What Is AVFS
------------
AVFS is a system, which enables all programs to look inside archived
or compressed files, or access remote files without recompiling the
programs or changing the kernel.
At the moment it supports floppies, tar and gzip files, zip, bzip2, ar
and rar files, ftp sessions, http, webdav, rsh/rcp, ssh/scp. Quite a
few other handlers are implemented with the Midnight Commander's
external FS.
AVFS is (C) under the GNU GPL (see the file COPYING). The shared
library supporting AVFS with LD_PRELOAD is (C) under the GNU LGPL (see
the file COPYING.LIB).
AVFS comes with ABSOLUTELY NO WARRANTY, for details see the file COPYING.
Where Is The Latest Version
---------------------------
Check out the page
http://www.inf.bme.hu/~mszeredi/avfs/
or
http://sourceforge.net/projects/avf
Forms of AVFS
-------------
AVFS can now be installed in four different ways. These are:
- Fuse
With fuse support, systems with 2.6 kernels are able to use avfs.
The requirements are
1) fuse support be compiled into the kernel or fuse modules
loaded.
2) the fuse package and library >= 2.4 be installed.
- Avfscoda
This method in theory works on any Linux system which has the
'coda' filesystem compiled in the kernel or as a kernel module.
In practice it works best with glibc-6.1 or higher, and it has
been tested on 2.2.X and 2.4.X kernels. It currently does not
work on 2.6.X kernels.
- Preload
Currently this works on solaris systems. There are problems
making the preload method work for GLIBC version 6.1 or
higher, so systems using GLIBC are not supported.
- Library
AVFS can be used as a shared library for programs written to
utilize AVFS. This is a pure userspace library so it should
work on any POSIX system.
Using AVFS is very similar in all cases. Differences will be indicated.
The installation method is different. For installation instructions
see the files 'INSTALL.fuse', 'INSTALL.avfscoda', 'INSTALL.preload',
and 'INSTALL.library' respectively all located in the doc/ directory.
Using AVFS
----------
These instructions are not for the fuse installation. Please see the file
README.avfs-fuse for details on how these commands are applied.
It is quite simple, you just do everything with the virtual files, as
you would do with real files. Here are some examples:
Listing a tar archive:
ls -l avfs-0.9.1.tgz#/
ls -l avfs-0.9.1.tgz#/avfs-0.9.1/
Obtaining information about avfs itself:
cat /#avfsstat/copyright - prints copyright information and version
cat /#avfsstat/modules - lists available handlers
cat /#avfsstat/version - prints version information
'cd' into an archive:
(For the 'preload' method the shell itself must be started with
avfs)
cd avfs-0.9.1.tgz#/
less avfs-0.9.1/README
Some more examples: (these are all shell commands, but of course you
could use any program: file manager, browser, editor, etc.)
Unpacking an archive:
cp -a tarfile.tgz#/dir .
cp -a zipfile.zip#/* .
(For the 'preload' method, using '*' means that the shell must be
started with AVFS)
Creating an archive:
mkdir tarfile.tgz#+
cp -a dir tarfile.tgz#+/
Note: The efficiency of this method is not yet the same as the
'normal' archive creation method, but it should not be more than 2
times slower.
NOTES:
1) ('preload' only) Input and output redirection to/from virtual files
does not work, since, in the 'preload' method, virtual file
descriptors cannot be kept open over exec(). This is not a problem
with the 'avfscoda' method.
E.g. you can't do
patch -p0 < patchfile.gz#
only
cat patchfile.gz# | patch -p0
If something doesn't work, then check the section 'Common Problems'.
Format of an AVFS Path
----------------------
(For a full explanation of the format see the file FORMAT)
As you've seen, the '#' magic character makes a virtual file or
directory from an ordinary file. Actually this is just a shorthand for
the full specification of an AVFS path:
'tarfile.tgz#' is the same as 'tarfile.tgz#ugz#utar'
Note, the short version will only work if the file-extension is
recognized (most are), but you can always tell exactly what should be
done with the file by using the second method.
There are handlers which do not have a "base" file. The following
handlers are like this: floppy, ftp, rsh, ssh, http, dav, avfsstat,
volatile, rpms, ucftp.
