[MPlayer-mirror] MPlayer mirroring HOWTO

Diego Biurrun diego at biurrun.de
Fri Jun 16 13:46:36 CEST 2006 

Attila and I just finished composing a mirroring HOWTO.  It's available
directly through Subversion at

http://svn.mplayerhq.hu/*checkout*/mplayer/trunk/DOCS/tech/mirrors/mirror_howto.txt?rev=HEAD

I'm also attaching it to this mail for convenience.  Please let me know
what you think of it and point out mistakes or unclear parts you notice.

Thanks

Diego
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                          How to build an MPlayer mirror
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WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING!
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This is a preliminary version. Do not rely on anything here.
Please send feedback + corrections to the mplayer-mirror mailing list.
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About this document
~~~~~~~~~~~~~~~~~~~

Mirroring MPlayer is quite easy but requires a few steps to be taken
and a few things taken care of. This document describes these steps
in detail so that anyone wishing to build an official or an unofficial
mirror can do that without much trouble.



A note on performance issues
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

A few of the commands used here will generate some load on our main server.
Too many clients executing them at once will overload our server and cause
a performance degradation for all our users. Thus we kindly ask you to be
considerate about what you do. We do not want to restrict mirroring to a
few select people, but this requires everyone using the system described
here to behave.


Outline of the mirroring system
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The mirroring system uses rsync to transfer the data and to perform
updates. A script (update_mplayer_rsync) is provided to call the rsync
client with the right set of parameters. This script should be run
periodically via cron.
Additionally, official mirrors should set up an ssh account so that
updates can be triggered when important changes on the main server
are performed.
Mirrors should provide their data over HTTP or FTP or both. Each official
mirror will be assigned a mirror number (wwwXXX.mplayerhq.hu or
ftpXXX.mplayerhq.hu where XXX is the mirror number). This mirror
number determines the hostname over which it will be reached.


Getting the data, mirroring script and cron setup
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The mirroring script is located in our Subversion repository at

  svn://svn.mplayerhq.hu/mplayer/trunk/DOCS/tech/mirrors/update_mplayer_rsync

or on the web at

  http://svn.mplayerhq.hu/*checkout*/mplayer/trunk/DOCS/tech/mirrors/update_mplayer_rsync

This script requires a working `rsync` client. The handling of the
lock file is done by using `lockfile` from the procmail package.
Using a lock file is recommended but not necessary. The temporary file
generation is handled by `mktemp` which is available from
http://www.mktemp.org/mktemp/ .

The script contains a few configuration variables at the begining that
can and should be set:
PATH: The $PATH to be used within the script (recommended).
LOCK: The full path to the lock file to be used (/var/lock/mplayer-mirror-lock
      or something similar, recommended).
MIRROR_ROOT: The root of the mirror. This is the directory where all files
             are downloaded to (required).
MAILADR: The mail address where reports should be sent to (required).
TMPDIR: The directory where temporary files should be created.
        If you set this explicitly, you have to uncomment the export below
        (defaults to /tmp if not set).

Install this script and set the variables according to your setup. Then run
it once to get the first checkout of the mirror. This will require (at the
time of this writing - 2006-06) about 500MB of disk space.
You should get two directories in your $MIRROR_ROOT: homepage and MPlayer.
The former containing the HTML pages for the mirror and the latter the
downloadable files.

If this worked out OK, you should set up a cron job that periodically updates
the files. If you run an official mirror you should run the script every
6h to 12h (6h recommended). If you do not run an official mirror, you should
not run the script more often than once a day. Please use an "odd" time
to run the script when it is unlikely that any other cron job is running.
Bad times are e.g. full hours, or minutes that are divisible by 5.
An example crontab line would look like this:
---
17 1,8,13,19 * * * /path/to/update_mplayer_rsync
---
(please change the minute and hours to something random)

You can change the rest of the script as you see fit, although it is not
recommended. Please DO NOT CHANGE the options of the rsync commands.
Especially DO NOT REMOVE the -t and -W options. These prevent calculating
checksums on the server side which are very expensive.


Setting up an SSH account for update triggers
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Official mirrors should provide an ssh-based trigger to run the update script
on request. This makes it possible to distribute releases and other important
files immediately to all mirrors.

The setup does not need a special user other than the one as which the update
script is run and does not allow running any other command.

First you need to create an ssh key pair by running:
---
ssh-keygen -t dsa -C MPHQ_rsync_trigger -f www#_sshkey
---
(replace the '#' by your mirror number)

You should send the private key to us by mail and specify the host and
user to be used. Please use a private mail of one of the admins and
DO NOT send the private key to the mirror mailing list.

The public key should be placed in the ~/.ssh/authorized_keys file of the
user running the updates. To restrict the ssh key to only one command place
the following directives at the begining of the line with the key:
from="*.mplayerhq.hu",command="<path_to_update_mplayer_rsync>"
e.g.:
---
from="*.mplayerhq.hu",command="/path/to/update_mplayer_rsync" ssh-dss AAAA
B3NzaC1kc3MAAAEBAI20yhE3/bRjzojUhhMz4DHnGhcJUiPWOfoP9CygnFOYOxJTFlxgqM3iJiHWRxgK
FJ/Uw40eV9K4Ww4fp2pe1guXJzKna8+6vBXaPPVEVxSyaxgtt4Xt3zpUuCnNljgArcEhwcNyOyH2RVln
yhyxsrKhuq5ZoNHD3caBGjZu3eOR2atPGS1NOdeN/hytIoh8T8DicPqPI29yWX9yAjnHv6wdPutwMLu6
[...]
n0Fs3CJY6/1UpgDGH7VPey0SdpJEDewltRLA+buP++2vJD/NUOeGzcRydo2NdZ1wiiaytXxkaec928JC
NABTeBh6NKAg4vnPvcRLKEBVdSrar/fARSbOmf3HOcsw3uZoAIE9jDGhnMKcnXfHjPZ2tZP9CHs6Wo4n
yDOxIfDZmJ7VJqMRc6//p5k81pkkGvawbPA63StI/Dkv/648l4XONuJc2z5gaUdjrTA8TsD/VJGiGcHl
mlGj3IWCBz7e4+XB3L64kFZwLCYN8kwDUAaHq4EtcMVOnQ== MPHQ_rsync_trigger
---
(lines split for readability)


Setting up a webserver
~~~~~~~~~~~~~~~~~~~~~~

Set up Apache or whatever web server you prefer. We just have static pages,
so no fancy configuration is necessary. However, we need a few aliases so that
links on our pages work correctly. /MPlayer and /DOCS should redirect to the
directory with the downloadable files and /homepage should redirect to the
directory with the HTML pages.

Here is an example stanza to paste into your Apache configuration:

<VirtualHost www#.mplayerhq.hu>
        DocumentRoot /path/to/htdocs
        Options FollowSymLinks
        Alias /homepage /path/to/htdocs
        Alias /MPlayer  /path/to/MPlayer
        Alias /DOCS     /path/to/MPlayer/DOCS
</VirtualHost>


Setting up an FTP server
~~~~~~~~~~~~~~~~~~~~~~~~

Any FTP server will do. We use vsftpd, it's fast and secure. You should have
the same directory layout as we do on our server, so there should be a
subdirectory named 'MPlayer' (notice the capitals) that contains the
downloadable files.


Mailinglist
~~~~~~~~~~~

TO BE DONE

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