BINDFS(1) General Commands Manual BINDFS(1)
NAME
bindfs - mount --bind in user-space
SYNOPSIS
bindfs [options] dir mountpoint
DESCRIPTION
A FUSE filesystem for mirroring the contents of a directory to another directory. Additionally, one can change the permissions of files in
the mirrored directory.
FILE OWNERSHIP
-u, --user, --owner=user, -o owner=...
Makes all files owned by the specified user. Also causes chown on the mounted filesystem to always fail.
-g, --group=group, -o group=...
Makes all files owned by the specified group. Also causes chgrp on the mounted filesystem to always fail.
-p, --perms=permissions, -o perms=...
Takes a comma- or colon-separated list of chmod-like permission specifications to be applied to the permission bits in order. See
PERMISSION SPECIFICATION below for details.
This only affects how the permission bits of existing files are altered when shown in the mounted directory. You can use --cre-
ate-with-perms to change the permissions that newly created files get in the source directory.
Note that, as usual, the root user isn't bound by the permissions set here. You can get a truly read-only mount by using -r.
-m, --mirror=user1:user2:..., -o mirror=...
Takes a comma- or colon-separated list of users who will see themselves as the owners of all files. Users who are not listed here
will still be able to access the mount if the permissions otherwise allow them to.
You can also give a group name prefixed with an '@' to mirror all members of a group. This will not change which group the files are
shown to have.
-M, --mirror-only=user1:user2:..., -o mirror-only=...
Like --mirror but disallows access for all other users (except root).
--map=user1/user2:@group1/@group2:..., -o map=...
Given a mapping user1/user2, all files owned by user1 are shown as owned by user2. When user2 creates files, they are chowned to
user1 in the underlying directory. When files are chowned to user2, they are chowned to user1 in the underlying directory. Works
similarly for groups.
A single user or group may appear no more than once on the left and once on the right of a slash in the list of mappings. Cur-
rently, the options --user, --group, --mirror, --create-for-*, --chown-* and --chgrp-* override the corresponding behavior of this
option.
Requires mounting as root.
FILE CREATION POLICY
New files and directories are created so they are owned by the mounter. bindfs can let this happen (the default for normal users), or it
can try to change the owner to the uid/gid of the process that wants to create the file (the default for root). It is also possible to
have bindfs try to change the owner to a particular user or group.
--create-as-user, -o create-as-user
Tries to change the owner and group of new files and directories to the uid and gid of the caller. This can work only if the mounter
is root. It is also the default behavior (mimicing mount --bind) if the mounter is root.
--create-as-mounter, -o create-as-mounter
All new files and directories will be owned by the mounter. This is the default behavior for non-root mounters.
--create-for-user=user, -o create-for-user=...
Tries to change the owner of new files and directories to the user specified here. This can work only if the mounter is root. This
option overrides the --create-as-user and --create-as-mounter options.
--create-for-group=group, -o create-for-group=...
Tries to change the owning group of new files and directories to the group specified here. This can work only if the mounter is
root. This option overrides the --create-as-user and --create-as-mounter options.
--create-with-perms=permissions, -o create-with-perms=...
Works like --perms but is applied to the permission bits of new files get in the source directory. Normally the permissions of new
files depend on the creating process's preferences and umask. This option can be used to modify those permissions or override them
completely. See PERMISSION SPECIFICATION below for details.
CHOWN
/CHGRP POLICY
The behaviour on chown/chgrp calls can be changed. By default they are passed through to the source directory even if bindfs is set to show
a fake owner/group. A chown/chgrp call will only succeed if the user has enough mirrored permissions to chmod the mirrored file AND the
mounter has enough permissions to chmod the real file.
--chown-normal, -o chown-normal
Tries to chown the underlying file. This is the default.
--chown-ignore, -o chown-ignore
Lets chown succeed (if the user has enough mirrored permissions) but actually does nothing. A combined chown/chgrp is effectively
turned into a chgrp-only request.
--chown-deny, -o chown-deny
Makes chown always fail with a 'permission denied' error. A combined chown/chgrp request will fail as well.
--chgrp-normal, -o chgrp-normal
Tries to chgrp the underlying file. This is the default.
--chgrp-ignore, -o chgrp-ignore
Lets chgrp succeed (if the user has enough mirrored permissions) but actually does nothing. A combined chown/chgrp is effectively
turned into a chown-only request.
--chgrp-deny, -o chgrp-deny
Makes chgrp always fail with a 'permission denied' error. A combined chown/chgrp request will fail as well.
CHMOD POLICY
Chmod calls are forwarded to the source directory by default. This may cause unexpected behaviour if bindfs is altering permission bits.
--chmod-normal, -o chmod-normal
Tries to chmod the underlying file. This will succeed if the user has the appropriate mirrored permissions to chmod the mirrored
file AND the mounter has enough permissions to chmod the real file. This is the default (in order to behave like mount --bind by
default).
