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Restore FAQ file 

This commit restores the FAQ file present in sshfs versions up to 2.5.
Changes since the version in the 2.5 release:
 - Remove most wiki markup
 - Edit question about bug reports to point to the Github issue tracker
 - Remove unanswered questions
 - Minor formatting
This commit is contained in:
George Vlahavas 2016-02-25 15:10:50 +02:00
parent 451f2075f2
commit adc55c9d2b
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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. cvs fails with "cvs [status aborted]: cannot get working
directory: No such file or directory" in a sshfs mounted directory
6. Changes on the server are not immediately visible in the
mounted directory.
7. Configuring the ssh connection
8. What are the no_readahead and sshfs_sync options for?
9. Why does df return strange values on partitions mounted via
sshfs?
10. How do I specify the remote mount point (since the example
defaults to the home directory)
11. sshfs hangs after a while
12. Following symlinks on the server side
13. Making absolute symlinks work
14. Mounting as root
15. Exporting via NFS
16. Automatical mounting using /etc/fstab
17. Why does SVN (etc...) fail with permission denied?
18. Why does SVN (etc...) fail to rename files?
19. Is there some neat way to do it in reverse?
20. Might it be reasonable to disallow loops?
21. How to mount through an intermediary ssh server, eg:
localhost -> A -> B; mount B from localhost
22. Alternative Solution
23. 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. cvs fails with "cvs status aborted?: cannot get working directory: No such
file or directory" in a sshfs mounted directory
Use the -oreaddir_ino option. Example:
sshfs -oreaddir_ino hostname:remote_dir mount_point
6. Changes on the server are not immediately visible in the mounted directory.
By default, sshfs caches things for 20 seconds, use -o cache_timeout=N
to change the default cache timeout (in seconds) or -o cache=no for
disabling the cache.
You can also control cache timeouts for directory listing etc with
-o cache_stat_timeout=N,
-o cache_dir_timout=N, and
-o cache_link_timout=N.
7. 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.
8. 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.
9. 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.
10. 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.
11. 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.
12. Following symlinks on the server side
The -o follow_symlinks option will enable this.
13. 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.
14. 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...
15. Exporting via NFS
Use the userspace NFS daemon http://sourceforge.net/projects/unfs
16. 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
17. 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.
18. 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.
19. 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?)
20. Might it be reasonable to disallow loops?
sshfs localhost:/mnt /mnt
This seems to produce undesirable results. --JoshuaRodman
21. 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
22. 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
23. 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).