Ubuntu Manpage: SSHFS - filesystem client based on SSH

NAME

       SSHFS - filesystem client based on SSH

SYNOPSIS

       To mount a filesystem:

          sshfs [user@]host:[dir] mountpoint [options]

       If host is a numeric IPv6 address, it needs to be enclosed in square brackets.

       To unmount it:

          fusermount3 -u mountpoint   # Linux
          umount mountpoint           # OS X, FreeBSD

DESCRIPTION

       SSHFS  allows  you  to  mount  a  remote  filesystem  using  SSH (more precisely, the SFTP
       subsystem). Most SSH servers support and enable this SFTP access by default, so  SSHFS  is
       very simple to use - there's nothing to do on the server-side.

       By default, file permissions are ignored by SSHFS. Any user that can access the filesystem
       will be able to perform any operation that the  remote  server  permits  -  based  on  the
       credentials  that  were  used  to  connect  to  the  server.  If  this is undesired, local
       permission checking can be enabled with -o default_permissions.

       By default, only the mounting user will be able to access the filesystem. Access for other
       users  can be enabled by passing -o allow_other. In this case you most likely also want to
       use -o default_permissions.

       It is recommended to run SSHFS as regular user (not  as  root).   For  this  to  work  the
       mountpoint  must  be  owned  by the user.  If username is omitted SSHFS will use the local
       username. If the directory is omitted, SSHFS will mount the (remote) home  directory.   If
       you  need  to  enter a password sshfs will ask for it (actually it just runs ssh which ask
       for the password if needed).

OPTIONS

-o opt,[opt...]
mount options, see below for details. A a variety of SSH options can be given here
as well, see the manual pages for sftp(1) and ssh_config(5).

-h, --help
print help and exit.

-V, --version
print version information and exit.

-d, --debug
print debugging information.

-p PORT
equivalent to '-o port=PORT'

-f do not daemonize, stay in foreground.

-s Single threaded operation.

-C equivalent to '-o compression=yes'

-F ssh_configfile
specifies alternative ssh configuration file

-1 equivalent to '-o ssh_protocol=1'

-o reconnect
automatically reconnect to server if connection is interrupted. Attempts to access
files that were opened before the reconnection will give errors and need to be
re-opened.

-o delay_connect
Don't immediately connect to server, wait until mountpoint is first accessed.

-o sshfs_sync
synchronous writes. This will slow things down, but may be useful in some
situations.

-o no_readahead
Only read exactly the data that was requested, instead of speculatively reading
more to anticipate the next read request.

-o sync_readdir
synchronous readdir. This will slow things down, but may be useful in some
situations.

-o workaround=LIST
Enable the specified workaround. See the Caveats section below for some additional
information. Possible values are:

rename Emulate overwriting an existing file by deleting and renaming.

renamexdev
Make rename fail with EXDEV instead of the default EPERM to allow moving
files across remote filesystems.

truncate
Work around servers that don't support truncate by coping the whole file,
truncating it locally, and sending it back.

fstat Work around broken servers that don't support fstat() by using stat instead.

buflimit
Work around OpenSSH "buffer fillup" bug.

createmode
Work around broken servers that produce an error when passing a non-zero
mode to create, by always passing a mode of 0.

-o idmap=TYPE
How to map remote UID/GIDs to local values. Possible values are:

none no translation of the ID space (default).

user map the UID/GID of the remote user to UID/GID of the mounting user.

file translate UIDs/GIDs based upon the contents of --uidfile and --gidfile.

-o uidfile=FILE
file containing username:uid mappings for -o idmap=file

-o gidfile=FILE
file containing groupname:gid mappings for -o idmap=file

-o nomap=TYPE
with idmap=file, how to handle missing mappings:

ignore don't do any re-mapping

error return an error (default)

-o ssh_command=CMD
execute CMD instead of 'ssh'

-o ssh_protocol=N
ssh protocol to use (default: 2)

-o sftp_server=SERV
path to sftp server or subsystem (default: sftp)

-o directport=PORT
directly connect to PORT bypassing ssh

-o passive
communicate over stdin and stdout bypassing network. Useful for mounting local
filesystem on the remote side. An example using dpipe command would be dpipe
/usr/lib/openssh/sftp-server = ssh RemoteHostname sshfs :/directory/to/be/shared
~/mnt/src -o passive

-o disable_hardlink
With this option set, attempts to call link(2) will fail with error code ENOSYS.

-o transform_symlinks
transform absolute symlinks on remote side to relative symlinks. This means that if
e.g. on the server side /foo/bar/com is a symlink to /foo/blub, SSHFS will
transform the link target to ../blub on the client side.

-o follow_symlinks
follow symlinks on the server, i.e. present them as regular files on the client. If
a symlink is dangling (i.e, the target does not exist) the behavior depends on the
remote server - the entry may appear as a symlink on the client, or it may appear
as a regular file that cannot be accessed.

-o no_check_root
don't check for existence of 'dir' on server

-o password_stdin
read password from stdin (only for pam_mount!)

