nnfs.sgml

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<!DOCTYPE RefEntry PUBLIC "-//Davenport//DTD DocBook V3.0//EN" [
<!ENTITY nnfs "<Command>nnfs2</Command>">
<!ENTITY medium "<Emphasis>NNFS medium</Emphasis>">
<!ENTITY fs "<Emphasis>NNFS filesystem</Emphasis>">
<!ENTITY % paper-type "A4">
]>


<RefEntry>

<DocInfo>
    <address>
      <email>[e-mail]</email>
    </address>
    <author>
      <firstname>Thierry</firstname>
      <surname>EXCOFFIER</surname>
    </author>
<Date>2002 november 3</Date>
</DocInfo>


<RefMeta>
<RefEntryTitle>nnfs2</RefEntryTitle>
<ManVolNum>1</ManVolNum>
</RefMeta>

<RefNameDiv>
<RefName>nnfs2</RefName>
<RefPurpose>Synchronise filesystems between Non-Networked hosts</RefPurpose>
</RefNameDiv>

<RefSynopsisDiv>

<CmdSynopsis>
<Command>nnfs2</command>
<Arg Choice=Req> <Option>--no-x11</Option></Arg>
<Group>
<Arg><Option>--add-first <Replaceable/directory-name/</Option></Arg>
<Arg><Option>--add <Replaceable/directory-name/</Option></Arg>
<Arg><Option>--add-nickname <Replaceable/directory-name/</Option></Arg>
</Group>
</CmdSynopsis>

<CmdSynopsis>
<Command/nnfs2/
<Group>
<Arg><Option>--help</Option></Arg>
<Arg><Option>--licence</Option></Arg>
</Group>
</CmdSynopsis>

</RefSynopsisDiv>


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<RefSect1>
<Title>INTRODUCTION</Title>
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<Para>
The NNFS goal is to provide to ``one'' user a consistent file system
over all the hosts used by the user.
</Para>

<Para>
With hosts connected on a LAN you must use NFS instead of NNFS.
In the case of hosts not connected by a network or
connected by a slow network (modem) NFS is not the answer.
</Para>

<Para>
With NNFS, the files are duplicated on all the computers.
The up to date files are on the computer on which the user works.
The &fs; is stored on the &medium;.
Usually the &medium; is a floppy disk,
it could be whatever you want (easily customisable),
if there is much data, several floppies will be asked.
</Para>

<Para>
When the user stops his work on a computer,
he runs as last command: &nnfs;.
Then all his modifications (change, creation, deletion)
are recorded on the &medium;.
</Para>

<Para>
When the user starts to work on a computer,
he runs as first command: &nnfs;.
Then all modifications (change, creation, deletion)
stored on the &medium; are retrieved on current system.
</Para>

<Para>
If the user forgot to run an update, &nnfs; will nevertheless optimally work.
The only drawback is that some files will not be up to date on
the host used by the user.
</Para>

<Para>
It is also possible to have a numbered backup 
of modified/deleted files.
So you cannot lose a file when you run &nnfs;
(because the file is modified/deleted on another host)
</Para>

</RefSect1>




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<RefSect1>
<Title>USAGE</Title>
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<Para>&nnfs; has a text and a graphical user interface.
If you run the command for the first time or with a &medium;
formatted or not, the command will provide contextual informations and help
and will ask contextual questions.
The graphical user interface allows you to edit the configuration.
</Para>

<Para>The interactive help is extensive and guide the user.
This documentation is here to give general principles.
</Para>

<Para>By default the &nnfs; works with standards tools: floppy disk
and <Command>gzip</Command>. The floppy disk access is done
<FOREIGNPHRASE>via</FOREIGNPHRASE> system dependent commands
(IRIX, AIX, HPUX and <Command>mcopy</Command> in the other cases).
If you want to change these defaults, see the configuration section.
</Para>

<Para>As the default configurations use floppy disk, the &nnfs;
default filter does not synchronise big files or ``garbage'' files.
If you want to change these defaults, see the configuration section.
</Para>

<para>It is not recommended to continue to modify files while &nnfs;
is running. It is not dangerous but the result is unpredictable.
</para>

<para>Be carefull, some applications wrote their data on disk only
when you stop them. So you must stop these applications before
running &nnfs;. For example <command>netscape</command> wrote
some folder information only when you quit the program, so you
must run &nnfs; only if <command>netscape</command> is not running.
To avoid this you can create a shell script killing these applications
and cleaning some file before launching &nnfs;.
</para>

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<RefSect2>
<Title>To do before using &nnfs;</Title>
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<Para>
If the file hierarchy you want to synchronise is yet identical
on all the hosts you can go to the next section.
The root of the file hierarchy may have a different name on each host.
To avoid problems you should use only relative internal symbolic links,
so the links are correct on all the hosts.
</Para>
<Para>
If the files hierarchy are not identical, you have two solutions:
<Itemizedlist>
<Listitem><Para>You create yourself an identical hierarchy on all the hosts.
<Emphasis>The file modification date should be identical on all the
hosts.</Emphasis></Para>
</listitem>
<Listitem><Para>Or, you let &nnfs; create the identical hierarchy on all
the hosts. In this case, a hierarchy made of the union of all the
files is created, conflicts are solved using the modification date.
It is the only case where the modification date is used to solve conflicts.
</Para>
</listitem>
</Itemizedlist>