--chmod-ignore, -o chmod-ignore
Lets chmod succeed (if the user has enough mirrored permissions) but actually does nothing.
--chmod-deny, -o chmod-deny
Makes chmod always fail with a 'permission denied' error.
--chmod-allow-x, -o chmod-allow-x
Allows setting and clearing the executable attribute on files (but not directories). When used with --chmod-ignore, chmods will only
affect execute bits on files and changes to other bits are discarded. With --chmod-deny, all chmods that would change any bits
except excecute bits on files will still fail with a 'permission denied'. This option does nothing with --chmod-normal.
XATTR POLICY
Extended attributes are mirrored by default, though not all underlying file systems support xattrs.
--xattr-none, -o xattr-none
Disable extended attributes altogether. All operations will return 'Operation not supported'.
--xattr-ro, -o xattr-ro
Let extended attributes be read-only.
--xattr-rw, -o xattr-rw
Let extended attributes be read-write (the default). The read/write permissions are checked against the (possibly modified) file
permissions inside the mount.
MISCELLANEOUS OPTIONS
-h, --help
Displays a help message and exits.
-V, --version
Displays version information and exits.
-n, --no-allow-other, -o no-allow-other
Does not add -o allow_other to FUSE options. This causes the mount to be accessible only by the current user.
--realistic-permissions, -o realistic-permissions
Hides read/write/execute permissions for a mirrored file when the mounter doesn't have read/write/execute access to the underlying
file. Useless when mounting as root, since root will always have full access.
(Prior to version 1.10 this option was the default behavior. I felt it violated the principle of least surprise badly enough to
warrant a small break in backwards-compatibility.)
--ctime-from-mtime, -o ctime-from-mtime
Recall that a unix file has three standard timestamps: atime (last access i.e. read time), mtime (last content modification time)
ctime (last content or metadata (inode) change time)
With this option, the ctime of each file and directory is read from its mtime. In other words, only content modifications (as
opposed to metadata changes) will be reflected in a mirrored file's ctime. The underlying file's ctime will still be updated nor-
mally.
--hide-hard-links, -o hide-hard-links
Shows the hard link count of all files as 1.
FUSE OPTIONS
-o options
Fuse options.
-r, -o ro
Make the mount strictly read-only. This even prevents root from writing to it. If this is all you need, then (since Linux 2.6.26)
you can get a more efficent mount with mount --bind and then mount -o remount,ro.
-d, -o debug
Enable debug output (implies -f).
-f Foreground operation.
-s Disable multithreaded operation. bindfs should be thread-safe.
PERMISSION SPECIFICATION
The -p option takes a comma- or colon-separated list of either octal numeric permission bits or symbolic representations of permission bit
operations. The symbolic representation is based on that of the chmod(1) command. setuid, setgid and sticky bits are ignored.
This program extends the chmod symbolic representation with the following operands:
`D' (right hand side)
Works like X but applies only to directories (not to executables).
`d' and `f' (left hand side)
Makes this directive only apply to directories (d) or files (f).
e.g. gd-w would remove the group write bit from all directories.
`u', `g', `o' (right hand side)
Uses the user (u), group (g) or others (o) permission bits of
the original file.
e.g. g=u would copy the user's permission bits to the group.
ug+o would add the others' permissions to the owner and group.
Examples
o-rwx Removes all permission bits from others.
g=rD Allows group to read all files and enter all directories, but nothing else.
0644,a+X
Sets permission bits to 0644 and adds the execute bit for everyone to all directories and executables.
og-x:og+rD:u=rwX:g+rw
Removes execute bit for others and group, adds read and directory execute for others and group, sets user permissions to read, write
and execute directory/executable, adds read and write for group.
EXAMPLES
bindfs -u www -g nogroup -p 0000,u=rD ~/mywebsite ~/public_html/mysite
Publishes a website in public_html so that only the 'www' user can read the site.
bindfs -M foo,bar,1007,@mygroup -p 0600,u+X dir mnt
Gives access to 'foo', 'bar', the user with the UID 1007 as well as everyone in the group 'mygroup'. Sets the permission bits to
0600, thus giving the specified users read/write access, and adds the user execute bit for directories and executables.
bindfs -ono-allow-other,perms=a-w somedir somedir
Makes a directory read-only and accessable only by the current user.
bindfs#/home/bob/shared /var/www/shared/bob fuse perms=0000:u+rD 0 0
An example /etc/fstab entry. Note that the colon must be used to separate arguments to perms, because the comma is an option separa-
tor in /etc/fstab.
NOTES
Setuid and setgid bits have no effect inside the mount. This is a necessary security feature of FUSE.
MacFuse caches file contents by default. This means that changes in source files are not always immediately visible under the mount point.
-o nolocalcaches can be used to disable the cache.
BUGS
Please report to the issue tracker on the project home page at http://code.google.com/p/bindfs/
AUTHOR
Martin Partel <martin dot partel at gmail dot com>
SEE ALSO
chmod(1), fusermount(1)
BINDFS(1)