SSHFS FAQ
=========

1.     I've found a bug and there's no solution in this FAQ, what
       should I do?
2.     Advantage of sshfs over NFS and Samba
3.     Create the device node
4.     mv fails with "Operation not permitted"
5.     Configuring the ssh connection
6.     What are the no_readahead and sshfs_sync options for?
7.     Why does df return strange values on partitions mounted via
       sshfs?
8.     How do I specify the remote mount point (since the example
       defaults to the home directory)
9.     sshfs hangs after a while
10.    Following symlinks on the server side
11.    Making absolute symlinks work
12.    Mounting as root
13.    Exporting via NFS
14.    Automatical mounting using /etc/fstab
15.    Why does SVN (etc...) fail with permission denied?
16.    Why does SVN (etc...) fail to rename files?
17.    Is there some neat way to do it in reverse?
18.    Might it be reasonable to disallow loops?
19.    How to mount through an intermediary ssh server, eg:
       localhost -> A -> B; mount B from localhost
20.    Alternative Solution
21.    I seem to have successfully mounted a remote directory, but
       performing an `ls -l` on the directory above the mount point shows
       the mount point's attributes as `? ? ? ? ? ?`. Nothing shows up in
       the directory either. What am I doing wrong?

--------------------------------------------------------------------------

1. I've found a bug and there's no solution in this FAQ, what should I do?

   Please report the bug in the Github issue tracker:
   https://github.com/libfuse/sshfs/issues

   Also logs with debugging output can be useful for diagnosing the
   problem. Try running sshfs with the following options:
     sshfs -odebug,sshfs_debug,loglevel=debug ...

   Doing strace on the application which fails may also sometimes help:
     strace -f -o /tmp/strace application args ...

   Note that large messages (over 40k) will be rejected from the mailing
   list. So try to keep the logs as short as possible.


2. Advantage of sshfs over NFS and Samba

   Users can mount remote resources they already have ssh access to,
   without requiring the remote machine to export the resource.

   The remote resource can be mounted when it is needed in a location
   that is convenient for the user at that time, without needing to rely
   on a central, root-controlled file system table.

   Automatic mounting, if desired, can be added to a shell script such as
   .bashrc (provided authentication is done using RSA/DSA keys).

   Resources can be mounted over slow and unreliable (distant)
   connections.

3. Create the device node

   If you don't use udev, you may get this error message:

   fusermount: failed to open /dev/fuse: No such device or address

   Before loading the fuse kernel module, create the device node
   manually:

     mknod -m 666 /dev/fuse c 10 229

4. mv fails with "Operation not permitted".

   Use -o workaround=rename (requires sshfs version >= 1.3).

5. Configuring the ssh connection

   In addition to flags like -C, -p, and -o SSHOPT...=, you may find it
   easier to edit your /.ssh/config file. You can add an entry with any
   customization you want, test it with ssh, and finally use it with
   sshfs. As a bonus, you get a short mnemonic for your configuration.

6. What are the no_readahead and sshfs_sync options for?

   These disable read and write optimizations respectively. They don't
   really make sense unless you're doing something special.

7. Why does df return strange values on partitions mounted via sshfs?

   Because the SFTP protocol doesn't have a statfs operation this is
   currently not possible to display proper usage on remote partition.

8. How do I specfy the remote mount point (since the example defaults to the
   home directory)

   The example shows:
     sshfs hostname: mountpoint

   To specify a remote mount point use:
     sshfs hostname:remotemountpoint mountpoint

   This might be obvious to others, but I ended up looking up the
   interface to sftp to see if I could learn how to specify the remote
   mount point, then thought about the way that scp specifies the remote
   directory, and it worked.

9. sshfs hangs after a while

   Mounting works fine, I can use the files in Mountpoint as good as any
   other files on my system, but after bit of time, changing nothing on
   the remote files sshfs crashes. This means, I can not cd into the
   Mountpoint (xterm hangs, nautilus hangs... every program trying to
   access the Mountpoint gets stuck, and won't return).

   Solution: add
     ServerAliveInterval 15

   in your .ssh/config (or use -o ServerAliveInterval=15 on the sshfs
   command line but I did not test that solution). This will force the
   ssh connection to stay alive even if you have no activity.