</Para>
</RefSect2>


<!-- ********************************************************************** -->
<RefSect2>
<Title>Initialisations</Title>
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<Para>
When you run the &nnfs; command on an host not known by the &fs;
it will explain you how to add the host in the &fs;.
</Para>

<para>
If the &fs; does not fit in one medium, you will be asked
to introduce medium.
</para>

<Para>
Now, the initialisation for 2 hosts named A and B will be detailed
for the 2 user interfaces.
</Para>

<RefSect3>
<Title>Initialisations with X11 interface</Title>

<para>First run on host A.
<Itemizedlist>
<listitem><para>You click on: <GUIBUTTON>Continue without reading the medium</GUIBUTTON></para></listitem>
<listitem><para>you enter the local name of the hierarchy to synchronise,</para></listitem>
<listitem><para>you click on: <GUIBUTTON>Continue the update</GUIBUTTON>,</para></listitem>
<listitem><para>you click on: <GUIBUTTON>Medium AAA is ready for writing</GUIBUTTON>,</para></listitem>
<listitem><para>you click on: <GUIBUTTON>Quit</GUIBUTTON></para></listitem>
</Itemizedlist>
</para>

<para>Second run on host B, assuming medium is ready.
<Itemizedlist>
<listitem><para>You click on: <GUIBUTTON>Continue the update</GUIBUTTON></para></listitem>
<listitem><para>you enter the local name of the hierarchy to synchronise,</para></listitem>
<listitem><para>you click on: <GUIBUTTON>Continue the update</GUIBUTTON>,</para></listitem>
<listitem><para>you click on: <GUIBUTTON>Quit</GUIBUTTON></para></listitem>
</Itemizedlist>
</para>



<para>Normal run when initialisations are done, assuming medium is ready.
<Itemizedlist>
<listitem><para>You click on: <GUIBUTTON>Continue the update</GUIBUTTON></para></listitem>
<listitem><para>you click on: <GUIBUTTON>Continue the update</GUIBUTTON>,</para></listitem>
<listitem><para>you click on: <GUIBUTTON>Quit</GUIBUTTON></para></listitem>
</Itemizedlist>
</para>

</RefSect3>








<RefSect3>
<Title>Initialisations with text interface</Title>

<para>First run on host A.
<Itemizedlist>
<listitem><para>You type: &nnfs; <option>--add-first</option> <replaceable>dirname</replaceable></para></listitem>
<listitem><para>You answer: <keycap>c</keycap> <keycap>return</keycap> to continue the update</para></listitem>
<listitem><para>You hit : <keycap>return</keycap> when medium is ready</para></listitem>
</Itemizedlist>
</para>

<para>Second run on host B, assuming medium is ready.
<Itemizedlist>
<listitem><para>You type: &nnfs; <option>--add</option> <replaceable>dirname</replaceable></para></listitem>
<listitem><para>You answer: <keycap>c</keycap> <keycap>return</keycap> to continue the update</para></listitem>
</Itemizedlist>
</para>



<para>Normal run when initialisations are done, assuming medium is ready.
<Itemizedlist>
<listitem><para>You type: &nnfs;</para></listitem>
<listitem><para>You answer: <keycap>c</keycap> <keycap>return</keycap> to continue the update</para></listitem>
</Itemizedlist>
</para>

</RefSect3>




</RefSect2>





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<RefSect2>
<Title>How to recover from &medium; read failure</Title>
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<para>If there is a read error you can rerun &nnfs; a few times with the
hope that the error will vanish. If it is not the case, put the
bad medium in a trash, take a new one and create immediately
a new &fs; with the current host.</para>

<Para>
If the read error is before you start to work on an host.
Try to not work on non-synchronized file in order to avoid future
conflicts. Run &nnfs; as always before stopping to work on the host.
</Para>

<para>
If the read error is before you leave an host. You will want to copy
the file modified by your session on the other host. To do so,
modify all the file you want to synchronise and rerun &nnfs; on the host.
For example by running <command>find . -mtime -1 -print | xargs touch</command>.
If you do not do this, these files will be synchronised but only
after adding the other host on &fs;, a run on local the host and a run on the other
host.
</para>

<para>My experience about floppies is that there is floppies usable
only 2 or 3 times and some usable hundreds of time.
<emphasis>Even if they are from the same box</emphasis>.</para>


</RefSect2>





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<RefSect2>
<Title>Historised backups</Title>
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<Para>
Each time you run &nnfs; the files deleted or modified are
moved in a directory. This directory is not mirrored!
<example>
<title>Archiving modified files in default directory</title>
<para>
Current date: Sun Sep 16 14:57:47 CEST 2001
</para>
<para>
Modified file: <filename>foo/bar/Makefile</filename>
</para>
<para>
Historised file: <filename>.nnfs/history/2001_09/16_14:57.47/foo/bar/Makefile</filename>
</para>

</example>
</Para>
<para>
So you can easily remove old historised files by date.
</para>


</RefSect2>





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<RefSect2>
<Title>Conflicts</Title>
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<Para>
If you don't run &nnfs; before and after working, some update conflicts
may be raised if you work on the same files.
<example>
<title>A simple conflict</title>
<Itemizedlist>
<listitem><para>You run &nnfs; on host A</para></listitem>
<listitem><para>You modify <filename>foo</filename> on host A</para></listitem>