nnfs.txt

Non-Networked File System在几个非网络的（或慢网络的）Unix 计算机上提供了一个兼容的文件系统。

ADVANCED USAGE

Alias

   If you run nnfs2 on several hosts using NFS, you must indicate to
   nnfs2 that the hosts use the same file system. The mirrored directory
   must have the same name on all aliased host

   Assuming that the medium is ready, adding an alias with X11 interface.

     * You click on: Continue the update
     * you click on: +Nickname,
     * You click on: Continue the update
     * you click on: Quit

   Assuming that the medium is ready, adding an alias with text
   interface.

     * You type: nnfs2 --add-nickname hostname-yet-known-by-nnfs
     * You answer: c return to continue the update

Configuration

   The configuration file is .nnfs/nnfsrc, it is created the first time
   you run nnfs2. It is a hugely commented shell script you can edit. It
   is a shell script to allow some default values to be computed from the
   system.

   If you find this configuration file too complex to edit, you can use
   the nnfs2 X11 interface to edit the file. There is many tips to help
   you configure.

   The more useful options are :

     * READ_MEDIUM shell script called by nnfs2 to read from the medium
     * WRITE_MEDIUM shell script called by nnfs2 to write on the medium
     * COMPRESS_FILTER shell script filter called by nnfs2 to compress
     * UNCOMPRESS_FILTER shell script filter called by nnfs2 to
       uncompress
     * MEDIUM_SIZE size of the medium in bytes
     * OUTPUT_FILTER indicate which files should not be mirrored
     * CONFIRMATION choose which questions nnfs2 will ask you
     * AUTO_START if true, nnfs2 X11 interface start update without user
       intervantion.
     * TMP_FILE set this to none if you use nnfs2 with a big medium
     * CROSS_MOUNT_POINT if true nnfs2 will synchronise all the files
       even if they are on several file systems. The default is false so
       the mount points are not crossed.
     * COPY_HARD_LINK if true nnfs2 will copy hard links as several files
       not hard linked, this is dangerous so the default is false and the
       hard linked files are not copied at all.

   The option hard to configure is OUTPUT_FILTER. The default value is
   fine for me but certainly not for you. The minimal filter must stop
   the copy of nnfs2 history and all backup files.

   Example 3. Required minimal filter
-regex=~$
-regex=^\.nnfs/history/

   But, to run nnfs2 you must be connected, and the connection modify
   some file you don't want to copy on other hosts because it is a
   security breach or it is a non-sense. For example, any dot file in
   connection directory ending by history or authority

   Example 4. Filter files modified by the connection
-regex=^\.[^/]*(history|authority)$

   If the medium is small, you need to filter the files that are garbage
   as core, the executable files or the results of compilation as .o
   files. I assume here that executables biggers than 50k are not scripts
   shell or perl.

   Example 5. Filter garbage files
-type=f size=+50k perm=+111
-regex=(\.(o|a|so|sl|aux|log|dvi|summary|old)|/(core|a\.out))$

   The big shell or perl script are filtered, if you don't want this.
   Tell nnfs2 to not filter them.

   Example 6. Do not filter scripts
+regex=\.(pl|sh|tcl)$
+regex=/configure$

Reference of the filter description

   Each line starts by - or +, to remove or add to the file set the files
   verifying all the conditions in the line.

   The conditions are:

     * perm=+xxx: The condition is verified if any bit indicated in octal
       are in the file mode. If you indicate 0111 the file mode 0100,
       0111, 0750 are verified.
     * perm=-xxx: The condition is verified if all the bits indicated in
       octal are in the file mode. If you indicate 0111 the file mode
       0755 is verified but not 0750.
     * perm=xxx: The condition is verified if the file mode is exactly
       equal to the value indicated in octal.
     * size=+xxx: The condition is verified if the file size if bigger
       than the size specified. A size in kilo-bytes may be specified as
       56k and in mega-bytes as 2m
     * size=-xxx: same as above, but the file size must be smaller. The
       two conditions may appear on the same line.
     * type=dfl: The type is regular file (f), directory (d) or symbolic
       link (l)
     * regex=aregularexpression: If you want the expression to match the
       full name, add ^ at the begin and $ at the end. This condition
       must be at the end of the line.

Synchronisation of UID and GID

   If you want to synchonise the files with there UID and GID you need to
   be root and to run the rootnnfs2.

   This command had never been used in real cases. So use it with care.

FILES

   ~/.nnfs/nnfsrc
          nnfs2 configuration

   ~/.nnfs/gtkrc
          nnfs2 GTK configuration

   ~/.nnfs/history
          Directory where modified or deleted files are saved

   ~/.nnfs/log~
          Some log about nnfs2 last work

BUGS

   Limitations:

     * Directories must contains less than 65536 files (need to
       recompile).
     * Less than 16 hosts to synchronise (need to recompile).
     * No mirroring of 000 mode file (it is more a feature than a bug).
     * No mirroring of hard links (will not be corrected).
     * A file may be not mirrored if it is modified in the same second
       that nnfs2 modify it (will not be corrected).
     * If A, B and C are 3 hosts, B filter some files. nnfs2 runs on A,
       B, C, A, B, C, A, B, C, A, B, C, ... The modified files on A are
       filtered by B and are not copied on C. (very difficult to correct)
     * When adding an host to nnfs2, symbolics links are copied because
       the NNFS medium doesn't contain the content of the link. The real
       problem is that you can't create a symbolic link with all the good
       attributes (modification time, mode and on some systems UID and
       GID). So it is impossible to fully mirror symbolic links
     * In g_file.h should use off_t in place of long but it doesn't
       compile on IRIX MIPS IP30 gcc. So files are limited to 2GB.
     * On Mac OS X the symbolic links are often copied because the file
       system does not store modification date of symbolic links.
     * On Mac OS X is nnfs2 is unpredictable if only the case is
       different between two file names as with README and Readme

   Bugs:

     * In some cases, the GTK progress bar go over 100%.

NO WARRANTY

   This program is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
   General Public License for more details.

   It is nearly impossible that nnfs2 do an irrecoverable error. In the
   worst case, nnfs2 will stop. The returned value (error) of all the
   system calls are verified and the program tries to analyse the error.

   The parameters of the more stressing test on nnfs2 are the following:

     * 4 hosts
     * On each host a program create/delete/modify file/links/directories
       at the maximum speed.
     * nnfs2 runs continuously on each of the host randomly. So, while
       nnfs2 runs, files are modified while it is reading/writing them.
       Or worstly, directories are deleted while nnfs2 analyse the
       content, or files are created in directories that nnfs2 tries to
       delete

   Incredibly, nnfs2 works in this case thousands of time on a Linux 386
   Debian host.

   nnfs2 had been compiled and tested on HPPA 1.1 HPUX 10.20 and MIPS
   IP30 IRIX 6.5

   On Mac OS X it does not work optimaly with symbolic links (see BUGS).

SEE ALSO

   gzip(1)
   mcopy(1)

AUTHOR

   Author: Thierry EXCOFFIER, Author Home Page:
   http://www710.univ-lyon1.fr/~exco

   nnfs2 home page: http://www710.univ-lyon1.fr/~exco/nnfs.html