-o dir_cache=BOOL
Enables (yes) or disables (no) the SSHFS directory cache. The directory cache
holds the names of directory entries. Enabling it allows readdir(3) system calls to
be processed without network access.

-o dcache_max_size=N
sets the maximum size of the directory cache.

-o dcache_timeout=N
sets timeout for directory cache in seconds.

-o dcache_{stat,link,dir}_timeout=N
sets separate timeout for {attributes, symlinks, names} in the directory cache.

-o dcache_clean_interval=N
sets the interval for automatic cleaning of the directory cache.

-o dcache_min_clean_interval=N
sets the interval for forced cleaning of the directory cache when full.

-o direct_io
This option disables the use of page cache (file content cache) in the kernel for
this filesystem. This has several affects:

1. Each read() or write() system call will initiate one or more read or write
operations, data will not be cached in the kernel.

2. The return value of the read() and write() system calls will correspond to the
return values of the read and write operations. This is useful for example if
the file size is not known in advance (before reading it). e.g. /proc
filesystem

-o max_conns=N
sets the maximum number of simultaneous SSH connections to use. Each connection is
established with a separate SSH process. The primary purpose of this feature is to
improve the responsiveness of the file system during large file transfers. When
using more than once connection, the password_stdin and passive options can not be
used, and the buflimit workaround is not supported.

In addition, SSHFS accepts several options common to all FUSE file systems. These are
described in the mount.fuse manpage (look for "general", "libfuse specific", and
"high-level API" options).

CAVEATS / WORKAROUNDS

Hardlinks
If the SSH server supports the hardlinks extension, SSHFS will allow you to create
hardlinks. However, hardlinks will always appear as individual files when seen through an
SSHFS mount, i.e. they will appear to have different inodes and an st_nlink value of 1.

Rename
Some SSH servers do not support atomically overwriting the destination when renaming a
file. In this case you will get an error when you attempt to rename a file and the
destination already exists. A workaround is to first remove the destination file, and then
do the rename. SSHFS can do this automatically if you call it with -o workaround=rename.
However, in this case it is still possible that someone (or something) recreates the
destination file after SSHFS has removed it, but before SSHFS had the time to rename the
old file. In this case, the rename will still fail.

Permission denied when moving files across remote filesystems
Most SFTP servers return only a generic "failure" when failing to rename across filesystem
boundaries (EXDEV). sshfs normally converts this generic failure to a permission denied
error (EPERM). If the option -o workaround=renamexdev is given, generic failures will be
considered EXDEV errors which will make programs like mv(1) attempt to actually move the
file after the failed rename.

SSHFS hangs for no apparent reason
In some cases, attempts to access the SSHFS mountpoint may freeze if no filesystem
activity has occured for some time. This is typically caused by the SSH connection being
dropped because of inactivity without SSHFS being informed about that. As a workaround,
you can try to mount with -o ServerAliveInterval=15. This will force the SSH connection to
stay alive even if you have no activity.

SSHFS hangs after the connection was interrupted
By default, network operations in SSHFS run without timeouts, mirroring the default
behavior of SSH itself. As a consequence, if the connection to the remote host is
interrupted (e.g. because a network cable was removed), operations on files or directories
under the mountpoint will block until the connection is either restored or closed
altogether (e.g. manually). Applications that try to access such files or directories
will generally appear to "freeze" when this happens.

If it is acceptable to discard data being read or written, a quick workaround is to kill
the responsible sshfs process, which will make any blocking operations on the mounted
filesystem error out and thereby "unfreeze" the relevant applications. Note that force
unmounting with fusermount -zu, on the other hand, does not help in this case and will
leave read/write operations in the blocking state.

For a more automatic solution, one can use the -o ServerAliveInterval=15 option mentioned
above, which will drop the connection after not receiving a response for 3 * 15 = 45
seconds from the remote host. By also supplying -o reconnect, one can ensure that the
connection is re-established as soon as possible afterwards. As before, this will
naturally lead to loss of data that was in the process of being read or written at the
time when the connection was interrupted.

MOUNTING FROM /ETC/FSTAB

       To  mount  an SSHFS filesystem from /etc/fstab, simply use sshfs` as the file system type.
       (For backwards compatibility, you may also use ``fuse.sshfs).

GETTING HELP

       If you need help,  please  ask  on  the  <fuse-sshfs@lists.sourceforge.net>  mailing  list
       (subscribe at https://lists.sourceforge.net/lists/listinfo/fuse-sshfs).

       Please      report     any     bugs     on     the     GitHub     issue     tracker     at
       https://github.com/libfuse/libfuse/issues.

AUTHORS

       SSHFS is currently maintained by Nikolaus Rath <Nikolaus@rath.org>,  and  was  created  by
       Miklos Szeredi <miklos@szeredi.hu>.

       This  man  page was originally written by Bartosz Fenski <fenio@debian.org> for the Debian
       GNU/Linux distribution (but it may be used by others).

                                                                                         SSHFS(1)