Examples
/#floppy:a - a: drive
/#a - a: drive (alias for /#floppy:a)
/#rsh:otherhost/foo/bar - /foo/bar on 'otherhost'
/#ssh:user@host/dir - /dir on 'host', login as 'user'
/#ftp:ftp.funet.fi/pub/Linux - anonymous ftp
/#ftp:user@host.domain.org/home/xyz/file - ftp with username 'user'
/#ftp_ctl:user@host.domain.org/password - write the password to this file
(ftppass is a nice utility for this)
/#http:www.inf.bme.hu|~mszeredi|avfs| - homepage of AVFS
/#http:ftp:||ftp.funet.fi|pub|Linux - use HTTP to get an ftp URL
(useful if you use a HTTP-only proxy)
The environment variable 'http_proxy' is used to set the default value
of the proxy server. You can also set it's value by writing to the file
/#avfsstat/http_proxy
The following "handlers" are available now:
name of handler type of operation notes
--------------- ----------------- -----
#a first floppy drive alias for #floppy:a
#avfsstat meta information builtin
#bz2 bzip2 uses bzip2
#dav webdav builtin
#dav_ctl control dav sessions
#floppy floppy uses mtools (mdir, mcopy, ...)
#ftp ftp builtin
#ftp_ctl control ftp sessions
#gz gzip uses gzip
#iso9660 CD/DVD filesystem no need to use mount -t iso9660!
#local local filesysem only for internal use
#rsh rsh/rcp only works if rsh needs no password
#ssh ssh/scp only works if ssh needs no password
#uar un-ar builtin
#ubz2 bunzip2 builtin
#ubzip2 bunzip2 uses bzip2
#ucftp ftp builtin (write support, no file cache)
#ucftp_ctl control ftp sessions
#ugz gunzip builtin (1)
#ugzip gunzip uses gzip
#urar unrar builtin list + uses rar to extract
#utar untar builtin
#uxz unxz/unlzma builtin
#uxze unxz/unlzma uses xz
#uz uncompress uses gzip
#uzip unzip builtin
#volatile 'memory fs' mainly for testing
(1) With the '-s' option (blala.gz#-s) the gunzip module will use the
size stored at the end of the gzip file. This will make some
operations on a .gz file much faster, but it isn't usable for huge
(>=4GByte) files, since the size is stored in 32 bits :(.
The following handlers are available through Midnight Commanders
'extfs'. These were not written by me, and could contain security
holes. Nonetheless some of them are quite useful. For documentation
on these, see the files in /usr/lib/avfs/extfs.
name of handler type of operation
--------------- -----------------
#deb debian packages
#ftplist ?
#hp48 ?
#lslR directory tree listings
#mailfs ?
#patchfs browse patch files
#rpm rpm packages
#rpms List of installed rpms
#trpm Useful inside #rpms
#ucpio cpio archives
#ulha lha archives
#uzoo zoo archives
Writing new modules
-------------------
You want to write a handler module for XY? Great! Please contact me,
and I can give you some advice regarding this.
Credits
-------
David Hanak (dhanak@inf.bme.hu) has contibuted the "rar" and the
"archive" modules, and lots of ideas to AVFS.
The VFS in Midnight Commander, written by Jakub Jelinek and Miguel de
Icaza <miguel@nuclecu.unam.mx>, has greatly helped me write this
library, and will probably continue to do so in the future.
Pavel Machek, who is the current maintainer of Midnight VFS, and who
has contributed lots of ideas and the alien module (which
unfortunately I did not have time to get into shape) to AVFS. The
'avfscoda' solution grew out of Pavels 'podfuk'. Most of it has been
changed, but the original idea is from Pavel.
Justin Mason <jm-avfs@jmason.org> contributed the dav module.
Koblinger Egmont <egmont@fazekas.hu> has written the "recursive
profile" scripts, set up the mailing list, and also sent me many good
ideas.
The zip and gzip file handler is based on the zlib compression and
decompression library, written by Jean-loup Gailly and Mark Adler.
The bzip2 handler uses the libbzip2 library written by Julian R
Seward.
The tar file handler is based on the GNU tar source, originally
written by John Gilmore.
People, who sent me ideas or bug-reports:
Jan Niehusmann <jan@gondor.com>
Demon of the Known Universe <psycho@dodds.net>
Duncan Pierce <cmrdrp@soc.staffs.ac.uk>
Scott F. Johnston <scott@fleetingimage.com>
Larry Riedel <larry@riedel.org>
The Future
----------
I hope AVFS will grow up to be a standard virtual file library, for which
people can write handler modules (or plugins, if you like) for whatever
they want.
If you think AVFS is a good idea, and you have any comments or suggestions,
please send me an email about them.
Have fun,
Miklos Szeredi <miklos@szeredi.hu>
