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# GO-FUSE
[](https://travis-ci.org/hanwen/go-fuse)
[](https://godoc.org/github.com/hanwen/go-fuse)
native bindings for the FUSE kernel module.
## Highlights
* High speed: as fast as libfuse using the gc compiler for single
threaded loads.
* Supports in-process mounting of different FileSystems onto
subdirectories of the FUSE mount.
* Supports 3 interfaces for writing filesystems:
- `PathFileSystem`: define filesystems in terms path names.
- `NodeFileSystem`: define filesystems in terms of inodes.
- `RawFileSystem`: define filesystems in terms of FUSE's raw
wire protocol.
* Both NodeFileSystem and PathFileSystem support manipulation of true
hardlinks.
* Includes two fleshed out examples, zipfs and unionfs.
## Examples
* `example/hello/main.go` contains a 60-line "hello world" filesystem
* `zipfs/zipfs.go` contains a small and simple read-only filesystem for
zip and tar files. The corresponding command is in example/zipfs/
For example,
```shell
mkdir /tmp/mountpoint
example/zipfs/zipfs /tmp/mountpoint file.zip &
ls /tmp/mountpoint
fusermount -u /tmp/mountpoint
````
* `zipfs/multizipfs.go` shows how to use in-process mounts to
combine multiple Go-FUSE filesystems into a larger filesystem.
* `fuse/loopback.go` mounts another piece of the filesystem.
Functionally, it is similar to a symlink. A binary to run is in
example/loopback/ . For example
```shell
mkdir /tmp/mountpoint
example/loopback/loopback -debug /tmp/mountpoint /some/other/directory &
ls /tmp/mountpoint
fusermount -u /tmp/mountpoint
```
* `unionfs/unionfs.go`: implements a union mount using 1 R/W branch, and
multiple R/O branches.
```shell
mkdir -p /tmp/mountpoint /tmp/writable
example/unionfs/unionfs /tmp/mountpoint /tmp/writable /usr &
ls /tmp/mountpoint
ls -l /tmp/mountpoint/bin/vi
rm /tmp/mountpoint/bin/vi
ls -l /tmp/mountpoint/bin/vi
cat /tmp/writable/DELETION/*
```
* `union/autounionfs.go`: creates UnionFs mounts automatically based on
existence of READONLY symlinks.
Tested on:
- x86 32bits (Fedora 14).
- x86 64bits (Ubuntu Lucid).
## Benchmarks
We use threaded stats over a read-only filesystem for benchmarking.
Automated code is under benchmark/ directory. A simple C version of
the same FS gives a FUSE baseline
Data points (Go-FUSE version May 2012), 1000 files, high level
interface, all kernel caching turned off, median stat time:
platform libfuse Go-FUSE difference (%)
Lenovo T60/Fedora16 (1cpu) 349us 355us 2% slower
Lenovo T400/Lucid (1cpu) 138us 140us 5% slower
Dell T3500/Lucid (1cpu) 72us 76us 5% slower
On T60, for each file we have
- Client side latency is 360us
- 106us of this is server side latency (4.5x lookup 23us, 1x getattr 4us)
- 16.5us is due to latency measurements.
- 3us is due to garbage collection.
## macOS Support
go-fuse works somewhat on OSX. Known limitations:
* All of the limitations of OSXFUSE, including lack of support for
NOTIFY.
* OSX issues STATFS calls continuously (leading to performance
concerns).
* OSX has trouble with concurrent reads from the FUSE device, leading
to performance concerns.
* Tests are expected to pass; report any failure as a bug!
## Credits
* Inspired by Taru Karttunen's package, https://bitbucket.org/taruti/go-extra.
* Originally based on Ivan Krasin's https://github.com/krasin/go-fuse-zip
## Bugs
Yes, probably. Report them through
https://github.com/hanwen/go-fuse/issues
## Disclaimer
This is not an official Google product.
## Known Problems
Grep source code for TODO. Major topics:
* Missing support for network FS file locking: `FUSE_GETLK`, `FUSE_SETLK`,
`FUSE_SETLKW`
* Missing support for `FUSE_INTERRUPT`, `CUSE`, `BMAP`, `IOCTL`
* In the path API, renames are racy; See also:
http://sourceforge.net/mailarchive/message.php?msg_id=27550667
Don't use the path API if you care about correctness.
## License
Like Go, this library is distributed under the new BSD license. See
accompanying LICENSE file.
--------
## Appendix I. Go-FUSE log format
To increase signal/noise ratio Go-FUSE uses abbreviations in its debug log
output. Here is how to read it:
- `iX` means `inode X`;
- `gX` means `generation X`;
- `tA` and `tE` means timeout for attributes and directory entry correspondingly;
- `[<off> +<size>)` means data range from `<off>` inclusive till `<off>+<size>` exclusive;
- `Xb` means `X bytes`.
Every line is prefixed with either `rx <unique>` or `tx <unique>` to denote
whether it was for kernel request, which Go-FUSE received, or reply, which
Go-FUSE sent back to kernel.
Example debug log output:
```
rx 2: LOOKUP i1 [".wcfs"] 6b
tx 2: OK, {i3 g2 tE=1s tA=1s {M040755 SZ=0 L=0 1000:1000 B0*0 i0:3 A 0.000000 M 0.000000 C 0.000000}}
rx 3: LOOKUP i3 ["zurl"] 5b
tx 3: OK, {i4 g3 tE=1s tA=1s {M0100644 SZ=33 L=1 1000:1000 B0*0 i0:4 A 0.000000 M 0.000000 C 0.000000}}
rx 4: OPEN i4 {O_RDONLY,0x8000}
tx 4: 38=function not implemented, {Fh 0 }
rx 5: READ i4 {Fh 0 [0 +4096) L 0 RDONLY,0x8000}
tx 5: OK, 33b data "file:///"...
rx 6: GETATTR i4 {Fh 0}
tx 6: OK, {tA=1s {M0100644 SZ=33 L=1 1000:1000 B0*0 i0:4 A 0.000000 M 0.000000 C 0.000000}}
rx 7: FLUSH i4 {Fh 0}
tx 7: OK
rx 8: LOOKUP i1 ["head"] 5b
tx 8: OK, {i5 g4 tE=1s tA=1s {M040755 SZ=0 L=0 1000:1000 B0*0 i0:5 A 0.000000 M 0.000000 C 0.000000}}
rx 9: LOOKUP i5 ["bigfile"] 8b
tx 9: OK, {i6 g5 tE=1s tA=1s {M040755 SZ=0 L=0 1000:1000 B0*0 i0:6 A 0.000000 M 0.000000 C 0.000000}}
rx 10: FLUSH i4 {Fh 0}
tx 10: OK
rx 11: GETATTR i1 {Fh 0}
tx 11: OK, {tA=1s {M040755 SZ=0 L=1 1000:1000 B0*0 i0:1 A 0.000000 M 0.000000 C 0.000000}}
```
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