| General Information |
| =================== |
| |
| FUSE (Filesystem in Userspace) is a simple interface for userspace |
| programs to export a virtual filesystem to the linux kernel. FUSE |
| also aims to provide a secure method for non privileged users to |
| create and mount their own filesystem implementations. |
| |
| You can download the source code releases from |
| |
| http://sourceforge.net/projects/fuse |
| |
| or alternatively you can use CVS to get the very latest development |
| version by setting the cvsroot to |
| |
| :pserver:anonymous@cvs.sourceforge.net:/cvsroot/fuse |
| |
| and checking out the 'fuse' module. |
| |
| Installation |
| ============ |
| |
| ./configure |
| make |
| make install |
| modprobe fuse |
| |
| You may also need to add '/usr/local/lib' to '/etc/ld.so.conf' and/or |
| run ldconfig. |
| |
| For more details see the file 'INSTALL' |
| |
| How To Use |
| ========== |
| |
| FUSE is made up of three main parts: |
| |
| - A kernel filesystem module |
| |
| - A userspace library |
| |
| - A mount/unmount program |
| |
| |
| Here's how to create your very own virtual filesystem in five easy |
| steps (after installing FUSE): |
| |
| 1) Edit the file example/fusexmp.c to do whatever you want... |
| |
| 2) Build the fusexmp program |
| |
| 3) run 'example/fusexmp /mnt/fuse -d' |
| |
| 4) ls -al /mnt/fuse |
| |
| 5) Be glad |
| |
| If it doesn't work out, please ask! Also see the file 'include/fuse.h' for |
| detailed documentation of the library interface. |
| |
| Security |
| ======== |
| |
| If you run 'make install', the fusermount program is installed |
| set-user-id to root. This is done to allow normal users to mount |
| their own filesystem implementations. |
| |
| There must however be some limitations, in order to prevent Bad User from |
| doing nasty things. Currently those limitations are: |
| |
| - The user can only mount on a mountpoint, for which it has write |
| permission |
| |
| - The mountpoint is not a sticky directory which isn't owned by the |
| user (like /tmp usually is) |
| |
| - No other user (including root) can access the contents of the mounted |
| filesystem. |
| |
| Configuration |
| ============= |
| |
| Some options regarding mount policy can be set in the file |
| '/etc/fuse.conf' |
| |
| Currently these options are: |
| |
| mount_max = NNN |
| |
| Set the maximum number of FUSE mounts allowed to non-root users. |
| The default is 1000. |
| |
| user_allow_other |
| |
| Allow non-root users to specify the 'allow_other' or 'allow_root' |
| mount options. |
| |
| |
| Mount options |
| ============= |
| |
| These are FUSE specific mount options that can be specified for all |
| filesystems: |
| |
| default_permissions |
| |
| By default FUSE doesn't check file access permissions, the |
| filesystem is free to implement it's access policy or leave it to |
| the underlying file access mechanism (e.g. in case of network |
| filesystems). This option enables permission checking, restricting |
| access based on file mode. This is option is usually useful |
| together with the 'allow_other' mount option. |
| |
| allow_other |
| |
| This option overrides the security measure restricting file access |
| to the user mounting the filesystem. This option is by default only |
| allowed to root, but this restriction can be removed with a |
| configuration option described in the previous section. |
| |
| allow_root |
| |
| This option is similar to 'allow_other' but file access is limited |
| to the user mounting the filesystem and root. |
| |
| kernel_cache |
| |
| This option disables flushing the cache of the file contents on |
| every open(). This should only be enabled on filesystems, where the |
| file data is never changed externally (not through the mounted FUSE |
| filesystem). Thus it is not suitable for network filesystems and |
| other "intermediate" filesystems. |
| |
| NOTE: if this option is not specified (and neither 'direct_io') data |
| is still cached after the open(), so a read() system call will not |
| always initiate a read operation. |
| |
| large_read |
| |
| Issue large read requests. This can improve performance for some |
| filesystems, but can also degrade performance. This option is only |
| useful on 2.4.X kernels, as on 2.6 kernels requests size is |
| automatically determined for optimum performance. |
| |
| direct_io |
| |
| This option disables the use of page cache (file content cache) in |
| the kernel for this filesystem. This has several affects: |
| |
| - Each read() or write() system call will initiate one or more |
| read or write operations, data will not be cached in the |
| kernel. |
| |
| - 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). |
| |
| max_read=N |
| |
| With this option the maximum size of read operations can be set. |
| The default is infinite. Note that the size of read requests is |
| limited anyway to 32 pages (which is 128kbyte on i386). |
| |
| hard_remove |
| |
| The default behavior is that if an open file is deleted, the file is |
| renamed to a hidden file (.fuse_hiddenXXX), and only removed when |
| the file is finally released. This relieves the filesystem |
| implementation of having to deal with this problem. This option |
| disables the hiding behavior, and files are removed immediately in |
| an unlink operation (or in a rename operation which overwrites an |
| existing file). |
| |
| It is recommended that you not use the hard_remove option. When |
| hard_remove is set, the following libc functions fail on unlinked |
| files (returning errno of ENOENT): |
| - read() |
| - write() |
| - fsync() |
| - close() |
| - f*xattr() |
| - ftruncate() |
| - fstat() |
| - fchmod() |
| - fchown() |
| |
| debug |
| |
| Turns on debug information printing by the library. |
| |
| fsname=NAME |
| |
| Sets the filesystem name. The default is the program name. |
| |
| nonempty |
| |
| Allows mounts over a non-empty file or directory. By default these |
| mounts are rejected (from version 2.3.1) to prevent accidental |
| covering up of data, which could for example prevent automatic |
| backup. |