10. Following symlinks on the server side

    The -o follow_symlinks option will enable this.

11. Making absolute symlinks work

    Use the -o transform_symlinks option, which will transform absolute
    symlinks (ones which point somewhere inside the mount) into relative
    ones.

12. Mounting as root

    Generally it's not possible to use an sshfs mount as a "real"
    filesystem shared between multiple users. Some of this functionality
    can be enabled with the -o allow_other and -o default_permissions
    options, but files will not be created with the correct ownership,
    etc...

13. Exporting via NFS

    Use the userspace NFS daemon http://sourceforge.net/projects/unfs

14. Automatical mounting using /etc/fstab

    A line in /etc/fstab has the following format:
      sshfs#USERNAME@REMOTE_HOST:REMOTE_PATH MOUNT_POINT fuse SSHFS_OPTIONS 0 0

    eg.
      sshfs#guest@guest.login.com:data /mnt/guest fuse \
        uid=1003,gid=100,umask=0,allow_other 0 0

15. Why does SVN (etc...) fail with permission denied?

    This is a bug that happens when an application creates a read-only
    file opened for writing (e.g. open("foo", O_WRONLY|O_CREAT, 0444))

    It has been fixed in sshfs version 1.3, but also requires FUSE version
    >=2.5.X and Linux kernel version >=2.6.15.

16. Why does SVN (etc...) fail to rename files?

    $ svn co svn://anonsvn.kde.org/home/kde/trunk/KDE/kdelibs
    svn: Can't move 'kdelibs/.svn/tmp/entries' to 'kdelibs/.svn/entries':
    Operation not permitted

    The reason is that SFTP protocol version 3 (which is implemented by
    OpenSSH's sftp-server) defines the rename operation slightly
    differently than POSIX. The difference is that renaming to an existing
    file or directory will fail instead of atomically replacing the old
    file.

    The -o workaround=rename option will try to emulate POSIX rename
    semantics, but it cannot guarantee atomicity. In most of the cases
    this doesn't matter, and things will work fine with this option.

17. Is there some neat way to do it in reverse?

    You want to mount a USB thumb drive onto a file server that is rather
    remote.

    Assuming this is difficult because the laptop with the thumb drive is
    sitting behind NAT, firewalls, etc. then you need to create a
    port-forward:
      client$ ssh -R 2222:localhost:22 server
      server$ sshfs -p 2222 localhost:/media/usb1 myusb1

    (Now, is there is there a smarter way that does not involve port
    opening login permissions in an undesireable direction?)

18. Might it be reasonable to disallow loops?

    sshfs localhost:/mnt /mnt

    This seems to produce undesirable results. --JoshuaRodman

19. How to mount through an intermediary ssh server, eg: localhost -> A -> B;
    mount B from localhost

    Start by mounting the folder you need that is on "a" to a folder on
    "b" then mount the new folder that is on "a" to a folder on localhost.

    IE: (These are NOT real commands, but a sequence of steps.
    A mounts B:/home/x on /mnt/Bx
    localhost mounts A:/mnt/Bx on ~/mydir

20. Alternative Solution:

    1) Create a shell script to wrap the tunneling of one ssh command over
    another,
      $ cat >Atunnel <<EOF
      #!/bin/bash
      ssh -q A ssh -q "$@"
      EOF
      $ chmod u+x Atunnel

    N.B. make sure to put this somewhere on your path. 2) sshfs mount as
    normal but using this script as the ssh command.
      $ sshfs -o ssh_command='Atunnel' B: ~/mydir

21. I seem to have successfully mounted a remote directory, but performing an
    `ls -l` on the directory above the mount point shows the mount point's
    attributes as `? ? ? ? ? ?`. Nothing shows up in the directory either. What
    am I doing wrong?

    You probably specified a remote path with the tilde (~) in it. This
    doesn't seem to work. Instead, specify an absolute remote path:
      sshfs username@remote.host:/home/username/whatever my/mount

    What options do i use to make playing media files (music) over sshfs more
    efficient?

    MacFUSE doesn't seem to let me move files from one directory to another. It
    first asks for my local user password (i.e. the password on my Macbook Pro)
    and then produces the error message "The operation cannot be completed
    because one or more required items cannot be found. (Error code -120).